Philadelphia Local Section
Younger Chemist Committee
Student Poster Session 2017
Abstract Book
Poster Number: 1
High School Student
Sophia Breslin and Kellena Smith
Dock Mennonite Academy
Reducing protein aggregation caused by metal ions in aqueous solution
Protein based medicines are used to treat many diseases like cancer, diabetes, and immune
system disorders. One challenge with these types of treatments is aggregation of the proteins in
the solutions to be administered. These protein aggregates can cause an immune response in the
patient being treated. Metal ions are known agents to cause protein aggregation in solution. The
goal of this project was to use metal salt solutions to discover which metals would be able to
aggregate the albumin protein or monoclonal antibodies. The hypothesis is that the metal ion
solutions will cause the protein to aggregate. The metals tested included Na, K, Ca, Mg, Ba, Cu,
Fe, Zn. Using dynamic light scattering, the particle size of the protein was measured. The
aggregation depended on the metal type and its concentration. At high concentrations Mg caused
aggregation of the protein. At low concentrations, the Iron and Copper salt solutions were able to
aggregate the protein. To “de-aggregate” the iron-protein and copper- protein aggregates, EDTA
or carbonates were added to reduce free Iron and Copper in solution. Results showed that metalprotein aggregation was reduced when the EDTA or carbonate were added to the protein
solutions. The hypothesis that metal ions aggregate proteins was confirmed. This research
demonstrates that EDTA and carbonate are effective at preventing protein aggregation in
monoclonal antibodies which will improve the effectiveness of these proteins that help cure
diseases.
Poster Number: 2
Undergraduate Student
Oleg Davydovich, Steven Geiger, Preston Moore, Alexander Sidorenko
University of the Sciences
Characterization and synthesis of CoOrdinated Responsive Arrays of Linked polymer islands
(CORALs)
CoOrdinated Responsive Arrays of Linked polymer islands (CORALs) are dense, patch-like
arrays tethered to a substrate that can respond to stimuli by changing conformations. The
synthesis of CORALs consists of the grafting of functional blocks of block-copolymer
supramolecular assemblies (SMA) to self-assembled anchors of the substrate. In this study, we
used block-copolymer of PS (major block) and poly(4-vinyl pyridine) (functional block)
assembled with 2-(4-hydroxyphenylazo) benzoic acid or homopolymer of PS. Depending on the
composition of the SMA and of the block copolymer, a broad range of MPB with different
parameters can be obtained. We observed drastic morphological variations of CORALs. Specific
conformations a achieved upon exposure to solvents of different nature. This facilitated
substantial contrast in surface properties upon switching reveals the responsive behavior of the
CORALs. Conformational switching of the CORALS was characterized using atomic force
microscopy, cyclic voltammetry, water contact angle measurements and null ellipsometry.
Coarse grain Molecular dynamics simulations were used to model experimental data and
determine the mechanism of switching.
Poster Number: 3
Undergraduate Student
Michael Donohue, Adetoun Adeniji-Adele, John Tomsho
University of the Sciences
Mutational analysis of amino acids within the lariatin A precursor peptide
Lariatin A, an 18 amino acid long lasso peptide produced from Rhodococcus jostii, has antimycobacterial activity in vitro. To further the understanding of the specific role that each amino
acid serves, the sequence dependence of this activity will be determined. In this report, we
discuss the results from mutating three amino acids in the loop, ring and tail region of the
peptide. Three valines in the loop (V5), ring (V10), and tail (V15) regions of the peptide were
mutated to alanine via site-directed mutagenesis. These precursor peptide mutants were then
placed into our lariatin A heterologous system for lariatin A production. The mutant peptides
were recovered by methanol extraction, resuspended in ddH2O, and assayed by disk diffusion.
We observed that these mutant lariatin A peptides exhibited efficacy against Mycobacterium
smegmatis indicating that these mutations had little effect on anti-microbial activity. It was also
observed that bioactivity was greater in extracts from “uninduced” cultures than IPTG induced
cultures.
Poster Number: 4
Undergraduate Student
Sara Dornblaser, Vincent Voelz, Bettina Buttaro
Temple University
Molecular simulations reveal the importance of disulfide bridging in PrgW, a putative redox
switch for plasmid replication
PrgW is a protein found in the antibiotic resistance pathogen Enterococcus faecalis, which is
responsible for various gastrointestinal infections. A primary function of PrgW is to initiate
replication of the plasmid pCF10, which encodes the bacteria’s virulence. This is induced by the
binding of the pheromone peptide pre-cCF10 to PrgW. Pre-cCF10 is in competition for binding
with truncated cCF10; however, a structurally homologous protein, iCF10, does not compete for
binding. Oxidative stress increases pCF10 copy number, through a hypothetical mechanism
involving the formation of disulfide bridges in PrgW that critically modulate its function, by
altering its activity and/or its binding affinity to pre-cCF10. Experiment has shown that when all
cysteines are replaced with alanine, lower pCF10 copy numbers result. To gain insight into
structural changes in PrgW that may occur with disulfide formation, computer models of PrgW
were constructed both with and without a disulfide bond between cysteine residues CYS275 and
CYS307. Large-scale molecular dynamic simulations were then performed on the
Folding@home distributed computing network, using the amber99sbnmr1-ildn force field and
the TIP3P explicit water model. Additionally, each prgW model was simulated with pre-cCF10,
cCF10, and iCF10 co-factors, initiated from different starting arrangements to avoid bias in the
results. The simulations provide information on (1) how disulfide bonds affect PrgW
conformation and stability, and (2) how oxidative stress may modulate the affinity of peptide
ligands to PrgW. These results will help generate specific hypotheses about structural
mechanisms that can be tested experimentally.
Poster Number: 5
Undergraduate Student
Joseph Duffield, James Gamrat, John Tomsho
University of the Sciences
The synthesis of a boron analogue of glyphosate
Over 1.6 billion kilograms of glyphosate, the herbicide known as Roundup®, have been used in
the United States since it was first developed in 1974. Although glyphosate itself is relatively
nontoxic, it has been linked with diseases such as cancer. We are synthesizing an analogue of
glyphosate where the phosphonate functional group has been replaced with boronic acid.
Boronic acid is being explored as a bio-isosteric replacement for the phosphonate group. Since
boric acid, the major decomposition product, is a key micro-nutrient in plants and has limited
human toxicity, it is hoped that such an analogue will retain the herbicidal activities of
glyphosate while being more environmentally friendly. We will discuss our initial synthetic
strategies and report on our synthetic progress.
Poster Number: 6
Undergraduate Student
Caroline McKeon, Samuel Epstein, Casey Londergan, Louise Charkoudian
Haverford College
Probing substrate sequestration in carrier proteins using vibrational spectroscopy labels
Carrier proteins are considered “lynchpin” enzymes of biosynthetic pathways. The E. coli acyl
carrier protein (ACP) is composed of multiple alpha helices that form a hydrophobic, solventprotected pocket that sometimes provides a cavernous hiding spot to protect substrates bound to
the ACP’s phosphopantetheine (Ppant) arm. The action of “chain sequestration” is thought to be
important for driving the biosynthetic process. In this study, selected amino acid residues inside
the ACP sequestration channel were targeted as possible incorporation sites for para-substituted
aromatic nitrile or alkyne vibrational spectroscopic probes. Using stop codon suppression, noncanonical amino acids were incorporated into the ACP via a co-transformed aminoacyl tRNA
synthetase. In addition, artificial substrates containing unique vibrational labeling groups like
nitriles were covalently ligated to the ACP’s Ppant arm. The vibrational frequencies of these
labeling groups, measured via IR absorption or Raman scattering, report on mainly the solvent
exposure of the CN group, and the lineshape reports the distribution of environments around the
label on either the protein or the growing substrate. IR and Raman results that report on the
sequestration of substrates of different length, as well as methodological advances that enable
this spectroscopic approach, will be discussed.
Poster Number: 7
Undergraduate Student
Bryan Figula, James Gamrat, John Tomsho
University of the Sciences
Analogues of fosmidomycin with modified chelating functionality as inhibitors of the nonmevalonate isoprenoid synthesis pathway
Many infectious diseases, including malaria and tuberculosis continue to ravage the world. These
pathogens utilize the non-mevalonate isoprenoid biosynthesis (MEP) pathway to synthesize
isopentyl pyrophosphate, a key building block for many vital processes. Fosmidomycin is the
most potent inhibitor to the MEP pathway known to date. The potency of fosmidomycin may be
improved by optimization of binding to a key magnesium ion present within the target enzyme,
1-deoxyxylulose-5-phosphate reductoisomerase (IspC). This project investigates the synthesis of
analogues of fosmidomycin with modifications to the metal chelating functionality and
subsequent evaluation as inhibitors of IspC. If this approach provides favorable results, other
structural modifications to fosmidomycin will be incorporated with the goal of significant
improvements to the pharmacological properties of fosmidomycin.
Poster Number: 8
Undergraduate Student
Janelle Gerardi and Tamanna Sultana
Villanova University
Detection of lipid accumulation in algae resulting from nitrogen deprivation
Our world today relies almost completely on fossil fuels, a resource which is depleting in supply,
contributing to global political conflicts, and negatively affecting our environment. For these
reasons, a renewable, environmentally friendly fuel source must be found. Of the various
renewable fuel sources that have been considered, biofuels generated from algal systems seems
to be the most promising to be integrated into our current energy infrastructure. The research
presented, will explore the effects that nitrogen deprivation, in the form of nitrates, will have on
the growth rate and lipid accumulation in the algae specie, Nannochloris eukaryotum. A suite of
analytical techniques including: fluorescence spectroscopy, transmission electron microscopy
(TEM), and gas chromatography coupled with mass spectrometry (GC/MS) will be used to
quantitatively and qualitatively explore the extent of these effects on the lipid storage mechanism
inside these cells. The fluorescent stains Nile Red and BODIPY 505/515 were explored for their
effectiveness to pass through the algae cell wall and bind to the internally stored acylglycerides.
These stains were also used to understand the nature of these stored algal lipids by investigating
how standards of polar (phosphoacylglycerides) and neutral (mono-, di-, and triacyclglycerides)
lipids can cause a shift in the lipid fluorescent peak. Due to a complex sample matrix, a
monoacylglyceride standard was used in a standard addition technique to quantify the amount of
lipids produced in this algal system as an effect of nitrogen deprivation. A significant increase in
lipid production was observed as nitrogen concentration was decreased in the growing medium.
To visualize this effect, TEM was used and a significant increase in lipid body formation can be
viewed in the cells that were grown in a nitrogen deprived environment. GC/MS measurements
revealed that the chemical makeup of these lipids includes four major fatty acids: stearic,
palmitic, oleic, and linoleic acid with the major contribution coming from saturated forms.
Understanding the fundamental chemistry behind increasing lipid storage in these algal systems
will aid in the utilization of this renewable resource for future generations.
Poster Number: 9
Undergraduate Student
Meghan Guagenti and Thomas P. Umile
Chestnut Hill College
Microbial chemical warfare: Interactions between Janthinobacterium lividum and the pathogenic
fungus Batrachochytrium dendrobatidis
Batrachochytrium dendrobatidis (Bd) is an aquatic fungal pathogen that causes the lethal
amphibian skin infection chytridiomycosis. In order to combat the fungus, bacteria found on the
frog skin, Janthinobacter lividum (J. liv), produces a metabolite, violacein, to fight those of the
fungus. To look into this relationship, the production of violacein was monitored via a
quantification of the violacein concentration using a high performance liquid chromatograph and
the counting of bacterial colonies.
Poster Number: 10
Undergraduate Student
Shannon Knight, Kurt Kolasinski, Bret Unger
West Chester University
Crystalographically defined silicon membranes
Laser ablated and anisotropically etched silicon wafers can create macropores that extend all the
way through the wafer. The walls of these pores can be either porous or smooth and exhibit
crystallographic properties depending on the orientation of the single-crystal silicon substrate.
The exact method for creating the pores is currently being studied. Once a membrane is created
the silicon wafer can be used further in electronics, optics and sensors.
