ATP Synthase is a complex integral membrane protein consisting of two rotary motors: the FO portion, which is embedded in the cell membrane, and the F1 portion, which is located on the inside of the cell. ATP synthase is the primary generator of adenosine triphosphate (ATP), which is an energy rich molecule required for a variety of critical cellular functions. As important as ATP synthase is, the mechanics of exactly how it works are still not completely known. The FO rotor transduces an electrochemical gradient of protons into mechanical rotation of an oligomeric ring of c subunits. Several amino acids, e.g. phenylalanine 54 (F54), have been identified within subunit c that, when mutated to cysteine, have shown to allow synthesis of ATP while inhibiting ATP-driven proton pumping. I plan to chemically and genetically alter the structure of these amino acids to try to understand the specific characteristics that affect subunit c’s function. The addition of a propyl group to the cysteine side chain at the F54 position has shown to restore some function in the ATP-driven proton pumping direction. These results suggest that hydrophobic bulk may have a functional role at that position.
Strongly chelating ligands such as sulfonamides (sulf) are important in separation of metals, particularly in isolating trace elements. Further understanding of the nature of sulfonamide bonding could lead to a strong extraction agent for specific metals found in natural mineral deposits. It was determined experimentally that copper(II) coordinated to two sulfonamide ligands, Cu(sulf)2, had unusual geometric and potentiometric properties, being particularly stable with respect to multiple oxidations and reductions. Starting from the single-crystal X-ray generated geometry of Cu(sulf)2, a series of oxidized and reduced forms are studied using Density Functional Theory (DFT) and the Quantum Theory of Atoms In Molecules (ATAIM), in order to determine likely oxidation and reduction sites, and the nature of bonding of the ligand.
Pestalone is a natural product originally isolated in 2001 from a cofermentation of a marine fungus and bacterium. It has been synthesized by multiple groups including Nishiyama et al., Nikolay Slavov et al., and Ling Liu et al who found pestalone to have highly potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MIC = 37 ng/mL) and vancomycin-resistant Enterococcus faecium bacteria (MIC = 78 ng/mL). Unfortunately, this natural product can be rendered inactive due to an intramolecular cyclization between the C9 aldehyde and the bridging ketone forming a lactone. The goal of this project is to develop a reaction scheme to successfully produce pestalone analogs replacing the aldehyde with a range of electronic and steric functional groups to reduce the undesired reactivity while maintaining or improving antibacterial activity. Eighteen analogs were synthesized using a two step synthesis involving first a grignard addition of bromobenzene to a substituted phthalic anhydride(30-99% Yield) and then modifying the produced carboxylic acid through esterification(15-76% Yield) or amidation(7-93% Yield). These analogs were then subjected to a broth dilution minimum inhibitory concentration assay against Staphylococcus aureus and it was found that the analogs with the carboxylic acid only showed activity.
G proteins relay information from G-coupled protein receptors (GPCRs) to downstream molecular targets, driving large scale cellular process such as proliferation, differentiation, and migration. Overexpression of Gα13, a member of the G12/13 subfamily, is demonstrably oncogenic and has been implicated in breast, oral, esophageal and colon cancer. Lipidation is a post translational modification universal to G proteins, in which a fatty acid chain is attached to the protein, localizing it to the plasma membrane. These fatty acid adducts play a large role in how G proteins are regulated, and there is evidence they are involved in protein binding. Lipidations such as myristoylation (14:0) and palmitoylation (16:0) occur in all G proteins, sometimes in combination. Gα13 which is only palmitoylated, was previously engineered with PCR mutagenesis to remove amino acids necessary for palmitoylation to occur. These mutants were then modified at the N terminus with the DNA coding sequence from GαT and Gαi, both of which are myristoylated. Lysates from HEK 293 cells transfected with these plasmids were then tested for their ability to drive an SRE-luciferase assay. Loss of SRE signaling by non-palmitoylated chimeras was rescued by the addition of myristoylation sites. Future work will use GST fusion proteins to determine each chimera’s ability to bind with known G13 effectors.
HCl2I was synthesized with the intention of using photocatalysis facilitated by Hg2I2 to generate chemically activated CHCl2CHCl2 from radical CHCl2. The unimolecular decomposition reactions and their rates would then be quantified based on the ratio of decomposed products. Radical CF3 and radical CHCl2 would then be reacted to form chemically activated CF3CHCl2. Its decomposition reactions and rates would then be determined based on the ratio of products. The intention behind this project is to expand data on the reactions that hydrochlorofluorocarbons will undergo, as they are a commercially important class of greenhouse gases, which are in the process of being re-engineered to be more environmentally friendly. Understanding the reactions they will undergo is key to their efficient recycling.
