Absorption
(gen.) The taking in, incorporation, or reception of gases, liquids, light, or heat.
(phys/chem) Penetration of one substance into the inner structure of another (cf.
adsorption, in which one substance is attracted and held on the surface of another).
Occurs between a gas or vapor and a liquid.
(pharm.) The process of movement of a drug from the site of application into the
extracellular compartment of the body.
Acholeplasma laidlawii
Microorganism (Mycoplasma) used in sterility testing of < 0.1 µm-rated filters.
Acid
A hydrogen-containing compound which itself or its solution has an acidic pH < 7.0
and which can react with a base to form a salt.
Active Site
The region of a protein molecule that binds the specific substrate and chemically
modifies it (in an enzyme) or interacts with it (in a receptor).
Adsorption
Retention of gas, liquid, solid, or a dissolved substance on a surface due to positive
interaction (attraction) between the surface and the molecules of the adsorbed
material. The interactive forces can be electrostatic (coulombic) or non-electrostatic
(dipole-dipole and hydrophobic). Adsorption to a membrane or filter device can
occur in a specific manner (affinity) or non-specifically.
Aerobic
This term is applied to organisms which grow in the presence of oxygen. An
organism which requires oxygen to grow is termed an obligate aerobe.
Affinity
Generally refers to the ability that two molecules have to bind to each other. It is
typically measured in a binding assay where increasing amounts of one molecule
are added until the binding sites are saturated. The concentration of the variable
molecule that achieves half of the saturation value is called the Kd (binding
constant) and is a direct measure of the strength of binding. The stronger the
affinity, the higher the Kd. When researchers refer to “affinity purification,” they are
usually talking about the use of an antibody to catch and purify a specific protein.
Agar
A polysaccharide plant product isolated from red algae. It is used as a gelling agent
and also is used to make solid media for the growth of microorganisms.
Agarose Gel
Agarose is a purified component of agar, a naturally occurring high molecular weight
polysaccharide obtained from red algae. It forms highly porous yet rigid gels that are
used as stabilizing media for electrophoresis of DNA and RNA. The nucleic acids
can be recovered from the gel using Nanosep® and Nanosep MF ultrafiltration
devices.
Agarose Gel Electrophoresis
A method used to separate, identify and purify molecules of different weight and/or
structure. It is specifically applied to the separation of DNA fragments. It is a rapid,
simple, and accurate process. The separated molecules can be visualized directly
by staining with dyes. The electrophoretic migration rate of molecules through
agarose gel is dependent on the following parameters:
Molecular size: Molecules pass through the gel at rates that are inversely
proportional to the log of their molecular weight.
Agarose concentration: A molecule of a given size migrates at different rates
through gels containing different concentrations of agarose.
Molecular conformation: A molecule of the same molecular weight but of a
different conformation will migrate at different rates. Generally closed circular or
globular forms will migrate faster than linear forms.
Electric current: At low voltages, the rate of migration is proportional to the voltage,
but as the voltage is increased the rate of migration of high molecular weight
fragments is increased differentially. See Electrophoresis.
Agglutination
The sticking together of insoluble antigens such as bacteria, viruses, or erythrocytes
caused by a specific antibody. Agglutination assays are used to type human blood
before a transfusion.
Alcohol
An organic compound containing a -OH group. Often alcohol can be used as a
sanitization agent by treating a sample with 70% ethanol. Alcohols that are miscible
in water (such as methanol, ethanol, or isopropanol) can be used to prewet a
hydrophobic membrane (such as PTFE) prior to filtration of an aqueous liquid. They
can also be used to verify the integrity of membrane filters with small pores.
Aliquot
A representative sample of a larger quantity.
Ampholyte
An amphoteric molecule or substance, such as amino acid or protein. Ampholytes
can ionize to form either cations (acids) or anions (bases) because they have both
acidic (proton donor) and basic (proton acceptor) groups. The sum of charges
carried by these groups determines the net charge of the molecule. There is a pH
called the isoelectric point (pl), at which the sums of negative and positive charges
are equal and the molecule has zero net charge.
Amphoteric
See Ampholyte. Capable of acting both as an acid and as a base. Amphoteric
membranes may contain positively- and negatively-charged surface groups but
carry a net neutral charge (for example, Biodyne® A membrane).
Ampicillin
An antibiotic widely used in clinical treatment and rDNA research. It is a derivative of
penicillin which kills bacteria by interfacing with the synthesis of the cell wall.
Anaerobic
Literally, "life without air." This term is applied to organisms which do not require
oxygen to grow and for which oxygen is toxic. An organism which requires the
absence of oxygen is termed an obligate anaerobe.
Analog
In drug discovery, it is a molecule that is able to bind to the same site as another
molecule. This ability is often due to structural similarities between the molecules.
Often analogs are added in increasing concentrations to a binding assay in order to
confirm that the binding is truly specific. The half-saturation level of binding inhibition
seen by adding analogs is called the Ki (inhibition constant) and is a measure of the
relative affinities of the two molecules.
Analyte
Any molecule that is measured by physical, chemical, or biological means.
Anion
When a salt is dissolved it has two charged molecules: a cation (positively charged)
which can behave as an acid and an anion (negatively charged) which can act as a
base. If a surface has a positive charge it is called anionic and can be used to
capture negatively-charged molecules.
Anisotropic (Asymmetric) Membrane
A membrane in which the pore size and structure are not the same throughout the
thickness of the membrane. Such membranes are usually considered "directional"
because of the difference in flow characteristics depending on which side of the
membrane faces the feed stream.
Anode
Positive pole or electrode of an electrolytic system. Anionic molecules are attracted
to the anode.
Antibiotic
Any of a group of substances that has the ability to kill or weaken bacteria.
Antibodies
Antibodies are proteins (immunoglobulins) synthesized by the immune system in
response to an antigen. They are Y-shaped, with a "tail" and two "arms." The arms
have a unique shape that enables them to combine specifically with the antigen.
This plays an important role in the body’s defense against infection (bacteria,
viruses) or other foreign protein substances. The specificity of the antibody-antigen
reaction forms a basis for highly specific and sensitive immunoassays. They can be
used to purify specific molecules from a mixed solution using affinity.
Antigen
A foreign substance (usually proteinaceous or high molecular weight
polysaccharide) that induces the formation of antibodies. Examples are bacteria,
viruses, endo/exotoxins, pollen, and vaccines.
Antiserum
The blood serum obtained from an animal after it has been immunized with a
particular antigen. It will contain antibodies that are specific for that antigen as well
as antibodies specific for any other antigens, against which the animal has
previously been immunized.
Aqueous
Similar to or resembling water. In reference to solution made in water.
Array
For life sciences, an array is usually a series of spots of a collection of molecules
that are arranged on a membrane in a very specific pattern. A second labeled
molecule or probe can be used to detect binding or hybridization to a particular spot.
The address of that spot indicates which molecule is present in the complex
mixture. Gene expression profiles are commonly analyzed using hybridization
arrays. Dot blots and "gene chips" are examples of arrays.
Aseptic
Refers to an operation performed in a sterile environment or using appropriate
precautions (such as flaming pipettes) designed to prevent contamination through
introduction of bacteria.
Assay
Analytical procedure to determine purity, concentration, or biological activity of a
specific substance in a mixture. In drug discovery, an assay is performed to
determine the relative affinity that a ligand has for its respective target.
Autoclave(ing)
A chamber for sterilizing filters or equipment with saturated steam by using constant
high temperature and pressure (commonly 121 °C, 15 psi). Many materials requiring
sterilization (such as cell culture media and injectable drugs) are degraded by the
heat of an autoclave and must be sterilized by other means, such as filtration.
Autoradiography
A technique for imaging an object that has been radiolabeled by exposing a
photographic film to the object itself. Used to detect the location of transferred DNA
fragments on a membrane (such as Biodyne® or BioTrace™ membranes) that has
been hybridized with radiolabeled probes. The photographic image generated by
this process is called an Autoradiogram. Recently, the same procedures have been
used to detect chemiluminescent probes.
Avidin
AKA streptavidin. A molecule found in egg whites which has a high affinity for the
molecule biotin. This strong and specific binding property is used widely in
molecular biology for labeling and detection. One molecule can be attached to an
avidin molecule and a second molecule can be bound to biotin. When mixed, the
two molecules are now bound together through the action of the avidin and biotin
allowing two molecules that do not normally interact to be forced into proximity. Like
antibodies, these molecules can be used for affinity purification.
Background
Effects that obscure a specific signal such as background "noise" in chart recorders.
In transfer membranes, background results from probes attaching to sites other than
the specific or complementary molecules. Blocking the nonspecific sites with
substances to which the probe will not bind can prevent this. In drug discovery, high
fluorescence background from filtration membranes often prevents the researcher
from using a filter plate to screen libraries.
Backwash
Reversing the flow of liquid through a filter in order to remove trapped solids.
Bacteria (Bacterium)
Free living, simple celled, microscopic organisms having a cell wall and
characteristic shape (e.g., round, rod-like, spiral, or filamentous); lack a defined
nucleus.
Bactericide
A substance that destroys bacteria.
Bacteriophage
A virus that exclusively infects bacteria. A protein coat surrounds the organism’s
genome (DNA or RNA). One of the bacteriophages most extensively studied is the
lambda phage, which is also one of the most important viral vectors used in rDNA
work. Lambda promoters have been used to make eukaryotic proteins in E. coli.
Bacteriostasis
The inhibition of the growth and reproduction of bacteria without their destruction.
Bacteriostatic Water For Injection, USP
Same as WFI, but contains a preservative. See WFI (Water-For-Injection, USP).
Baking
Technique used to permanently immobilize nucleic acids on a membrane blot. Has
been largely replaced by UV crosslinking.
Bar
A unit of pressure. One bar = 14.5 psi.
Base Pairs
In double-stranded DNA, the bases of one strand are hydrogen-bonded to those of
the other strand to form specific base pairs: adenin-thymine (A-T) and
guaninecytosine (G-C). Base pairing is one of the most important features of the
DNA structure. It ensures that (1) the base sequence of the two strands are
complementary, (2) the replica of each strand is given the base sequence of its
complementary strand, and (3) the base sequence of DNA is easily transcribed into
RNA molecule. The number of base pairs is used as a measure of the size of the
DNA fragment. Often expressed as kilobases (103 bases) or kb.
Baseline
Detector signal for zero concentration for HPLC, GC, IC, and other analytical
instruments.
Basic Medium Eagles (BME)
One of the most common mammalian tissue culture media composed of isotonic
salts, carbohydrates, and vitamins. When combined with animal serum, BME is a
good medium for mammalian cell proliferation. See Fetal Calf Serum.
Beta Rating
An industry standard method of measuring a filter's ability to remove particles. A
beta rating for a specific particle size is defined as:
See Titer Reduction.
Beta Ratio
Measurement of filter retention efficiency. Ratio of particles exposed to a filter (as
feed stream) to particles present in the filtrate.
Binding Constant
Defined as the concentration of a ligand that saturates the binding of half of the
available binding sites. It is a combination of the available target (receptor) and the
affinity of the ligand. AKA the dissociation constant Kd.
Bioassay
The determination of the biological activity of a substance (e.g., a drug) by
observing its effect on an organism, organ or tissue culture.
Bioburden
The load or level of microorganisms in a substance to be filtered. Detection of
bioburden is a good application of the Pallchek™ Luminometer.
Biohazard
Biological refuse, possibly pathogenic in nature (e,g., HIV). This is often applied to
genetically engineered organisms as well as body fluids. Hydrophobic vent filters
are used to prevent workers and the workplace from exposure to aerosolized
biohazardous organisms.
Biological Indicators
Resistant microorganisms (spores) employed to confirm that a sterilization process
is effective. They may, for example, be placed within a filter housing in order to
determine if a proposed autoclave cycle is effective. After the autoclave cycle is
complete, they are removed and cultured to determine if the microorganisms have
been killed.
Biomass
The total weight of living matter present in a specific area.
Bioreactor
A vessel, usually stainless steel or glass, used for growing mammalian, bacterial, or
plant cells. A fermentor.
Biosynthesis
The synthesis of molecules by living cells. Many tissue culture systems have
organisms that are engineered to synthesize a desired protein. Often filtration and
even ultrafiltration are needed to capture, collect, and purify the expressed protein.
Biotechnology
The use of wild type and genetically engineered microbial forms to obtain
biologically produced products.
Biotinylated
Labeled with biotin. Biotinylated probes are used in assays (such as Southern
blotting) based on the strong affinity that the glycoprotein avidin (or streptavidin) has
for biotin. Chromogenic, fluorogenic, or enzyme conjugates of avidin are used in
such assays.