Poster Number: 11
Undergraduate Student
Laura Lupin and Karen Wendling
Chestnut Hill College
An analysis of caffeine and theobromine in cocoa beans from unique sources in Africa
The purpose of this experiment was to analyze cocoa beans from unique sources in Africa and
determine their caffeine and theobromine content. Caffeine and theobromine are structurally
similar and have similar effects on the body. Both caffeine and theobromine are found in
chocolate and contribute to the feelings of euphoria and energy when consuming chocolate. A
previous researcher found that chocolate bars produced from cocoa beans in Madagascar had
higher caffeine content than chocolate bars utilizing beans from other countries in Africa. In
order to determine whether the caffeine and theobromine content may be affected by the
processing of the bean, testing the caffeine and theobromine content in the bean itself is
necessary. To determine the content of caffeine and theobromine within the bean, the bean had to
be ground using a coffee grinder and then pushed through a sieve. The bean grinds must then
undergo an extraction procedure to move the caffeine and theobromine into a liquid. As a way of
increasing the potential variation from bean to bean, beans from the top and bottom of each bag
of beans were tested. This required vortex mixing .05 g of the ground bean in a mixture of
85/5/5/5 water/MeOH/ACN/Acetic Acid for 15 min, centrifuging for 5 min, and filtering the
liquid using a PTFE syringe filter. Then 20 µL of this filtered sample was then injected into a
high performance liquid chromatography (HPLC) instrument. Each sample was run for 10 min
with the flow rate set at 0.50 mL/min and the UV-Vis detector was set at 273 nm. The
theobromine peak eluted at approximately 2.35 min and the caffeine peak eluted at
approximately 5.15 min. The results showed that Madagascar beans had statistically lower
theobromine content than all of the other bean types tested except for the Ghana bean.
Madagascar beans also had statistically higher caffeine content than all of the other beans tested
with the exception of the Uganda bean. This data confirmed that the caffeine and theobromine
content is related to the bean itself and may not be significantly affected by the processing of the
bean.
Poster Number: 12
Undergraduate Student
Megan Malvoisin and Karen Wendling
Chestnut Hill College
An analysis of nicotine and flavorings in E-juices used for vaping
This project focused on detecting nicotine concentrations in e-juices for electronic cigarettes (0
mg/mL, 9 mg/mL, 10 mg/mL, 12 mg/mL, 18mg/mL, 24mg/mL). The project also studied the
flavorings used in the different brands. Diphenhydramine was used as an injection standard for
the quantification of nicotine using Gas Chromatography-Mass Spectrometry (GC-MS), operated
in Selected Ion Monitoring (SIM) mode. The e-juices were diluted with methylene chloride
prior to injection. The results of analyzing four brands of e-juices in various concentrations
showed statistically significant variation in the concentration of nicotine for many of the e-juices
studied. Headspace analysis by GC-MS allowed for the identification of several flavoring
additives in the e-juices.
Poster Number: 13
Undergraduate Student
Aaron McLeod, Taryn Anthony, Katherine Willets
Temple University
Super-resolution imaging of fluorophores bound to silica coated gold nanorods
Gold nanorods are coated in silica shells of different thicknesses, which are functionalized with
fluorophores via a (3-Aminopropyl)triethoxysilane linker. We are studying the utility of these
samples for super-resolution imaging, in which the fluorescent dye molecules are excited using a
laser. As individual molecules relax back to their ground state from an excited triplet state, the
intensity and location of each dye molecule is recorded. This data is used to map out the structure
of the silica coated gold nanorod and understand coupling between the plasmon resonance of the
rod and the fluorescence.
Poster Number: 14
Undergraduate Student
Kevin Millan, Richard Remsing, Leah Magidson, Vincenzo Carnevale, Michael L. Klein, Eric
Borguet
Temple University
A molecular dynamics simulation study of adsorption of alkali chlorides to the water-alumina
interface
Mineral surfaces are emerging as earth-abundant and cost-effective alternatives to many
expensive catalysts. However, our understanding of fundamental processes governing chemistry
at such surfaces is still incomplete. In particular, a predictive model of electrolyte solutions near
mineral surfaces is highly desirable. In this work, we use classical molecular dynamics
simulations to characterize the adsorption of alkali halide ions at the water-alumina surface.
More precisely we focus on Lithium Chloride, Sodium Chloride, Potassium Chloride, Cesium
Chloride adsorptions. We find a dependence of the adsorption thermodynamics on ion size. By
examining the electrostatic properties of such interfaces, we additionally uncover an ion-size
dependent transition in how the interface is screened by the electrolyte solution, suggesting that
interfacial electrostatics can be tuned by varying ion size. We also discuss the dependence of our
results on the empirical force field parameters chosen to model the ions in solution.
Poster Number: 15
Undergraduate Student
Alexandra Nagelski, Douglas R. Gisewhite, Benjamin R. Williams, Sharon J. N. Burgmayer
Bryn Mawr College
Probing pterin reduction dynamics in synthetic molybdenum cofactor models
Molybdoenzymes catalyze oxygen atom transfer reactions and exist in nearly all organisms. In
their catalytic site, molybdoenzymes contain the molybdenum cofactor (Moco). Moco is not
stable outside of the protein matrix, therefore the use of small molecule analogues provides an
alternate way to study Moco. This research focuses on the molybdopterin (MPT), which
describes one or two conserved pyranopterin dithiolene ligands on Moco and its role in the
catalytic function of Moco. Although there is little known about the relationship between MPT
and the catalytic function of Moco, without MPT, Moco loses its catalytic efficiency. MPT is the
most redox active ligand in all of biology, which suggests that the oxidation state may play a role
in catalysis. The Burgmayer lab has created the model systems
[TEA][Tp*Mo(O)(S2C2(pterin)(C(CH3)2R)], where TEA is tetraethylammonium, Tp* is
tris(3,5-dimethylpyrazolyl)hydroborate, Mo exists in the Mo(IV) or Mo(V) oxidation state, and
R can be a hydroxyl (1) or methyl (2). In (1), the complex experiences reversible intramolecular
cyclization that is dependent upon the dielectric constant of the solvent, producing a pyran ring.
The related complex (2), where the hydroxyl group is isosterically replaced with a methyl group,
prevents this intramolecular cyclization, thereby creating a standard to compare the behavior of
(1). The tetrahydropyranopterin form of (1), which has already been synthesized in our lab,
closely resembles the Moco pyranopterin structure observed in molybdoenzymes crystal
structures. We have attempted to achieve the reduced dihydro form and the fully reduced
tetrahydro form of (2). From reducing the oxidized pterin in these model complexes, we can
learn more about the changes on the catalytic efficiency and the electronics that it may exhibit.
Poster Number: 16
Undergraduate Student
Jorna Sojati, Connor Ott, Nadia Galchak, Jennifer B. Palenchar
Villanova University
Engineering the reversal of Pseudomonas putida β-hydroxybutyrate dehydrogenase cofactor
specificity
Prior work has revealed that trypanosome β-hydroxybutyrate dehydrogenase (β-HBDH) can
utilize NADP(H), unlike nearly all other β-HBDHs characterized. Using the trypanosome
enzymes as a guide, we sought to alter the cofactor specificity of an NADH-dependent β-HBDH.
In the work presented, we describe amino acid changes in the Rossman fold region of an NADHdependent bacterial β-HBDH from Pseudomonas putida. The histidine-tagged recombinant
enzymes were overexpressed, purified from E. coli, and characterized kinetically. In the bacterial
β-HBDH, one amino acid change is sufficient to loosen specificity, while a combination of
mutations allows for cofactor preference reversal. The kinetic characterization of these mutant
enzymes will be presented. Long term, we seek to use this information to alter the cofactor
specificity of the parasite enzyme in vivo to better understand the role of this enzyme in the
trypanosomes.
Poster Number: 17
Undergraduate Student
Olivia Stepanic, Corey Herbst-Gervasoni, Ann M. Valentine
Temple University
Deferasirox as a titanium (IV) delivery system
Titanium is a bioactive material, and some Ti(IV) compounds have shown potential as anticancer
drugs. One of the issues with Ti(IV) concerns its transportation and uptake. Deferasirox, initially
developed as an orally active tight binder of Fe(III) for treatment of iron overload, was
investigated as a potential binder of Ti(IV) through spectrophotometric methods. Ti(IV) binds
deferasirox (DSX) in a 2:1 ratio with two species, Ti(DSX)HDSX- and TiDSX22-, in a pHdependent equilibrium The behavior of these complexes was explored, as was the potential
release of titanium from this compound to human serum transferrin and albumin.
Poster Number: 18
Undergraduate Student
Renee Kontos, Caroline Stow, Amanda Tallon, Linda Bui, Elise Burtschea
Saint Joesph's University
Synthesis of new precursors to pyramidalized alkene pentacyclonon-4-ene
We have previously reported that 4,5-diiodopentacyclo[4.3.0.02,4.03,8.05,7]nonane acts as a
precursor to the pyramidalized alkene pentacyclonon-4-ene via dehalogenation with
alkylithiums. Trapping pentacyclonon-4-ene with dienes affords the Diels-Alder adduct
accompanied by several alkylithium products. We will report our progress toward new
precursors to pentacyclonon-4-ene that do not use alkylithium for its synthesis.
Poster Number: 19
Undergraduate Student
Julia Tasca and Thomas P. Umile.
Gwynedd Mercy University
Chemical ecology of the amphibian microbiome: Janthinobacter lividum metabolizes a bioactive
compound produced by the fungal pathogen Batrachochytrium dendrobatidis
The fungal pathogen Batrachochytrium dendrobatidis (Bd) inhibits the amphibian immune
system using compounds such as methylthioadenosine (MTA). The bacterium Janthinobacter
lividum, which provides protection to amphibians by producing the antifungal compound
violacein, is shown here to metabolize MTA to a new compound tentatively identified as
methylthioinosine (MTI).
Poster Number: 20
Undergraduate Student
Thi M. Tran, Yaroslav V. Aulin, Ian G. McKendry, Dan Trainer, Maria Iavarone, Eric Borguet.
Temple University
Functionalization of MoS2 with organic molecules.
Two-dimensional (2D) materials are emerging materials with unique electronic properties.
Transitional metal dichalcogenides (TMDC) are 2D materials of the type MX2 (M = Mo, W and
X = S, Se, Te). TMDC materials are especially attractive for optoelectronic applications since
they are atomically thin semiconductors. Molybdenum disulfide (MoS2) monolayer is a direct
band gap semiconductor and bright emitter, while bilayer has indirect band gap and low
luminescence quantum yield. Despite of their unique properties, the main problem of 2D
materials is the lack of tunnability. We use organic molecules such as tetracyanoquinodimethane
(TCNQ) and phthalocyanines (Pc) to modify the properties of MoS2. We observe enhancement
of luminescence quantum yield upon modification by TCNQ and luminescence quenching upon
modification by Pc. We attribute these effects to charge transfer between MoS2 ¬and organic
molecule.To summarize, modification of MoS2 with organic molecules further enhances the
properties of the material.
Poster Number: 21
Undergraduate Student
Mary Lockwood, Kimberly Wodzanowski, Thomas Nagle, Jose Cerda
Saint Joseph's University
Thermodynamics of fluoride binding in heme proteins
The temperature dependence of fluoride binding was studied in hemoglobin (Hb), myoglobin
(Mb), and horseradish peroxidase (HRP) from 10 oC to 55 oC. Thermodynamic properties such
as the enthalpy change and entropy change for fluoride binding were determined for all three
proteins at pH 5 and pH 7. We found that the entropy change of fluoride binding can vary from 12.8 J/K (for Mb at pH 5 and below 45 oC) up to 434 J/K (for Hb at pH 7 and above 45 oC).
Concomitantly, enthalpy change for fluoride binding varied from -18.4 kJ/mol to 131 kJ/mol.
Our study shows a strong correlation between the entropy and enthalpy of fluoride binding, a
thermodynamic phenomenon that has been observed in the past for oxygen binding heme
proteins such as Mb and Hb and better known as the entropy-enthalpy compensation. Our results
show that the entropy-enthalpy compensation behavior of ligand binding is also present in HRP
which is not an oxygen binding protein. These results contribute to the idea that the entropyenthalpy compensation is a general behavior of proteins due to the solvation of the globin
structure upon ligand binding.
Poster Number: 22
Undergraduate Student
Kenneth Wong and Zhihong Wang
University of the Sciences
Illuminating the intricate activating mechanism of CRAD in vitro
Resistance to drug therapy in BRAF associated melanoma is a critical issue that can arise
through a plethora of secondary mutations and other pathways. One notorious mechanism of
resistance is transactivation of BRAF through CRAF by heterodimerization. Although the basal
activity of CRAF is extremely low, when dimerized with BRAF, the activity overcomes that of
BRAF alone. The rare variant CRAFR391W has been recently discovered to be a driver
oncogene with enhanced expression level and kinase activity. Similarly, to BRAFV600E,
CRAFR391W harbors the capacity to signal independent of upstream facilitation. These attribute
highlights the variant as a potential culprit in BRAF inhibitor resistance. Here, we verify the
oncogenic traits of CRAFR391W and investigate the biochemical basis for its hyperactivation of
the MAPK Pathway. By deciphering the activating mechanism of CRAFR391W, we can develop
insight into the regulations of CRAFWT to clarify the process of transactivation.
