Abstracts Submitted from Chemistry and Biochemistry
Undergraduate Summer Research Symposium August 12, 2009

Ordered alphabetically by student's last name

Allen Genoese Linton McAneny Sforza
Bugglin-Borer Hailey LoGiurato Meyer Shurtleff Wheatley
Darrington Hartman Mahon
Michira Straney

Davis, K Larsen Marsan Polotti Styer

Structural Studies of Microtubule assemblies: Dynein and Dynactin

Donald Allen, Nicholas Audette, Jayme Wildin, Shangjin Sun, Si Yan, John C. Williams1, Tatyana Polenova
Department of Chemistry and biochemistry and 1City of Hope, Dept. of Molecular Medicine, 1500 East Duarte Road, Duarte, CA 91010

The cytoskeleton is an integral part of eukaryotic cells, and is involved in maintaining cell shape and facilitating intracellular movement.  Disruption of the cytoskeleton and associated proteins has been implicated in a wide range of diseases ranging from motor neuron disease1 to mechanisms involved in viral infections2.  This project focuses on structural studies of microtubules and their associated motor proteins.  The long-term goal is to pursue structural analysis of dynein and its activator dynactin and to investigate their interactions with the microtubules.  The main current objective has been to isolate and purify isotopically labeled tubulin from S. cerevisiae (yeast), which will allow us to study these motor proteins bound to microtubules in addition to structural studies of CAP-Gly and DLC8 that are currently under progress.

(Eric, at right, could not present his poster because, as a member of a Delaware wildland firefighting crew, he was called to duty in California. See News J. story.)
Parkinson's Disease: Exploring the Role of Nitration of Tyrosine 125 in the Aggregation of α-synuclein

Eric D. Bugglin-Borer and  Neal J. Zondlo
Department of Chemistry and Biochemistry

Parkinson's Disease is the second most prevalent  disease among the elderly in the US. A key symptom is the formation of Lewy bodies which are composed of iron and insoluble aggregates of nitrated α-synuclein, a protein found in neurons.  Nitration decreases both the pKa of the Tyrosine residue and the electron density of the phenolic ring, which may increase reactivity necessary for aggregation. TXPN  (X=3-nitrotyrosine), a model peptide, was used to explore the altered electronic state of the residue. Amino acids, such as Tyrosine, containing an electron rich phenolic ring have been shown to stabilize Proline's electron deficient α- Carbon by adopting a cis conformation. It was hypothesized that the electron deficiency of nitrated Tyrosine will favor the trans conformational state.  1H NMR was used to compare the incidence of cis/trans isomerism of TYPN and TXPN.  A peptide from the C-terminus of α-synuclein important to aggregation was synthesized in both the nitrated and wild-type forms. 1H NMR was used to assess differences in coupling constants, which would suggest altered secondary structure. Metal binding assays were done with TbCl3 in order to determine a binding constant for each peptide which could be indicative of chelating properties..  This has the potential to increase our understanding of the mechanism of the formation of Lewy Bodies in Parkinson's disease.

Kinetic and Product-Ratio Analysis of Propargyl Chloroformate

Anthony M. Darrington, Malcolm J. D'Souza, and 1Dennis N. Kevill
Wesley College, Dover DE.,  1Northern Illinois University, DeKalb IL.

For almost 150 years, scientists have been trying to understand the correlation between solvent effects, chemical structure and chemical reactivity. This knowledge has been applied to the development of compounds, which are designed to either stimulate or block other chemicals from interacting with targeted receptors on cells. The effect of solvent variation on the specific rates of solvolysis of the pharmaceutical precursor propargyl chloroformate was analyzed using the extended Grunwald-Winstein equation. By understanding this linear free energy relationship (LFER), we can determine the reaction mechanism supported of this compound. Understanding the reaction mechanism will allow pharmaceutical researchers to better utilize this important precursor and lead to enhanced drug designs. This project was supported by NIH NCRR INBRE grant number 2 P20 RR016472-09 and NASA Grant NNG05GO92H Delaware Space Grant College and Fellowship Program.

