Student
Abstracts of ACS Meeting in
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Emily M. Andrews and David S. Cafiso |
Department of Chemistry, |
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Conformational Changes of the N-terminal Domain of
FecA in Presence of Solutes and Proteic
Fragment of TonB by EPR Spectroscopy |
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FecA is a protein located in the outer membrane of Escherichia coli. It transports extracellular iron into the cell using energy provided by the inner membrane proteins of the TonB System. Not only is iron necessary for the metabolic processes of the cell, but the binding of iron on FecA also triggers transcription of the genes for iron transport. FecA is composed of three domains: a barrel, a plug and an N-terminal extension. The interaction of this N-terminal domain with FecR, an inner membrane protein, initiates the transcription of the FecABCDE genes. With the use of site-directed spin labeling (SDSL) and continuous wave electron paramagnetic resonance (cw EPR), we studied possible conformational changes of the N-terminal domain in the presence of substrate, viscous solutions, osmolytes and a fragment of TonB protein. Upon addition of ferric citrate and TonB, no change was seen in the line shape of the EPR spectra. In viscous solutions such as Ficoll 400, no change was evident in the lineshapes of the mutants. This result signifies that Ficoll does not have an effect on the global rotation of the protein. In the presence of osmolytes—PEG or sucrose, the spectra showed decreased mobility, indicating that osmolytes cause the protein to fold into a more compact structure. In addition, TonB does not alter the shape of the spectral lines. All these data suggest that the N-terminal domain was in an unfolded state, refolding in presence of PEG and sucrose, and that the presence of the fragment of TonB does not induce conformational changes on the N-terminal extension of FecA.
Student: Gordon Zrelak
Preparation of a
Solid Phase Baylis-Hillman Catalyst on Grafted Glycidyl Methacrylate/Nylon-6,6
Support.
Gordon
Zrelak and Paul H. Mueller. Department of Chemistry,
The Baylis-Hillman is the tertiary amine-catalyzed reaction of an acrylate ester with an aldehyde to form a b-hydroxy-a-methylene ester. The products of these reactions have new carbon-carbon bonds and densely packed functionality which makes them useful intermediates. This research focused on the creation of a solid support catalyst for the Baylis-Hillman reaction. Nylon-6,6 mesh was chosen for the base support due to its regular structure, durability, and low cost. To this nylon, glycidyl methacrylate was grafted as a polymer in a reaction promoted by Na2S2O3, K2S2O8, and CuCl2. An imidazole moiety¸ which serves as the Baylis-Hillman catalyst, was attached by nucleophilic attack of N-(3-aminopropyl)imidazole on the gycidylic epoxide. The material was tested for catalytic activity.
Student’s Name: Ashley
Zimmerman
Institution:
Poster Title: Effect of frozen packaging on total phenolic content of strawberries and blackberries
Abstract: Consumption of fruits has been linked to reduced health risks based on their antioxidant activities. However, availability of fresh fruits varies seasonally which produces a need to assess the total phenolics of frozen fruits as compared to fresh fruits. The purpose of the study is to determine whether there is a significant difference in antioxidant levels of fresh and frozen berries. The total phenolic, as well as soluble free and bound phenolic, content of fresh and frozen strawberries and blackberries will be determined and compared. The isolation of the phenolic compounds include, but are not limited to, solvent extraction and solid-phase extraction; the total phenolic content will be analyzed using a colorimetric assay with results compared to a gallic acid standard curve. It is expected that freezing the fruits would preserve the phenolic content and subsequent analysis would reflect little difference between the fresh and frozen forms of the berries.
Progress in the Development of Protecting Group Strategies for Alkylguanidines
Rebecca Funkhouser, Jennifer Yox, Dr. Janet Asper
The guanidine functional group has attracted increasing attention from biological, medicinal and organic chemists due to its prevalence in many biologically occurring molecules and pharmaceutical compounds. Alkylguanidines are strongly basic, requiring protecting groups to allow the synthesis and handling of alkyguanidines in organic solvents. Our group has done work developing new methods for the synthesis of alkylguanidines, including solid phase deprotection of Boc protected alkylguanidines and development of a new guanidine protecting group which includes a polymer support suitable for liquid phase organic synthesis (LPOS). Recent progress in both projects will be discussed.