Poster Number: 23
Undergraduate Student
Thao Duong, Isabella Goodenough, Melissandre Richard, Piret Pikma, Stefan Piontek, Maryam
Hajfathaliam, Eric Borguet
Temple University
Ambient oxidation kinetics and size reduction of sapphire-immobilized hemispherical Ag
nanoparticles via dissolution in water
Noble metal nanoparticles (NPs) have demonstrated versatility as plasmonic materials for
applications in sensing, catalysis, and energy conversion. Of particular interest, silver NPs
(AgNPs) have recently been recognized for use as biomedical agents where their activity may be
governed by oxidative dissolution. Here, the catalytic and plasmonic activity of AgNPs
immobilized on sapphire substrates are monitored under ambient and aqueous environments.
Unlike other noble metal nanoparticles, AgNPs readily oxidize to form a water soluble Ag2O
layer in the presence of atmospheric oxygen. This instability has promoted research exploiting
various environmental and structural parameters capable of directly probing the transformations
of AgNPs. The growth and disappearance of the Ag2O layer are most likely accompanied by
changes in NP shape, size and distribution. Time-dependent UV-Vis spectroscopy monitors the
oxidation of AgNPs in air suggesting that this process follows Langmuir kinetics. Multiple
cycles of formation and removal of Ag2O encasing the AgNPs reveal a correlation between the
optical response and size reduction of the NPs evinced through spectral blue shifts in the LSPR.
AFM measurements are expected to track the dissolution in situ and the evolution of surface
morphology of NPs before and after removal of the oxide layer.
Poster Number: 24
Undergraduate Student
Nam Nguyen, Haley Varnum, Doug Gisewhite, Sharon Burgmayer
Bryn Mawr College
Synthetic pathway to molybdenum cofactor model complexes
Molybdenum-dependant enzymes are present in almost every living organism and play a central
role in mammalian sulfur catabolism, anaerobic respiration in bacteria, and nitrate assimilation in
plants. These enzymes utilize a molybdenum cofactor (Moco) composed of a molybdenum (Mo)
metal center and one or two highly conserved pyranopterin dithiolene ligands (MPT), completing
oxygen atom transfer reactions on a large variety of substrates. Due to the instability of Moco
outside of the protein matrix, there is still little known on the contributions of MPT on catalytic
function. It is, however, clear that without MPT, Moco loses its catalytic efficiency. In order to
investigate the role of the MPT ligand in molybdenum cofactors, the Burgmayer lab has
developed a family of synthetic models with the structure [TEA][Tp*Mo(X)pterin-C(CH3)2R-
dithiolene], where TEA is tetraethylammonium, Tp* is tris(3,5-dimethylpyrazolyl)hydroborate,
X is either oxygen or sulfur, and R is either hydroxyl or methyl. In the current study, we report
our investigations into pterin function in Moco catalysis through the synthesis of critical organic
precursors to multiple variations of model complexes. Characterization with FT-IR, H1 NMR,
and MS confirm our success in synthesizing these ligands and assess the quality of our products.
Poster Number: 25
Graduate Student or Post-doc
Adetoun Adeniji-Adele, Michael Donohue, Cassandra van Horn, John Tomsho
University of the Sciences
Biosynthesis of the anti-tuberculosis peptide lariatin A
Lasso peptides are ribosomally assembled and post-translationally processed natural products
with a unique threaded lariat structure. This architecture makes them highly stable and is
important for their activity as antibacterials, antivirals and antimycobacterials. The tuberculosis
(TB) bacterium are worryingly resistant to drugs that target translational or transcriptional
regulation. The lasso peptide Lariatin A has been chosen for study since it exhibits high
specificity and activity against TB and may act via a novel mechanism of action. Because lasso
peptides are inaccessible to organic chemical synthesis, we have successfully constructed a
heterologous expression system for lariatin A in E. coli. Utilizing this system, we have shown
that the wildtype and several alanine mutants have activity against Mycobacterium smegmatis.
We are working to create a more robust production system by RBS optimization of the vectors in
the system and differential induction of enzymes in the biosynthetic pathway. We believe that
this process will produce a regulable and robust system for lariatin A production. This increased
production will generate material that can be used to investigate the mechanism of action of
lariatin A against mycobacteria.
Poster Number: 26
Graduate Student or Post-doc
Jieutonne J. Archer, Santosh Karki, Fengjian Shi, Habiballah Sistani, Robert J. Levis
Temple University
Quantification of protein-ligand interactions by Laser Electrospray Mass Spectrometry (LEMS)
Laser electrospray mass spectrometry (LEMS) measurement of the dissociation constant (KD)
for hen egg white lysozyme (HEWL) and N,N’,N”-triacetylchitotriose (NAG3) revealed a KD
value of 284.8±30.6 µM for the ligand titration method. In a second approach, calibrated NAG3
measurement was used to determine a KD value of 6.7±1.4 µM. The neutral capture efficiency of
LEMS was measured to be 3.5±1.7%. When this percentage is factored into the ligand titration
measurement, the adjusted KD value was 10 µM.
Poster Number: 27
Graduate Student or Post-doc
Nuwann Attanayake, Akila Thenuwara, Yaroslav Aulin, Eric Borguet, Daniel Strongin
Temple University
Effect of the interlayer spacing and charge on the electrocatalytic activity of 1T-MoS2 for the
hydrogen evolution reaction
In this work we report the improvement in the catalytic activity of the hydrogen evolution
reaction (HER) on 1T-MoS2 by intercalating cations in the interlayer region of the 1T-MoS2
sheets. By the judicious use of cations (Na+, Ca2+, Ni2+ and Co2+) the interlayer distance and
the charge on these MoS2 nanosheets were varied.Its observed that there is an overall increase in
the activity (decreasing the overpotential) with all the cations intercalated. Moreover intercalting
strong electropositive Na+ shows the smallest interlayer distance between sheets and also lowest
overpotential for HER.Tafel slopes of the intercalated 1T-MoS2 remains unchanged which
proposes that the reaction mechanism has not changed due of intercalation.
Poster Number: 28
Graduate Student or Post-doc
Yaroslav V. Aulin, Thi M. Tran, Johanan H. Odhner, Nuwan H. Attanayake, Dan Trainer, Ian G.
McKendry, Akila C. Thenuwara, Robert J. Levis, Maria Iavarone, Xiaoxing Xi, Daniel R.
Strongin, Eric Borguet
Temple University
Optical characterization and ultrafast spectroscopy of MoS2 monolayers, bilayers, and ion
intercalated structures
Molybdenum disulfide (MoS2) monolayer is a two dimensional material with unique electronic
properties different from the bulk. Chemical modification, e.g., doping and ion intercalation, is
a powerful and convenient method to tune its properties. Chemically modified MoS2 was
characterized using a range of static optical techniques such as Raman spectroscopy, UV/Vis,
and fluorescence. For example, Raman spectroscopy helps to determine the number of layers in
layered structure and to track the transformation between the 2H (semiconductor) and 1T
(metallic) phases. 1T-MoS2 monolayer sheets can be produced by liquid exfoliation of bulk 2H
MoS2 in presence of n-butyllithium. The sheets were assembled into ion intercalated layered
structures. We show that ion intercalation maintains 1T phase. The intercalated samples can be
transformed to 2H phase upon annealing in argon atmosphere. Interlayer environment is
important for applications in electrocatalytic water splitting. The low frequency interlayer
breezing mode is sensitive to interlayer environment. Hence, doping and intercalation effects
should be detectable by coherent phonon spectroscopy. The dynamics of photoexcited species
determines the properties of the material relevant for applications in optoelectronics and
photocatalysis. We use ultrafast transient absorption spectroscopy with supercontinuum probe to
study the dynamics of excitons and trions in MoS2. We show the importance of multi-particle
effects such as trion formation and exciton-exciton annihilation.Taken together, these advanced
optical characterization tools help us understand how the properties of layered materials can be
manipulated.
Poster Number: 29
Graduate Student or Post-doc
Gloria Bazargan, Evan Curtin, Karl Sohlberg
Drexel University
Characterization of intramolecular proton transfer times in dicarbonyl compounds
Proton transfer is a key step in many acid-base, enzymatic, and tautomeric reactions. Due to the
ubiquity of proton transfer in chemical reactions, quantifying the timescale on which proton
transfer occurs is key to gaining a full understanding of chemical kinetics. This is particularly
true if proton transfer in a multi-step reaction is the rate-limiting step. For example, many simple
compounds including β-diketones, ɣ-diketones, and naphthazarins, interconvert between
tautomers through an intramolecular proton transfer between two oxygen atoms. In such cases,
proton transfer occurs over a short distance along a hydrogen bond, typically on a short timescale
(≈10-13 s). Consequently, theoretical methods for estimating the transit time of a proton between
two sites within a molecule may provide valuable insight into chemical reaction kinetics. Herein
we apply a probabilistic method for quantifying the transit times of quantum particles, to
intramolecular proton transfer in several dicarbonyl compounds. This method yields estimates of
proton transfer times on the sub-picosecond timescale, consistent with published experimental
and theoretical estimates.
Poster Number: 30
Graduate Student or Post-doc
Pratip Chakraborty and Spiridoula Matsika
Temple University
Excited state reaction path of ultrafast isomerization reactions
Isomerization has a big role to play in a lot of processes such as vision and naturally there has
been a lot of interest in controlling isomerization reactions using shaped ultrafast laser pulses. An
important isomerization reaction that has been studied extensively is the ultrafast photochemical
ring opening of 1,3-cyclohexadiene (CHD) to 1,3,5-cyclohexatriene (HT). Although many
studies have found a pathway for this reaction and have managed to assign the experimental
lifetimes properly, still there is a lot to explore. Here, we tried to calculate the pathway of the
reaction both maintaining the symmetry and without maintaining the symmetry. We have also
calculated the corresponding cation states and the Franck-Condon factors between the neutral
ground state and the cation ground state. We have also looked at the excited state decay of 1,3cyclooctadiene(COD) to itself and its isomers.
Poster Number: 31
Graduate Student or Post-doc
Srinivasa Rao Chintala and Joseph M. Fox
University of Delaware
Rhodium catalyzed enantioselective transformations of α-alkyl α-diazoesters with selectivity
over β-hydride migration
Rhodium(II)-catalyzed intermolecular cyclopropanation of diazoesters and alkenes has been
widely studied and applied to complex synthesis. however, reports of intramolecular
cyclopropanation had been quite limited. In particular, enantioselective bicylobutanes can be
constructed via intramolecular cyclopropanation of diazoesters by using Rhodium(II) catalysts
with sterically demanding carboxylate ligands. Herein we present the enantiomerically enriched
cyclobutanes are constructed by a three-component process in which t-butyl (E)-2-diazo-5arylpent-4-enoates are treated with Rh2(S-NTTL)4 to provide enantiomerically enriched
bicyclobutanes, which can subsequently engage in Cu-catalyzed homoconjugate addition/enolate
trapping sequence with desired electrophiles to give densely functionalized cyclobutanes with
high diastereoselectivity.The applications of the mixed-ligand dirhodium(II) catalysts were
investigated for enantioselective reactions of α–alkyl-α-diazoesters. Herein we present the
synthesis of the mixed ligand paddlewheel complexes of Rh2(S-PTTL)3L and Rh2(S-NTTL)3L
{L= Achiral ligand}, the structures of which bears similarity to the chiral crown complexes
Rh2(S-PTTL)4 and Rh2(S-NTTL)4 respectively. A mixed-ligand dirhodium(II) catalyst engages
substrate classes (aliphatic alkynes, silylacetylenes,a-olefins) that are especially challenging in
intermolecular reactions of α–alkyl-α-diazoesters, and catalyzes enantioselective
cyclopropanation, cyclopropenation and indole C–H functionalization with yields and
enantioselectivities that are comparable or superior to Rh2(S-PTTL)4 and Rh2(S-NTTL)4.
Mixing ligands on paddlewheel complexes offers a versatile handle for diversifying catalyst
structure and reactivity. The results described herein illustrate how mixed-ligand catalysts can
create new opportunities for the optimization of catalytic asymmetric processes.
Poster Number: 32
Graduate Student or Post-doc
Nicholas Cope, Christine Candelora, Kenneth Wong, Borna Novak, Yana Li, Philip Cole,
Zhihong Wang
University of the Sciences
Enzymological characterization of full-length BRAF mutations
My research focuses on the analysis of full-length (FL) BRAF mutations, which are found in 50
% of patients with melanoma and 7 % of all human cancers. Other labs are studying the catalytic
domain (CD) for the development of BRAF drugs. Two FDA approved drugs have inhibited the
most common mutation BRAFV600E; however, secondary tumors emerged in the majority of
these patients. I will use in vitro and cell-based assays to reveal how BRAF mutations behave in
the MAPK pathway, whilst revealing the key phosphorylation sites on BRAF. The full analysis
of BRAF mutations in vitro will help synthetic chemists develop superior drugs towards this
highly mutated enzyme.