Blinding
The reduction or cut off of flow due to particles filling the pores of a filter.
Blocking
The act of preventing unwanted molecules from binding to a surface. It is commonly
used to prevent antibodies from binding directly to a membrane instead of binding to
a desired biomolecule. It is often done by adding milk protein (casein) to a protein
blot after the analyte proteins have been attached.
Blood Plasma
Blood from which all blood corpuscles, with the exception of platelet cells, have
been removed (e.g., by centrifugation) resulting in a clear, straw-colored fluid that
clots as easily as whole blood.
Blood Serum
The liquid expressed from clotted blood or clotted blood plasma.
Blotting
The process of transferring macromolecules from gels to an immobilizing matrix
(such as Biodyne® or BioTrace™ transfer membranes). See Northern, Southern
and Western Transfer. The matrix (membrane) containing transferred
macromolecules is called a blot. Most transfers from agarose gels are done with
wicking a capillary flow overnight, while acrylamide transfers require electrophoretic
transfer.
Blow (Form), Fill, Seal
Refers to machines that combine formation of a plastic container by blow molding,
aseptic filling, and sealing of the liquid product into the final package.
Bovine Serum Albumin (BSA)
A blood protein that makes up approximately 55 to 65% of the proteins in bovine
serum. Used as a size marker on gels and as a carrier protein.
Bovine Viral Diarrhea (BVD)
Viral contaminant found in bovine sera.
Bowl
A removable casing that encloses filter elements. It mates with a filter Head.
Brevundimonas diminuta
Formerly known as Pseudomonas diminuta. A type of bacteria used to rate the
efficiency of sterilizing filters during validation testing. One of the smallest bacteria
(0.3 µm in diameter). Sterilizing filters must retain a challenge of this organism
under challenge conditions (107 cfu/cm2).
Buffer
A solution containing both a weak acid and its conjugate weak base whose pH
changes only a little despite addition of acid or alkali. A strong buffer often contains
multiple groups that can absorb a lot of ions before the pH changes significantly.
Cake
Solids deposited on the filter media.
Capillary Transfer
Capillary flow of transfer buffer draws the electrophoretically separated nucleic acids
from the gel to the membrane matrix. This is done by placing a wick below the gel in
the buffer solution and placing a stack of dry paper towels or blotting paper and a
transfer membrane on top of the gel.
Capsid
The external protein shell or coat of a virus particle.
Carboy
A vessel, usually glass or plastic and usually under 100 liters in volume, used in
laboratories for DI or distilled water and reagent solutions.
Cartridge or Filter Cartridge
A filtration or separation device (usually in the shape of a cylinder) that is designed
for easy installation and removal.
Catalyst
A compound that increases the rate of a reaction, although it does not itself undergo
any net chemical change. Enzymes are biological catalysts.
Cathode
Negative pole or electrode of an electrolytic system.
Cation
When a salt is dissolved, it has two charged molecules: a cation (positively charged)
that can behave as an acid, and an anion (negatively charged) that can act as a
base. If a surface has a negative charge it is called cationic and can be used to
capture positively-charged molecules.
Cell Culture
The growth of cells in a vessel such as a flask, spinner bottle, or bioreactor (in vitro).
It is used to study the effect of environmental factors on a population of cells and
also to produce large quantities of proteins expressed by the cells. Microfiltration is
used to sterilize the media and growth enhancers are added to media. If human,
animal, or plant cells are being grown, it is often called tissue culture.
Cell Fusion
The fusing together of two or more cells to become a single cell. This technique has
had important consequences in immunology, developmental biology, and genetics.
For example, monoclonal antibodies are produced by fusing a spleen cell with a
mouse myeloma cell to produce a hybridoma. The resultant form has an indefinite
life expectancy and secretes a specific antibody.
Cell Harvesting
The act of recovering cells that have been grown in tissue or cell culture. By
removing the cells from solution and washing them, the Centramate™ tangential
flow filtration system works well for large-scale cell harvesting. Small-scale cell
harvest may be done in the AcroWell™ 96-well filter plates or Nanosep® MF
centrifugal devices.
Cell Washing
The act of exchanging cell culture media or cell harvesting.
Center for Biologics Evaluation and Research (CBER)
The FDA successor to the Bureau of Biologics concerned with biologic drugs and,
most importantly, with the new protein and peptide drugs developing from
biotechnology.
Center for Drug Evaluation and Research (CDER)
The successor to the Bureau of Drugs of the FDA concerned with all small volume
parenterals (SVPs), and large volume parenterals (LVPs) and non-biological drugs.
Centipoise (cP)
(N*s/m2; N = Newton) A unit of absolute viscosity. One centipoise equals 0.01 poise.
Centistoke (cSt)
A unit of kinematic viscosity (10-6 m2/s). One centistoke equals 0.01 stoke.
Centrifugation
Process of separating two substances of differing densities by high speed spinning
to create centrifugal force. Typically used to separate suspended particles from
liquid such as the pelleting of cells or DNA. It is also used to provide the necessary
force to create trans-membrane pressure to drive solutions through an ultrafiltration
membrane in a centrifugal device.
Chelate
Complex formed between a metal ion and another molecule that has more than one
binding site. EDTA is a common chelating agent to remove Mg or other metal ions
from availability in solution. Patented chelating groups have been created that can
chelate Europium so that it can be attached to a molecule as a tag.
Chemiluminescence
Process by which an enzyme is able to catalyze a chemical reaction that results in
the production of light. This is commonly used by attaching an enzyme to an
antibody. This conjugate is then allowed to bind to a blotted protein mixture on a
membrane that has been blocked. The enzyme complex is used to detect the
specific protein to which the antibody has affinity. A subsequent step is needed to
add chemicals that react with the conjugated enzyme to produce light that can be
detected on X-ray film. It is also used to detect DNA hybridization by adding an
antibody step to the detection process. While this works well in most cases,
researchers prefer a direct label if possible.
Chromatography
Separation of substances in a mixture based on their affinity for certain solvents and
solid surfaces. It can also be used to separate labeled DNA from free nucleotides
with the Princeton clean-up kits.
Chromosome
A single, large DNA molecule containing many genes that functions to store and
transmit genetic information. It contains proteins that enable the DNA to fold into
very compact morphologically distinct structures. Bacterial chromosomes are small
circular molecules (about a few thousand base pairs) while the 26 human
chromosomes are about a billion base pairs in length.
Clarification
To clear a liquid by filtration, by the addition of agents to precipitate solids,
centrifugation, or by other means.
Class 100 Environment
A room environment maintained by air conditioning and filtration so that fewer than
100 particles of size 1 µm or larger are found in a cubic foot of air.
Clearing Solution
Solution used to render the membrane transparent. Used in analytical procedures
for airborne fibers and asbestos, and in membrane cytology procedures to allow
microscopic examination of samples collected on the "cleared" filter. Also used to
clear electrophoregrams on cellulose acetate for densitometry.
Cleavage
Act of cutting a molecule, usually referring to a specific cut or digestion that is
catalyzed by an enzyme.
Clinical Trials
Testing of new drugs in human subjects to prove safety and efficacy prior to the
drug’s approval for marketing.
Clone
A population of genetically identical cells derived from the multiplication of a single
cell. The basis of rDNA and monoclonal antibody production.
Cloning
Generation and selection of a genetically homogenous population (of cells or DNA
sequences) that expresses genes of interest from a single progenitor.
Cellular cloning: derivation of a cell line from a single cell.
Molecular cloning: propagation of a single gene or segment of DNA in a host cell
after molecular recombination in vitro using a suitable vector (plasmid or phage).
Organisms that contain genetically engineered molecules are referred to as
recombinants.
Coagulation
The destablization and initial aggregation of finely divided suspended solids by the
addition of a polyelectrolyte or a biological process.
Code of Federal Regulations (CFR)
The CFR is the codification of the general and permanent rules published in the
Federal Register by the executive departments and agencies of the Federal
Government of the USA
Coefficient of Variation (CV)
A measure of the variation that can occur between samples during a binding assay.
Variation can result from liquid transfer, non-specific binding, improper washing, and
anomalies with the plate. Studies indicate that the AcroWell™ plate has low CVs
making it useful for binding assays.
Cold Sterilization
Removal of all bacteria by filtration through a sterilizing grade 0.2 µm absolute filter.
Also the retention of Mycoplasma by a 0.1 µm filter.
Colony Forming Unit
An entity (usually a single living cell) which can form a colony on an agar plate or
membrane.
Colony Hybridization
Colonies of bacteria are transferred from an agar medium to a membrane. The cells
are lysed and the released DNA that binds to the membrane is hybridized to a
specific radioactive DNA probe. The autoradiogram serves as a map that can
identify the colonies of bacteria containing the desired DNA fragments. BioTrace™
NT, Biodyne® A, or Biodyne B membranes can be used for this application.
Colormetric
A detection system or assay that utilizes enzyme tags or other chemical reactions
that produce color to detect and quantitate molecules. A common colormetric
detection system utilizes alkaline phosphates to produce a blue color.
Column
In chromatography, it is a tube or cylinder containing the chromatographic bed or
stationary phase, usually in the form of beads. It can refer to size exclusion, affinity,
or HPLC analysis.
Combinatorial Biosynthesis
Act of creating a library for drug screening using bacteriophage display. Genes are
engineered into the phage particles coding for proteins that will be produced on the
surface of the phage. During screening successive rounds of binding allows the
phage containing the SAR (ligand shape) to be selected and the genes producing
the peptide (small protein subunit) to be subcloned.
Combinatorial Chemistry
A relatively new approach to drug discovery, it is the act of creating a library of
randomly generated molecules to be used in a screen in hopes of finding a
molecular configuration that will bind to a specific target (receptor). Once a lead
(ligand) is found it can be used to identify a configuration that could be used to
create new drugs. These small-molecule libraries can be tagged with a Europium
label. The AcroWell™ plate can be used to detect the bound ligands with a robotic
detector; any unbound labels can be washed away.
Compatibility
Term used in relation to the non-reactivity of filter materials with the substance to be
filtered. Chemical compatibility is used to describe the resistance of the materials of
construction to degradation by a solution that is filtered.
Concentrate
Sample not filtered by a membrane. See Retentate.
Concentration
Crossflow filtration in which the desired substance (product) remains on the
upstream side of the membrane (does not pass through). The opposite of
diafiltration.
Concentration Polarization
During ultrafiltration, molecules of dissolved substances (solutes) build up on the
surface of the filter membrane. The rate of polarization can be affected by
transmembrane pressure, concentration of the solute(s), and flow rate. See Gel
Layer.
Concentrator
An apparatus or method for reducing the amount of a sample to concentrate the
substances dissolved or suspended in it; usually used to concentrate solutions of
biological macromolecules, e.g., proteins and nucleic acids. Stirred cells, TFF
systems, and centrifugal devices are common concentrators containing ultrafiltration
membranes.
Conformation
The characteristic three-dimensional shape of macromolecules such as proteins,
DNA, carbohydrates, etc.
Contact Angle
Angle between a drop of liquid and a surface of a solid.
Contract Research Organization (CRO)
Organization that supplies development support to pharmaceutical companies
including: research, pharmacology, regulatory, and toxicology services. They
manage Phase I to Phase IV clinical trials and account for 20% of drug companies’
development business.
Counts Per Second (CPS)
Relates to the number of photons detected that are given off by the scintillant or as
a result of a fluorescence emission. Measured by a scintillation counter
(radioactivity) or multi-label counter (fluorescence).
Cross-contamination
The phenomenon of contamination of one substance by another during
manufacturing. Potential cause for rejection of product.
Crossflow
Flow of solution parallel to the upstream surface of the membrane (see also
Tangential Flow Filtration). This contrasts with direct flow seen in traditional filters, in
which the liquid flows perpendicular to the surface of the filter.
Crossflow (Tangential Flow) Filtration
A filtration system in which the feed stream flows across the filter media and exits as
a retentate stream. The retentate stream is recycled to merge into the feed stream,
while a portion of it passes through the filter media, resulting in concentration of the
feed stream (referred to as retentate or concentrate). Tangential flow is by far the
most effective way to perform ultrafiltration for samples greater than 150 mL.
Minimate™ and Ultrasette™ tangential flow devices can be used to purify and
desalt protein solutions for most lab applications. TFF systems can easily be scaled
up to larger scale process applications.
Crosstalk
Sample preparation often involves the side-by-side handling of numerous samples.