New Pyranine Receptor for Use in
Endovesiculation Assay
Ryan M. Wood,a Vladimir Sidorov*a
a Department
of Chemistry,
E-mail: vasidorov@vcu.edu
Chlorpromazine
(CPZ) and other local anesthetics have been shown to induce endovesiculation,
which is mechanistically similar to endocytosis.1 The endovesiculation assay is a
method for determining the amount of external surroundings that have been
internalized by large unilamellar vesicles (LUVs). In our assay, internalization of
8-hydroxypyrene-1,3,6-trisulfonate (HPTS, pyranine) is used to quantify the extent of
endovesiculation. After endovesiculation
of the surroundings is induced, a receptor for HPTS is applied. The fluorescence of the external dye is
quenched by the receptor, and the residual fluorescence corresponds to the
amount of dye internalized by endovesiculation.
In
a structure-activity relationship study of cyclen-based receptors for anionic
pyrene derivatives, nitrophenyl-urea-cyclen was identified
as an excellent candidate for use in determining the extent of
endovesiculation. The endovesiculation
experiments are conducted with very low concentrations of LUVs. Thus, the amount of HPTS dye internalized is
low, and a receptor that is highly sensitive is needed. The dynamic quencher p-xylene-bis-pyridinium bromide (DPX)
provides the necessary sensitivity because of its ability to quench 99.7%
fluorescence of HPTS.1 However, DPX requires 40mM concentrations
that do not mimic biological conditions.
The cyclen-based receptors offer better alternatives because they have a
much higher affinity for HPTS, allowing them to operate at significantly lower
concentrations.2 Nitrophenyl-urea-cyclen
has the highest fluorescence quench (97.6%) of the derivatives that we have
synthesized. The synthesis of nitrophenyl-urea-cyclen, development of the
endovesiculation assay, and the application of the endovesiculation assay will
be discussed.
References
1 Tedesco, M. M.; Matile, S. Bioorg. Med. Chem. 1999, 7, 1373–1379.
.
Authors: Dominique Williams, Dr. Garry Glaspell, Dr. Jon Anderson
Department of Chemistry,
“Microwave Synthesis of Uniform Rare Earth Oxides”
Abstract: We report the microwave synthesis and characterization of uniform binary rare earth oxides (Er/Eu, Er/Ho, Ho/Eu). The results shows that by varying the ratio of the rare earths you can control the emission wavelength. The ability to produce tunable structures by changing the composition leads to highly tunable luminescent properties.
Spectrophotometric studies of complexes formed by cucurbit[7]uril with organic dyes
Abigail Turner and Karl Zachary, Department of Chemistry,
The object of this research was to establish binding constant (K) values for the complexation of cucurbit[7]uril (CB7) with the organic dyes methyl viologen, and acridine orange. UV-Vis absorption as a function of temperature and host-guest molar ratio was studied and compared to quantum chemical and molecular mechanics calculations.
A Comparative Study of
Antioxidant Levels in Fresh, Frozen and Canned Vegetables
Student’s Name: Paresa Taghavie-Moghadam
Institution:
Abstract: The health benefits from the consumption of vegetables are well documented and include, but are not limited to: supplying vitamins, providing dietary fiber, and reducing risk of diseases. However, the effects of the processing of these vegetables on the antioxidant content of the vegetables are not as well documented. The purpose of this study is to extract and quantify the antioxidant levels, more specifically the soluble phenolic content, of fresh, frozen, and canned vegetables. The soluble phenolics were isolated from the fresh, frozen, and canned samples of spinach, green beans, and peas using solvent extraction. The soluble phenolic content of each extracted sample was quantified by a colorimetric assay using gallic acid for a standard. The phenolic content for each were compared to determine if the difference in processing could affect the antioxidant content of the vegetables. From the results of the study, there was no significant comparison or linkage between the three studied vegetables and their processing.