Poster Number: 33
Graduate Student or Post-doc
David DiGuiseppi, Stefanie Farrell, Nicolas Alvarez, Reinhard Schweitzer-Stenner
Drexel University
Exploring the unexpected gelation of tripeptides in binary mixture of water and ethanol
Hydrogels formed by peptides of different length are a special class of materials that have been
heavily researched in the past due to their inherent biodegradability. In this context, some low
molecular weight di- or tripeptides with aromatic residues and terminal groups have been shown
to form gels after self-assembling into large supramolecular structures above critical
concentrations in the centimolar range. Contrary to expectations, our group recently discovered
that cationic glycylanalylglycine (GAG), a tripeptide of rather limited hydrophobicity, forms a
gel in 55 mol% ethanol/45 mol% water at room temperature if the concentration exceeds 200
mM. The underlying structure is comprised of unusually long crystalline fibrils (in the 10-5m
range), which do not exhibit the canonical β-sheet structure. Rheological measurements revealed
a particularly strong gel with G' and G" values in the upper 104 Pa range. Still, the gel melts if
the temperature is increased above 36°C. Melting curves measured by increasing and decreasing
temperature revealed a significant hysteresis. Kinetic experiments revealed that the gelation of
GAG is a multi-step mechanism that can be disentangled by spectroscopic means. By using UV
circular dichroism as a novel indicator of gelation we are currently performing measurements
that are aimed at constructing a three-dimensional phase diagram of the peptide with regard to its
melting temperature, peptide concentration and cosolvent fraction. Rheological measurements
and optical microscopy will allow us to identify and characterize different gel phases. Thus, we
will identify conditions which make the gel usable for practical applications such as ointments,
sensors, and drug release systems.
Poster Number: 34
Graduate Student or Post-doc
Janna Domenico, Michael E. Foster, Mark D. Allendorf, Karl Sohlberg
Drexel University
The effect of solvent and substrate on dye molecule orientation for DSSC applications
Dye-sensitized solar cells (DSSCs) can employ metal organic frameworks (MOFs), instead of
traditional dye molecules, to harvest light and impose order. In these MOF-sensitized solar cells
(MSSCs), MOFs are grown on a semiconducting substrate, and the structure of the
MOF/semiconductor interface is governed by the preferred orientation of MOF linkers on the
surface. Herein, we investigate the effect of substrate, solvent, and protonation state on the
orientation of dye molecules and MOF building blocks for MSSC construction. On dry
substrates, it was found that dispersion-binding can dominate over perpendicular binding for
adsorbates of a certain size, and most carboxylic-acid-containing molecules are predicted to lie
flat on the surface. Once solvation effects are considered, however, these dye molecules will
always orient themselves perpendicular to the surface of the semiconductor. To predict preferred
binding for an adsorbate/substrate/solvent interface, a two-part model was derived by fitting
results of DFT calculations and MD simulations, one part which predicts parallel binding energy
for each titania surface, and another part which quantifies solvation energy for each solvent
studied. The model results are consistent with the results of the calculations for 90% of the cases
studied here and can reasonably predict a binding preference based on the size and spread of the
adsorbing molecule and the surface/solvent environment.
Poster Number: 35
Graduate Student or Post-doc
Michael Dybek, Jason Wallach, Nadine Filemban, Tristan Colestock, Adeboye Adejare
University of the Sciences
Syntheses and evaluations of arylcycloalkylamines as NMDAR antagonists
Glutamate is the major excitatory neurotransmitter in the CNS. When activity of glutamate
becomes excessive, cellular damage can ensue, leading to apoptosis (programmed cell death) or
necrotic cell death due to oxidative stress. NMDAR (N-methyl-D-aspartate receptor, a type of
glutamate receptor) over-activity has been associated with pathological observations that stem
from excess glutamate concentration during states such as ischemic stroke, neuropathic pain,
epilepsy, and Alzheimer’s disease. A developing treatment strategy is to use NMDAR
antagonists to help alleviate excessive glutamate agonism. The purpose of this study is to
synthesize and evaluate the pharmacological properties of arylbicyclo[2.2.2]octylamines as well
as other arylcycloalkylamines as NMDAR probes. Our studies have demonstrated the advantage
of a simple one-pot method utilizing a modified Mannich reaction to successfully synthesize a
range of diverse arylcycloalkylamines in good yields. This has led to the synthesis of over 30
novel arylcycloalkylamines in a rapid efficient manner. Further investigation is being carried to
understand the scope of this method.
Poster Number: 36
Graduate Student or Post-doc
Katherine C. Elbert, Davit Jishkariani, Yaoting Wu, Jennifer D. Lee, Bertrand Donnio,
Christopher B. Murray
University of Pennsylvania
Self-assembly of novel dendritic ligands on nanocrystal surfaces
The study of coordination behavior of ligands on nanoparticle surfaces are of critical importance
to nanotechnology as it provides the key to understanding and engineering various properties
such as solubility, optical, magnetic, electronic, and catalytic. To this end, the most commonly
used ligands are limited to various commercially available alkyl containing molecules that have
either acid, amine, phosphonate, or thiol surface binding groups. To better understand how
ligands assemble and interact with one another on nanoparticle surfaces, we produced a series of
dendritic ligands. The synthesis was designed with a strategy that adds the surface binding group
last, giving us the flexibility to modify dendron end groups and surface anchoring functional
groups independently, reducing the number of synthetic steps. The dendritic ligands obtained
were introduced on nanoparticle surfaces through solution phase ligand exchange, and the
resulting dendron-nanoparticle hybrids were studied using various analytical techniques such as
TEM, NMR, IR, DSC, and X-ray scattering (WAXS and SAXS). The full synthetic strategy,
nanoparticle functionalization methods, and self-assembly details will be discussed with a focus
on how these ligands direct higher order assembly in these nanoscale materials.
Poster Number: 37
Graduate Student or Post-doc
Paul Freidhoff and Michael Bruist
University of the Sciences
In silico analysis of potential ligation motifs of viroids in the Pospiviroidae family
Viroids are pathogens that consist of 240 to 600 nucleotides of circular capsid-free RNA.
Viroids do not encode for any polypeptides so their replicative and maturation activity is
completely dependent on host enzymes. The Pospiviroidae family has twenty-eight classified
species, all of which replicate via asymmetric rolling circles in the nucleus. The asymmetric
rolling circle ultimately synthesizes an oligomeric strand containing at least two full sequences
of the viroid which are cleaved into multiple monomeric strands each containing the full
sequence of the viroid. These monomers mature when they ligated into circles. Interestingly,
evidence indicates DNA ligase, not RNA ligase, matures potato spindle tuber viroid (PSTVd).
To be recruited, ligase needs a binding-recognition element. A well-studied RNA motif (defined
strand fold), sarcin-ricin domain (SRD), is postulated as the recognition element of PSTVd. All
other Pospiviroidae viroid species show sequence conservation in the region of PSTVd’s SRD.
This suggests that every species in the family might form an SRD or SRD-like motif. However,
some viroids do not have a sequence that matches known SRD or SRD-like domains. It is
postulated that these viroids produce an unrecognized SRD-like motif. In this research the
possible positions of these motifs were predicted using computational tools that align sequences
and predict secondary structure. Possible novel SRD-like structures for these sequences were
predicted based on known non-canonical base-pairs found with the Web FR3D server. Twostranded structures were built on the three-dimensional visualization program Chimera. The
motifs were submitted to the molecular dynamics package AmberMD to observe their stability.
Key distances and communication propensities (distance variances) among bases indicate
whether the base stacking and pairing is stable during the simulation. Energies of these motifs
will be computed using MMPBSA on AmberMDSeveral potential SRD-like domains have been
generated. A few viroids still lack a convincing structure.
Poster Number: 38
Graduate Student or Post-doc
Daria Ruth Galimberti, Alberto Milani, Chiara Castiglioni, Marie-Pierre Gaigeot
Universite d'Evry val d'Essonne, Université Paris Saclay, France
Simplifying calculations of IR spectra from DFT-based molecular dynamics simulations
We present our recent work on the simplification of the calculation of IR and Raman spectra
from DFT-based molecular dynamics simulations (DFT-MD). In order to calculate these spectra
from DFT-MD, one has to Fourier transform the time-correlation function of the dipole moment
(IR) or polarisability tensor (Raman) of the investigated system. Calculating such dipole or
polarisability tensor has a computational cost, which is very expensive especially in complex
condensed matter systems such as liquids. It is especially crucial when one is interested in the
IR/Raman spectrum of solute(s) immersed in liquid (water for instance), as one does not want to
get the IR/Raman spectrum of the whole system, which would be the default route if one
calculates the dipole/polarisability tensor of the simulation box. On the contrary one wants to
evaluate the dipole/polarisability tensor of each single molecule of the system, and thus extract
the IR/Raman spectrum only of chosen molecules within the whole system (typically the
solute(s)). This requires apply a localization procedure of the wavefunction of the whole system
(the only entity known) onto each molecule of the liquid at each time step of the trajectory. This
can now routinely be done through e.g. a Wannier localization procedure. This is however
computationally costly to achieve at each time-step of the dynamics, and the cost can be
estimated as roughly doubling/tripling the computational cost of the trajectory. We have
developed a method to avoid such computational cost and instead rely on Fourier transforms of
time-correlation functions of velocities, weighted by well-chosen observables. Velocities being
natural variables from the dynamics, these Fourier transforms are computationally calculated for
free. Observables such as APT tensors for IR spectroscopy have been chosen for the necessary
weights/pre-factors. We will present our methodology, and will demonstrate how it works for
molecules (of increasing complexity and flexibility) in the gas phase, and how good the IR
spectra can be in comparison to the exact calculation. We will then show the extension of the
method to IR spectroscopy of complex systems, i.e. spectroscopy of solute(s) immersed in liquid
water.
Poster Number: 39
Graduate Student or Post-doc
Annastassia D. Gallo and Ann M. Valentine
Temple University
Rhodococcus ruber GIN-1 titanium incorporation via cell-oxide interactions
Titanium is very abundant in the environment and generally exists in the form of insoluble
mineral oxides.1,2 However, if a small fraction of this is solubilized, it can translate as a
significant amount of material. Biomolecules such as siderophores can bind and solubilize Ti(IV)
from the surface of mineral oxides.3 Not only biomolecules, but also whole organisms may have
similar interactions with mineral oxides. The non-pathogenic aerobic Gram-positive bacterium
Rhodococcus ruber GIN-1 (NCIMB 40340) was isolated from an environmental sample of
Mediterranean seawater near a coal power plant at Hadera, Israel by exploiting its ability to
strongly adhere to titanium dioxide (TiO2).4 The GIN-1 bacterium incorporates titanium ions
into its biomass after adhering to TiO2 surfaces. This phenomenon provides an opportunity to
investigate the cell-oxide interactions related to the potential biogeochemical cycling of titanium.
After exposure to TiO2, the adhesive bacteria are desorbed, washed, and acid-digested for metal
quantitation by inductively coupled plasma optical emission spectroscopy (ICP-OES). Ti
incorporation by GIN-1 was evaluated as a function of TiO2 crystal form. Significant Ti
accumulation into biomass was observed, with concomitant decreases in Fe and Zn.(1)KM
Buettner, AM Valentine. “Bioinorganic Chemistry of Titanium” Chem Rev 2012, 112, 18631881.(2)MR Van Baalen. “Titanium Mobility in Metamorphic Systems – a Review” Chem Geol
1993, 110, 233-249.(3)KE Jones, KL Batchler, C Zalouk, AM Valentine. “Ti(IV) and the
Siderophore Desferrioxamine B: A Tight Complex Has Biological and Environmental
Implications” Inorg Chem 2017, 56 (3), 1264-1272.(4)Y Shabtai, G Fleminger. “Adsorption of
Rhodococcus Strain GIN-1 (NCIMB 40340) on Titanium-Dioxide and Coal Fly-Ash Particles”
App. Environ. Microbiol. 1994, 60, 3079-3088.
Poster Number: 40
Graduate Student or Post-doc
James M. Gamrat and John W. Tomho
University of the Sciences in Philadelphia
Synthesis and evaluation of boron-containing analogues of inhibitors of the non-mevalonate
isoprenoid synthesis pathway
With the increase in resistance of pathogens to common anti-infective agents, there is an urgent
need to develop new classes of therapeutic molecules and discover drug with new mechanisms of
action to overcome this resistance. The non-mevalonate isoprenoid synthesis pathway (MEP
pathway) is essential to the survival of several pathogens including Plasmodium falciparum and
Mycobacterium tuberculosis. This pathway has emerged as an attractive therapeutic target for
drug design since it is not present in the human body. A phosphonate-containing natural
product, fosmidomycin, is the most potent inhibitor of the MEP pathway to date. The molecular
target of fosmidomycin is 1-deoxyxylulose-5-phosphate reductoisomerase (IspC), an enzyme
which catalyzes the first committed step in this biosynthetic pathway. Historically, the
phosphonate moiety has been used to mimic the phosphate fragment of the natural substrates.