During sample handling and transfer, it is critical that the one sample not
contaminate an adjacent sample. Contamination can occur at several stages during
sample preparation; however, for sample handling using the AcroWell™ plate, the
greatest concern relates to crosstalk due to either lateral flow through the
membrane or sample mixing after the filtrate passes into the receiver plate. The
AcroWell plate’s sealing design minimizes the lateral flow crosstalk, and filtrate
crosstalk is minimized by centrifugal filtration.
Cryptosporidium
A protozoan parasite that can live in the intestines of humans and animals.
Current Good Manufacturing Practices (cGMP)
Current accepted standards of operation in a regulated industry. The FDA is
empowered to inspect drug manufacturing plants in which drugs are processed,
manufactured, packaged, and stored for compliance with these standards.
Cytokine Assay
An assay that measures the growth of cells in order to determine the level of growth
stimulatory molecules (cytokines) present in the media. Small-molecule growth
factors are detected from cells to see if a particular drug is capable of effecting the
initiation of cell growth. This assay can be done in a 96-well plate with a binding
membrane such as BioTrace™ NT or PVDF membrane. See ELISpot.
Cytology
The subdivision of biology that deals with the study of cells.
Cytolysis
The destruction of cells resulting from disintegration of their cell membrane.
Cytopathic
Damaging to cells.
Cytopathology
The study of diseases of the cells.
Cytoplasm
The inside of a cell excluding the nucleus. It consists of a continuous aqueous
solution (cytosol) with the organelles and inclusions suspended in it.
Cytotoxic
Substance that inhibits or stops growth of cells.
Cytotoxicity Test
A test designed to determine the biological reactivity of mammalian cell cultures
following contact with the plastic or membrane with specific extracts prepared from
the material under test. The procedure allows for extraction of the material at
physiological to non-physiological temperatures for varying intervals.
D Value
The time under a stated set of exposure conditions required to reduce a microbial
population by a factor of 90%, from 104 to 103.
D5W (5 D/W)
Five percent dextrose in water. One of the most prevalent of LVPs (Large Volume
Parenterals). Presence of dextrose presents significant filtration problems because
it usually requires activated charcoal pretreatment.
Dalton
Unit of measure for molecular mass. One Dalton is the mass of one Hydrogen atom.
Dead End (Conventional) Filtration
Feed stream flows in one direction only, perpendicular to and through the filter
medium to emerge as product of filtrate. Sometimes referred to as "single pass"
filtration. Syringe filters, disc membranes, capsules, and cartridges are used in this
process.
DEAE Cellulose
An ion exchange media (resin or membrane) that can be used for the purification of
DNA.
Deaeration (Degassing)
Process that removes dissolved air or gases from liquids.
Denaturation
The process of changing the tertiary and/or quaternary structure of a proteinous
macromolecule, thus causing inactivation or change in biological activity. Proteins
may be denatured by heat, pH, or addition of agents such as urea or guanidinium
hydrochloride.
Densitometry
The relative quantification by measurement of the optical density of transparent
materials (e.g., electrophoregrams with stained serum fractions) using the principles
of spectrophotometry (i.e., a way of making quantitative measurements using
absorption of light in various parts of the visible and ultraviolet spectrum).
Deoxyribonucleic Acid (DNA)
The genetic material of most living organisms. It consists of two chains joined
together as a double helix. Each chain is composed of a polymer of nucleotides
(consisting of a nitrogenous base, a deoxyribose sugar ring, and a phosphate
group) joined by phosphodiester bonds between the 5'-phosphate of one nucleotide
and the 3'-hydroxyl of the next. The two chains run in opposite directions and are
held together by hydrogen bonds between complementary bases in equivalent
positions in the two chains. There are various forms of double helical DNA.
Depth Filtration
Depth filtration is the process that traps contaminants both within the matrix and on
the surface of the filter media. Depth filters are composed of random mats of
metallic, polymeric, or inorganic materials. These filters rely on the density and
thickness of the mats to trap particles, and generally retain large quantities of
contaminants within the matrices. Media migration, which is the shifting of the filter
medium under stress, and particulate unloading are potential problems.
DI Water
De-ionized water; water processed through an ion exchange process by passing
through both cation and anion exchange resin beds, or a mixed resin bed to remove
both positive and negative ions. The purity of water is measured by its electric
resistance. High quality DI water has a minimum resistance of 18 megohm per cm
at 25 °C. Molecular biology grade water is free of magnesium.
Diafiltration
The process of removing salts or solvents by the addition of fresh solvents to wash
through or exchange the original buffer.
Dialysis
The phenomenon of a diffusible, dissolved substance moving across a selectively
permeable membrane. This movement is motivated by a concentration gradient.
Used for gradual buffer exchange but cannot concentrate the sample.
Diatomaceous Earth, Diatomite, Kieselguhr (DE)
Fine siliceous powder used as a filter aid.
Differential Pressure
Differential Pressure ( P) is the difference between the pressure in the system
before the fluid reaches the filter (upstream pressure) and the system pressure after
the fluid flows through the filter (downstream pressure) in a constant flow situation.
As the filter begins to clog, differential pressure increases.
Direct Flow Filtration
Filtration in which liquid flow is directly through the filter medium.
Distillation
The vaporization and subsequent condensation of a liquid. It is used to purify liquids
and to separate liquid mixtures.
Dot Blotting
Minute amounts of solution containing DNA, RNA, or protein are spotted onto
membrane sheets or placed in small wells that contain membrane. After fixation,
labeled probes are applied and developed. The spots or wells where a positive
reaction has occurred (e.g., DNA hybridization or immune specific reaction) can be
identified visually, radiometrically, etc. Unlike blots made from gels, dot blots allow a
greater quantification of the signal.
Downstream Side (of Filter)
The filtrate or product stream side of the filter.
Drug Candidate
Name given to a positive hit during a receptor/ligand library screen. These
candidates are then tested for toxicity and their ability to produce a desired drug
response.
Drug Master File (DMF)
A written document that explains the formulation of an active ingredient, and is
referenced in an Investigational New Drug (IND), New Drug Application (NDA), or
Amendment to New Drug Application (ANDA) from a company.
(chem.) Dimethyl formamide.
Dry Heat Sterilization
Sterilization at or above 180 °C using a convection or forced air oven without
moisture; may concurrently depyrogenate if adequate time and elevated
temperature are employed.
Dye Terminator
Used in DNA sequencing. It is a fluorescently labeled dideoxynucleotide, which is
added to a DNA synthesis reaction. When it randomly incorporates into a growing
DNA strand it terminates the synthesis at one of the 4 bases. This allows the
determination of the sequence of the DNA when the samples are electrophoresed
and detected.
Effective Filtration Area (EFA)
EFA is the filter area that is available for filtration. For a given membrane, the larger
the filter area, the higher the flow rate at a given initial differential pressure. Filter
media and devices are available in a wide range of sizes with different EFAs.
Effluent
The fluid that has passed through a filter. See Influent.
Electroblotting
Electrophoretic transfer of proteins or nucleic acid (DNA or RNA) fragments from a
gel to the matrix of a membrane. Most electroblotting is used for protein transfers
because capillary blotting works well for nucleic acids.
Electroelution
Electrophoretic transfer of proteins or nucleic acid (DNA or RNA) fragments from a
gel to the matrix of a membrane. Most electroblotting is used for protein transfers
because capillary blotting works well for nucleic acids.
Electrolyte
Substance that will conduct an electrical current either in molten state or in solution.
Example: NaCl in water solution.
Electrophoresis
A technique for separating molecules based on their differential mobility in an
electric field. Mobility is a function of both size and charge of the molecule. In the
presence of sodium dodecyl sulphate (SDS), however, the charge effect is
abolished and mobility is a simple logarithmic function of molecular weight. It is
usually carried out on a solid support such as polyacrylamide or agarose.
Electrophoretic Mobility
A measure of migration velocity produced by the effect of an electric field on
charged particles. Its magnitude is determined by the net charge of the particle, the
electric field strength, and the electrophoretic medium. In sieving media (agarose
and polyacrylamide gels), the mobility is affected by the size of the migrating
macromolecule.
ELISA (Competitive)
Used to define antigenic specificity. Sample antibodies and enzyme-labeled
antibodies compete for binding sites on an antigen-coated plate. Color change is
inversely proportional to the amount of specific sample antibodies.
ELISA (Enzyme-linked Immunosorbent Assay)
ELISA relies on the specific interaction of an antibody with its matching target
protein, referred to as an antigen, to analyze complex protein samples. It may be
used to detect either antibodies or antigens, and comes in many forms such as
indirect, sandwich, and competitive. ELISAs can take place in solution or at a solid
surface such as coated plastic or a membrane.
ELISA (Indirect)
Used to screen for antibodies. Sample antibodies bind to an antigen-coated plate.
Enzyme-labeled secondary antibodies then induce a color change directly
proportional to sample amount.
ELISA (Sandwich)
Used to quantitate antigen. Sample antigen is bound to an antibody-coated plate.
Enzyme-labeled secondary antibodies detect the amount of sample.
ELISpot
A membrane-bottom plate ELISA assay where the first biomolecule is bound to a
membrane instead of a styrene plate.
Elution
Capture and recovery of a solution containing a molecule that has been bound to
some sort of matrix. For example, when a molecule is bound to an affinity matrix
and washed to remove contaminants, it is then eluted from the matrix.
Emission
Release of light at a different color (wavelength) indicating the presence of a
specific fluorescent molecule (picoseconds after excitation). Time resolved
emissions are longer (microseconds) allowing the background emission from other
fluorescent molecules to decay prior to reading. This allows greater sensitivities.
Endotoxin
A complex molecule (lipopolysaccharide) that forms an integral part of gram
negative bacterial cell walls and is released when the integrity of the wall is
disturbed, i.e., cell division, growth, and death. Endotoxins may be released during
biosynthesis of a recombinant DNA product, thus necessitating purification steps to
ensure their removal.
Enzyme
Functionally specialized protein that acts as a catalyst in a chemical reaction, itself
remaining unchanged by the process. Each enzyme can catalyze only a single
reaction or a closely related set of reactions. They are usually present in very small
concentrations and can perform their “activity” for many cycles until the substrate
(what the enzyme acts upon) is depleted.
Enzyme Assay
An experiment in which enzymes are used to perform some sort of specific reaction.
Assays can include the determination of the rate of reaction (activity) as well as the
specificity for a particular molecule.
Escherichia coli (E. coli)
A bacterium commonly used in recombinant DNA technology. Because E. coli occur
naturally in the human intestine, safe strains have been produced that are incapable
of survival in humans.
Ethical Drug
A drug sold by prescription only.
Ethylene Oxide (EtO)
A toxic compound used in gaseous form as a sterilizing agent, usually as a 10%
mixture with carbon dioxide or 12% mixture with freon (referred to as 12-88).
Sterilization using EtO leaves residual chemicals such as ethylene chlorohydrin and
ethylene glycol. Residual EtO can be difficult to remove completely from a device,
so most filtration devices are now sterilized by gamma irradiation.
EU Dilutions
An assay used to show that the AcroWell™ plate filter containing the GHP
membrane has the lowest background fluorescence emission. As the Eu is diluted
to a point where it can no longer be detected, it shows a signal-to-noise ratio that is
as good as a plate that contains no membranes. PVDF and cellulose acetate
membranes have higher backgrounds resulting in much lower signal-to-noise ratios.
Eukaryotes
Family of cells having a membrane-surrounded nucleus, multiple chromosomes,
and internal organelles. Yeast, plants, animals, and humans are eukaryotes.
Europilated
Refers to the attachment of Europium (Eu) as a tag for the detection of timeresolved fluorescence. Most Eu assays include the attachment of an Eu chelate to a
ligand or antibody that is opened by a releasing agent after washing. This allows the
Eu to be detected in solution.
Europium (Eu)
A metal of the rare earth group that has a chemical property that allows it to be used
for time resolved fluorometry. It can only be used as a tag by attaching a Europium
chelate to a ligand or antibody. Typically Eu is detected in solution after release
from the chelate.
Excipient
An inert substance used as a diluent or vehicle for a drug.
Excitation
Laser light of a specific color (wavelength) that is absorbed by certain types of
molecules exciting them to a higher energy state. It is important that the stokes shift
be large enough that the excitation wavelength be far enough away from the
emission wavelength to prevent interference.
Exon
The segment of an eukaryotic gene that is transcribed into mRNA; it codes for a
specific domain of a protein. See Transcription/Transfection.
Exotoxins
Bacterial proteins that diffuse into the growing medium through the bacterial cell
membrane and cell wall. They are generally more potent and specific in their actions
than endotoxins.