Detection of Amino Acids in
sexually mature Odocoileus virginianus by Gas Chromatography Mass Spectrometry
Daniel Swale and Megan Houck
Dr. Geoffrey C. Klein and Dr. Lisa
S. Webb
Research has provided minimal amounts of literature in the area of detection and quantification of amino acids (AAs) within various species of deer. This project describes a procedure for derivatization, separation, and quantification of amino acids by Gas Chromatography-Mass Spectrometry (GC-MS). The multifunctional aspect of amino acids makes them difficult to analyze by a single technique. Detection and analysis by GC-MS can be facilitated by derivatization of the amino acids with N-tert-butyldimethylsilyl-N-methyltrifluroacetemide in the presence of a catalyst. A standard curve of the was produced for five common amino acids (Glycine, Gly; Lysine, Lys; Phenylalanine, Phe; Tryptophan, Trp; Tyrosine, Tyr) to illustrate the linearity between the concentration of the AAs and the total ion current response of the Gas Chromatograph. The mass spectra were analyzed to unambiguously identify the AAs based on fragmentation patterns. GC-MS is a quick and easy method for the separation and identification of AAs. All five AAs are completely separated and are unambiguously identified by their unique fragmentation pattern in the mass spectrum. This method will be implemented for the analysis and quantification of muscle within whitetail deer, (Odocoileus virginianus).
cis-Platinum
Mononucleobase Compounds: Reaction Profile Studies
Involving Protein, DNA, and Zinc Finger Models, and Implications For Possible
Antiviral Activity
Joseph V. Strukl, Queite A. de Paula,
John Mangrum, Yun Qu, Nicholas Farrell
The reactivity of cis-platinum mononucleobase compounds containing cis amines, cis-[PtCl(L)(L’)2]+ where L = mononucleobase and L’ = amine ligand will be monitored using 1H NMR. Compounds will be synthesized using a general reaction scheme. The binding selectivity of trans-platinum mononucleobase compounds towards the model substrates 5’-guanosine monophosphate (5’-GMP) and N-Acetylmethionine (N-AcMet) has been studied. A preferential binding in a 6:1 ratio favoring N-AcMet (protein model) was observed. Reactions with zinc models were studied by 195Pt NMR and Mass Spectrometry. The cytotoxicity of the cis-platinum mononucleobase compounds was also studied. This binding preference for the trans compounds paired with low cytotoxicity has lead to the discovery of anti-viral activity. It was observed that the cis compounds also exhibited a low cytotoxicity and had a much higher (2-3 times in some cases) preference for N-AcMet.
Title: Determination of Total Arsenic in Chickens
from the Local Supermarkets
Undergraduate Students: Andrea Snead, Ferdinand Udoye
Advisor: Dr. Diep V. Ca
Chemistry Department,
Abstract:
Roxarsone has been the most common arsenic-based additive used in chicken feed for growth promotion and pigmentation improvement. Within the bird, roxarsone converts into inorganic arsenic, such as arsenite [As(III)] and arsenate [As(V)], which is far more toxic than the organic form, roxarsone. The European Union banned arsenic additives in 1999. However, in the U.S. 2.2 million lbs of roxarsone are used to feed at least 70% of the 9 billion broiler chickens produced annually.
Although the concern about roxarsone is increasing due to the evidence of arsenic as a carcinogen, neither the Food & Drug Administration nor the Department of Agriculture has reported the level of arsenic in the poultry meat. Only arsenic in chicken livers was measured by USDA. Literature search has shown only one report on arsenic in poultry meat, which was written by David Wallinga.
This research aimed to determine the residual arsenic in raw
chicken breasts of four most popular brands in
PULMONARY ARTERIAL CAPACITANCE PREDICTS SURVIVAL OF
PATIENTS WITH PULMONARY ARTERIAL HYPERTENSION ASSOCIATED WITH SCLERODERMA AND
IDIOPATHIC PULMONARY ARTERIAL HYPERTENSION
Dea J. Sloan1, Paul Hassoun2, MD, Stephen
Mathai2, MD
2Division of Pulmonary and Critical Care
Medicine,
Pulmonary Arterial Hypertension (PAH) is a vascular disease that is characterized by abnormally high pressure in the pulmonary arteries. Common symptoms include shortness of breath, syncope, angina, and edema. The disease is associated with right-sided heart failure. PAH belongs to Group I of the 2003 WHO classification of pulmonary hypertension. Group I includes, among other diseases, idiopathic PAH (IPAH) and diseases associated with PAH (APAH), among which is scleroderma-related PAH.