Phthalate monoesters, the endocrine-active primary metabolites of phthalate diesters found in a variety of common products, affect reproductive development in male fetuses. Lipases convert phthalate diesters into monoesters during Phase I metabolism. During Phase II, phthalate monoesters further biotransform using UDP-glucuronosyltransferase enzymes (UGTs) and are excreted in urine, eliminating their toxic potential. Data suggest a significant minority of people glucuronidate poorly, leaving them more susceptible to the effects of phthalate diesters, as well as conditions like Gilbert’s syndrome and Crigler-Najjar syndrome. Little data exists on the enzymatic kinetics of UGTs on most phthalate monoester substrates, so the goal of the present study is to determine the kinetic relationship between three UGT isoforms UGT1A3, UGT1A8, and UGT2B7; and three phthalate monoester substrates mono(2-ethylhexyl) phthalate (MEHP), monobutyl phthalate (MBP), and mono-n-octyl phthalate (MNOP). Previous research suggests that these isoforms fit the Michaelis-Menten model on MEHP substrates, so the selected isoforms will be tested to see if they show similar kinetic behavior when metabolizing other long chain phthalate monoesters to provide a deeper understanding of the glucuronidation of phthalate monoesters. In addition, using a dataset from a previous study, we will examine the relationship between the ratio of conjugated to unconjugated phthalate monoester and total monoester concentration in a single human subject to better understand factors that relate to lower levels of UGT expression in an individual.
Steam reforming reactions that generate hydrogen from biomolecules using a non-precious metal catalyst are becoming ever more valuable as the need for sustainable energy production processes increase. Thirteen transition metals were examined for their catalytic ability in ethanol dehydrogenation reactions: Ag, Au, Cd, Co, Cu, Fe, Ir, Ni, Pd, Pt, Rh, Ru, and Zn, which includes both precious metal and non-precious metal catalysts. The reactions were examined using periodic density functional theory models of the catalyst surface as a (111) surface and (211) surface plane and reaction energies were calculated after a multi-step geometry optimization of the surface-adsorbate system. Optimum geometries and reaction energies were determined for C-H and O-H cleavage reactions over all metals to investigate periodic trends in catalytic activity. Trends in C-C and C-O bond distances of ethanol and its dehydrogenation products, as markers of changes in intramolecular bonding, and trends in ΔEC-H and ΔEO-H reaction energies were examined and will be presented.
Issues related to the burning of fossil fuels have prompted a world-wide search for clean and sustainable alternative fuel sources in the 21st century. Hydrogen powered fuel cells show great promise among the most recent alternatives due to their fuel efficiency and remarkably low emission levels. However, as hydrogen gas is not abundant in the atmosphere, it is mostly generated via steam reforming (SR) of natural gas, which is a nonrenewable resource. Instead, SR of organic materials from plants, such as sugars and alcohols, is a more sustainable way to produce hydrogen gas for use in fuel cells. The heterogeneous catalytic reactions that occur in SR are still being intensively researched in order to improve the process’ efficiency and viability. This study uses computational chemistry to investigate potential trends in the cleaving of C-C double bonds in simple alcohols by comparing results of reactions taking place over a Rhodium (111) planar surface to the findings of a previous research that looked at reactions over a stepped Rh (211) surface. Density functional theory (DFT) calculations were performed using the software Vienna Ab-Initio Simulation Package (VASP). Preliminary results are currently being evaluated.
There is a need for mobile-styled, low resource laboratory experimental methods, which do not require the use of expensive chemicals, chemical glassware, and instrumentation, as well as running water, and constant electricity. The purpose of this experiment is to create qualitative and quantitative laboratory methods, with the primary goal to produce these mobile styled, low resource experimental methods. The focus of the experiment is to be able to apply these experimental methods to be used by rural institutions and countries, such as Ghana. Is it possible to create mobile-styled and low resource experiments, which reach a specific set of student objectives?