Extractables
Substances present in the composition of the filter media or the filter manufacturing
process that may be leached into the fluid as it is filtered, thereby affecting its purity.
Extractables may include manufacturing debris, surfactants, and adhesives. The
type and amount of extractables will vary with the type of liquid being filtered.
Extractable components that can end up as contaminants may be minimized with
sufficient preflushing.
Facultative Anaerobe
An organism which does not require oxygen for growth, but may use it if available,
which grows well under both aerobic (presence of oxygen) and anaerobic (absence
of oxygen) conditions, and for which oxygen is not toxic.
FDA
U.S. Food and Drug Administration.
Feed
The unfiltered liquid. Often used in the phrase "feed stream," the flow of liquid into
the filtration system.
Fermentation
The process of growing microorganisms within an enclosed tank (fermentor) under
controlled conditions of aeration, agitation, temperature, pH, and carbon/nitrogen
sources.
Fetal Calf Serum
The liquid portion remaining after natural coagulation of blood drawn from the heart
of an unborn calf. Because of the absence of gamma globulin, fetal calf serum is a
good tissue culture serum.
Fiber
Any extraneous threadlike structure. If fibers are shed during filtration they can
cause sample contamination.
Filter (Noun)
An apparatus that performs filtration.
Filter (Verb)
To pass a fluid through a porous medium in order to remove solid particles.
Filter Element
A filter element is a single component that includes filter media and any supporting
materials and other hardware that must be installed or replaced as a single unit. A
common example is a filter cartridge.
Filtrate (Permeate)
Portion of the solution that has passed through the membrane. Synonymous with
Effluent.
Filtration
Process by which particles are removed from a fluid by passing the fluid through a
permeable material. See Crossflow (Tangential Flow) Filtration, Dead End
(Conventional) Filtration, Depth Filtration, Direct Flow Filtration, Nanofiltration,
Reverse Osmosis (RO), Sieve Filtration, Tangential Flow Filtration (TFF),
Ultrafiltration.
Flow Decay
Decrease in flow rate as a result of filter plugging or clogging.
Fluorescein
A very common fluorescent molecule that excites and emits in the blue-green color
range. The AcroWell™ filter plate has an extremely low background for fluorescein
allowing greater sensitivity for many fluorescent assays.
Fluorescence
Light emitted from a fluorophore (fluorescent molecule) as a result of excitation. The
excitation wavelength (color) is different than the emission wavelength. This
difference between these wavelengths is known as the stokes shift. The emitted
light is detected in a specialized detector like the Victor (PerkinElmer) multi-label
counter. Most fluorophores give a simple emission that is about 1 picosecond after
excitation while in time-resolved fluorescence the emission occurs after a
microsecond lag.
Fluorometric
Analytic procedure based on the ability of an analyte to emit light upon excitation.
Flux
The amount of solution that passes through a unit of membrane area in a given
amount of time. For example, a filter might have a flux of 1 liter per minute per
square centimeter. Flux decreases as the membrane fouls.
fmol
Femtomole (10-15 moles), a very small amount of a particular chemical. The
AcroWell filter plate is able to reliably detect Europium at concentrations down to 3
fmol (a few thousand molecules).
Form, Fill, Seal
See Blow (Form), Fill, Seal.
Forward Flow Test
A filter is wetted and a predetermined constant air pressure is applied. A
measurement of pure diffusional air flow through the wetted membrane is made. If
the diffusional air flow across the membrane is below the maximum allowable value
given, then the filter is integral. Forward flow is an objective and quantitative method
of determining integrity of sterilizing-grade filters.
Fouling
Contamination (plugging) of the membrane, decreasing flux. Often requires
chemical cleaning of the membrane. See Membrane Recovery and Gel Layer.
Fractionation
In densitometry, the division of peaks into fractions in order to quantitate the
electrophoretically separated bands. In chemistry, separation of a mixture of
components into different portions (fractions). Ultrafiltration can be used to
fractionate molecules in solution based on their relative sizes (molecular weight).
Gamma Globulins
The major class of serum proteins among the immunoglobulins.
Gas Chromatography (GC)
Similar to HPLC except that mobile phase is an inert gas such as helium.
Gas Liquid Chromatography (GLC)
Like HPLC except that the sample is ignited and passed through a special
chromatography column to a detector.
Gel Layer
Thin layer of retained particles or molecules that forms on a membrane surface
during filtration. See Concentration Polarization.
Gel Polarization
The phenomenon of formation of a layer of insoluble/semi-soluble material at a
liquid/filter interface. Common occurrence with excessive linear velocity flow through
filters of colloidal suspensions and macromolecular solutions.
Gene
A segment of DNA that contains genetic information, i.e., the base sequence of
chromosomal DNA (or RNA in some viruses), that specifies the amino acid
sequence of a single polypeptide chain or the nucleotide sequence of functional
RNA. The portion of DNA that codes for genes is a small fraction of the total
genome. When researchers try to clone genes they make libraries of the entire
genome and use probes to detect the gene sequence.
Gene Expression
The production of a protein from a gene. This is accomplished by the transfer of
genetic information from DNA to RNA (transcription) and then from RNA to
polypeptide (translation). The expression is the end result of all of these processes.
Researchers tend to focus on a variety of steps in the expression of genes using
DNA, RNA, and protein blots.
Gene Probe Testing
Use of tagged molecules (probes) and hybridization to a membrane to determine
the amount of RNA and protein produced during gene expression. It also refers to
the attempt to identify the sequence of a gene using specific sequence probes.
Gene Sequencing
The determination of the sequence of bases in a DNA strand. The two most widely
used methods are the chain-termination method, developed by Sanger and the
chemical method developed by Maxim and Gilbert.
Generic Drug
A drug product produced and marketed under its chemical or common name. This
can only be done after a proprietary drug goes off patent after 17 years. While
generic drugs are less expensive for consumers, they must still meet the stringent
standards of cGMPs as specified in the FDA CDER.
Genome
The full complement of chromosomes and extra-chromosomal DNA contained
within each cell of a given species.
Genomics
The study of the genes present in a genome. Recently, it refers to the study of the
expression of a collection of genes that are detected using membrane, glass slide,
or microchip arrays. Also called genomic profiling.
Genotype
The genetic make-up of an individual organism, including all genes whether
physically expressed or not.
Giardia Lamblia
A protozoan parasite responsible for giardiasis. Capture giardia with Envirochek®
capsules.
Glycoproteins
Proteins that contain covalently attached carbohydrates. They occur in extracellular
fluids (e.g., most of the plasma proteins), cartilage, epithelium, mucous excretions,
etc. Some hormones, enzymes, antibodies, and structural proteins found in cell
membranes are glycoproteins. Sometimes these proteins can be very difficult to
isolate and can cause problems during ultrafiltration.
Good Manufacturing Practices (GMPs)
Regulations promulgated by the Food and Drug Administration governing the
manufacture of drugs (Ref. Code of Federal Regulation 21 CFR 210 and 211),
medical devices (21 CFR 820), and Large Volume Parenterals (21 CFR 212
proposed). See cGMP (Current Good Manufacturing Practices).
Gram Stain
A technique for identification of bacteria. A differential test whereby organisms that
retain a crystal violet stain are considered gram positive and organisms that exhibit
only the safranin counterstain are gram negative.
Head
An end closure for the filter Bowl, which contains one or more connections through
which the fluid to be filtered passes. The component to which a filter cartridge is
sealed.
Health Industry Manufacturer's Association (HIMA)
Develops and implements products and solutions for safety related automation
tasks.
Heat Labile
Able to be destroyed by high temperature. Heat labile pharmaceuticals are sterilized
by filtration.
Heparin
A sulfur containing polysaccharide which stops blood from clotting by preventing the
conversion of prothrombin, and by neutralizing thrombin. It is contained in most cells
and is extractable from various tissues, notably the lungs.
Heterogeneous
A mixture. It can refer to a solution that contains a complex mixture of molecules. In
drug discovery, it refers to a library screening assay where the tagged ligand is
added to a cell-based assay, unbound label is washed away, and detection
reagents are added. This is the type of assay that the AcroWell™ plate is useful,
e.g., the DELFIA assay from PerkinElmer. It has greater sensitivity than the
homogeneous assay.
High Efficiency Particulate Air (HEPA) Filter
Any air filter device that is at least 99.97% efficient in retaining 0.3 µm particles as
measured by the Dioctyl Phthalate (DOP) test.
High Pressure Liquid Chromatography (HPLC)
Allows separation and analysis of very small quantities of complex mixtures with
high resolution and great sensitivity. Purpose is to identify the nature of a compound
or measure the amount or concentration of a compound. Filtration is often needed
prior to HPLC to prevent clogging the column or fouling the injectors.
High Throughput Screening (HTS)
The process of performing a binding assay for a collection of millions of different
compounds at one time. These assays can be heterogeneous or homogeneous; the
ultimate goal is to find drug candidates (leads) from this large collection of randomly
synthesized chemicals.
Hold-up Volume
Volume of fluid retained in a filter and/or housing after purging the assembly with air
or suitable gas. Hold-up volume is usually considered to be lost volume.
Homogeneous
In drug discovery, it refers to a high throughput screening assay where all of the
cells and detection components are added together and detected. This assay is
more capable of miniaturization and does not require a filtration step. It uses a dual
label system that is able to give a specific and measurable signal when the two
labels are held in proximity by specific molecular interaction.
Homogenize
To mix a solution so well that oils and water do not separate (homogenized milk). In
biology it can refer to mixing a sample until it is completely mixed and all
components are uniformly dispersed.
Housing
The device that encloses a filter element and directs the flow of fluid through it. See
Bowl.
Human Serum Albumin (HSA)
The main protein constituent of human serum. It has no prosthetic group and is
soluble in water and dilute salt solution. It is sometimes used in the treatment of
shock, hypoproteinanemia, and erythroblastosis fetalis.
Hybridization
If single-stranded fragments of DNA from different species are mixed,
complementary segments will combine by means of base-pairing to form hybrid
duplexes. This property of DNA (and also RNA) is used to identify genes of interest
by using a labeled single-stranded segment of DNA as a probe that is
complementary to the gene of interest. It is useful for probing blots on Biodyne® A,
Biodyne B, and BioTrace™ NT transfer membranes.
Hydrolysis
A chemical reaction between water and organic compounds particularly esters,
ketones, and alcohols. This reaction can lead to the breakdown of some plastics.
Hypochlorite
A weak, unstable salt of hypochlorous acid used in aqueous solutions as a bleach,
oxidizer, deodorant, and disinfectant.
Immunoassay
A sensitive analytical procedure using a highly specific antigen-antibody reaction
and principles such as fluorescence, radioactivity, or enzymatic activity to measure
biochemical substances that are either the antigen or the antibody in that reaction.
BioTrace PVDF and BioTrace NT membranes are often used for immunoassays
while other assays may be like an ELISA.
Immunodiagnostics
The use of antibodies to detect genetic markers linked to diseases. Recently
microarrays and protein arrays are being used to test the expression of a whole
collection of genes at the same time.
Immunogen
A substance that is capable of provoking an immune response.
Immunoglobulin (Ig)
A member of a class of proteins that functions as an antibody. The wide range of
different specificities of antibodies depends on subtle differences in their structure.
Immunoglobulin A (IgA)
IgA is the body’s first line of defense against infectious diseases. It is a protein
produced by specialized white blood cells and present in blood serum and other
body fluids.
Immunoproteins
All the proteins concerned with the immune system (antibodies, interferon, and
cytokines).
Incubation
Placing a sample in a controlled condition to allow growth or chemical/enzymatic
reaction to take place. In drug discovery assays, it is important that the filter plate
not weep during the incubations.
Inert
Chemical inactivity; unable to move; totally unreactive.
Influent
The fluid entering the filter system. (See Effluent.)
Infusion
The introduction of a solution, e.g., glucose, into a vein.
Inhibitor/Inhibition
The process of stopping a chemical/enzymatic reaction using a variety of chemical
and physical means. In drug discovery, inhibition of a binding assay is a method to
determine that the detected binding is specific to the target receptor. A known
receptor-binding analog is added at increasing concentrations; if it is able to reduce
the binding of the ligand, then it is competing for the binding of the same site.
Injector
System for introducing the sample or mobile phase into the column. May be either
manual or automated. It is a good idea to filter the analyte to prevent the injector
from clogging.
Inoculum
An aliquot of a pure culture of microorganism added to the primary seed tank to
initiate fermentation.
Inorganic
Being or composed of matter that is not of plant or animal origin; mineral-like.