Primary pulmonary arterial hypertension, also known as idiopathic pulmonary arterial hypertension (IPAH), is of unknown etiology. This form of PAH is rare but more severe than the other form of PAH. Some patients have a genetic cause (alteration in the BMPRII gene), however the majority of patients have no identifiable cause for their disease.
Studies have shown that there are clinical differences between patients that have idiopathic pulmonary arterial hypertension and pulmonary arterial hypertension associated with scleroderma. Additionally, there are differences in the survival times between these two groups with those patients having pulmonary hypertension associated with scleroderma having lower survival rates[i]. Several factors have been examined in an effort to describe the higher mortality rate in patients that have scleroderma-related PAH.
Pulmonary arteriolar capacitance has been shown to be predictive of mortality in patients with IPAH[ii]. The aim of this research study was to investigate the relationship between the pulmonary arterial capacitance as it relates to the varied rates of survival between patients with IPAH and patients with PAH-Scl. We hypothesized that patients with scleroderma-related PAH have a lower pulmonary arteriolar capacitance than those patients with idiopathic PAH making the survival time of patients with scleroderma-related PAH much shorter.
The results showed that the PAH-Scl patients have a significantly lower survival time than those patients in the IPAH group (p≤0.0014). However, the differences in the pulmonary arterial capacitance between the two groups were not statistically significant (p≤0.888). This value did not explain the difference between the mortality rates of the two groups of study.
Design of Functional Organic Materials:
Propargylic Alcohol Derivatives as Components of Molecular Rotors
Sara G. Sadiq-Ali, Marilise A. Hyacinth, Lin Pu and Michal Sabat, Department of
Chemistry, University of Virginia, Charlottesville, VA 22904
Molecular devices based on
rotational movements of molecules play an important role in nanotechnology. X-ray
crystallography, solid-state NMR and Hirshfeld analysis of intermolecular
forces were applied to investigate possible rotational motion of the central
phenyl ring in propargylic alcohol derivative 1.
Electron Spin Resonance [ESR] Spectroscopic Studies of Some Organosilyl-substituted Styrene Radical Anions. James W. Rawles III and H. J. Sipe, Jr. Department of Chemistry,
Radical anions of trans-beta-trimethylsilyl styrene, cis-beta-methyl-trans-beta-trimethylsilyl styrene, and para-methyl-trans-beta-trimethylsilyl styrene were prepared using the sodium/potassium reduction technique in a solvent of 2:1 ratio of MeTHF:DME in sealed evacuated sample tubes. The radical anions were studied using variable temperature electron spin resonance spectroscopy. Hyperfine coupling constants were estimated from the experimental spectra by direct measurement and by simulation using a software package, WinSim, that is available from NIEHS. WinSim was used also to refine and optimize the coupling constant assignments through a simplex optimization algorithm. Theoretical values of the hyperfine coupling constants were calculated using density functional theory in the Gaussian 03W software package. Hyperfine interactions with the silyl methyl group hydrogens were significantly non-zero in all cases indicating an extended electron delocalization over the entire molecules. As the p orbitals of the silicon atom are all providing sigma bonds to the four carbons around the silicon, the silicon p orbitals can not participate in the pi system of the styryl moiety. It is proposed that one or more of the unoccupied silicon d orbitals participates in the pi electron system of styryl pi electron system thereby providing a means of electron delocalization throughout the silyl-substituted styrene molecules.
Title: Analysis of Lead and Iron Content of Synthetic
and All-Natural Lipsticks
April M. Queen and Dr.