Characterization of HIV-1 gp41 mimic six-helix bundle formation

Kyle F. Davis, Aaron Lee and Neal J. Zondlo
Department of Chemistry and Biochemistry

The gp41glyco-protein of the HIV virus plays an integral role in CD4+ cellular membrane fusion and subsequent infection. Before membrane fusion, gp41 assumes a fusogenic state, exposing C- and N- terminal α-helical heptad repeats (HR) in the protein’s sub-structure. At this stage in gp41’s entry, these trimeric coiled coil HRs seek to form a six-helix bundle, bringing the viral and cellular membranes in close proximity. Their exposure however provides an attractive site for HIV inhibition. A highly conserved hydrophobic pocket near the N-terminus of gp41 has been of particular interest as a target for HIV inhibitory molecules. Previous studies targeting the fusogenic state of HIV have employed short complimentary alpha-helical peptides.   In our studies we seek to take advantage of the correspondent distances between the functional groups on the alpha-helix face and a designed molecular scaffold. By optimizing functional groups attached to this scaffold, we hope to obtain a high affinity molecule capable of inhibiting HIV-1 membrane fusion. To characterize six-helix bundle formation, our assay development utilizes two main techniques. First we have developed a fluorescence polarization assay using a designed gp41 N region mimic (KDII) and a fluorescein labeled C-peptide mimicking the gp41 C-region (C15), of which we have determined the dissociation constant and demonstrated the peptides’ relative affinities. Circular dichroism was performed at varying concentrations and ratios of both peptides to examine the extent of bundle formation. This research was funded by HHMI.

Unspecific Incorporation of Selenium in Proteins by
Escherichia coli

Angela A. Genoese, Wayne A. Wilkie, and Sharon Rozovsky
Department of Chemistry and Biochemistry

Selenium is an essential trace element located below sulfur in the periodic table. Selenium can replace sulfur in many biological reactions due to similar chemical properties. While sulfur is not easily detectable by NMR, selenium (specifically isotope selenium-77) is suitable for NMR detection. Therefore, selenium NMR may be used to investigate the role of sulfur in protein structure and function. The purpose of this research was to find an efficient method of incorporating selenium in the place of sulfur in Escherichia coli. Two proteins were used in testing the incorporation of selenium; these proteins were a Green Fluorescence Protein and Thioredoxin. Several sulfur free growth medias were used to test to ensure that sulfur is indeed excluded from the media. After a suitable sulfur media was identified, we tested the effect of the presence of selenite (SeO32-) and selenate (SeO42-) in the media on cell growth and protein overexpression. At selenite concentrations of 50.0μM protein expression was greatly reduced. However, for selenate at concentrations of 50.0μM protein expression was about a tenth of that in the presence of sulfur. The samples of Thioredoxin grown in the presence of selenite or selenate will be further analyzed by mass spectroscopy to see whether selenium is incorporated in the protein.

Analysis and Comparison of Thionocarbonyl Compounds

Stefan M. Hailey and Malcolm J. D’Souza
Department of Chemistry, Wesley College, Dover, DE

Many thionocarbonyl esters such as 4-fluorophenyl chlorothionoformate are used as precursors to prepare low molecular weight protease inhibitors which can be effective anti-HIV agents or useful AIDS treatments.  These compounds have also proven to be effective as pro-drugs against the microbial infection, Pneumocystis carinii pneumonia (PCP) and have other potential for their anti-Hepatitis B virus activity.  The specific rates of solvolysis of 4-fluorophenyl chlorothionoformate and methyl chlorothioformate have been analyzed and compared using the extended Grunwald-Winstein equation.  Previous research from this laboratory has shown that methyl chlorothioformate solvolysis occurs via a bimolecular, addition-elimination pathway in the more nucleophilic solvents.  This dominant pathway changes to a unimolecular, SN1, pathway in the more ionizing solvents.  Thus, comparing the solvolytic trends of both 4-fluorophenyl chlorothionoformate and methyl chlorothioformate is of great interest in understanding electronic effects. We acknowledge the NIH NCRR INBRE grant 2 P20 RR016472-09 and the Delaware Biotechnology Institute.