Molecules that do not contain carbon bonds.
In Situ
Latin for "in place." Sterilization or integrity testing of a filter in the system rather
than as an ancillary operation such as in an autoclave or bubble point stand. It also
refers to the analysis of the expression of genes in tissue sections fixed to glass
slides.
Integrity Test
A test to ensure that a sterilizing-grade filter is intact and will function as intended.
Recommended integrity tests are the Forward Flow Test, Bubble Point test, and the
Pressure Hold test. Integrity tests on sterilizing grade filters are correlated with
bacterial challenge data.
Interferon (IFN)
A class of glycoproteins produced by the body in response to a viral infection. They
inhibit the multiplication of viruses in protected cells.
Investigational New Drug (Application) [IND(A)]
A document filed with the FDA prior to clinical trial of a new drug. It gives a full
description of the new drug, where and how it is manufactured, all QC information,
etc. The IND is followed by a NDA (New Drug Application).
In Vitro
Literally "in glass," an experiment performed without the involvement of a whole,
living organism. For example, testing a drug using a blood sample instead of an
entire animal.
In Vivo
Literally "in life," an experiment performed using a living organism.
Ion Chromatography/Ion Exchange Chromatography (IC/IEC)
Used for analysis of substances that are ionic or ionizable. The desired molecules
have been washed away. Often a concentration and desalting step by ultrafiltration
can be used to fully purify the captured molecule.
Ion Exchange Columns
Vessels filled with ion exchange resin (anion, cation, or mixed) for producing
conditioned solutions or DI Water. Also, type of column used for Ion Exchange
Chromatography (IEC) . After a sample is bound to the column, the salt molarity or
pH is changed to allow a molecule of interest to be eluted and recovered. Ion
exchange can also be achieved using membranes instead of columns. Often an
ultrafiltration step can be used on the eluted sample to desalt and concentrate.
Isotopic Assay
An assay in which the tag is radioactive. In drug discovery, radioactive iodine has
been used for years to detect the binding of ligands. Recently, these assays have
been replaced by fluorescent assays.
Isotopic (Symmetric) Membrane
Membrane in which the pore openings are the same diameter throughout the
thickness and on both sides of the membrane. Such membranes are nondirectional, i.e., their flow characteristics are independent of which side faces the
feed stream.
Kd (Dissociation Constant)
It is the concentration of a molecule (ligand) that is needed to saturate the binding of
half of the available binding sites on the receptors. This is an important value
because it is in the center of the region of linear response. Any changes to binding
can be reliably assayed if you start at the Kd concentration.
Kinase Assay
An assay that detects the activity of an enzyme that can add or remove phosphate
groups to other molecules. It has been demonstrated that kinase activity is
important for controlling gene expression, making them good targets for the
development of drug leads.
Label/Labeled
A label is a molecule that can be attached to another molecule. It has some property
such as radioactivity, fluorescence, or luminescence to allow it to be detected along
with the molecule to which it was attached. A molecule containing a label
attachment is called tagged or labeled.
Laminar Flow
Non-turbulent flow. In the pharmaceutical industry, this particularly refers to the air
flow in a clean air bench.
Large Volume Parenteral (LVP)
Intravenous injection packaged in containers of 100 to 1000 mL used to correct
electrolytic imbalances, replace body fluid, and provide general nutrition. Typically
infused to a patient over an extended period of time.
Lead
Molecule that binds to a target. It is used to describe a positive hit from a high
throughput screen of a combinatorial library.
Lead Discovery
The process of creating libraries and screening them in order to detect ligands that
are able to bind to a specific target receptor.
Lead Optimization
Further research to determine if a bound lead is able to stimulate a target. This
stimulation is usually in terms of changes in gene expression that are assayed using
gene expression microarrays. Additional tests include toxicity to ensure that the lead
is not toxic or does not have other undesirable side effects.
Library
(Drug discovery) Refers to a collection of Random Chemical Groups that are
targeted, split, and pooled for use as drug leads. These libraries are usually
addressed somehow so that once a lead is detected they can go back and see
exactly how that one-in-a-million combination was synthesized.
(Molecular biology) Refers to a collection of bacterial cells or phage, each
containing a unique recombinant DNA construct created from a digested
chromosome, cDNA (from RNA), and protein (called an expression library). These
cells or phages are transferred onto Biodyne A, Biodyne B, or BioTrace NT
membranes for permanent attachment and detection.
Ligand
A molecule or ion that can form a complex with another molecule, usually a
macromolecule. Also, an organic molecule capable of forming coordinate covalent
bonds with metallic ions. Can be natural or synthetic in origin.
Limulus Amoebocyte Lysate (LAL) Test
An LAL gel clot test prescribed by the United States Pharmacopeia (USP.) to detect
and determine the level of bacterial endotoxins in a substance. The reagent is made
from the circulating blood cells (amoebocytes) of limulus polyphemus, the
horseshoe crab.
Line Pressure
The pressure in the supply line. Also called inlet pressure, upstream pressure.
Lipids
Any numerous fats and fat-like materials that are insoluble in water but are soluble
in common organic solvents.
Lipopolysaccharide (LPD)
Predominant component of endotoxins produced by gram negative bacteria. The
causative agent of pyrogenic (temperature rise) reactions in parenteral products.
Lipoproteins
Lipid-protein complexes present in human serum. Their measurement is used as a
diagnostic tool.
Liposome
An artificial phospholipid vesicle. They can be useful for the enclosure of
macromolecules such as nucleic acids or, after loading with an appropriate drug,
they may be used therapeutically to achieve slow release of the drug into
circulation.
Live Stream
Sterilization by flowing saturated steam through a vented vessel or sterilization
system, usually at 125 °C and 20 psi (but can be performed up to 140 °C and 35
psi.)
Log Reduction
The logarithm to the base 10 of the ration or organisms in the feed to value (LRV)
organisms in the filtrate.
Also used as a ratio of in/out bioburden in other sterilization methods such as
autoclaving. In simple terms, a log reduction means a ten-fold reduction.
Luminescence
The emission and detection of light produced by chemical reactions or
bioluminescence due directly to the enzyme light production. These enzymes can
be used as labels to trace a molecule of interest. It does not require laser excitation
like fluorescence because it is a result of a chemical reaction. Luminescence
reactions can be carried out on membranes (blots), in a plate (such as the
Pallchek™ Luminometer), as well as in solution. If the reaction is being done in a
96-well form, the use of a white plate enhances the recovery of photons.
Lymphocyte
A type of white blood cell accounting for 20 to 25% of the white cells in humans.
They are mostly non-phagocytic and actively mobile. They are continuously made in
the bone marrow.
Lyophilization
Freeze drying. A drying process in which water is sublimed (evaporated under
vacuum) from the product after freezing. It is carried out in a lyophilizer. At the end
of the drying cycle, sterile filtered air or nitrogen is introduced to the chamber.
Lysis/Lyse
Destruction of a cell and release of its contents by disrupting the cell wall. This can
be achieved by various agents such as detergents or lytic enzymes. Following lysis,
a series of purification steps can occur that may require filtration (microfiltration to
remove cell debris and ultrafiltration to purify and desalt macromolecules).
Macromolecules
Complex molecules whose molecular weights are greater than about 5,000
molecular weight (also called Daltons).
Mass Spectrometry (MS)
A method for the analysis of the structure of molecules. The analyte is processed to
high purity with HPLC and gas chromatography before being passed through an
electron beam, and the molecular weight of the fragments is determined. It is
important that none of the steps add particulate or extractables.
Mean Flow Pore Measurement
The theoretical diameter of the mean pore. It is calculated as the diameter of the
pore of a wetted membrane partially voided of liquid such that air flow of the partially
wetted membrane is equal to 1/2 the dry air flow.
Media Migration
A process in which solid components of the filter (for example, fibers) break free and
are found in the Effluent. Compare to Extractables.
Medical Device
An instrument, apparatus, implant, etc., which achieves its principal purpose
through physical action, within or on the body and which is not dependent on being
metabolized for the achievement of its principal intended purpose. The primary
differentiation between a device and a drug are the words "chemical action" and
"metabolized."
Medium (Media)
The filter medium is the component of the filter system that actually permits the fluid
to pass while retaining contaminants. In a typical drip coffee maker, the medium is
the paper filter.
Note that "media" is the plural of "medium.”
Membrane Recovery
Restoration of the original flux of a membrane after Fouling.
Messenger RNA (mRNA)
The RNA molecule that conveys from the DNA the information that is to be
translated into the structure of a specific polypeptide molecule.
Metabolism
The sum of the biochemical processes involved in the maintenance of life.
Metabolite
Any of the various bio-organic compounds produced by metabolism.
Microarray
Refers to the spotting of biomolecules on a membrane or glass in a pattern that can
be addressed. (Larger arrays, such as standard dot blots, are sometimes referred to
as macroarrays.) These molecules are permanently attached, and tagged molecule
samples are allowed to bind or hybridize. Analysis of the strength of the signal from
the spots after washing allows researchers to quantitate the expression of a large
number of genes. Recently, arrays have been placed on slides and microchips. This
process is also called genomic profiling.
Microbe
Microorganism; microbial, adj. Typically referring to an organism that cannot be
seen by the naked eye.
Microfiltration
Microfiltration is the process of removing particles from a liquid or gas by passing it
through a porous medium. It generally involves removing particles between the
sizes of 10 and 0.02 microns in liquids, and down to 0.003 microns in gases. [See
Ultrafiltration, Nanofiltration, Reverse Osmosis (RO)].
Micron (Micrometer)
One one-millionth (0.000001) of one meter, or 0.00003937 inch. Bacteria are
typically less than one micron in length. The smallest object visible to the naked eye
is approximately 40 microns across. Human hairs are between 60 and 80 microns in
diameter.
Microorganisms
Microscopic organisms such as bacteria, protozoans, yeast, viruses, or algae.
Typically refers to single-celled organisms that can only be observed under the
microscope.
Microporous Membrane
A membrane is a thin, porous film that has flow paths or channels passing through
it. The size of these channels is related to the pore size rating of the membrane
(0.01 µm to 10 µm). Membranes can be used in the separation or filtration of
suspended matter from liquids and gases.
Mil
A unit of measure equal to one thousandth of an inch. 1 mil = 0.001 in. = 0.025 mm.
Commonly used to describe the thickness of a membrane or film.
Mixed Cellulose Esters (MCE)
Synthetic materials derived from naturally occurring cellulose. First materials used in
the manufacture of membrane filters. Mixed cellulose esters membranes are used in
a wide variety of applications, e.g., concentration of bacteria during water analysis
(GN-6 Metricel® membrane) and sampling of air quality (GN-4 Metricel membrane).
Mobile Phase
The flowing solvent of HPLC. May be a single solvent or a mixture of two or more
solvents.
Molarity (M)
A term used to indicate the concentration of dissolved substance in a given solution.
The measurement is in moles of dissolved substance per liter of solution. (A mole is
the weight of a substance in grams equal in number to its molecular weight.) Usually
a 1 molar solution is considered to be fairly concentrated.
Molecular Weight Cutoff (MWCO)
Nominal rating system for ultrafiltration and nanofiltration membranes. MWCO is
defined as the molecular weight of solute of which the membrane retains 90%.
Often defined by the molecular weight of dextran particles retained.
Molecule
The name given to any single chemical entity. It can refer to a single atom or a
larger collection of atoms that are covalently bonded. Molecular weights can range
from 1 Dalton to many millions of Daltons.
Monoclonal Antibody
Immunochemically identical antibodies produced by a clone of plasma cells.
Monoclonal antibodies are now being produced commercially using hybridomas.
They can be purified using TFF.
Mycoplasma
Microorganisms without cell walls (therefore, deformable), having a size between
bacteria and virus, and mostly parasitic. They can persist within cultured cells and
may disrupt normal cellular processes without necessarily causing cell death,
leading to experimental artifacts. There are about 125 currently recognized
Mycoplasma and Mycoplasma-like species. A 0.1 µm membrane is needed to retain
Mycoplasma.
Nanofiltration
Filtration that removes both particles and small dissolved molecules and ions. Finer
than Ultrafiltration, not as fine as Reverse Osmosis (RO).
National Formulary (NF)
A compendium of purity and testing criteria for chemicals and usually published in
combination with the USP.
New Drug Application (NDA)
The New Drug Application contains most of the information included in the IND.
Only after FDA approval of the NDA can distribution and marketing of a new drug
begin.