Kenneth S. Overway
Department of Chemistry,
Abstract:
Choosing a cosmetic brand or
type does not seem like a trivial task for most consumers, especially when it
comes to the area of safety. However,
with the latest speculations proclaiming that lipstick contains lead, and that
the average woman consumes pounds of it in her lifetime, the safety of those
cosmetics seems more important. Leading
brand-name cosmetic companies whose products have recently been tested for lead
claimed that it was found in their product as a contaminant from the mining of
iron oxides. Therefore it could be
hypothesized that the more iron a cosmetic product has, the more lead
contaminant it has. This project tested
the levels of both lead and iron in a variety of synthetic and all-natural
lipsticks. First the lipstick samples
were burned in ceramic crucibles, and their ashes were dissolved in nitric
acid. Calibration curves and metal
concentrations were measured using an atomic absorption spectrometer. The results showed that while there is no
significant trend between the different lipstick brands, there does seem to be
a trend in the individual lipstick. If
the lipstick contains iron, it generally contains a significant amount more of
lead. Even those products that had
undetectable amounts of iron still seemed to have some amount of lead over the
background level. Most lipsticks showed
a significant and dangerous amount of lead, when compared to the allowable lead
of candy according to the FDA, since federal laws have yet to be established
for legal limits of lead in cosmetics.
Development of GC-MS and Chemometric Methods for the Analysis of Accelerants in Arson Cases
Boone M. Prentice, Sarah E. G. Porter, and Melissa C. Rhoten
Department of Chemistry and Physics,
There is an interest in the forensic community in identifying accelerants by their gas chromatography-mass spectrometry (GC-MS) profile. In this work, samples of accelerants were analyzed by GC-MS and compared using chemometric analysis. Four analytical standards (unweathered gasoline, diesel fuel, kerosene, and mineral spirits) were purchased from Restek®, and regular, mid-grade, and premium unleaded gasoline were purchased at the local Valero gas station. GC-MS analysis was performed on a 30m x 0.25 mm x 0.25 µm VF-1ms capillary column using a Varian GC-MS system with the following conditions: split injection (3:1) at 250 ºC; temperature programmed from 50 (2.5 min isothermal) to 300 (5.83 min isothermal) at 15ºC/min; helium carrier gas at a flow rate of 1 mL/min. The GC-MS chromatograms were assembled into a single data set and compared using principal component analysis. A pattern recognition algorithm was developed based on the variance-covariance matrix of the data set. Replicate analyses of the analytical standards constituted a set of training data to which the purchased gasoline samples could be compared.
The Effect of Land
Use on the Nutrients and Organic Contaminants in the Water and Sediment of the
Jenae Pinney1, Rebecca
Shapiro2, Charles Sharpless1, Ben Odhiambo2. (1) Department of Chemistry (2) Department of
Earth and Environmental Sciences,
The degradation of the
Graywater Recycling Using a Biological Treatment
System
Anna M. Pavlovskaya
and Dr. Kenneth S. Overway
Department of Chemistry,
The demand for and scarcity
of clean water in some areas of the world has made water recycling an appealing
solution. The reuse of blackwater has been an
unattractive venture in some municipalities; however, the reuse of graywater, which contains minimal contaminants, is a better
solution. The main objective of this project was to determine whether a soil
and plant system could be used to clean up household graywater
containing laundry detergent as the main contaminant. Household gutters were
set up so that the graywater would run through the
soil containing grass, clover or ornamental peppers and be collected at the end
of the gutter. Synthetic graywater was made using tap
water and Tide Clean Breeze powder detergent which also contains some
fluorescing compounds. Fluorescence spectroscopy and Chemical Oxygen Demand
(COD) were used to analyze the removal of detergent from the waste water. The
fluorescence levels in the graywater were a factor of
three higher than the levels in the remediated water,
indicating that some clean up had occurred. The COD qualitatively confirmed
that lower levels of nutrients are present in those samples that were remediated through the biological system.
Electrochemical
detection of gonadotropin releasing hormone
Abstract:
Dynamics of chemical signaling are not well understood because there are few rapid techniques to measure neurochemicals. Gonadotropin releasing hormone (GnRH) is a peptide hormone that stimulates the synthesis and secretion of the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The goal of this study is to detect GnRH, which contains trytpophan and tyrosine residues. Fast-scan cyclic voltammetry (FSCV) at a carbon fiber microelectrode was used to make measurements. We first looked at electrochemical properties of tryptophan and tyrosine and observed a main oxidation peak. Then, we studied the electrochemical activity of GnRH and observed both main and secondary oxidation peaks. In the near future, this could be used to study GnRH signaling in the brain.