Inherent Antibacterial Activity of a β-Hairpin Peptide Hydrogel:
The Effect of the Lysine Side Chain Length on Activity

Heather A. Hartman, Daphne A. Salick, Monica C. Branco, and Joel P. Schneider
Department of Chemistry and Biochemistry

Self-assembling peptide hydrogel scaffolds have the potential for use in tissue regenerative therapies.  Hydrogels provide an ideal, hydrated, porous environment for tissue growth.  However, for the implantation of a biomaterial, many design considerations and precautions must be met, in particular preventing the introduction of infection.  We have designed a lysine-rich peptide, MAX1, which self-assembles to form a hydrogel whose surface is active against Gram-positive (Staphylococcus epidermidis, Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Klebsiella pneumoniae and Escherichia coli) bacteria, all prevalent in hospital settings.  Although detrimental towards bacteria, the surface is cytocompatible towards a variety of mammalian cells, making these hydrogels attractive candidates as tissue engineering scaffolds. This study will focus on determining the effect of the length of the lysine side chains of MAX1 on the material properties as well as the antibacterial activity of the hydrogel surface.  A new peptide sequence, HPL1, was designed, in which the lysine residues were homogenously replaced by ornithine, a methylene deficient derivative of lysine.  The biophysical properties of HPL1 were be analyzed using circular dichroism spectroscopy and oscillatory shear rheology and were found to be similar to that of the parent peptide, MAX1.  Within 24 hours of exposure to gram-positive Staphylococcus aureus, HPL1 surfaces showed a reduced efficacy of antibacterial activity.  After 48 hours, the HPL1 hydrogels showed reduced antibacterial activity at S. aureus concentrations as low as 2 x 105 colony forming units(CFU)/dm2.  By comparison, HPL1 showed an increase in antibacterial activity against gram-negative Escherichia coli when compared with MAX1 hydrogels.  Next, the antibacterial activity of HPL1 surfaces were assessed to determine the efficacy of the antibacterial activity against other gram-positive and gram-negative species. This research was funded by and HHMI summer scholarship.

Inherently Antimicrobial Hydrogels - Altering Behavior via Tryptophan/Arginine Interactions

Tyler Larsen, Daphne A. Salick, Radhika Nagarkar,  and Joel P. Schneider
Department of Chemistry and Biochemistry

Hydrogels are heavily hydrated materials that show considerable promise as artificial extracellular matrices for use in tissue regenerative therapies.  The development of antibacterial hydrogels has been of great interest to the hydrogel research community as a means to combat the threat of infection during material implantation. We have developed MAX1, a self-assembling beta-hairpin peptide hydrogel whose surface exhibits inherent antibacterial activity against several pathogens prevalent in hospital settings.  Under physiological conditions, MAX1 self-assembles into a highly crosslinked, mechanically rigid hydrogel whose solvent-exposed fibrils display positive charge, which is thought to be important for antibacterial activity.  This study aims to investigate the contributions of a cation-pi interaction to the antibacterial activity of a newly designed peptide hydrogel.  Cation-pi interactions are a common feature of many antibacterial peptides, where they assist in the disruption of bacterial membranes.  Thus, a new beta-hairpin peptide(RWMAX1) was designed, incorporating a cross-strand Tryptophan/Arginine pair, with the aim of creating a more potent antibacterial hydrogel.  The folding and self-assembly properties were assessed using circular dichroism and rheology and the antibacterial activity was investigated against gram-positive S. aureus.  This work is supported by funding from the Arnold and Mabel Beckman Foundation.