The highly charged nature of this moiety hinders absorption and leads to poor pharmacokinetic
properties thus fosmidomycin has found limited utility as a therapeutic agent. In an effort to
overcome these issues, our work investigates the synthesis and evaluation of boron-containing
compounds that may act as neutral phosphate/phosphonate isosteres. Here, we report the
synthesis of a small library of aryl boronic acid and benzoxaborole analogs of fosmidomycin and
their evaluation as inhibitors of IspC. Current work involves completing the compound library,
assessing their inhibitory activity against IspC, and evaluating their anti-microbial activity via
Kirby-Bauer disc diffusion assays.
Poster Number: 41
Graduate Student or Post-doc
Michael Gau and Michael Zdilla
Temple University
Activated carbon disulfide-bridged diiron complex
The iron-molybdenum cofactor (FeMoco) is the primary cofactor in the molybdenum dependent
nitrogenase. The FeMoco cluster’s stoichiometry is Fe7MoS9C. The Fe and Mo metal centers
are bridged by sulfides with a core carbon atom. Researchers have been synthesizing structural
models of the FeMoco in order to more closely study the mechanism in which nitrogen fixation
proceeds in nature. A recent review by Holland, et. al.1 presents an in-depth look at various
structural models of the FeMoco that have been synthesized to date. Mentioned in the review are
models that include FeS clusters 2-4, Fe-carbide complexes5-9 and Fe-dinitrogen complexes 10-
12. A challenge that is highlighted is the synthesis of an FeS complex or cluster that includes an
interstitial carbide. Bontemps, Sabo-Etienne and co-workers have reported the synthesis of a
two-coordinate [K(18-crown-6] [FeI(N(SiMe3)2)2] complex and have shown its ability to reduce
I2.13 We proposed that with the highly reducing FeI compound that we may be able to
synthesize an FeS-carbide species via reduction of carbon disulfide (CS2). With further reaction
of the trimethylsilylamide ligands, self-assembly with other sulfur containing ligands and Fe
reactants might form an FeS-carbide cluster. Upon the addition of CS2, the solution immediately
changed color to a dark red and crystals were isolated from a layer diffusion. The synthesis,
characterization and reactivity of K2(18-Crown-6)3 Fe2(µ-CS2-1:2κ2S,S’,1:2κC)(N(SiMe3)2)4
are presented.
Poster Number: 42
Graduate Student or Post-doc
Yunhui Ge, Brandon Kier, Niels Andersen; Vincent Voelz
Temple University
Computational and experimental evaluation of designed beta-cap hairpins using molecular
simulations and kinetic network models
Developing accurate and efficient computational methods to design peptidomimetics is
challenging and nontrivial. Simulation-based techniques such as replica exchange molecular
dynamics (REMD) can efficiently overcome the barriers needed to predict peptide hairpin
conformational properties, but can be expensive. For this reason, we are interested in exploring
the ability of implicit-solvent (GBSA) simulations to accurately screen for favorable design
properties. As a test, we performed screening simulations for a series of b-hairpinpeptides
designed to mimic a conserved hairpin of LapD, a bacterial intracellular signaling protein. Such
designs are potential inhibitors of the LapD-LapG interaction involved in bacterial biofilm
formation. To screen for favorable folding properties in solution, we performed REMD with
GBSA implicit solvent for three different AMBER force fields (ff96, ff99sb-ildn and ff99sbildn-nmr), and compared our results to experimental measurements of melting temperature,
folded state population, and NMR chemical shifts. We find AMBER ff96 with OBC GBSA is
the most accurate, despite that fact that ff96 is too biased toward b-sheet when used in explicitsolvent simulations. The overall accuracy of our results suggest that implicit-solvent REMD can
be highly useful for the purpose of simulation-based peptide design, particularly as an initial
screening step preceding more expensive explicit-solvent simulations.
Poster Number: 43
Graduate Student or Post-doc
D.R. Gisewhite, A. L. Nagelski, D. Cummins, G. P. A. Yap, S.J. N. Burgmayer
Bryn Mawr College
Molybdenum pyranopterin dithiolene complexes: Synthetic models for pyran cyclization in the
molybdenum cofactor
The molybdenum cofactor, Moco, is found in all living organisms, excluding Saccharomyces
cerevisiae, and participates in global nitrogen, carbon, and sulfur cycles. There is a conserved
pterin dithiolene ligand which coordinates molybdenum (Mo) in the cofactor of mononuclear
enzymes. Crystal structures of several bacterial molybdoenzymes suggest the pterin dithiolene
ligand can exist in both a tricyclic and a bicyclic state. Interconversion of the two states has been
thought to play a critical role in the catalytic mechanism of Moco. Therefore, understanding the
pyran cyclization and scission, a type of ring-chain tautomerism, is an important aspect of study
to understand its role in catalysis. Here, we report the synthesis, characterization, crystal
structure, and reactivity to acid of two Moco model complexes with the formula
[TEA][Tp*Mo(O)quinoxaline-C(CH3)2R-dithiolene] where TEA is tetraethylammonium, Tp* is
tris(3,5-dimethylpyrazolyl)hydroborate, Mo is in either the Mo(IV) or Mo(V) oxidation state,
and R is either methyl or hydroxyl. 1H and 13C NMR, UV-Vis, and cyclic voltammetry
experiments indicate the hydroxyl group undergoes irreversible intramolecular cyclization
producing a pyran ring upon acid addition. Instability created by protonation of the quinoxaline’s
pyrazine ring encourages pyran degradation yielding pyrrole formation. Analysis of each stable
species will be discussed.
Poster Number: 44
Graduate Student or Post-doc
Yaoting Wu, Natalie Gogotsi, Benjamin Diroll, Matteo Cargnello Christopher B. Murray
University of Pennsylvania
Structural diversity and properties of quantum dot self-assemblies
Semiconductor nanocrystals are being extensively applied as building blocks for applications
ranging from solar cells to photodetectors to transistors. These materials can range from onedimensional quantum dots to two-dimensional rods or plates to three-dimensional superballs,
with their size and compositions providing unique and easily tunable physical, optical, and
electrical properties. The assemblies of these nanocrystals expands the achievable electronic and
optical landscapes with their long-range order and crystal structure.
Poster Number: 45
Graduate Student or Post-doc
Corey Herbst-Gervasoni and Ann M. Valentine
Temple University
Interactions of the siderophore Enterobactin with titanium(IV)
The siderophore that has the strongest known affinity toward Fe(III) is enterobactin (ent). Ent
has a dissociation constant with Fe(III) of 10-49.1 Enterobactin, apart from interactions with
Fe(III), has documented interactions with Ti(IV).2 Titanium (IV) has a smaller ionic radius than
iron (III) and is increasing in relevance in modern lifestyles.3,4 Due to the reduced radius of
titanium and the increase in oxidation state by one, Ti(IV) is a harder Lewis acid than Fe(III)
leading to a possible reduction in KD. Following the synthetic route of Baramov as a guide, the
synthesis of enterobactin will be carried out. Spectrophotometric titration of Ti(ent)2- from p[H]
2-11 is performed with no observed change in complexation to titanium. Competition titrations
between disodium tiron and Ti(ent)2- from 0-3000 equivalents of tiron were carried out and no
reduction in Ti(ent)2- was observed. Ti(tiron)38- was also titrated with 0-1.3 equivalents of ent
and a reduction of Ti(tiron)38- was observed. Data fitting with SPECFIT software leads to log
b = 51.8 in regards to the Ti(tiron)38- and ent competition titration. Discussion of measured
stability constant as well as further investigations will be discussed.1.L. D. Loomis, K. N.
Raymond. Inorg. Chem. 1991, 30, 906-911.2.T. Baramov, K. Keijzer, E. Irran, E. Mosker, M.-H.
Baik, R. Sussmuth. Chem. – Eur. J. 2013, 19 (32), 10536-10542.3.R. D. Shannon. Acta. Cryst.
1976, A32, 751-767. 4.K. M. Buettner, A. M. Valentine. Chem. Rev. 2011, 112, 1863-1881.
Poster Number: 46
Graduate Student or Post-doc
Jason M. Imamoto and Michael F. Bruist
University of the Sciences
A molecular dynamics investigation of the stability of Sarcin/Ricin domains: Towards using
adaptively biased MD to find the full dynamic range of RNA
Over the past decade our understanding of RNA’s biological role has greatly expanded. As much
as 80% of the DNA in the human genome is transcribed, but only 2% of this is translated. The
conservation of numerous nontranslated sequences across mammals, and even distantly related
eukaryotes, indicates that these structures have specific functions. Understanding these RNAs
will require efficient deciphering of their two- and three-dimensional structures as well as the
dynamics of these structures, a daunting task. Luckily, RNA tertiary structure is guided by
motifs. These are specific structures that occur frequently in RNA, often with the same or
related functions. Therefore, understanding the dynamics of various RNA motifs will be pivotal
to decoding the vast number of complex RNAs.Our work focuses on the sarcin/ricin domain
(SRD), an RNA motif that ranges from multiple occurrences in the ribosome, where it has
structural and protein binding roles, to a replication control region in the potato spindle tuber
viroid (PSTVd), where it may direct RNA ligation. The SRD is stable under normal MD and
consists of non-canonical base pairs, one above and two below, that surround a base triplet. We
use adaptively biased molecular dynamics (ABMD) to build a negative of the free energy surface
(FES) based on two collective variables (CVs) that each measures a structural feature. ABMD
increases the sampling speed of the surface by using multiple walkers that start at different
places on the FES and a repulsive bias to prevent a walker from returning to the same CV value
allowing us to observe structures that rarely occur in standard MD.Three models of the SRD
were made: one model contains only the SRD, while the other two contain GC and AU rich
regions in the format of GC/SRD/AU or AU/SRD/GC. Numerous sequence variations of the
simple SRD model are being studied. We are looking for changes that range from subtle
alterations in the quality of base stacking to structural rearrangements in the modeled motifs. We
have found that the SRD region is as stable as an AU-rich region, and the SRD tends to denature
from the bottom of the domain.
Poster Number: 47
Graduate Student or Post-doc
Jamal Jenkins, Nicholas Grant, Bryan Eigenrbodt
Villanova University
Effects of different synthesis processes on the material properties of Sr2Fe1.5Mo0.5O6
With the current deteriorating state of our environment and an increasing demand on a limited
supply of fossil fuels, finding technologies that utilize renewable resources efficiently while
producing minimal pollution is of great importance. Of the available alternative energy
technologies, solid oxide fuel cells (SOFCs) have attracted considerable attention because of
their ability to provide electricity from a variety of different fuels with efficiencies as great as
80%. Currently, SOFC anode materials do not support the direct use of complex hydrocarbon
fuels, which can lead to eventual device failure brought upon by unwanted graphitic and metal
sulfide formations. These limitations have spurred the investigation of new mixed ionic and
electronic conducting (MIEC) anode materials that can be effective at blocking these detrimental
formations. In these studies, different synthesis methods will be used to create a single phase
material of the MIEC materials Sr2Fe1.5Mo0.5O6-δ (SFMO). Specifically a solution and solid
state synthesis will be compared to observe effects on phase purity, particle size and
electrochemical catalytic efficiency. In these experiments, the use of X-ray diffraction will
monitor the phase purity of our SFMO products, while SEM will be used to monitor particle size
and effective catalytic surface area. The different SFMO materials were then integrated into
working SOFC devices and tested with standard electroanalytical methods for performance. Our
research revealed that both synthesis method were capable of producing a pure phase of SFMO.
However, the materials created by solution state methods produced smaller particle sizes. This
increase in catalytic surface area proved to be beneficial in electrochemical performance.
Poster Number: 48
Graduate Student or Post-doc
Sarah Jenny, Marianne Donley, Laura Thierer, Lindsey Round, Nicholas Piro, Scott Kassel,
Deanna Zubris
Villanova University
Development of iron(II) catalysts for atom transfer radical polymerization
Atom Transfer Radical Polymerization (ATRP) uses a metal catalyst to mediate controlled
radical polymerization. Styrenic and acrylic polymers can be produced with a narrow
polydispersity. Prior studies by Gibson revealed that imino(pyridine) and amino(pyridine) iron
(II) complexes can have modest ATRP activity, where the most electron-rich ligands in these
studies displayed the highest ATRP activity. Our group has targeted a set of iron(II) complexes
with electron-rich nitrogenous ligands with the goal of achieving ATRP utility. We have isolated
and characterized examples of monomeric, dimeric, and bis-ligated cationic iron(II) complexes,
and have demonstrated their success as polymerization catalysts for styrene. While competing
mechanisms such as Catalytic Chain Transfer (CCT) exist, the primary polymerization
mechanism is ATRP. Current work is focused on identifying the parameters that help favor
ATRP versus CCT for our catalysts to help drive future catalyst development.