Title: Cloning, expression and purification
of Opa proteins from Neisseria gonorrhoeae and a human CEACAM binding
partner
Author
List: Huong Thien Nguyen, Christopher Reyes, Izabela
Bielnicka, (Linda Columbus)
Department: Chemistry
The obligate pathogen Neisseria gonorrhoea
depends on adhesion membrane proteins known as Opa
proteins for host infection. Studies
have shown that specific binding of Opa proteins to
receptors such as heparin and CEACAM on endothelial cell membranes induces endocytosis of the bacterium. The overall goal of this project is to study
the binding interactions of the human CEACAM1 N-domain with the pathogenic Opa hypervariable (HV)
domains. Preliminary steps have been
taken to clone the genes of Opa 60 and CEACAM1,
express the genes in E. coli, and
purify the proteins. Progress thus far
includes the successful cloning of the gene for Opa
60 (Opa I) into the pET28b vector, induction of overexpression of the gene, and harvesting of the protein
from inclusion bodies. CEACAM1 was
prepared according to previously documented protocols. Current work is dedicated to optimization of
refolding Opa proteins and the purification of the
binding partner CEACAM1 in various detergents to maximize stability of the
protein-detergent complex. Functional
forms of these proteins will allow for future, systematic, biophysical
characterization of individual proteins and their interactions.
“Soil Testing at
the
Richard Mullenberg, Dr. Everett Carpenter
Department of Chemistry,
Abstract: Soil samples were taken from various sites at the Inger and
NMR Analysis of Alcohol/Water and Alcohol/Alcohol
Mixtures
Ian J. McNeil and Dr. Erich
E. Brumbaugh
Department of Chemistry,
Understanding the molecular
environment of aqueous solutions is important to both biological and nonbiological systems. The physical characteristics of
mixtures such as partial molar volume, density, and heat of mixing have been
examined and documented in the past. The effects of hydrogen bonding upon these
physical phenomena however are still a mystery. This project uses NMR spectra
to analyze the change of the electron environment caused by hydrogen bonding of
the protons in alcohol/water and alcohol/alcohol mixtures. The solutions
analyzed were methanol/water, 1-propanol/water, 2-propanol/water,
1-Propanol/methanol, and 2-propanol/methanol. The results corroborated with the
literature in the fact that the methyl protons experience less change in
environment than the hydroxyl protons. Also the hydroxyl protons experienced
maximum changes most often at around 0.3, 0.5, and 0.7 mole fraction,
which correspond to the stoichiometric ratios of 1:2,
1:1, and 2:1.
Charge transfer
interactions in complexes formed by fullerene with derivatives of calix[4]arenes
Kathryn Lukehart and Karl Zachary,
The complexation behavior of C60 (fullerene) with a series of ether and ester derivatives of calix[4]arene was investigated using UV-Vis spectroscopy and quantum chemical methods. Evidence of charge transfer interactions was observed in the UV-Vis spectrum of these complexes. Ab initio and semi-empirical quantum chemical calculations were carried out in order to interpret the experimental results.
"Electrophoretic Trapping and Elution of DNA on a
Conductive Polymer/Glass Hybrid Micro-device"
Chrystal
Lopez (
Inexpensive
materials such as conductive silicon sheets, glass, copper tapes and epoxy can
be used to fabricate a functioning micro-device for the electrophoretic trapping
of DNA. With smaller volume fractions at high concentrations, DNA was eluted
from the micro-device, a characteristic desired in integrated microchip genetic
analysis. The conductive silicone layer serves as both the
conductive electrode and a layer for channel formation; inexpensive air plasma
oxidation bonded the silicone layer to glass. Access holes were drilled in the
glass, and reservoirs were glued to the top using epoxy. The fabrication
process was simplified dramatically by eliminating the photolithographic
procedure. The electrophoretic movement of fluorescein dye and
negatively-charged fluorescent polystyrene beads was investigated using
single-channel micro-devices. A DC voltage was applied
perpendicular to the channel direction, generating an electric field across the
channel during fluid flow. Preliminary
results showed that 2.4 V was enough to drive fluorescein toward the cathode
sidewall while flowing at a rate of 3.0 µL/min; with fluorescence microscope, a 5-fold concentration increase was observed
close to the outlet within 2 minutes. With the 2 um fluorescent beads, a
concentrated stream was formed within 30 seconds using 3.0 V and a flow rate of
1.0 µL/min. With a split channel design, lambda phage or human
genomic DNA could be captured using 3.0V at flow rates up to 42 µL/sec.