Prevention of Aggregation of Platelet-Activating Factor Acetylhydrolase Type II Through Site-Directed Mutagenesis

Sam S. Linton, Elizabeth M. Sedlack, and Brian J. Bahnson
Department of Chemistry and Biochemistry

Human Platelet-Activating Factor Acetylhydrolase Type II (PAF-AH II) is a 44 kD monomeric enzyme that belongs to group VII of the PLA2 superfamily. A medically important enzyme, PAF-AH II plays a role in inflammation events such as sepsis, atherosclerosis, and asthma. Often thought of as a scavenger, PAF-AH II seeks and subsequently hydrolyses oxidized phospholipids, Platelet-Activating Factor (PAF), and other structurally similar molecules that contribute to inflammation events in vivo. Using a recently constructed homology model of the enzyme, it was predicted that PAF-AH II contains five hydrophobic amino acid residues, namely Leu-76, Leu-79, Leu-327, Ile-328, and Phe-331 that embed themselves in the inner membrane. Presumably, the nature of these hydrophobic residues is the cause of aggregation observed when the wild-type protein is overexpressed, making PAF-AH II exceedingly difficult to crystallize. The five aforementioned hydrophobic residues of interest were targeted for site-directed mutagenesis. The main aim of this project was to systematically change each of the five hydrophobic residues to serine, a compatible hydrophilic amino acid residue in an effort to keep the protein from aggregating. Polymerase Chain Reaction (PCR) was implemented in creating the mutants. The work done thusfar represents the first step in the eventual crystallization of mutant PAF-AH II. Funding provided by HHMI and the following NIH grants: COBRE 2P20RR015588 and 1R01HL084366.

Using 4-Fluoroprolines to Investigate cis-trans Isomerization in Tau Peptides

Brendan LoGiurato, Agata A. Bielska, Krista M. Thomas, Devan Naduthambi, Gasirat Tririya, and Neal J. Zondlo
Department of Chemistry and Biochemistry

Tau pathologies, termed tauopathies, are among the most promising therapeutic targets for Alzheimer's disease. In an Alzheimer's patient, tau protein aggregates into neurofibrillary tangles (NFTs), one of the hallmarks of Alzheimer's-related neurodegeneration, that primarily consist of hyperphosphorylated tau. Tau contains a proline-rich domain with several Ser/Thr-Pro sites that are particularly susceptible to hyperphosphorylation and that, upon phosphorylation, cause a conformational change in tau that may promote aggregation. These Ser/Thr-Pro motifs are inherently subject to cis-trans isomerization due to proline's unique ability to adopt a cis amide bond. The Thr231-Pro232 sequence in tau is particularly crucial since it can be phosphorylated by tau kinases and is recognized by the Pin1 prolyl isomerase, which plays a pivotal role in AD since the protein phosphatase 2A enzyme can only dephosphorylate this site in the trans-conformation. Thus, the conformation of the Thr231-Pro232 bond is crucial to the understanding of tau aggregation. In order to probe the role of the cis and trans conformation of the Thr231-Pro232 bond, we have synthesized three tau peptides incorporating fluoroproline that favor either the cis or trans conformation of this bond, as well as a peptide that reduces the activation energy for isomerization. 4-(S)-fluoroproline uniquely stabilizes a cis-peptidyl-prolyl bond, 4-(R)-fluoroproline stabilizes a trans peptidyl-prolyl bond, and 4,4-difluoroproline reduces the energy of isomerization. These peptides, both phosphorylated and non-phosphorylated versions, were analyzed by CD and NMR spectroscopy to identify conformational changes dependent upon the proline derivative. This research was funded by HHMI.