With the increase in presence of common industrial waste solvents in the nation’s water supply, it has become increasingly necessary to find affordable and viable means of water purification that are commercially viable. Nanoparticles (NPs) with their size and resultant large surface area offer new pathways to such successful purification. Titanium Dioxide (TiO2), as a widely available, non-toxic material, is optimal for use as a filtration medium. The photocatalytic properties of these NPs are of particular interest in the filtration of contaminants due to their photocatalytic characteristics in the presence of the organic contaminants and ultraviolet light. In this study, the effectiveness of TiO2 NPs as a medium for the photodegradation of trichloroethylene (TCE) is explored. Preliminary data suggest that TiO2 is an effective medium for the removal of TCE from aqueous solutions.
The Okavango Delta in northern Botswana is a 6,000-15,000 km2 seasonal wetland which is home to hundreds of species of wildlife, including birds, fish, crocodiles, and hippopotami. The delta fluctuates in size based on time of year and rainfall. The many species that inhabit the area rely on its waters to reproduce and feed. The presence of phthalates is an area of emerging concern in this water system because of recent changes in agricultural practices upstream. The presences of 9 monoester phthalates were analyzed using LC/MS/MS on samples taken from the summer of 2016. Initially, levels of monobutyl, monoisobutyl, and monoethyl phthalate were found to be above 100 parts per billion (ppb). A healthy water system may have phthalates at approximately 5-10 ppb. Further analysis will provide information on the source and the effects of these compounds. Preserving the reproductive health of wildlife in the Okavango Delta relies on a natural and clean water system. Quantitative analysis of monoester phthalates is a necessary step in ensuring that the Okavango Delta continues to be a functioning habitat for the wildlife of northern Botswana.
ATP synthase catalyzes the synthesis of adenosine triphosphate by use of two rotary, designated F1 and FO, within the F1FO complex. ATP is the primary carrier of chemical energy in all life forms. The membrane-embedded FO motor uses a H+ gradient created by the electron transport chain to drive rotation of the c ring, which drives the conformational changes within the subunits α and β subunits of the F1 motor that catalyze ADP and phosphate into ATP. The mechanism of how the protons flow through ATP synthase to generate the torque on the c-ring remains unclear. Prior research has shown that the lipid composition of the membrane can influence the functions of the proteins embedded within it. To examine the effects of lipid composition on ATP synthase, the F1F0 complex was purified out of E. coli cells and tested for ATPase activity. F1FO will be reconstituted back into liposomes with varying lipid composition, especially focusing on the concentration of phosphatidylethanolamine, which is usually found in the membranes of E. coli. The ultimate objective of this project is to see if the presence or lack of specific lipids has any effect on ATP synthesis.
F1Fo ATP synthase is present in all life and is responsible for the production of almost all adenosine triphosphate (ATP), which is one of the most prolific energy molecules that are synthesized during metabolism. Fo converts electrochemical potential into mechanical rotation, which drives conformational changes in F1 that facilitate the synthesis of ATP. The mechanism of rotation of the subunit c ring is not known, but there are currently two hypotheses. This study will look for evidence of the ratcheting mechanism of rotation, which states that the helices of subunits a and c act like mechanical gears during rotation. This mechanism would require the α-helices of subunit a that lie on the a-c interface to move during rotation. Site directed mutagenesis was used to mutate a residue on one of these helices into a cysteine. This mutant ATP synthase will be purified and then chemically modified with a spin label, which can be observed using electron paramagnetic resonance (EPR) spectroscopy. The EPR signal is sensitive to the protein environment and will provide data on the mobility of the residue to which the spin label is attached. This could also clarify the possibility of mechanical movement in the Fo complex.
Adenosine triphosphate (ATP), the energy currency of the cell, is primarily synthesized by F1FO ATP synthase. This protein complex converts the proton motive force set up by cellular metabolism into chemical energy through a set of coupled molecular motors. The FO region of ATP synthase is embedded in the membrane, and proton translocation at the subunit a/c interface generates torque on the c ring. This mechanical rotation drives conformational changes in the catalytic sites of F1. A Brownian ratchet mechanism has been proposed for the FO motor in which the conversion of thermal motion to unidirectional motion occurs by regulating aqueous access to two compartments with different pH. However, this mechanism neglects evidence that subunit a may undergo conformational changes during ATP synthesis, which if correct, could have functional importance that sheds light on the problem of extracting torque from random motion. This study will use electron paramagnetic resonance (EPR) spectroscopy to measure structural dynamics of subunit a under various conditions. Cysteine mutations have been genetically introduced into the a subunit, and the mutant proteins will be purified and chemically modified with spin labels, which can be detected by EPR. EPR data will be analyzed with aim of inferring protein movements and integrating these into a description of the FO motor mechanism.