Application of a -3.0 volt pulse was effective at releasing the captured DNA in
the channel. Using PicoGreen
quantification, it was found that a fraction of 5 fold increased concentration
was achieved at the releasing phase with reduced volume. With the low voltage
required for operation, this simple hybrid device has the potential to capture
a plethora of charged species other than DNA such as dyes and polymer beads
using only battery power. Accordingly,
the direction of concentrated fractions into designated reservoirs for
downstream applications in an integrated micro-fluidic system that could be
achieved within minutes.
Conformational Changes in Synaptotagmin I C2A Upon Membrane Binding
Authors: Judith Lin, David Cafiso and April Frazier
Synaptotagmin I is believed to function as the calcium sensor in neurotransmitter release. This synaptic vesicle membrane protein contains two water soluble C2 domains, C2A and C2B, that bind independently to membranes in the presence of Ca2+. The structures of C2A and C2B have been determined in solution, but their structures bound to the membrane are not known. To determine whether the structure of the C2 domain changes upon membrane binding, distances were measured within C2A in the presence and absence of membranes. A method termed site-directed spin labeling (SDSL) was used, which involves the incorporation of nitroxide spin labels by site-directed mutagenesis. To measure distances, pairs of cysteine mutants in C2A were derivatized using a methanethiosulfonate spin label. A dipolar interaction between a pair of spin labels produces linebroadening in the EPR lineshape, which can be used to estimate distances. Preliminary results indicate that the EPR spectrum broadens upon the binding of C2A to unilamellar vesicles consisting of phosphatidylcholine and phosphatidylserine. This broadening is due to a dipolar interaction between spin labels and indicates that structural changes take place in C2A upon association with the membrane.
Design and Development of H8-BINOL
Derivatives for Applications in Asymmetric Catalysis
Megan Kobiela, Mark Turlington, Albert DeBerardinis
Dr. Lin Pu,
H8-BINOL and its derivatives have shown to be effective chiral ligands in asymmetric catalysis. Novel catalysts are designed by functionalizing the 3 and 3’ positions of the H8-BINOL template; the Mannich-type reaction of H8-BINOL, paraformaldehyde, and a secondary amine has proven to be a highly useful synthetic strategy in the synthesis of these ligands. The chiral ligands will be screened for their application in asymmetric alkynylations, arylations, and kinetic resolution of secondary alcohols.
Palladium Catalyzed Decarboxylative Allylation: Asymmetric Induction and Tandem C-C Bond Formation
Ali K. Khan, Michelle M. Archibald, Wendy H. Fields, Andrew A. Yeagley, and Jason J. Chruma,*
Department of Chemistry,
Homoallylic imines are valuable building blocks in organic synthesis, typically generated by the addition of organometallic nucleophiles into electrophilic imines. Our protocol, which employs an inverse reactivity profile, proceeds rapidly at room temperature in the presence of a palladium (0) catalyst without generating stoichiometric amounts of inorganic and/or organic byproducts (one equivalent of CO2 is the sole byproduct). Additionally, the use of palladium catalysts allow for the possibility of one-pot tandem C-C bond forming events. To this end, we have demonstrated a tandem decarboxylative allylation-Heck cyclization manifold with o-iodo and o-bromoarylaldimines to create a variation of bicyclic systems useful for natural product synthesis. Progress toward an enantioselective variant of the novel palladium-catalyzed dercarboxylative allylation will also be presented.