Thermodynamic Analysis of Solvolytic Reactions Involving Thiolesters

Brian Mahon, Malcolm J. D'Souza, and Dennis N. Kevill
Wesley College, Department of Chemistry.Northern Illinois University Department of Chemistry and Biochemistry

Thiolesters are very useful in many pharmaceuticals. Their use in viricidal drugs and elastase inhibitors has shown to be successful treatments of many diseases. The purpose of this experiment is to fully analyze the mechanism of these compounds, specifically S-isopropyl chlorothioformate, at a range of temperatures. The results will be compared to previous research where this particular compound was tested at one temperature.  In the past what was shown was a favoring of the ionization mechanism in most solvents. This was predicted by the assumption that sulfur would use its electrons in a stabilizing interaction with the adjacent electron deficient carbocation. Here, the variance in activation energy was thought to play a role in the influence of the formation of the alkene during solvolysis. This was shown using various equations involving enthalpy and entropy changes to determine the amount of change in activation energy. Also, to observe the dependence of the rate constant of chemical reactions on the temperature the Arrehenius Equation was used. This in combination with the extended Grunwald-Winstein equation allowed the rates of reaction to be fully analyzed.

Preparing a fluorigentic ubiquitin substrate using intein chemistry

David Marsan, Jialiang Wang, and Zhihao Zhuang
Department of Chemistry and Biochemistry

Modification of proteins by ubiquitin and ubiquitin-like proteins is an essential part of biological processes in eukaryotes, such as the control of stability, function and intracellular localization of different proteins. The development of Ubiquitin-7-amino-4-methlycoumarin allows it to be used as a fluorescence substrate for a variety of deubiquitinating enzymes (DUBs). This compound is capable of being used for ubiquitin C-terminal hydrolyses and ubiquitin specific proteases. Though this compound has many uses the cost to manufacture this compound makes it difficult for individual researchers to use it in large amounts. Here we show a way to develop Ubiquitin-7-amino-4-methlycoumarin using much cheaper and readily available compounds. Using intein chemistry we have developed a way that allows us to prepare a fluorigentic ubiquitin substrate that can be used as an assay for monitoring the enzymatic activity of deubiquitiniating proteases.

Kinetic Evaluation of s-Isobutyl Chlorothioformate

Matthew J. McAneny and Malcolm J. D’Souza
Department of Chemistry, Wesley College, Dover, Delaware

Thiochloroformate esters are often used as intermediates in the synthesis of novel pro-drugs that are activated by the organism by means of natural biochemical processes.  As a result there has been there has been significant interest in their hydrolysis, alcoholysis, and aminolysis processes, as such reactions are useful models for enzymatic mechanisms. The effects of solvent variation of the available specific rates of solvolysis of s-isobutyl chloroformate, are analyzed in terms of the extended Grunwald-Winstein equation using the NT scale of solvent nucleophilicity (S-methyldibenzothiophenium ion) combined with a YCl scale based on 1-adamantyl chloride solvolysis. Previous studies found that alkyl or phenyl chlorothioformates solvolyze in the more nucleophilic solvents by an addition-elimination mechanism with the addition step being rate-determining and in the highly ionizing solvents, the mechanism is unimolecular.

Reactivity of Cobalt, Copper, and Chromium Bis-Pyrazolyl Alkane Complexes

Andrew J. Meyer, John F. Young, and Klaus H. Theopold
Department of Chemistry and Biochemistry

Poly-pyrazolyl alkanes are highly versatile neutral ligands, which form transition metal complexes that are potentially useful as catalysts for important industrial processes. The structure and reactivity of these compounds are similar to well known poly-pyrazolyl borate complexes in that they both can be used to control the electronic and steric environment around a transition metal. Two bis-pyrazolyl ligands were examined: bis-(pyrazolyl)cyclopentane and bis-(3,5-dimethylpyrazolyl)methane. These ligands were successfully coordinated with cobalt(II), copper(II), and chromium(II) halide salts to form ligand-metal-halide complexes, which were characterized by paramagnetic NMR and X-ray diffraction crystallography. Carbonyl compounds were formed by reducing the metal halide complexes with potassium graphite and introducing carbon monoxide gas. The carbonyl compounds were characterized by infrared spectroscopy to examine the electronic nature of the metal-ligand bonds. Finally, the metal halide complexes were alkylated using methyl-Grignard and methyl lithium reagents. These compounds have yet to be fully characterized due to solubility issues. Future work will focus on different bis-pyrazolyl alkane ligands as well as compounds that bind oxygen and dinitrogen. This research was made possible by the assistance of the members of the Theopold Group, and funded by a generous grant from Mr. David Plastino through the Chemistry Alumni Fellows program.