Poster Number: 49
Graduate Student or Post-doc
Connor Koellner, Jeffrey McCall, Shivaiah Vaddypally, Michael Zdilla
Temple University
Reactive unchelated manganese complexes
We hypothesize that manganese clusters with lower coordination numbers and reduced chelation
will produce systems with unprecedented multi-Mn reactivity and uncover fundamental
reactivity properties relevant to the oxygen evolving complex. We propose the use of imido
ligands (RN2-), which are isolobal and isovalent to O2- and offer a similarly sized heteroatom.
Imido ligands can be tuned through organic (R) groups to vary sterics and electronics resulting in
alteration of the corresponding coordination chemistry. Current studies have examined the
reaction of Li2NtBu with MnF3. When reaction conditions include THF and a 1:1 mixture of
THF and toluene, MnLi2(NHtBu)4 is observed. This product is supported by crystal structures
and suggests C-H bond activation through the reduction of Mn(III) to Mn(II); proposed
mechanisms of reactivity will be discussed.
Poster Number: 50
Graduate Student or Post-doc
Alexander B. Koval, Amy E. Solinski, Kelly R. Morrison, Anisa R. Eshraghi, William M. Wuest
Temple University
The diverted total synthesis of Carolacton inspired analogs yields three distinct phenotypes in
Streptococcus mutans
Encompassing approximately 1000 species of bacteria, the oral microbiome is a dynamic
environment inhabited by both commensals and pathogens. Among these is Streptococcus
mutans, the causative agent of dental caries, the most prevalent childhood disease. Carolacton, a
myxobacterial natural product, has remarkably specific activity inhibiting S. mutans growth only
as it forms a biofilm at nanomolar concentrations. We hypothesized that by incorporating a
simplified structural isostere of the complex side chain we could both shorten the chemical
synthesis and retain biological activity. Herein, we report the diverted total synthesis of sixteen
carolacton inspired analogs, which includes an optimized route to a key intermediate and
leverages strategic late-stage derivatization. Confocal imaging of the analog library revealed
three unique phenotypes, one akin to carolacton and two others that were not previously seen
from this natural product scaffold. Among these is a phenotype in which biofilm growth was
arrested at the microcolony stage and a second that inhibits the formation altogether. We disclose
the synthesis of a library, molecular modeling studies of the rationally designed analogs, and the
unique microbiological phenotypes observed. These findings further validate the role of natural
product total synthesis in discovering new biological phenomena.
Poster Number: 51
Graduate Student or Post-doc
Giulia Mancini and John W. Tomsho
University of the Sciences
Synthesis and evaluation of fluorophosphonates analogues of fosmidomycin and FR900098
Malaria and tuberculosis (TB) are the most widespread infectious diseases in the world. Each
year there are approximately eight million new cases of TB diagnosed and 500,000 deaths due to
malaria. The causative agents of TB and malaria infections are Mycobacterium tuberculosis and
the parasite Plasmodium falciparum respectively. Some strains of both P. falciparum and M.
tuberculosis have become highly resistant to a variety of available drugs. One way we can
address the crisis of drug resistant infections is the development of antimalarial and
antituberculosis drugs with novel modes of action. For several reasons, the 2C-methyl-Derythritol-4-phosphate (MEP) isoprenoid biosynthesis pathway constitutes an attractive target for
the development of new anti-infective agents. Isoprenoids are a large class of natural products
and they play an important role in the life cycle of many pathogens. The MEP pathway, which is
absent in human system, is responsible for the biosynthesis of the isoprenoid precursors,
isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). It is exclusively present
in pathogens such as bacteria, fungi. The natural products fosmidomycin and its acetyl
counterpart FR900098 are potent inhibitors of the MEP pathway. They prevent the biosynthesis
of isoprenoids by inhibition of the enzyme 1-deoxylulose-5-phosphate reductoisomerase (IspC),
leading to the death of the pathogens. Despite potent in vitro activity against IspC, these
phosphonate-containing compounds are highly hydrophilic and suffer from poor bioavailability.
To address these shortcomings, we aim to replace the phosphonate moiety of fosmidomycin and
FR900098 with a fluorophosphonate group. This functionality should impart a more liphophilic
character to improve cellular penetration. In addition, the fluorophosphonate moiety also has the
potential to provide covalent inhibition of the enzyme. Currently, we are working on the
synthesis of a library of fluorophosphante analogs of fosmidomycin and their evaluation against
IspC.
Poster Number: 52
Graduate Student or Post-doc
Gabriel Andrade, Rachel C. Pupillo, Alize Marango, Jiyoon Kim, Wu Wenbo, Joel Rosenthal
University of Delaware
The development of electrochemiluminescent platforms for detection of biomolecule binding
Many biological activities, including cell division, cell death, immune response and intercellular
communication rely on a cascade of complex non-covalent interactions between DNA, proteins
and other biomolecules. Current efforts in ourlab are aimed at development of new platforms to
detect and monitor these interactions using a combination of electrochemical and spectroscopic
techniques. Toward this end, we are developing the fundamental chemistry required to
buildmultielectrode arrays onto which large biomolecules such as DNA and transcription-factor
binding proteins can be immobilized onto optically transparent conducting surfaces. The success
of such bioconjugate interfaces is reliant on the use of robust and well-defined linkages that have
topologies that we have identified as being optimal for interfacial charge transfer. Similarly, we
have worked to develop methods to incorporate redox and photochemically active probes onto
these conducting surfaces and the biomolecules anchored on these platforms. Recent progress on
the construction of these platforms and their incorporation into multielectrode arrays will also be
highlighted.
Poster Number: 53
Graduate Student or Post-doc
Tim Marshall, Yaroslav Aulin, Kyle Gilroy, Svetlana Neretina, Ares Aguilera, Eric Borguet
Temple University
Second harmonic generation spectroscopy of substrate-based surfactant free gold and silver
nano-hemispheres
Plasmonic nanomaterials are well known for their optical properties, which have been largely
studied using linear spectroscopy. Time resolved second harmonic generation (SHG), a second
order nonlinear optical phenomenon, from substrate-based, surfactant-free gold and silver nanohemispheres can yield the plasmon dephasing time. The SHG signal was collected in
transmission and reflection configurations while varying the angle of the incident ultrafast laser
beam. By varying the angles of incidence and the polarization, the longitudinal and transverse
plasmons are accessed to different degrees. This opens the door to further understanding the
properties of plasmonic nanomaterials that could provide applications in solar-energy induced
photocatalysis.
Poster Number: 54
Graduate Student or Post-doc
Andrea M. Potocny, Maxwell I. Martin, Joel Rosenthal
University of Delaware
Synthetically accessible tetrapyrrole metal complexes as efficient photosensitizers of singlet
oxygen
Photodynamic therapy (PDT) involves illuminating a photosensitizing drug in the presence of
molecular oxygen to produce singlet oxygen, which is a reactive oxygen species that triggers cell
death. Historically, macrocyclic tetrapyrrole derivatives including porphyrins, phthalocyanines,
chlorins, and bacteriochlorins have been pursued as potential PDT agents since they can sensitize
the production of singlet oxygen with good quantum yields. Despite these efforts many PDT
agents developed to date have significant limitations or shortcomings, including high dark
toxicity, complicating low yield syntheses, poor solubility in biological media and/or slow
clearance from biological tissues post procedure. With this in mind, we are actively developing
new photochemotherapeutic agents to confront these issues. As such, we have developed a
family of linear tetrapyrrole derivatives which obtained via a modular synthetic approach and are
readily metallated with a variety of transition metals. These dimethylbiladiene (DMBil)
complexes can serve as effective photosensitizers for the production of singlet oxygen in high
quantum yields upon irradiation with light of wavelengths longer than 550 nm. Furthermore,
conjugation of the ligand scaffold with water-solubilizing functional group and polymers have
allowed us to assess the efficacy of these new photochemotherapeutic agents will be discussed.
Poster Number: 55
Graduate Student or Post-doc
Ian G. McKendry, Akila Thenuwara, Sam Shumlas, Yaroslav Aulin, Haowei Peng, Rick
Remsing, Daniel Strongin, Michael Zdilla
Temple University- Department of Chemistry
Modification of 2D complexes for cheap and efficient water-oxidation catalysis.
Cheap and efficient water-oxidation catalysts remain one of the major hurdles in the
implementation of a hydrogen economy. A promising solution to this hurdle is the use of
inexpensive oxide minerals, particularly manganese oxides due to their low cost, large
abundance, and ability to easily tune it physical and chemical properties. Through combined
experimental and theoretical approaches, we have explored the roles of oxidation states, lattice
dopants, and interlayer ions on the material’s properties and water oxidation capabilities. Our
finding suggest increasing manganese(III) and cobalt(III) content in the lattice as well as
introduction of harder, redox active species such as nickel in the interlayer greatly enhance water
oxidation activity through charge delocalization and increase of high energy, frustrated water
activity that rivals that of ruthenium and iridium oxide OER catalysts can be achieved.
Poster Number: 56
Graduate Student or Post-doc
Debopreeti Mukherjee, Brei Ding, Jianxin Chen, Jianxin, Feng Gai
University of Pennsylvania
Interaction of guanidinium and tetrapropylammonium ions with aromatic amino acid side chains
The stability of proteins is often governed by naturally occurring osmolytes or denaturants like
ions or certain organic compounds. Hofmeister ions is one such series, where the ions (mostly
denaturants) are arranged based on their abilities to precipitate a protein out of its solution.
However, the mechanisms by which these ions denature a protein are still not well understood.
We have tried to understand the peptide denaturing mechanisms of two Hofmeister ions, namely
guanidinium ion and tetrapropylammonium ion (TPA+), on a molecular level, using twodimensional infrared spectroscopy (2D-IR) and fluorescence measurements. For that purpose, we
used 5-cyanotryptophan (TrpCN) and 4-cyanophenylalanine (PheCN), two non-natural amino
acids, as probes of the local environment, thereby allowing us to investigate whether these ions
can have preferential interactions with aromatic side chains or not. If the Hofmeister ion would
interact directly with the aromatic side chain in order to denature the peptide, this interaction
would manifest itself as a change in the local solvation/hydration status of the non-natural amino
acid. This was indeed found to be true and the fast dynamics associated with the change in the
hydration environment of TrpCN/PheCN was easily captured by two-dimensional infrared
spectroscopy (2D-IR). Using our 2D-IR technique, we have showed that guanidinium ion does
not significantly alter the spectral diffusion dynamics of the nitrile functionality in the aromatic
side chain, thereby confirming the fact that guanidine hydrochloride denatures a protein by
mostly interacting with the protein backbone or side chains bearing charges. On the other hand,
TPA+ shows a significant change in the spectral diffusion dynamics of TrpCN, thus proving the
fact that the four flat faces of this ion has the ideal geometry to interact with planar aromatic
rings. Fluorescence studies of a TrpCN containing peptide against varying concentrations of
TPA+ also showed a transition at a TPA+ concentration of 1.3M. This transition is similar to the
ones seen for micelles, thereby confirming the fact that TPA+ behaves in a way similar to ionic
surfactants by clustering around hydrophobic side chains and disrupting the interaction between
them. We have also showed that this clustering behavior of the TPA+ ion can also induce α-helix
formation in certain peptide sequences.
Poster Number: 57
Graduate Student or Post-doc
Owen O'Sullivan and Michael Zdilla
Temple University
Manganese-mediated covalent linkage of perchlorate to energetic aminotetrazoles: An energetic
material with at least twice the energy density of nitroamines under combustion conditions
There is a current need for novel high-energy-density materials (HEDMs) for the national
defense that possess increased shattering potential for focused target strikes to decrease collateral
damage. Current high energy materials are primarily CHNO based molecular or ionic species
containing low-oxidation state atoms (carbon, amine-nitrogens) in close proximity to high
oxidation state atoms (nitro-nitrogens) creating a redox-frustrated compound. Release of energy
occurs upon atoms reaching their most stable oxidation states in the products, liberating heat and
work. CHNO atoms have long been used in energetics due to their production of lightweight
gases upon detonation and subsequent increase of pressure-volume work through thermal
expansion. It has long been the belief that inclusion of atoms than CHNO, particularly metals,
will “dilute” the energy density of an energetic material due to their inability to produce gaseous
products. One oversight of the exclusion of transition metals is their ability to form covalent
bonds with both oxidants and fuels, which should decrease lattice energy and therefore increase
the energy released. This theory is exemplified in our synthesis of a tetrameric cubane cluster
(1,3-di-tert-butyltetrazolium-5-imidoperchlorato-manganese(II)) (1) consisting of a CHN based
fuel (1,3-di-tert¬-butyltetrazole) as well as an oxidant (perchlorate) covalently bonded to
manganese. The conventional theory suggests the incorporation of the manganese atoms into the
structure should lead to a diluted heat of combustion (∆Hc) however, comparison of the heats of
combustion for both the parent 1,3-di-tert-butyltetrazolium perchlorate salt as well as 1 show the
inclusion of manganese does not result in a 335 gain. Furthermore, in comparison with energetic
nitroamines (RDX, HMX, CL-20) 1 possesses a two-fold increase in ∆Hc. Characterization,
thermal stabilities, heats of combustion, as well as energetic properties of 1 will be discussed.