First-principles
determination of isotope effects on electric dipole moments
S. L. Hobson, E. F. Valeev, Virginia Tech
To facilitate interpretation of experimental high-resolution
molecular spectra, this project explores computationally how the isotopic
substitution affects the electric dipole moment. The dipole moments of three pairs of isotopomers – H2 and HD, LiH
and LiD, and BH and BD – were computed using an ab initio approach
implemented in an open-source quantum chemistry software package PSI3. The dipole moment function was evaluated by
numerical differentiation of the diagonal Born-Oppenheimer correction (DBOC)
and then vibrationally averaged. The predicted dipole moment for HD, 8.64x10-4
Debye, agrees perfectly with the experimental value of 8.31x10-4 Debye. The
agreement between theory and experiment is significantly worse for LiH and LiD. The isotope effect on the dipole moment in LiH/LiD seems to be anomalously large and suggests that
truly nonadiabatic effects may be at play. The validity
of using DBOC for dipole moment computation is therefore still under
evaluation.
Title: Carbon nanotube modification of carbon-fiber microelectrodes
Author: Neil Hershey
Carbon nanotubes have recently been studied because of their unique physical properties. In my studies, I coated carbon-fiber microelectrodes with carbon nanotubes to increase the sensitivity for the detection of neurotransmitters. The nanotubes increase the number of adsorption sites for the cationic neurotransmitter dopamine, which leads to a larger currents detected with cyclic voltammetry. However, the signal did not increase as much for the anionic dopamine metabolite, dihydroxyphenylacetic acid (DOPAC). Experimentation with other neurotransmitters and varying coating conditions will lead to more sensitive and selective neurotransmitter sensors.
Substrate Specificity of Tabersonine
16-Hydroxylase in Catharanthus roseus, Weslee S. Glenn, Department of Chemistry, Hampton
University; Lesley-Ann Giddings, and Sarah E. O’Connor, Department
of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, 02139.
Catharanthus roseus is a plant that produces thousands of biologically interesting natural products such as vinblastine, a terpene indole alkaloid, which is noted for its anti-cancer activity. In order to produce novel unnatural terpene indole alkaloids with potentially enhanced biological activity, the substrate specificity of the enzymes utilized in the biosynthesis of vindoline, vinblastine’s precursor, must be investigated. The enzyme tabersonine 16-hydroxylase is a key enzyme involved in the biosynthesis of vindoline.
The goal of the project was four-fold: (1) to isolate both the tabersonine 16-hydroxylase and P450 reductase genes from C. roseus cDNA; (2) to clone genes in an optimized plasmid for expression; (3) to express, isolate and purify the resulting fusion protein, tabersonine-16-hydroxylase-reductase and (4) to develop a sensitive radiolabeled assay to test for the activity of the resulting protein.
The work focused on the amplification and isolation of the tabersonine 16-hydroxylase, which was not protractable through the Polymerase Chain Reaction (PCR) method, and the 4-hydroxylase and acetyltransferase enzymatic genes downstream in the pathway from tabersonine to vindoline. Preliminary results show full protraction of the vindoline acetyltransferase gene.
Energy Minimization Simulations in Binary Liquid
Solutions Using HyperChem 7.5 with Emphasis on
Water/Alcohol Systems
Stephen R. Garletts and Dr. Erich E. Brumbaugh
Department of Chemistry,
When two different liquids
are combined to form a single solution, the behavior of the resultant system
can be difficult to predict. The goal of
this experiment was to gain a better understanding of how different
water/alcohol solutions interact in hopes that findings from this experiment
could help better predict how other solutions might interact with one
another. Bulk water hydrogen bonds with itself forming a shifting tetrahedral lattice. When just one molecule of non-water is
introduced into a bulk water system, the water molecules surrounding the
non-water molecule are forced to alter their bonding patterns to accommodate
the newly introduced molecule. A
software program called HyperChem 7.5 was used to
measure the amount of disturbance caused to a bulk water solution when
different alcohols were added to the water solution. The results at this time are insufficient for
identifying trends that may occur in such situations. It remains uncertain whether or not HyperChem 7.5 can be used to gain insight regarding the
behavior of binary liquid solutions and to compare with physical data we have
obtained as a group.
A VISUAL MICROFLUIDIC DNA
DETECTOR
Lindsay
A. Legendre**, David Finkler*, J. Patrick LeDuc*,
Gabriela Duarte, Carol Price and James P. Landers*,**
*
Phone: 434-243-8658, Fax: 434-982-3048
Contact
E-MAIL: finkler@virginia.edu
**