Antiandrogen Effect on Recruitment of CoRepressors and Nuclear Localization of Androgen Receptor

Alfayo Michira, John T. Koh, and Kathy Miller
Department of Chemistry and Biochemistry

Androgens such as testosterone activate the proliferation of prostate cancer through interaction with the androgen receptor. Antiandrogens are used for the treatment of prostate cancer by blocking and disrupting the androgen receptor’s trans-activation mechanism. Cancer cells can develop resistance to antiandrogens by altering cellular AR signaling by mutating AR so that it is activated by the antiandrogen or other hormones, over expressing the AR leading to the expression of genes in the nucleus and activating other cytokines responsive pathways.  These alterations in AR signaling can lead to recruitment of  coactivators to AR even in the presence of antagonists, whereas compounds that block nuclear localization should be able to block transcription by AR.  Over expression/ cytokine activation can lead to recruitment of coativators and abnormal AR signaling in the presence of antiandrogens. However, antiandrogens may cause co-activators not to be recruited indicating that corepressors may take part in the antagonistic activity leading to the blocking of the AR signaling in prostate cancer.  The Koh lab has recently developed a new structural class of antiandrogens with long extensions to more fully disrupt the co-activator binding surface.  Using AR-GFP ligand induced localization of AR has been evaluated in LNCaP cells and CV1 cells.  Additionally, constructs necessary to examine co-factor recruitment to AR by mammalian two hybrid assay have also been constructed.  Preliminary results suggest that Pan52,  a new antiandrogen developed at UD has a superior ability to reduce AR localization in cells.  Acknowledgement: This work is supported by HHMI and funded by the Department of Defense.

Redox Active Ligands: Ferrocenyl Substituted "NacNac" Ligands

Charles F. Polotti, Jr. and Klaus H. Theopold
Department of Chemistry and Biochemistry

Ferrocenyl-substituted ligands have many useful applications in coordination chemistry. Ferrocene exhibits reversible electrochemistry, thus allowing variation of complex charge by oxidation of the ligand. Redox active ligands have an ability to readily accept or donate electrons, which can affect the reactivity of the transition metal to which these ligands are coordinated.  The synthesis of our version of such ligands begins with the preparation of 1-aminoferrocene. We have studied two published synthetic routes to 1-aminoferrocene. The first involves the lithiation of ferrocene with t-BuLi followed by bromination using liquid bromine. Upon further investigation it was concluded that the selective monolithiation of ferrocene is a difficult task. After multiple attempts, we were unable to synthesize 1-bromoferrocene in high enough yield and purity to move on in the process. The second route was a more direct approach to the desired 1-aminoferrocene. It entailed the lithiation of ferrocene using t-BuLi, followed by reaction with alpha-azidostyrene and acidification with HCl. According to the characterization by NMR analysis 1-aminoferrocene has been prepared successfully using this procedure. The goal is now to optimize the yield of 1-aminoferrocene and to subsequently react it with acetylacetone and HCl to form the ferrocenyl-substituted “NacNac” ligand. This compound will then be coordinated to chromium to form a complex which can be used to further study oxidation states and reactivity of various chromium complexes.    This research has been funded by alumnus David Plastino’s contributions to the Alumni Undergraduate Research Fellows Program.