With antibiotic resistance becoming an increasing problem in society it is vital for chemists to search for more possibilities for antibacterial products to combat this growing issue. α-Pyrone analogs of Pseudopyronine A, an antibacterial natural product isolated from Pseudomonas species, are being synthesized and evaluated for improved antibacterial activity against both Gram positive and Gram negative bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. Synthetic analogs are accessed through either the commercially available acyl chloride or β-ketoesters, which will produce the α-pyrone in 5 or 3 steps respectively. The α-pyrones will then be further derivatized through alkylation, amidation, or halogenation reactions. All derivatives will then be evaluated for antibacterial activity in a growth inhibition assay against a panel of both Gram-positive and -negative bacteria.
Depsidones are a class of natural products that exhibit antibacterial activity (MIC = 0.0825-8 ppm). In order to increase the antibiotic potency of the depsidone family of natural products, modifications in size and connectivity are being explored. Although a synthesis scheme for the core 6,7,6-fused tricyclic structure of depsidone exists, the yields of the final product are low. In an effort to increase the yields, a new synthetic scheme has been derived which involves Chan-Lam copper catalyzed coupling of boronic acid and a diol substituted benzene rings followed by deprotection and esterification steps to close the central ring. Following this same synthesis scheme, the core structure of depsidone is being modified to change the ester linkage to both an amide and a thioester. These changes will provide insight into the affect the electronic interactions have on antibiotic activity. All analogs synthesized evaluated in an antibacterial assay against Gram-positive and Gram-negative bacteria in order to build a structure activity relationship profile for the depsidones.
Synthesis of pyrazoline derivatives has been an active field of research due to the established biological and pharmaceutical activities of these compounds such as antibacterial, anti-inflammatory, and anticancer properties. Pyrazoline derivatives are produced from the cyclization of chalcones with hydrazine hydrate and aryl aldehyde in the presence of ethanol. Due to the pharmacological effects associated with both chalcone and pyrazoline derivatives, it has been hypothesized that synthesizing a pyrazoline derivative from chalcone will enhance the product’s biological activity. However, the total synthesis of pyrazoline derivatives has been proven to be challenging due to its “one pot” synthesis producing low yields. Progress towards the synthesis of an unsubstituted pyrazoline derivative stemming from the reaction between an unsubstituted chalcone, hydrazine hydrate, and benzaldehyde in the presence of ethanol is presented. The synthetic pathway includes the formation of an unsubstituted chalcone via a Claisen Schmidt condensation to be used as a starting material. The reaction scheme for the unsubstituted pyrazoline acts as a basis for other research projects as the derivative is amenable to the addition of various functional groups. Modifications to enhance the activity of the pyrazoline derivative will be made, including the addition of methoxy groups.
Combretastatin A-4, a naturally occurring compound, isolated from the South African bush willow Combretum Caffrum, has analogs which have demonstrated to provide antibacterial, anti mitotic, anticancer, and antibiotic properties. This research consists of two foci, one for each project: (1) to increase the solubility and biological activity of analogs of Combretastatin A-4 in order to stop cancerous cells from replicating and (2) to induce DNA cleavage via the electrocyclization of derivatives of these analogs. Derivatives of the chalcone backbone will be the basis for the first focus, specifically, Lamellarin pyrroles. These pyrroles have proven to be positively bioactive in the apoptosis of cancerous and multidrug resistant (MDR) cells. Analogs of Lamellarins are recognized to have strong biological potency due to the five-membered nitrogenous ring and the relationship of the planarity between its ABCDE rings. For the first project, derivatives of the Lamellarins pyrrole analogs will serve the purpose of prohibiting cell division by acting as a substrate to bind to the beta-tubulin colchicine binding site during the metaphase stage of mitosis. The binding will occur via the trimethoxy feature of the A ring as the key. Furthermore, modifying the functional groups on the B rings can increase the solubility and biological activity within the bloodstream. For the second project, ynediene electrocyclizations of the Lamellarin pyrroles produce heterocyclic di-radicals which may have the ability to act as an unstable warhead to potentially induce DNA cleavage.