Nitrocellulose (NT)
Highly adsorptive membrane, typically used for DNA/RNA and protein hybridization,
also used for ELISA and RIA-based assays. This was one of the first membranes
made for molecular biology. It is still a favorite of many labs. Unsupported NT (such
as BioTrace™ NT membrane) generally gives superior performance in hybridization
assays compared to competitor supported materials.
Non-Fiber Releasing (NFR)
A filter that will not release fibers into the filtrate.
Nanomolar (nM)
10-9 or 0.000000001 molar, a very dilute sample or perhaps only a few thousand
molecules per mL of solution.
Northern Transfer (Blot)
Adaptation of the Southern procedure for transfer of electrophoretically separated
RNA fragments from gel to a binding matrix (membrane). Although still used, the
term Northern transfer is considered as slang. It should be referred to as RNA
blotting or transfer. Biodyne® A or Biodyne B membrane are the top choices for
RNA blot analysis.
Nuclease
An enzyme capable of degrading RNA or DNA. Can act in a general fashion or be
DNA sequence-specific (such as restriction nucleases used in cloning and to digest
DNA prior to electrophoresis and blotting). RNA is particularly sensitive to
degradation by nucleases.
Nucleic Acids
Biologically occurring poylnucleotides. Components of the utmost biological
importance, they comprise both DNA and RNA. Most living organisms have both;
some viruses have just one or the other.
Nucleotide
The recurring structural units of all nucleic acids; ribonucleotides constitute RNA,
the deoxyribonucleotides constitute DNA. Free nucleotides are the building blocks
of DNA that are used for synthesis of PCR products or probes. They can be
effectively removed by ultrafiltration.
Nucleus
The membrane-enclosed, spherical body that contains chromosomes in all
eukaryotic cells.
Nutraceuticals/Nutriceuticals
Fusion of food and pharmaceuticals. Genetically engineering foods with a palette of
antioxidants and anticancer compounds, as well as increasing vitamin and other
nutritional supplements. Also the manufacture of herbal supplements.
Nylon
Membrane that has high mechanical strength and compatibility with many different
kinds of chemicals. Biodyne® nylon membranes are commonly used for nucleic acid
analysis. Nylon membranes are hydrophilic.
Occupational Safety and Health Administration (OSHA)
Concerned with worker safety implementation and enforcement of safety practices.
Oleophobic
In addition to being hydrophobic, oleophobic membranes have the ability to repel
high viscosity fluids such as oil and lubricants, and low viscosity fluids such as
alcohols.
Operating Limits
Minimum and maximum parameters set for validation and processing pressures,
and temperatures.
Organic
Related to or derived from a living organism. Always contain carbon molecules.
Organic acids are acids that contain carbon molecules.
Original Equipment Manufacturers (OEM)
Refers to selling a product through a reseller with or without the manufacturer’s
name attached.
Osmosis
The net flow of solvent through a semi-permeable membrane from a region of high
solute concentration to a region of low solute concentration. The flow continues
across the membrane until the concentrations in both regions are the same.
Ozone Resistance
The ability of a material to resist the oxidizing power of ozone.
Parallel Filtration
Branching a filtration setup so that two assemblies of the same pore size are in
parallel, to increase flow rate or simplify filter changes.
Parenteral Drug (LVP, SVP)
A parenteral drug is defined as one infused (IV) or injected (IM or subcutaneous)
into the human body. A large volume parenteral (LVP) is a unit dose container of
greater than 100 mL which is terminally sterilized by heat. Small volume parenteral
(SVP) is a generic term used for all non-LVP parenterals except biologicals.
Particle
Any discrete unit of material structure; a discernible mass having an observable
length, width, thickness, size, and shape. By size, the particles range: subatomic or
fundamental (protons, neutrons, electrons, etc.); molecular (atoms and molecules,
from angstroms to 0.5 µm); colloidal; microscopic (can be resolved by optical
microscope, e.g., bacteria); macroscopic (can be resolved by the naked eye).
Particle Size Distribution (PSD)
Refers to the number fraction or weight fraction of particles (in a fluid) falling into
specified size ranges. For example:
Size Range # per Liter % by Number (PSD)
5 - 15 µm
1000
20
15 - 25 µm
3000
60
25 - 50 µm
1000
20
Particulate
Relating to or occurring in the form of fine particles.
Particulate Unloading
The process whereby a filter, particularly a depth filter, can become loaded with
particulate matter and subsequently release this matter downstream, e.g., because
of increased differential pressure and without damaging filter integrity.
Peptide
A protein is a polypeptide, and the term peptide is generally applied to small
proteins of 5 to 10 amino acids in length (only a few KDs). Ultrafiltration devices
(such as Nanosep centrifugal device) with 3K and 10K MWCOs are needed to
concentrate peptides.
Peristaltic Pump
A pump functioning by alternate pinching and releasing of tubing which drives the
fluid forward in a pulsing action. The major advantage is that the peristaltic pump is
non-invasive, i.e., the pump does not contact the fluid being filtered, and only the
inner wall of the tubing contacts the fluid. It is used for tangential flow filtration as
well as other pressure-driven filters.
Permeability
The degree to which a fluid will pass through a permeable substance under
specified conditions. The space or void volume between molecules allowing fluid
flow.
Permeate
Fluid that passes through a membrane. In ultrafiltration, this term is often used
interchangeably with filtrate. To pass through the pores or interstices of something.
pH
The pH value of an aqueous solution is a number describing its acidity or alkalinity.
A pH is the negative logarithm (base 10) of the concentration of hydrogen ions
(equivalents per liter). The pH value of a neutral solution is 7. An acidic solution has
a pH less than 7, while a basic solution has a pH greater than 7, up to 14.
Phage
See Bacteriophage.
Pharmacogenetics
A relatively new science that seeks to tailor therapeutic agents to an individual’s (or
group of individuals’) genetically determined responsiveness to a drug.
Pharmacokinetics
Term used in drug discovery to describe testing (during lead optimization) a drug
lead for its ability to produce some type of response. Drug leads found during
screening may be able to bind in a highly specific fashion but if they produce no
response in the body they are not very useful. Pharmacokinetic tests include the
analysis of drug absorption, distribution, cross-reaction, metabolism, and elimination
(urine).
Phosphorescence
The emission of light due to phosphorus contamination in a variety of product. It is
longer lived than fluorescence and can interfere with fluorescence detection by
increasing the background counts.
Picosecond
A psec is 0.000000000001 seconds or 10-12 seconds. A very short period of time.
This is the time it takes for an excited molecule to emit a fluorescent flash of light.
Plaque
A phage infected area in a lawn of bacteria. Since the phage infected bacteria lyse,
the plaque appears as a clear spot. The number of plaques on a plate is
proportional to the phage concentration in the suspension used to infect the
bacteria.
Plaque Lift
The transfer (imprint) of phage-infected areas or plaques on a bacterial culture to a
membrane. The membrane is then put through a hybridization procedure with
labeled DNA to identify and locate phages that contain recombinant DNA.
BioTrace™ NT, Biodyne® A, or Biodyne B membrane works well for this
application.
Plasma
The fluid portion of the blood in which the corpuscles (i.e., red and white blood cells
and platelets) are suspended.
Plasma Membrane
The physical barrier that surrounds the cytoplasm of all cells. It is composed of
lipids, proteins and carbohydrates and is semi-permeable.
Plasma Protein Fraction (PPF)
A blood plasma fraction. Identical to NHSA (neutral human serum albumin) but
contains no more than 15% w/w alpha and beta globulins. Dispensed as a 5%
solution.
Plasma Proteins
The proteins found in plasma, usually divided into albumin, globulin, and fibrinogen
fractions.
Plasmid
Extrachromosomal circular DNA molecule found in most bacteria. Plasmids can
pass from cell to cell and carry genes, which confer various properties on the host
cells, such as resistance to antibiotics. Recombinant plasmids containing DNA
segments of interest are used as vectors or cloning vehicles in genetic engineering.
They are very small (3000 base pairs) in comparison to whole chromosomes,
allowing them to act as effective gene shuttles.
Polyacrylamide Gel
Aqueous polymeric gel that is used as a stabilizing medium in electrophoresis. The
pore size (smaller than that of agarose) is controllable by the concentration of
acrylamide and the cross-linking agent. The pores can be restrictive to the migrating
macromolecules (sieving effect), which then separate according to size as well as
charge. It is used to separate DNA fragments smaller than 2 kb and proteins. Due to
the tight pore structure, transfer of molecules from a polyacrylamide gel is generally
achieved using electroblotting.
Polyacrylamide Gel Electrophoresis (PAGE)
See Polyacrylamide Gel.
Polyethersulfone (PES)
Polymeric material used in Supor® and Omega™ membranes. Provides superior
flow rates and is low in non-specific biomolecule adsorption.
Polymer
A long chain molecule formed of repeating structural units.
Polymerase Chain Reaction (PCR)
A DNA synthesis system that takes advantage of a number of unique properties of
DNA synthesis. Primers of a known sequence along with a DNA template, free
nucleotides, and buffers are added together. Repeated DNA melting and synthesis
allow the gene sequence between the primer sequences to be repeatedly
synthesized. After 30 cycles, billions of copies of that specific sequence are present
in the reaction tubes. At the completion of a PCR reaction, the researcher needs to
purify the PCR product away from the buffers, primers, and building blocks. This
can be done with a Nanosep® 100K centrifugal device.
Polynucleotide
A polymer of nucleotides. The nucleotide units are linked by phosphodiester bonds
spanning between the sugar moieties.
Polypeptide
A long chain of amino acids covalently bound by peptide bonds.
Polypropylene (PP)
A polymeric material that can be melted and that is resistant to a broad range of
chemicals. It is generally low in biomolecule binding, and is therefore a good choice
for devices used to purify and assay these molecules, such as Nanosep® MF
centrifugal devices and multi-well plates.
Polystyrene
A polymer commonly used in the production of 96-well plates as well as a number of
laboratory devices. It can be treated so that it will tend to bind to cells allowing the
culturing and washing of cells in plates that do not contain membranes. It is
generally high in biomolecule binding and is not a good choice for binding assays
because of the potential for high background.
Polysulfone (PS)
Commonly used membrane material that has good flow rates, high mechanical
strength, resistance to a broad range of temperatures (can be sterilized), and is
hydrophilic. Is not resistant to exposure to many organic solvents.
Polytetrafluoroethylene (PTFE)
Commonly known as Teflon®. PTFE membranes are highly durable and resistant to
a broad range of temperatures and chemicals. Hydrophobic. Used for the filtration of
air samples, aggressive solvents, and as the backing for AcroWell™ 96 filter plates.
Polyvinylidene Fluoride (PVDF)
PVDF membranes are naturally hydrophobic but can be modified to a hydrophilic
nature. Useful for a wide range of applications, both aqueous and non-aggressive
solvent-based. It is typically low protein binding and used frequently for sterilizing
filtration.
Precipitation
Process by which a molecule in a solution becomes insoluble and settles to the
bottom. Often a centrifugation step is used to speed up the settling of the
precipitated molecules. The addition of ethanol and salts can cause DNA in solution
to precipitate. This method has been used extensively in the past to concentrate
dilute DNA samples. However, it adds unwanted residual salts and ethanol to the
final DNA that is re-suspended. These contaminants can cause difficulty in
downstream handling and enzyme reactions. Ultrafiltration using Nanosep®
centrifugal devices is an excellent replacement for DNA precipitation.
Prehybridization
Blocking of unoccupied sites of a DNA blot by unlabeled DNA of another species.
This ensures that as many sites are occupied as possible to prevent non-specific
binding and high background levels. Salmon sperm DNA, fragmented by sonication,
is often used to prehybridize membranes. Recently many labs have done away with
prehybridization steps; whether these steps are required is dependent upon the
individual probe and hybridization conditions and must be determined empirically.
Preservative
A bacteriostatic or bacteriocidal agent added to some multiple dose parentals and
most cosmetics. Examples are benzalkonium chloride (BAC), formaldehyde, and
thimerosal (Merthiolate).
Primer
Commonly refers to a short (typically < 50 bases), single-stranded DNA molecule
that has been artificially synthesized. Except in very special cases, the researcher
requests and knows the sequence of the primer. The primer is hybridized to
complementary DNA sequences allowing DNA synthesis to proceed from the primer
sequences. They are used for PCR, probe synthesis, and a variety of molecular
biology applications.
Probes
Labeled substances that have specific affinity for the transferred proteins, DNA, or
RNA. They can be radioactive, chromogenic, fluorogenic, or enzyme conjugates of
antibodies. Lectins, protein A, and complementary DNAs or RNAs are among the
common probes used. See Tag and Label.