Characterization of the RAD5 HIRAN domain
and the Polη-PCNA interaction
in DNA damage tolerance

Kevin A. Sforza, William P. Bozza, and Zhihao Zhuang
Department of Chemistry and Biochemistry

Damaged DNA has many detrimental effects on proper cell function.  To properly cope with DNA damage during DNA replication, the cell has devised two main pathways: one involving error free replication of the DNA, and the other resorting to more error prone replication.  The goal of this project is to examine and characterize the Rad5 branch of error free DNA repair and the processes behind DNA Polymerase exchange in error prone DNA repair. The Rad5 protein, required for postreplicative DNA repair, possesses both DNA helicase and ubiquitin ligase activities. This dual activity has been suggested as essential for the regression of the stalled DNA replication fork.  However, little is known with respect to the specific domain(s) of Rad5 utilized in this process.  The goal of this project is to express and characterize the conserved HIRAN domain of Rad5 as an independent entity, and to test the DNA structures to which it binds.  When expressed as a standalone form in E. coli, the HIRAN domain was shown to be insoluble, presumably forming insoluble protein aggregates.  Soluble HIRAN domain was obtained by fusing it to a maltose-binding protein.  The fusion protein was tested with fluorescence anisotropy studies using Oregon Green 514 labeled DNA oligoes resembling stalled replication fork structures. It was concluded that the fusion protein did not bind to the ssDNA and fork structures generated.  In the error prone branch of repair, it was previously determined that monoubiquitinated PCNA was required for proper DNA polymerase exhange of Polδ and Polη.  Using the novel approach of incorporating unnatural amino acids into the structure of PCNA, photocrosslinking studies will be used to determine the specific residues necessary for polymerase exchange. This research was funded by and HHMI summer scholarship.

Iron-catalyzed Facially Directed and Regioselective Carbomagnesiation of Cyclopropenes

Valerie Shurtleff and Joseph M. Fox
Derpartment of Chemistry and Biochemistry

The inherent reactivity of highly functionalized cyclopropanes gives these strained molecules potential as synthetic building blocks. Nucleophilic additions to stereochemically enriched cyclopropenes offer a useful protocol for the synthesis of such cyclopropanes, and protocols providing access to highly functionalized chiral cyclopropanes have been reported. In the past, carbometallation reactions of cyclopropenes with a single alkene substituent gave quaternary centers.  A method for reversing the sense of regioselectivity in cyclopropene carbometallation reactions was unknown. Thus, a convenient method for the synthesis of tetrasubstituted products with two tertiary centers has proven elusive. Iron-catalyzed carbomagnesiation of 1,3-diphenyl-3-hydroxymethyl cyclopropenes has the potential to provide a convenient diastereoselective synthesis of cyclopropanes of this structure.

Synthesis of Nuphar Alkaloids

Patrick Straney, Douglas Taber, Peter DeMatteo
Department of Chemistry and Biochemistry

This poster will concern my work on the synthesis of a Nuphar Alkaloid, 2H-Quinolizine.  Nuphar Alkaloids are a class of molecules naturally found in aquatic plants of the Nuphar genus.  The molecules are characterized by the trisubstituted piperidine ring with a C-3 methyl and 3-furyl substituents.  This family of molecules is currently being investigated for their immunosuppressive, antimetastatic , and insecticidal  properties.   / Although the molecule has yet to be synthesized, considerable progress has been made toward its completion.  From the starting material Geraniol 1, a seven step synthesis procedure has been devised to yield the intermediate  2.  The proposed synthesis route for the conversion of 2 to 3 has been outlined and is expected to be completed by the end of the summer.

