Appendix
Conversion Tables and Formulas
II. Conversion Tables and Formulas
Metric Prefixes (International System)
Bigger
Smaller
Symbol
Prefix
Multiplication factor
Symbol
Prefix
Multiplication factor
T
tera
1012
m
milli
10–3
G
giga
109
µ
micro
10–6
M
mega
106
n
nano
10–9
k
kilo
103
p
pico
10–12
f
femto
10–15
a
atto
10–18
Moles, molar, molarity
Term
Symbol
Meaning
Example
Mole
mol
Absolute amount
of a substance
1 mol = 6.022 x 1023 molecules
Concentration
of a substance in
a liquid
1 mol/l = 6.022 x 1023 molecules/
liter = a one molar solution = a
solution with a molarity of one
Molar
or
Molarity
mol/l or M
Example of molar equivalence
Appendix
0.2 pmol in 100 µl means a concentration of 2 nM.
Example how to calculate: 0.2 pmol in 100 µl = 2 pmol in 1 ml = 2 nmol in 1l.
Physical conversions and formulas
Centrifugal force conversion (Dyson, 1991)
RCF = (1.11 x 10–5) (rpm)2 r
RCF = relative centrifugal force (x g; where g = 980 cm x sec–2)
rpm = rounds per minute
r = radius of rotor in mm
Contents
157
Appendix
Conversion Tables and Formulas
Nucleic Acid Data
Conversions
Spectral constants for nucleotides (Adapted from Sambrook, et al., 1989)
Compound
Molecular weight
(MW)
lmax (pH 7.0)
Absorbance
at lmax
(1 M solution)
ATP
507.2
259
15,400
dATP
491.2
259
15,400
CTP
483.2
271
9,000
dCTP
467.2
272
9,100
GTP
523.2
253
13,700
dGTP
507.2
253
13,700
UTP
484.2
260
10,000
dTTP
482.2
267
9,600
Note: Molar concentration of nucleic acid = (observed absorbance at lmax) ÷ absorbance at
lmax for 1 M solution.
Spectrophotometric equivalents
Appendix
1 A260 unit
*
Nucleic acid
Amount
Molarity
(in nucleotides)
double-stranded
DNA
50 µg /ml
0.15 mM
single-stranded
DNA
33 µg /ml
0.10 mM
single-stranded
RNA
40 µg /ml
0.11 mM
oligonucleotide*
20–30 µg/ml
0.06–0.09 mM
For exact determination of the molecular weight, see table “Conversions between weight and molarity of various DNAs” page 160.
Calculations
Determining purity of nucleic acid preparations
For pure DNA: A260/A280 ≥ 1.8
For pure RNA: A260/A280 ≥ 2.0
Note: An A260/A280 ratio of < 1.8 (DNA) or < 2.0 (RNA) means the nucleic acid preparation
contains contaminations (i.g. protein), or phenol.
158
Contents
Appendix
Conversion Tables and Formulas
Calculating molecular weight of nucleic acids (Adapted from Ausubel et al., 1988)
For molecular weight of
Use this calculation
DNA base pair (sodium salt)
1 base pair = 665 daltons
double-stranded DNA
molecule
(number of base pairs) x (665 daltons/base pair)
single-stranded DNA
molecule
(number of bases) x (325 daltons/base)
single-stranded RNA
molecule
(number of bases) x (340 daltons/base)
oligonucleotide
For dephosphorylated oligonucleotides: [(number of
A x 312.2) + (number of G x 328.2) + (number of
C x 288.2) + (number of T x 303.2)] – 61
For phosphorylated oligonucleotides: [(number of
A x 312.2) + (number of G x 328.2) + (number of
C x 288.2) + (number of T x 303.2)] + 17
Conversions between picomoles and micrograms of DNA
P For double-stranded DNA (dsDNA):
To convert
Calculate *
pmol to µg
660pg
1µg
- = µg
pmol × N × ---------------- × -------------1pmol 10 6 pg
µg to pmol
10 6 pg pmol
µg × --------------- × --------------- = pmol
1µg
660pg
* N = number of base pairs in DNA; 660, average molecular weight of a base pair.
To convert
Calculate *
pmol to µg
330pg
1µg
- = µg
pmol × N × --------------- × -------------pmol 10 6 pg
µg to pmol
10 6 pg pmol 1
µg × --------------- × --------------- × ---- = pmol
1µg
330pg N
Appendix
P For single-stranded DNA (ssDNA):
* N = number of nucleotides in DNA; 330, average molecular weight of a nucleotide
Contents
159
Appendix
Conversion Tables and Formulas
Calculating moles of ends
P Moles of ends for double-stranded DNA molecule:
2 x (grams of DNA) / (MW in daltons)
P Picomoles of ends per microgram of double-stranded DNA:
(2 x 106) / (660 x number of bases)
P Moles of ends generated by restriction endonuclease cleavage, circular DNA mole-
cule:
2 x (moles of DNA) x (number of sites)
P Moles of ends generated by restriction endonuclease cleavage, linear DNA mole-
cule:
[2 x (moles of DNA) x (number of sites)] + [2 x (moles of DNA)]
Conversions between weight and molarity of various DNAs
mg/pmol
Type
Size
pmol/mg
Molecules/mg
oligonucleotide
20 nucleotides
152
9.1 x 1013
0.0066
DNA
1000 bp
1.52
9.1 x 1011
0.66
pUC18/19 DNA
2686 bp
0.57
3.4 x 1011
1.77
pBR322 DNA
4361 bp
0.35
2.1 x 1011
2.88
M13mp18/19 DNA
7250 bp
0.21
1.3 x 1011
4.78
48502 bp
0.03
1.8 x 1010
32.01
l DNA
Protein data
Conversion between DNA and protein
1 kb of DNA = 333 amino acids of coding capacity = a protein of 3.7 x 104 daltons
Appendix
Conversion between protein molecular weight and absolute weight
100 pmol
160
MW of protein [kdaltons]
Amount in mg
100
10
50
5
10
1
Contents