Poster Number: 58
Graduate Student or Post-doc
Rachel Parise, Fengjian Shi, Evan M. Lutton, Servio Ramirez, Robert J. Levis
Temple University
Discovery of biomarkers for traumatic brain injury using Laser Electrospray Mass Spectrometry
(LEMS)
Traumatic brain injury (TBI) is a complex injury involving multiple physiological and
biochemical alterations to tissue. The potentially thousands of relevant biomarkers spread over a
volume of thousands of mm3 makes the spatial analysis of brain a big data problem. Laser
electrospray mass spectrometry (LEMS) is an ambient mass spectrometry system that merges
femtosecond laser vaporization with electrospray ionization/time of flight detection and has been
developed as a new chemical microscopy tool. LEMS was employed in this study to image TBI
mouse brain sample and assess the spatial distribution of biomarkers after trauma. The imaging
experiment was performed using a 100 µm laser spot size rastered over a 4 x 4 mm area of a
mild TBI brain tissue section to generate 100 Gbytes of data. Species identified by mass spectra
were spatially mapped and compared to corresponding optical images of the brain sample. A
present challenge for the method is the development of data mining techniques to identify
relevant biomarkers for TBI.
Poster Number: 59
Graduate Student or Post-doc
Ying Peng, Changqing Wu, Kaleigh Reno, Mingming Guo, Thomas H. Epps, III
University of Delaware
Evaluation of estrogenic activity of the novel Bisphenol-A alternative, four Bisguaiacol-F
compounds
Bisphenol-A (BPA), largely used in polycarbonate plastics and polystyrene resins, is considered
to be an endocrine disruptor due to its estrogenic activity. Recent extensive kinds of literature
have reported the evidence on the relationship between BPA exposure and chronic human
disease, including diabetes, obesity, reproductive disorders, breast cancer, birth defects, chronic
respiratory and cardiovascular diseases. Therefore, a sustainably sourced, and less toxic BPA
alternative is desirable for the manufacture of containers for edible products. Bisguaiacol-F
(BGF) is structurally similar to BPA, with two hydroxyphenyl groups. BGF can be synthesized
by reacting two derivatives of lignin and is considered as a green alternative to BPA. In this
study, estrogenic activity (EA) of four isomers BGF were evaluated at six concentrations (from
10-13 to 10-8 M) by cell proliferation assay. Chemicals with EA activate the ERs and ERdependent transcription of estrogen-responsive genes, which leads to proliferate of breast cancer
cells (MCF-7 cells).The MTT assays revealed that BPA at 100pM, 1nM, and 10nM significantly
promoted the in vitro proliferation of MCF-7 cells after exposure for 96 h (p<0.05). The EA of
BPA is dose dependent. There is no EA effect of BGF6 and BGF8 at the wide concentration
range from 10-13 to 10-8 M, or of BGF1 and BGF4 at 100pM and 1 pM when compared to the
no treatment group (p<0.05). Even BGF1 and BGF4 at 10 nM, 1 nM, and 10 pM significantly
increased the cell proliferation compared to the no treatment group, the cell proliferation was still
lower than that determined at the same concentration of BPA (p<0.05). All the results indicate
that both BGF6 and BGF8 are the potential less toxic and sustainable alternatives to BPA.
Poster Number: 60
Graduate Student or Post-doc
Simone Pezzotti, Daria Ruth Galimberti, Morgane Pfeiffer-Iaplaud, Marie-Pierre Gaigeot
Université d'Evry-Val-d'Essonne, France
SFG spectroscopy of silica/water interfaces by DFT-MD simulations
We present recent DFT-MD simulations of electrolytic silica/water interfaces (electrolytes being
KCl) in order to unravel the structural properties of electrolytes at the crystalline quartz/liquid
water interface and at the amorphous silica/liquid water interface, and how water and surface
both modulate each other response to the presence of electrolytes. The theoretical method
employed to calculate and interpret SFG spectra from DFT-MD simulations is presented. The
investigated systems are: fully hydroxilated α-quartz/water (QW) interface (pH=ZPC=1.9), QW
interface with 1M KCl concentration in water and fully hydroxilated amorphous silica/water
interface (AW).
Poster Number: 61
Graduate Student or Post-doc
Piret Pikma, Parisa Yasini, Eric Borguet
Temple University
In situ STM study of the effect of applied potential on the adsorption and electrical conductivity
of NDA
Molecular self-assembly at solid surfaces, resulting in the formation of nanostructures with wellcontrolled properties and functionality, reveals fascinating perspectives in science and
technology at nanoscale [1]. For instance, tailoring of the structural properties of functionalized
electrodes can be used to trigger specific electrochemical processes.Molecular-scale electronic
devices are often constructed by wiring a single molecule between two metal electrodes using
mechanically controlled break junctions in a scanning tunneling microscope (STM). Singlemolecule conductance (SMC) studies performed under electrochemical conditions mostly focus
on molecules with functional groups that provide efficient electronic coupling and connect the
molecule of interest to the electrodes [2].The intramolecular charge transfer states in π-electron
donor-acceptor systems have received much attention in the field of organic materials due to the
non-linear optical properties of these compounds which enable them to be used as molecular
switches, chemical sensors, and fluorescence probes [3]. In this study in situ STM imaging and
STM break junction techniques, supported by cyclic voltammetry, were applied to investigate the
adsorption and conductivity properties of 2,6-naphthalenedicarboxylic acid (NDA) on an
Au(111) single crystal electrode and their dependence on the applied surface potential. Ordered
structures were observed at potentials more negative than the zero charge potential and were
accompanied by the observation of a high SMC feature.References:[1] T. Wandlowski, In: A.J.
Bard, M. Stratmann (Eds.), Encyclopedia of Electrochemistry, Wiley VCH, Weinheim (2002) p.
383-471 [2] S. Afsari, Z. Li, E. Borguet, Angew. Chem. Int. Ed. 53 (37), (2014) 9771-9774 [3] I.
Gomez, Y. Mercier, M. Reguero, J. Phys. Chem. A, 110, (2006) 11455-11461
Poster Number: 62
Graduate Student or Post-doc
Stefan M. Piontek, Kevin Milan, Ruiyu Wang, Aashish Tuladhar, Rick Remsing, Vincenzo
Carnevale, Michael L. Klein, Eric Borguet
Temple University
Monovalent and divalent cations at the α-Al2O3 (0001)/water interface: How cation identity
affects interfacial ordering and vibrational dynamics
Although aluminum oxides are among the most abundant mineral oxides in the earth’s crust their
ability to structure interfacial water and affect its vibrational dynamics is still not well
understood. The α-Al2O3 (0001) surface also represents an ideal environment to study the
effects of surface charge on interfacial environments since the point of zero charge (PZC) occurs
at pH ~6, allowing for modulation of surface charge via bulk pH. Protonation of terminal
hydroxyl groups at pH <6 leads to a net positive charge on the surface while deprotonation at pH
> 6 leads to net negative charge on the surface. Vibrational sum frequency generation (vSFG) is
employed as a surface specific vibrational spectroscopy to probe the first few layers of interfacial
water. Using vSFG and pump-probe (PP-vSFG), the effects of monovalent and divalent cations
on structure and vibrational energy relaxation of interfacial water were investigated at constant
ionic strength. Monovalent cations, such as Li, Na, K, and Cs, affect the vibrational relaxation of
interfacial water as a function of surface charge. Divalent cations increase the vSFG response
suggesting enhanced ordering of interfacial water species. Collaboration with the Klein Group
provided molecular dynamics simulations guiding our interpretation of vSFG data.
Understanding the interfacial environment not only has an impact on computational models of
mineral oxide surfaces, but helps improve heterogeneous catalyst design, and understand how
interfacial water is structured at hydrophilic surfaces.
Poster Number: 63
Graduate Student or Post-doc
Lauren A. Profitt, Kayleigh E. Jones, Ann M. Valentine
Temple University
Titanium (IV) interactions with human serum transferrin
Titanium is the second most abundant transition metal in the Earth’s crust, yet a biological role is
not recognized. Titanium’s biological drawback is its insolubility in water, which can be
overcome by complexation with a ligand. Titanium alloys are used in implants, which are
passivated with a TiO2 layer. Corrosion of these implant surfaces leads to the dissolution of
Ti(IV) ions, a hydrolytically unstable species. The same hydrolysis prone tendencies are true of
putative Ti(IV) anticancer drugs such as titanocene dichloride (TDC). Transferrin (Tf) is an 80
kDa bilobal glycoprotein capable of binding two ferric ions. Titanium can bind stronger to Tf
than iron in solution [1]. Therefore, Tf is often thought to be responsible for Ti(IV) transport
through human serum, in order to warrant solubility to the otherwise insoluble Ti(IV). Recently,
it has been postulated that citrate and carbonate are both necessary synergistic anions in metal
binding to transferrin. Monitoring TiO2 dissolution is critical to provide insight into necessary
coordinating factors for insoluble species and to determine transferrin’s possible role in
introducing soluble titanium traces in the human body. Determining the extent and fashion in
which TDC binds to Tf would help to clarify dosage responses and formulation techniques that
previously hindered TDC in clinical trials.[1] Tinoco, A.D., Valentine, A.M. J. Am. Chem. Soc.
2005. 127(32), 11218-11219.
Poster Number: 64
Graduate Student or Post-doc
Gabriel Andrade, Rachel C. Pupillo, Alize Marangoz, Jiyoon Kim, Wenbo Wu, Joel Rosenthal
University of Delaware
The development of electrochemiluminescent platforms for detection of biomolecule binding
Many biological activities, including cell division, cell death, immune responseand intercellular
communication rely on a cascade of complex non-covalentinteractions between DNA, proteins
and other biomolecules. Current efforts in ourlab are aimed at development of new platforms to
detect and monitor theseinteractions using a combination of electrochemical and spectroscopic
techniques.Toward this end, we are developing the fundamental chemistry required to
buildmultielectrode arrays onto which large biomolecules such as DNA and transcription-factor
binding proteins can be immobilized onto optically transparent conducting surfaces. The success
of such bioconjugate interfaces is reliant on the use of robust and well-defined linkages that have
topologies that we have identified as being optimal for interfacial charge transfer. Similarly, we
have worked to develop methods to incorporate redox and photochemically active probes onto
these conducting surfaces and the biomolecules anchored on these platforms. Recent progress on
the construction of these platforms and their incorporation into multielectrode arrays will also be
highlighted.
Poster Number: 65
Graduate Student or Post-doc
Robert Rosano and Robert Giuliano
Villanova University
Synthesis of the phytotoxin diplopyrone
Diplopyrone is a phytotoxin isolated from the fungus Diplodia mutila and reported by Evidente
and coworkers in 2003. D. mutila is considered to be responsible for cork oak decline in parts of
southern Europe where the disease has a large and negative economic and environmental
impacts. The pyranopyran core structure found in diplopyrone also occurs in many other natural
products that encompass a range of biological effects including antibiotic activity. Viewing
diplopyrone as a “C-glycoside problem” opens up multiple synthetic routes that are based on
carbohydrate starting materials. My research has focused on the use of alkynyl glycosidis as
precursors which were furnished via the Ferrier rearrangement. Subsequent steps and
incorporation of an RCM allow for construction of (-)-diplopyrone’s pyranopyran core in
moderate yield.
Poster Number: 66
Graduate Student or Post-doc
Michael Rosen, Lok Pokhrel, Brajesh Dubey
Temple University, Division of Environmental Health, College of Public Health
Assessing risks of multiple heavy metals and metalloids leaching from retroreflective glass beads
used in road markings
Retroreflective glass beads are incorporated into road paints to improve visibility and road safety
for both drivers and pedestrians1. Majority of the glass beads which are imported in recent years
are reported to leach various metals and metalloids at both low and toxic levels2. Concerns about
heavy metals and metalloids leaching from glass beads into the soils and water systems have
often been raised3. About 67% of the drinking water in the US is sourced from surface waters4.