Expression, Purification, and Characterization of a New Sulfhydryl Oxidase from Trypanosoma brucei

Amy Styer, Vamsi Kodali, Vidyadhar Daithankar, and Colin Thorpe
Department of Chemistry and Biochemistry

A sulfhydryl oxidase from Trypanosoma brucei was expressed, purified and studied enzymologically for the first time.  The protein is homologous to ALR (augmenter of liver regeneration), an essential enzyme which catalyzes disulfide bond formation in the mitochondrial inner membrane space (IMS) of eukaryotes.  Trypanosomes lack a gene for Mia40, a necessary redox partner with ALR in yeasts and mammals.  Future research will determine how trypanosomes compensate for the lack of Mia40, and if this sulfhydryl oxidase has the same biological localization and function as ALR. First, however, expression and purification procedures must be optimized to prevent aggregation and degradation of the protein.   Preliminary research revealed that six of seven cysteines in the 33 kDa trypanosomal ALR are in the form of disulfide bonds.  In oxygen electrode assays, the enzyme catalyzed disulfide-bond formation in the model substrate dithiothreitol (DTT), but not the monothiols glutathione and cysteine.   Molecular oxygen was kinetically better as a terminal electron acceptor for trypanosome ALR than for human ALR (TbALR Km  = 15±1μM O2).   Understanding trypanosome redox biochemistry is important because Trypanosoma brucei, the causative agent of African Sleeping sickness, kills nearly fifty thousand people annually and current treatments are expensive, toxic, and impractical. This first foray into trypanosome mitochondrial IMS disulfide-bond formation may lead to biomedical advances in the fight against trypanosome diseases.

Preparations and Characterization of 1,1'-diaminoferrocene as a Ligand

Devan L. Turner and Klaus H. Theopold
Departmnent of Chemsirty and Biochemistry

Ferrocene derivatives have uses in many areas such as catalysis and biomedical chemistry¬[1]. Specifically, 1,1’-diaminoferrocene is of interest as a ligand in high valent assemblies; the redox-active center of ferrocene renders it particularly important because of its ability to participate in electrochemical processes and facilitate catalysis[2,3].  As an initial phase in the study of 1,1’-diaminoferrocene, it is necessary to both synthesize and fully characterize it using various spectroscopic techniques such as Nuclear Magnetic Resonance and Infrared spectroscopies.  In an improved procedure, ferrocene is lithiated to form a TMEDA complex 1,1’-dilithioferrocene (TMEDA = tetramethylethylenediamine). This reacts strongly with 1,1,2,2-tetrabromoethane to produce 1,1’-dibromoferrocene. The latter is then used to synthesize 1,1’-diazidoferrocene which is reduced with hydrogen gas and a palladium on carbon catalyst to form 1,1’-diaminoferrocene. We are currently in the process of synthesizing 1,1’-diaminoferrocene from 1,1’-diazidoferrocene[4] and in the future hope to coordinate it with cobalt. We plan to oxidize the resulting metal complex and investigate its catalytic properties. This research was funded by and HHMI summer scholarship.

Development of a Cancer Drug Database using KnowItAll®

Jordan M. Wheatley and Malcolm J. D’Souza
Wesley College Department of Chemistry

Prescribing information packets for Food and Drug Administration (FDA) approved chemotherapy drugs contain important pharmacological and chemical information for each drug including chemical structure, water solubility, and ADME/tox (absorption, distribution, metabolism, excretion, and toxicity) properties. The two major goals of this project were to: (1) extract pharmacological and chemical information from the prescribing information packets of 65 chemotherapy drugs (limited to drugs with packets containing a chemical structure); and (2) build a database of the drugs using the KnowItAll® Informatics System available through Bio-Rad Laboratories. Once the prediction tools are evaluated, pharmaceutical companies could use this database to analyze or predict a chemotherapy compounds’ missing pharmacokinetic properties. This project was supported by NIH NCRR INBRE grant number 2 P20 RR016472-09 and NASA Grant NNG05GO92H Delaware Space Grant College and Fellowship Program.

Links: Summer 2009 Undergraduate Research Symposium, Symposium Abstracts from other Colleges and Departments,
2009 Undergraduate Research Summer Enrichment ProgramUnversity of Delaware Undergraduate Research Program, Howard Hughes Undergraduate Program.
Created  7 August 2009. Last up dated 21 August 2009 by Hal White
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