Transfer hydrogenation is the process of adding hydrogen to a molecule from a non H2 source. This process is more efficient than direct hydrogenation because the non H2 sources are more readily available and inexpensive compared to H2 sources, as well as safer. Many different metal catalyst attached to ligands have been used to determine which is the best for the reaction as well as the most efficient way to get to the end product. Iridium sulfonamides have been shown to be effective transfer hydrogenation catalysts, however the mechanism of transfer hydrogenation is unknown. In this project the interaction of the catalyst with a source of hydrogen, formaldehyde, is investigated using computational chemistry, specifically Density Functional Theory (DFT) calculations. The method of abstraction of hydrogen atoms is investigated in order to determine if hydrogen abstraction is stepwise or concerted, and which orientation of formaldehyde leads to optimal hydrogen abstraction.
Cobalt complexes formed from 2,2’-bipyridine (bpy) have been used to study electron transfer mechanisms, facilitate redox reactions in solar cells, and catalyze alkyne reduction reactions. However, relatively few reports present the preparation and use of functionalized cobalt-bpy complexes, particularly those that could be used as reactants for additional chemical synthesis. This poster presents a scheme for the synthesis and characterization of the as-yet unreported functionalized complex [Co(4-brbpy)3]3+ (4-brbpy = 4-bromo-2,2’-bipyridine). The synthesis of this complex follows closely to that previously published for the related complex [Co(4-fbpy)3]3+ (4-fbpy = 4-fluoro-2,2’-bipyridine). Characterization of the synthetic product will be undertaken via nuclear magnetic resonance (NMR), infrared (IR), and ultraviolet/visible (UV/vis) spectroscopies. The goal of this project is to prepare the target complex and to combine these findings with those obtained from earlier investigations of [Co(bpy)3]3+ to begin developing an understanding of how functionalization of the bpy ligand changes the properties of these complexes. Future experimentation will include the preparation and characterization of additional related complexes with different functionalizations, including isomers of these complexes, with the aim to uncover information about how the type and position of functionalization impacts the chemical and electronic structure of the complexes.
In this experiment, dichloroiodomethane was synthesized using sodium iodide and chloroform. An aqueous potassium hydroxide solution was used as a solvent, while 18-crown-6 was used as a catalyst to separate organic and inorganic compounds in the reaction. The reaction was performed at a temperature of 0°C with constant stirring for 2 days. The solution was diluted with excess amount of ice water then separated. A yellow solution was observed and Roto-Vap until the solution turn dark orange. Nuclear Magnetic Resonance (NMR) was used to identify dichloroiodomethane in the solution, while Gas chromatography/Mass spectrometry (GC/MS) was used to analyze the ratio of chloroform and dichloroiodomethane in the solution. The NMR reading showed that dichloroiodomethane was formed in the reaction. Mass spectrograph also confirmed that dichloroiodomethane was prepared. Based on the NMR reading and mass spectrograph, the reaction produced a sufficient amount of dichloroiodomethane for use in further experiment. Dichloroiodomethane will be look at to determine if a photolysis reaction with mercury (I) iodide is possible to produce two CHCl2 radicals. If the production of the CHCl2 radicals is possible, we will study the formation of CHCl2CHCl2 by combination of the two CHCl2 radicals. Further studies will look at different pathways that CHCl2CHCl2 can undertake when chemically activated. Pathways such as 1,1-HCl elimination and 1,2-HCl elimination will be examined through reaction rate, threshold energies, and product ratio.
Hydrochlorofluorocarbons (HCFCs) are greenhouse gases and cause ozone destruction. To stop further ozone depletion, the Montreal Protocol was phase out HCFCs by 2020 for developed countries and 2030 for developing countries. We used CD3CD2CHFCl as a model system to emulate real HCFCs and better understand how they react. By looking at the unimolecular reaction of an energized CD3CD2CHFCl molecule, we can see the different degradation pathways it can take. The kinetic data together with computational results shows that 1,1-HX elimination process (X = Cl, F) can became competitive at higher temperatures with the well known 1,2-HX elimination reactions. By studying these degradation pathways, we can better understand how to destroy these HCFCs or convert them into feedstock for use by chemical industries.