Prokaryotes
One-celled organisms (e.g., bacteria and blue-green algae) whose nuclear material
consists of a single chromosome in the form of a circular DNA molecule and is not
enclosed in a nuclear membrane. Prokaryotes usually have a rigid cell wall and lack
internal organelles. Eukaryotes like yeast and humans have a lot of internal
organelles.
Propylene Glycol
A common solvent for antibiotics, particularly the tetracyclines. Miscible (soluble) in
water, but often filtered as pure propylene glycol prior to combination with the
antibiotic. Its high viscosity controls absorption of the dissolved drug. See Vehicle.
Protein
Made up of amino acids linked together in long chains. The individual chains are
called polypeptides. At intervals along their lengths the individual polypeptide
subunits are linked together via hydrogen and other types of weak bonds to make
up protein. Proteins are synthesized in a process called translation and are
extremely variable in structure. They are often described in terms of their molecular
weight in kilodaltons (Kd).
Protein Blotting (Transfer)
See Western Transfer.
Pseudomonas Diminuta
See Brevundimonas Diminuta.
Purified Water, USP
A pharmaceutical water produced by distillation, reverse osmosis, or deionization.
Common uses are as a rinse for equipment, vials, and ampoules, and as a base for
cosmetics and oral drugs. It is not used as raw material for parental drugs.
Quality Assurance (QA)
A program to assure that manufactured products will perform as intended in actual
end use.
Quality Assurance Procedure (QAP)
A written document that explains how a Quality Assurance program or system is
operated or used as part of a compliance program.
Quality Control (QC)
A regulatory process through which products are continuously monitored against
specifications via various test measurements and sampling techniques.
Quality Control Procedure (QCP)
A written procedure that explains how to complete specific laboratory assays for raw
materials, intermediates, or final products.
Radiation Sterilization
Sterilization using gamma radiation emitted from radioactive materials such as
cobalt 60, or cesium 137. If proper dosage of nuclear radiation can be documented,
sterility testing is not required.
Radioimmunoassay (RIA)
A radioactively (typically 125I) tagged antibody is used to detect extremely low
quantities of binding to sample proteins. This can be performed in a multi-well
format using glass fiber to capture and wash the samples.
Receptor
Commonly used to describe a target molecule when assaying the binding properties
of a second molecule (ligand). In drug discovery, it typically refers to a target that is
going to be used to screen millions of small molecules to find one that binds to the
receptor.
Recombinant DNA (rDNA)
DNA formed by the joining of DNA strands into new combinations. DNA from the
genes of two organisms is enzymatically spliced (joined) to form one piece of DNA.
The ultimate goal of making recombinants is to make fusion proteins or engineer
genes to perform specific tasks.
Reconstitute
Bring a sample up to its original volume and concentration by adding water or
solvent. See Lyophilization.
Recovery
Ability of a filter to retain bacteria, DNA, or other biomolecules from a solution.
Percentage of a chemical or organism population that can be recovered after
processing.
Refractive Index
Deflection of light from a straight path as a function of change in velocity caused by
the difference in densities of two mediums as the light passes between them. It can
be used as a chemical detection system following HPLC.
Rehybridization
Removing the initial DNA probe from a DNA blot and exposing it to a different probe
to identify and locate another DNA sequence of interest. Biodyne® B membrane
can be used for repeated strip and reprobe cycles.
Rejection
Amount (%) of a molecule that does not pass through a membrane. See Retention.
Renaturation
The restoration of tertiary structure and biological activity to a denatured protein or
nucleic acid. The strands of a DNA duplex, for example, are denatured at high
temperatures but can be correctly reformed by slow cooling.
Replication
The complex process in which two daughter DNA molecules are created that are
identical to the parent molecule. In each daughter molecule, one strand of the
parent molecule is preserved.
Residual
A substance, usually a chemical contaminant, left over after a process or test
procedure.
Resolution
In chromatography, a separation of one band or peak from another. It can also be
used to describe the separation of one molecule from another based on molecular
weight when using ultrafiltration membranes.
Restriction Enzyme
An enzyme that splits a DNA molecule at a sequence of base pairs that is specific to
that enzyme. The use of different restriction enzymes will result in different sets of
fragments from the same DNA molecule. An extremely important tool in genetic
engineering.
Retentate
That which is retained on the upstream side of a membrane filter in a tangential or
cross-flow system such as ultrafiltration or reverse osmosis. Often designated as
concentrate.
Retention
Ability of a filter to retain particles (total number or those of a specific size)
suspended in a gas or liquid. In the case of ultrafiltration, refers to the ability to
concentrate molecules in solution. Expressed as percent of particles or molecules
originally present.
Retention Volume
See Hold-up Volume.
Retrovirus
Has genes composed of RNA instead of DNA and is capable of making DNA
complementary to RNA. HIV is a retrovirus. The viral enzyme that synthesizes DNA
from an RNA template is called reverse transcriptase and can be used to create
cDNA libraries from isolated RNA.
Reverse Osmosis (RO)
Forcing a liquid through a nonporous membrane, removing particles along with
dissolved molecules and ions. Reverse Osmosis is the finest form of membrane
separation and is used to desalinate water for drinking and prepare ultrapure water
for various industries.
Ribonucleic Acid (RNA)
The molecule into which the DNA code is transcribed for the production of proteins.
Several functionally different types of RNA exist: messenger (mRNA), transfer
(tRNA), and ribosomal (rRNA). RNA synthesis: see Transcription. The mRNA is the
most important species and is the one detected using RNA blot (Northern) analysis
since it is the RNA that corresponds to the genetic code for a protein.
RNA Blotting (Transfer)
See Northern Transfer.
Saccharomyces cerevisiae (Baker's Yeast)
A strain of yeast used in rDNA research. Strains are also used in fermentation of
wines and beers.
Sanitization, Sanitize
To make clean by removing dirt and other extraneous materials with soap and
general disinfectant so as to reduce the possibility of growth and spread of
pathogenic organisms. A common sanitization agent is 70% ethanol. Bleach is also
commonly used.
Scintillation Count
Describes the process by which radioactivity is detected. Because radioactivity
alone is difficult to measure, a radioactive sample is added to a cocktail containing a
chemical that gives off light after it has been exposed to radiation. The light
emission is proportional to the amount of radiation present in the sample. A device
called a Scintillation counter contains a very sensitive light detector and can
approximate the radiation present in a sample to a high degree of accuracy.
Scintillation Proximity Assay (SPA)
Used to detect ligand:receptor binding during a high throughput screening assay. It
is a radioactive detection system in which a chemical that can emit light when
exposed to radiation is brought into molecular proximity during binding. Multi-well
filter plates can be used during screening because small-molecule ligands are
added and unbound molecules need to be washed away. A white colored screening
plate is preferred in order to minimize optical crosstalk and amplify the signal
through reflection.
Sedimentation
The removal of suspended solids from water or wastewater by gravity in a quiescent
basin or clarifier.
Selective Medium
Nutrient medium that will allow only a certain organism(s) to grow. When bacteria
are being plated for later analysis by Colony Hybridization, this is usually done by
including an antibiotic to which only the desired organism is resistant.
Separation
Separation is the process of dividing a fluid stream (either liquid or gas) into
separate components. This can include purification (removing something
undesirable). This can include separation of two phases (liquid from gas),
separation of soluble impurities (known as purification), or separation of solids from
a fluid (filtration). The products of a separation can themselves be separated further
in many cases.
Serial Filtration
Filtration through two or more filters of decreasing pore size one after the other to
increase throughput, increase filtration efficiency, or protect the final filter.
Serratia marcescens
A bacterium, ATCC No. 14756, used for defining and validating 0.45 µm removal
rated filters.
Serum
The clear liquid that separates from blood when it is allowed to clot. Blood plasma
from which fibrogen has been separated in the process of clotting. Animal serum
(such as bovine) is often a component in cell culture media. Its high protein and
(sometimes) particulate content can make serum-containing media difficult to filter,
requiring a prefiltration step or PF device.
Serum Proteins
The serum portion of human blood contains a variety of protein components that
when measured can give us information as to the condition of the patient. Paper
electrophoresis using clinical devices is commonly used to separate these proteins
for evaluation. Standard serum protein electrophoresis separates serum into five
major zones or fractions: albumin, alpha-1, alpha-2, beta, and gamma.
Sieve
A filter with straight-through capillary pores with identical dimension, e.g., a screen
filter.
Sieve Filtration
Process that traps contaminants larger than the pore size of the membrane.
Contaminants that are smaller than the rated pore size may pass through the
membrane but may be captured within the membrane by some other mechanism.
Membrane filters are generally polymeric films approximately 120 µm thick with a
narrow pore size distribution.
Signal-to-Noise Ratio
The ratio of signal to background level. The higher its value the better the ability of
the researcher to find weak signals.
Silicon
A chemical element having four valence electrons and forming brittle gray crystals
when pure. It is most commonly found as silicon dioxide or silica, a component of
sand. It is normally an insulator. A small amount of impurity such as boron or
phosphorous transforms it into a semiconductor. Silicon has become a basic raw
material in the fabrication industry.
Silt Density Index (SDI)
A measure of the fouling tendency of water based on the timed flow of a liquid
through a membrane filter at a constant pressure.
Single-Copy Genes
Genes that occur only once in a set of chromosomes. Single copy genes are the
most difficult to detect on a DNA blot.
Small Molecules
Generally refers to molecules that are smaller than proteins. In drug discovery, they
are often used as the backbone for the attachment of random groups forming a
library of compounds that are subsequently used to detect the binding of the small
molecule construct to a target molecule.
Small Volume Parenteral (SVP)
Typically administered to a patient as a bolus or single syringe injection.
Soluble Antigen
Generally used in reference to vaccine production. As opposed to a whole, live or
attenuated (inactivated) virus, a soluble antigen is a fragment of the virus that
produces immunity. Also refers to large molecular weight polysaccharides from
some bacteria, which can act as vaccines. See Antigen.
Solute
A solid that is dissolved in a solution. For example, the salt in salt water is a solute.
Sodium Dodecyl Sulfate (SDS)
An anionic detergent that uniformly binds to proteins, helps dissociate them into
their subunits, and confers a constant charge-to-mass ratio by masking their native
charge with its own negative charge. Because the proteins all have the same
charge-to-mass ratio, a polyacrylamide gel containing SDS (SDS/PAGE) can be
used to separate proteins electrophoretically strictly by molecular weight.
Solid Phase Extraction (SPE)
SPE is a process by which molecules in solution are bound to a solid matrix (beads
or membranes) allowing the solution and other contaminating molecules to be
washed away. After binding, the molecule can be eluted off the solid matrix and
collected. It is a very effective way to purify molecules.
Southern Transfer (Blot)
A technique developed by E.M. Southern for the isolation and identification of
specific genes or DNA fragments by gel electrophoresis followed by transfer of the
resulting bands to a membrane filter. The filter is then hybridized to a labeled probe
allowing the detection of DNA segments of interest. It should be referred to as DNA
transfer or blotting. Biodyne® A, Biodyne B, and BioTrace™ NT membranes are
good membranes for DNA blots.
Specifications
A detailed, precise description or parameter for identification of limits.
Stability
Generally, stability refers to the physico-chemical condition of a parental, biological,
or shelf life of labile drugs (sensitive to inactivation of drug properties by physical
and chemical means). Certain drugs must pass USP or CFR stability tests. For
example, human serum albumin must pass certain limits of turbidity. Manufacturers
must have documentation of products potency under labeled storage conditions.
Standard (Normal) Pressure
A pressure of 1 atmosphere (1 bar, 14.70 psi, or 760 mm of mercury) to which
measurements of quantities dependent on pressure are often referred.
Standard Operating Procedure (SOP)
A written document that explains how to complete a specific production-oriented
task.
Sterile, Sterility, Sterilization
To make or be free of any viable microorganisms. Demonstrated by testing to show
the absence of growth of microorganisms. If a high bioburden level was present
prior to sterilization, pyrogens may still be present afterward.
Sterile Water for Injection, USP
Same as WFI, but sterile packaged. See Water for Injection (WFI).
Sterilizing Filter
A non-fiber-releasing filter that produces an effluent in which no microorganisms are
demonstrable when tested by the method specified in the current edition of the
United States Pharmacopoeia. Usually accepted as 0.2 µm absolute pore-size
rating.
Stokes Shift
The amount of difference between the excitation and emission color wavelengths
given off by a fluorophore. The greater the difference the less likely that the
excitation light will interfere with the detection of the emission color (wavelength).
Streptavidin
The binding partner to biotin. See Biotinylated.