The purpose of this study was to evaluate both the total and extractable metals (Lead, Chromium,
and Cadmium) and metalloids (Arsenic and Antimony) concentrations in imported glass beads
simulating realistic leaching scenarios using multiple standard leaching protocols. Under some
leaching protocols, leachate concentrations were above the USEPA action level or maximum
contaminant level, particularly with As. Risk assessment indicated elevated cancer risk from As,
Cd, and Cr, and non-carcinogenic risk from As and Cd, exposure through contaminated drinking
water assuming ‘no dilution’ or ‘no loss’ scenario. However, no public health risk was indicated
for Pb and Sb leaching from the glass beads
Poster Number: 67
Graduate Student or Post-doc
David Rushmore and John Tomsho
University of the Sciences
Probing Influenza NS1A Homodimerization as a Target for Therapeutic Intervention
The rapid evolution of viral resistance to modern medical treatments is a major public health
concern. The influenza virus is a common, and potentially lethal, example of an infectious agent
that regularly gains resistance to drug treatments. To combat resistant organisms, it is necessary
to identify novel targets and/or active molecules. A potential target for therapeutic molecules in
influenza strain A is non-structural protein 1 (NS1A). NS1A is a two domain protein, with an N
terminal RNA Binding Domain (RBD) and a C terminal Effector Domain (ED) that has been
linked to pathogenicity and viral replication in the host cell. It has been that deletion of the NS1A
gene greatly diminishes the virus’ capacity to proliferate an infection, making NS1A a promising
target for the development of anti-influenza agents. Since the function of NS1A is dependent on
the monomeric protein dimerizing, disruptors of homodimerization should effectively abolish
NS1A activity. A reverse two hybrid system (RTHS) has been constructed to monitor the
dimerization of the full length NS1A protein or its individual domains. This reporter system was
made to screen libraries of cyclic peptides for potential inhibitors of this important proteinprotein interaction. We are currently validating potential active peptides and screening additional
libraries.
Poster Number: 68
Graduate Student or Post-doc
Evan Samples and Graham Dobereiner
Temple University
Polyketones for Hole Transport Materials
The achievements in conversion efficiency of Perovskite solar cells have established PSCs as a
credible alternative to liquid electrolyte solar cells, but these cells typically contain spiroOMeTAD, a solid hole transport material (HTM), which is very expensive to fabricate.
Polyketones are easily synthesized from carbon monoxide and terminal olefins, and the resulting
polymer contains is highly reactive making the polymer ideal for post-polymerization
functionalization reactions. These functionalized polyketones could yield new materials with
unexplored properties such as hole transport activity. Polymers synthesized have been modified
with Paal-Knorr reactions to yield new materials which will be explored as HTMs.
Poster Number: 69
Graduate Student or Post-doc
Jason Smith and Randy Zauhar
University of the Sciences
Computational development of indoleamine 2,3-dioxygenase inhibitors
Our group is focused on finding new cancer therapies through the computational development of
indoleamine 2,3-dioxygenase (IDO) inhibitors. IDO catalyzes the metabolism of tryptophan to
kynurenine, which allows tumors to escape detection by the immune system. IDO inhibition has
already proven to be a useful immunotherapy for cancer and has potential in the areas of
transplant medicine and autoimmune disease as well. Current computational lead development
methods are not suited to IDO because of its promiscuous and "floppy" binding site, and the
presence of a heme in the active site. To solve this problem, we are placing leads into the active
site and constraining the heme-nitrogen bond, minimizing the rest of the receptor around this
bond. This method has allowed us to successfully replicate the poses of native ligands from PDB
models and shows promise at optimizing the poses of hydroxylamine leads from our
collaborators.
Poster Number: 70
Graduate Student or Post-doc
Christiana Teijaro, Senzhi Zhao, Manish Walia, Rodrigo Andrade
Temple University
Progress toward Bis-Aspidosperma Alkaloids: (‒)-Melodinine K, (‒)-Conophylline, and (‒)Conophyllidine
In 1992 and 1993, Kam and coworkers isolated (‒)-conophylline (0.065%) and (‒)conophyllidine (0.0043%) from the leaves of Tabemaemontana divaricata. In 2010 (‒)melodinine K, a deoxygenated version of (‒)-conophylline, and (‒)-conophyllidine, was isolated
by Luo and coworkers from Melodinus tenuicaudatus in less than 0.006%. These dimeric
alkaloids have a wide range of biological activities. (‒)-Melodinine K was shown to have a low
µM IC50 against several human cancer cell lines compared to cisplatin and vinorelbine. (‒)Conophylline has been shown to be a potent inhibitor of the ras function, is capable of inducing
b-cell differentiation in fetal and neonatal pancreatic tissue and pancreatic acinar carcinoma
cells cultured in rats as well as in porcine neonatal pancreatic endocrine cells. These biological
activities, low isolation yields and the structural complexity of these natural products have
prompted their syntheses. These dimeric alkaloids can be disconnected via the dihydrofuran ring
to afford a northern and southern fragment that can be arrived at from the syntheses of 16methoxytabersonine and oxygenated analogs of tabersonine, respectively. Key steps in the
synthesis include a Glorius indole synthesis to build the oxygenated indole core, a domino
Michael/Mannich/N-allylation to form the E-ring and set the stereochemistry for the C and D
rings, and a late stage electrophilic aromatic substitution (EAS) coupling.
Poster Number: 71
Graduate Student or Post-doc
Akila Thenuwara, Samantha Shumlas, Nuwan Attanayake, Quing Kang, Elizabeth Cerkez, Ian
G. Mckendry, Laszlo Frazer, Richard Remsing, Eric Borguet, Michael Zdilla, Jianwei Sun,
Daniel Strongin
Temple University
Turning a poor catalyst into an efficient catalyst: Metal intercalated Birnessite as a water
oxidation catalyst
Oxygen evolution reaction (OER) catalysts play a central role in numerous renewable energy
technologies including rechargeable metal-air batteries and hydrogen generation. However,
enabling these technologies require efficient, cost effective and stable catalysts. In this
contribution we show that redox active metal ion (e.g. Ni2+, Co2+) intercalation into the
interlayer region of layered manganese oxide leads to excellent catalytic performance in both
neutral and alkaline media. Metal ion intercalation was carried out using an ion exchange
reaction using the respective metal-hydrazine complex. State-of-the-art analytical
characterization has revealed that interaction of interlayer water of layered manganese oxide with
the intercalated metal ion led to hydroxide like metal clusters in the interlayer region.
Electrocatalytic studies have revealed this hydroxide like metal cluster confined in the interlayer
region as the active site for water oxidation. Moreover, molecular dynamics simulations were
carried out to explain this system. Results from the simulation suggests that confinement of
metal ions in the interlayer region can promote complex dipolar interactions between the metal
cations, water, and layered manganese oxide and this can lead to improved OER catalysis.
Poster Number: 72
Graduate Student or Post-doc
Ruiyu Wang, Richard Remsing, Leah Magidson, Vincenzo Carnevale, Michael L. Klein, Eric
Borguet
Department of Chemistry, Institute for Computational Molecular Science, Temple U
Adsorption of sodium halides to the water-air and water-alumina interfaces
Chemistry at aqueous interfaces can differ significantly from that in bulk solution, with chemical
processes depending on the nature of the interface. However, little is known regarding the
molecular-scale behavior at interfaces. In a step toward understanding interfacial chemistry, we
use molecular dynamics simulations to investigate the process of ion adsorption to the watervapor interface, an ideal hydrophobic interface, and to the surface of the mineral alumina, a
hydrophilic surface. We demonstrate that larger, low charge density ions preferentially adsorb to
the water-vapor interface, while high charge density ions are repelled. The opposite is found at
the hydrophilic water-alumina interface. We also detail significant ion-specific effects for
fluoride binding to the alumina surface that could significantly impact interfacial processes.
Poster Number: 73
Graduate Student or Post-doc
Vivek Yadav and Michael Klein
Temple University
Comparative analysis of the structural determinants of endogeneous cannabinoids and activity of
illicit drugs on cannabinoid receptors
We performed molecular docking and molecular simulation of illicit drugs and endogenous
cannabinoids ligands in the Cannabinoids (CB) receptors. These CB receptors play vital roles in
various physiological events like pain transmission, immune and neurodegenerative conditions.
Till date, there is no available crystal structures for CB receptors, and therefore we used multiple
template comparative homology modeling algorithm to construct 3D models for CB1 and CB2,
two well known subtypes of CB receptors.
Poster Number: 74
Graduate Student or Post-doc
Parisa Yasini, Piret Pikma, Eric Borguet
Temple University, department of chemistry
Single molecule electronics: Fabricating an ON/OFF electromechanical single conductance
molecular switch
Single molecule junctions are potential building blocks of miniaturized electronics.
Interconversion between two states using external stimuli is a convenient way to generate single
molecule devices such as switches and sensors. We have devised an electromechanical single
molecule switch that transits between ON and OFF states employing the working electrode
potential as the external stimulus in an electrochemical environment. We used the scanning
tunneling microscopy (STM)-break junction method to measure the electrical properties of
molecules bridged between two electrodes (the conducting substrate and STM tip).The candidate
molecules should exhibit measureable high and low conductance states. Benzene derivatives are
promising due to the controllable formation of molecular junctions with desired geometry. We
have focused on tetracyanoquinodimethane (TCNQ) because it is considered as a π acceptor
molecule and has been widely used in the formation of charge transport compounds. At
potentials more negative than zero charge potentials, direct contact between the π -system of
TCNQ and the Au (111) electrode results in the formation of a highly ordered monolayer and
high conductance junctions are detected. Moving to potentials more positive than the potential of
zero charge triggers an order-disorder transition as revealed by STM. Accordingly, these initial
results suggest that TCNQ appears to be a viable molecular conductance switch that can be
toggled between high/low states as a function of surface potential.
Poster Number: 75
Graduate Student or Post-doc
Yike Zou, Yun Yang, Amos B. Smith
University of Pennsylvania
Indole diterpenoid total synthesis study: Construction of (−)-Nodulisporic acid C
A convergent total synthesis towards architecturally complex indole diterpenoid natural product
(−)-nodulisporic acid C is presented in this poster section. Key synthetic transformations
included a carbamate directed late-stage ortho lithiation/prenylation leading to a highly
functionalized aromatic ring and a palladium mediated cascade cross coupling/indole formation
to construct the multi substituted indole core of (−)-nodulisporic acid C.
Poster Number: 76
Graduate Student or Post-doc
Miad Siddiq and Rodney Wigent
University of the Sciences
A differential calorimetric study of the ternary tetra-n- butylammonium chloride/ sodium
chloride water semi-clathrate system
Gas sequestering, storage and transportation are ones of this century challenges. In the industry,
Tetra-n- ButylAmmonium Halides (TBAXs) have been used to form semi-clathrates with
stability at mild conditions of temperature and pressure. This work involves using a Differential
Scanning Calorimeter (DSC) to measure the freezing and melting points as well as the latent
heats of transitions of H2O and TBAC-H2O complexes. The results of studying the binary
solutions show that the most stable TBAC-H2O complex is formed from a solution that is 2.0
molal ionic strength. At this concentration there is little to no free (uncomplexed) water as all of
the water is tied up in the complex. During industrial process, it is likely that the TBAC- H2O
complexes may be exposed to electrolytes such as NaCl. This study involves using DSC to study
the effect of adding NaCl on the thermodynamic properties of the 2 molal TBAC-H2O
Complexes. The data shows that at a TBAC ionic strength fraction, (YTBAC), of 0.9, NaCl
enhances the stability of this most stable form of semi-clathrate found in the 2.0 molal binary
TBAC-H2O system. However, higher concentrations of added NaCl show existence of less
stable semi-clathrate complexes.
Poster Number: 77
Graduate Student or Post-doc
Miad Siddiq, Delicia Henriques, Rodney Wigent
University of the Sciences
A differential calorimetric study of the tetra-n-butylammonium chloride/ water semi-clathrate
system
Aqueous Tetra-n- ButylAmmonium Chloride (TBAC) solutions are known to form solid semiclathrate complexes with water. In these complexes, TBA+ is surrounded by a cage consisting of
a large number of water molecules (i.e., ~ 24 to 32 molecules of water per molecule of TBA+).
These semi-clathrates are stable at moderate temperatures and pressures which allows for the
sequestration, storage and transportation of green-house gases, such as carbon dioxide and
methane. Since the molal concentration scale is normalized to 1000 grams or 55.51 moles of
water, then there should only be enough water to form such semi-clathrate complexes from
solutions that are up to 1.73 to 2.31 molal TBAC. We tested the hypothesis that a stable semiclathrate is formed and will be in equilibrium with free, uncomplexed water at or below these
concentrations. Above these concentrations, it was hypothesized that no free water will exist and
that less stable TBAC/water complexes, which have fewer waters of hydration per TBA+
molecule, will predominate. A Differential Scanning Calorimeter was used to measure the
freezing and melting points of the water and TBAC complexes, as well as their latent heats of
transition, to thermodynamically characterize this system over the concentration range of 0 to ~ 8
molal. The observed data generally confirmed these hypotheses.