Stringency
The conditions of hybridization that increase the specificity of binding between two
single-strand portions of nucleic acids, usually the probe and an immobilized
fragment. Increasing the temperature or decreasing the ionic strength results in
increased stringency. High stringency washes allow the reduction of false bands or
high backgrounds due to erroneous hybridization.
Structure-Activity Relationship (SAR)
Structure-Activity Relationship describes the analysis of how the shape of a
molecule interacts with a given receptor to produce a pharmacokinetic response.
Understanding the shape relationship is important in order to design new molecular
configurations to test.
Substrate
A substance on which an enzyme acts. See Enzyme. If you are "substrate limiting"
then the conversion of substrate to product is being done at maximum speed. If you
are "enzyme limiting" then your reaction speed will be a product of the concentration
of enzyme.
Surface Tension
Also interfacial tension. Tendency of the surface of a liquid to contract to the
smallest area possible under the existing circumstances. Defined as a force in
dynes acting on a line 1 cm long lying in the surface of the liquid.
Surfactant
A surfactant (surface-active agent, also called a "wetting agent") is a chemical that
improves the wettability of surfaces or particles with some liquid (by increasing the
surface energy). A filter may be coated with a surfactant to make the filter easier to
wet. In these cases, the surfactant may be washed off the filter and combine with
the filtered liquid as undesirable extractables. Note that it is not desirable to use
surfactants on filters for this reason.
Suspension
A specific category of pharmaceutical product which must be in a colloidal
dispersion (suspension) for proper action. For example, Kaolin/Pectin works as an
adsorbent because of its high surface area in suspension.
Synthesize
To take building blocks and add them together in order to build a new desired
molecule. Synthesis can take place via chemical reactions directly between the
building blocks (as is generally the case in combinatorial synthesis) or may be
catalyzed by an enzyme. If some of the building blocks are tagged, then the newly
synthesized molecule can be used as a probe.
Tag
Addition of a molecule (label) to another to allow it to be detected. Common tags
include radioactivity, fluorophores, and enzymes.
Tangential Flow Filtration (TFF)
Filtration in which liquid flows tangential to (along) the surface of the membrane
while pressure is applied that forces liquid through the membrane. The sweeping
action of TFF acts to minimize gel layer formation and fouling. (Contrast with Direct
Flow Filtration.) See Crossflow (Tangential Flow) Filtration.
Target
Receptor chosen based on the possibility that binding to this receptor may elicit a
desired pharmacological response.
Target Selection
The process by which it is determined which target (receptor) is a good candidate
for use when screening a library of receptor binding ligands. The choice of targets
often results from previous disease studies but currently more targets are selected
from knowledge gained sequencing and cloning disease genes.
T-Cell (T-lymphocyte)
A blood cell originating from bone marrow that matures in the thymus. Some T-cells
are responsible for cell-mandated immunity and the production of antibodies.
Terminal Sterilization
This term refers specifically to the terminal heat sterilization of LVPs, usually by
steam.
Thermophilic
Literally, "heat loving." Thermophilic organisms have an optimum temperature for
growth above 45 °C. Many thermophilic bacteria exist at high temperatures (greater
than 80 °C) and many of their enzymes, which possess high thermal stability, are of
great commercial interest.
Thickness
Thickness is typically measured with a gauge called a micrometer and usually
expressed as microns or mils. A micron is a unit of length equal to one millionth of a
meter and a mil is a unit of length equal to one thousandth of an inch or 0.0254
millimeter.
Thin Layer Chromatography (TLC)
TLC utilizes the principle of partition to separate substances on a stationary phase
(like a TLC plate) being passed over by a mobile phase (solvent). It is used to
quantitate the concentrations of slightly different molecular structures.
Throughput
The amount of solution that will pass through a filter prior to clogging.
Time Resolved Fluorescence (TRF)
Measurement of a fluorescent emission at a predetermined time after excitation,
eliminating interference from short lived emissions from organic fluorophores that
accompany the sample as they have decayed prior to detection. A sensitive and
reliable labeling and detection system has been designed and patented by
PerkinElmer. It uses lanthanide chelates that give an intense and long-lived
fluorescence emission (> 1000 microseconds), making it possible to measure
fluorescence emission significantly later than excitation. This time delayed
fluorescence in combination with a large stokes shift (340 to 615 nm) effectively
reduces background emissions to a level that allows measurement sensitivity to
rival and possibly exceed sensitivities achieved using expensive and dangerous
radioactive tags.
Tissue Culture
A very broad term used to define the technology of propagating living cells in culture
medium. See In vitro.
Titer
In immunochemistry, titer is the maximum dilution of an antibody that can still
produce an antigen/antibody reaction. Conversely it is the maximum dilution of
antigen required to produce an antigen/antibody reaction with a standardized
antibody. For example, to say that one has an anti-tetanus titer of 1:256 means that
the person’s serum, when diluted 1:256 in saline, will react in a test system with
tetanus toxin.
Titer Reduction
For filters that remove microbes from a fluid, efficiency is often stated as titer
reduction. Titer reduction is calculated by this equation:
Where TR is Titer Reduction and CFU is Colony Forming Unit. For compactness,
these ratings are often stated as powers of 10, or as logs. If a filter removes
999,999 out of 1,000,000 Brevundimonas diminuta, that filter has a titer
reduction of 106, or six logs.
Tolerance
Failure to mount an immune reaction on exposure to what would normally be an
antigenic substance.
Total Suspended Solids (TSS)
The measure of particulate matter suspended in a sample of water or wastewater.
After filtering a sample of a known volume, the filter is dried and weighed to
determine the residue retained.
Toxicity Standards
Test to indicate adverse reactions or lethality to drugs or drug components, also
used to assess biosafety of filters. Tests include appropriate combinations of direct
injection, extraction, and implantation. Generally known as USP biological Reactivity
Test, In Vivo <88>.
Transcription/Transfection
A part of the gene expression process in which mRNA molecules are synthesized
by using the base sequence of one strand of DNA as the complementary template.
Entry of free DNA into a bacterial or mammalian cell rather than by infection by a
virus. This requires a change in cell membrane permeability to allow entry of DNA
that then can recombine with the host cell DNA and be expressed. "Resin carryover"
from some DNA purification kits can cause problems during transfection. This resin
can be removed by processing the DNA with a Nanosep® MF centrifugal devices
prior to use.
Transfer
See Blotting.
Transformation
A mode of bacterial genetic exchange in which a DNA fragment of one bacterial cell
(donor) is transferred to another cell (recipient). The incoming DNA undergoes
recombination with the recipient chromosome.
Translation
The complex process in which the genetic information present in a messenger RNA
molecule directs the sequence of amino acids during protein syntheses.
Transmembrane Pressure (TMP)
The force that drives liquid flow through a crossflow membrane. The upstream side
(the side of the membrane the solution enters by) of a TFF system is under a higher
pressure than the downstream side. This pressure difference forces liquid through
the membrane.
Turbidity
Suspended matter in water or wastewater that scatters or otherwise interferes with
the passage of light through the water.
Ultracentrifugation
Separation of macromolecules on the basis of their density and shape in a high
speed centrifuge. It is used in molecular biology for the separation of RNA and DNA.
Ultrafiltration
A low-pressure membrane filtration process that separates solutes in the 20 to 1000
angstrom (up to 0.1 micron) size range. Compare to Microfiltration, Nanofiltration,
Reverse Osmosis (RO).
Ultraviolet Radiation (UV)
Light in the wavelength region 150 to 350 nm. It can be used to detect RNA or DNA
which has the fluorescent dye, ethidium bromide, bound to it. Also used as a
method of sanitization of air and water.
Unit Dose
Defines an SVP which must be administered in one dose. Unused contents must be
discarded. LVPs by definition are unit dose.
United States Pharmacopeia (USP)
A compendium of testing and purity criteria for pharmaceuticals, excipients,
vehicles, ancillaries, and raw materials. Recognized and accepted as the standard
reference guide by FDA and other regulatory bodies. See NF (National Formulary).
Unloading
The release of contaminants that had initially been captured by a filter.
Upstream Side (of filter)
The feed side of the filter.
UV Crosslinking
Crosslinking of transferred DNA to binding membranes by means of UV irradiation.
Covalent bonds are formed between the DNA and the membrane allowing the
permanent attachment of molecules to membranes.
UV Fluorescence
In densitometry, refers to the mode of evaluating samples that fluoresce when
exposed to ultraviolet light.
UV Spectrophotometry
Uses the ultraviolet absorption of a substance to quantitatively evaluate the
concentration of a substance (such as DNA or protein) in samples. This is often
used to detect molecules separated by HPLC analysis.
Vaccine
A preparation of microbial antigens that provokes an immune response (i.e., the
production of antibodies) on injection, thus conferring immunity on the recipient.
There are three types of vaccines.
1. Those containing material from a non-virulent organism which retains its
immunogenicity but does not result in infection.
2. Those containing a modified toxin (a toxoid) which has lost its toxic properties
but retains its immunogenicity.
3. Those containing live, attenuated organisms (i.e., genetic variants of a virus or
bacterium) which are antigenically similar to the original strain but lack
virulence.
Recombinant DNA research has allowed the production of new and more specific
vaccines. For example, the gene for the B antigen of hepatitis virus has been cloned
in E. coli, the protein expressed and a specific anti-B antiserum produced that can
be used as a vaccine.
Vacuum
Depression of pressure below atmospheric pressure. The maximum vacuum
possible is about 63.5 cm (25 in.) of Hg.
Validation
Demonstration that a process or product does what it is supposed to do, and does
so reproducibly, i.e., with safety, efficiency, accuracy, and precision, by challenging
the system and providing complete documentation.
Vector
DNA capable of self-replication in a host bacterial cell (e.g., a plasmid or temperate
phage DNA). Such DNA sequences are used as cloning vehicles to carry DNA
segments of interest into the host cell and facilitate their replication.
Vehicle
Any solvent or carrier fluid in a pharmaceutical product which has no
pharmacological role. For example, water is the vehicle for xylocaine and propylene
glycol is the vehicle for many antibiotics.
Venting
Separation of the liquid contents of a vessel (tank, fermentor, bioreactor) as well as
its vapors and gas from the ambient air. Prevents the passage of microorganisms
and liquid (water) but allows the passage of gases to equilibrate the vessel’s
pressure to the atmospheric pressure. Hydrophobic filters such as Acro® 50 vent
devices are used.
Viral Antigens
Specific proteins on the capsid of a virus that can act as inducers of antibody
formation.
Virion
A fully-formed, mature virus. Infection is initiated in a cell by a virion.
Virus
Simple life forms that require a host cell in order to reproduce. Consists of a small
number of genes (DNA or RNA) encased in a coat of protein. Viral genes enter a
host cell and are replicated by the host cell. The newly formed viral particles are
then released to infect other cells. In some cases, the viral DNA becomes an
integral part of the host cell chromosome. Viruses are commonly used as cloning
vectors.
Volatile
Evaporates easily; converts easily from liquid form into vapors.
Water-For-Injection, USP (WFI)
WFI is a pharmaceutical solvent used as a raw material or ancillary in
pharmaceutical production. WFI is water purified by distillation or reverse osmosis. It
contains no added substance. WFI meets the purity requirements for "purified
water": pH between 5 and 7, total dissolved solids (TDS) less than 10 ppm, passes
USP test for oxidizables. In addition, WFI must pass the USP endotoxin test.
Weeping
The dripping of solution from the well of a 96-well plate through the bottom holes in
the absence of centrifugation or vacuum filtration. This problem not only invalidates
the data, but is messy and not friendly to robotic systems. The AcroWell™ plate is
designed to minimize this problem.
Western Transfer (Blot)
Adaptation of the Southern transfer procedure for transfer of electrophoretically
separated proteins from gel to a binding matrix. Although still used, the term
Western transfer is considered as slang. It should be referred to as protein blotting
or transfer. Proteins on western blots are detected using antibodies on BioTrace™
NT and PVDF membranes.
Wetting Agent
A surfactant added to a membrane to assure complete intrusion (wetting) by a high
surface tension fluid such as water.
Worst Case
A set of conditions encompassing upper and lower processing limits and
circumstances, including those within standard operating procedures, that pose the
greatest chance of process or product failure when compared to ideal conditions.
Such conditions do not necessarily induce product or process failure.
Yeast
A single cell Eukaryotic microorganism. The biochemical reactions of colonies of
some yeast cells create fermentation, e.g., produce ethanol and carbon dioxide from
sugars. These cells are more complex and larger than bacterial cells.
Zeta Potential
The charge, positive or negative, existing on the surface of a particle or membrane.