Chlorofluorocarbons (CFCs) were banned by the Montreal Protocol in 1987 due to their contribution to ozone depletion in the stratosphere through chlorine radical reactions. Their replacements, hydrochlorofluorocarbons (HCFCs), are less harmful because of their more reactive H-C bonds. We present a computational investigation of the singlet potential energy surfaces of specific HCFCs which could undergo either a 1,1-HF or 1,1-HCl elimination forming a carbene and then undergoing rearrangement into an alkene. Transition state geometries are reported for 1,1 HF and HCl elimination from CH3CHFCl, CHCl2CHCl2, and similar HCFCs using various levels of theories including Density Functional Theory (DFT), Complete-Active-Space-Consistent-Field theory (CASSCF), and Møller–Plesset perturbation theory (MP). These show that there is a very loose transition state, and in many cases DFT fails to predict a viable transition state geometry because of the late transition state with highly stretched bonds. There are also clear energy differences between these theories. We show that the transition state geometry does not lead to the dissociated products, but a “post transition state complex” with a weak interaction between HF or HCl and the carbene. This new mechanism for 1,1 HF or HCl elimination may explain the differences between experimental results and previous computational studies.
The increase in multi-drug resistant strains of pathogenic bacteria has made the issue of bacterial resistance a global health concern. New classes of antibacterial drug compounds, able to work outside existing mechanisms of resistance, are needed to combat these infections. Natural product-based drug discovery is an effective method in the development of new classes of antibiotics due to the chemically unique structures characteristic of naturally occurring compounds. This study aims to develop a viable antibacterial drug using Empetroxepin A and B, novel dibenz[b,f]oxepin natural products, as the lead compounds. The natural products will be synthesized in seven steps from commercially available 3,4,5-trimethoxytoluene. To date, the first five steps have been completed successfully through a Wittig olefination of trimethylsilane-protected salicyladlehyde with the phosphonium salt generated from the toluene starting material. The desired phosphonium salt was synthesized through aromatic bromination and radical benzylic bromination of the starting material. High yields (68-99%) have been achieved on large scales for each of these steps. Hydrogenation of the alkene bridge formed by the Wittig olefination has also been completed though only low yields have been obtained to date. The remaining two steps in the total synthesis include a copper oxide catalyzed etherification ring closure followed by selective deprotection to give both Empetroxepin A and B. Once synthesis of the lead compounds has been completed, the synthetic route will be used to develop analogs for structure activity relationship studies to optimize the natural product’s antibacterial activity.
Computational chemistry, in particular Density Functional Theory (DFT) calculations, were used to characterize the mechanism and energy profile of two chemical reactions involving the allyl functional group (-CH2CH=CH2). One reaction involves a 1,3-sulfur shift and provides information helpful to understanding the thioallylic rearrangement mechanism, while the second reaction contains an allyl ligand involved in the polymerization of norborene. In the first, the effects of different substituents on the transition state geometry and threshold energy of a thioallylic rearrangement of the allyl, RSCH2CH=CR2 are investigated. Substituents for the observed system were chosen based upon electron donating, electron withdrawing, and steric properties and were tested in a number of combinations on the available R positions. In the second, competing pathways are investigated for a proposed catalyst for the polymerization of norbornene containing a palladium atom with an allyl ligand. Competition between a β-hydride elimination and ligand insertion is addressed.
Phthalates are ubiquitous toxins found in a variety of household products. Phthalates are found in residential air, vehicle air, water, and soil. Phthalates have been shown to be endocrine active chemicals, specifically anti-androgenic. The disruption of testosterone is known to cause birth defects in male infants. Exposure to Diethyl Phthalate (dEP), Dibutyl Phthalate (dBP), Dibenzyl Phthalate (dBzP), and Diisobutyl Phthalate (diBP) was correlated with a decreased anogenital distance in male infants. This study measured the stability of Monoethyl Phthalate (mEP), Monobutyl Phthalate (mBP), and Monoisobutyl Phthalate (miBP) and their glucuronides at pH 4, 6, and 8 in urine. The urine was pooled from anonymous donors. PH 4 samples were acidified with formic acid. PH 8 samples were alkalized with Ammonium Hydroxide. Samples were purified by solid phase extraction. Samples were separated by High Performance Liquid Chromatography (HPLC) and detected by Electrospray Ionization tandem Mass Spectrometry/Mass Spectrometry (ESI-MS/MS). No samples were found to be statistically different from the control.
Hyder Pasture is a recently-restored fen near Flat Rock, North Carolina. It contains a population of the federally-endangered Bunched Arrowhead (Sagittaria fasciculate), a small herbaceous plant typically found in saturated soils near groundwater seeps. Bunched Arrowhead are found in only eleven locations in the world, all in North and South Carolina. This study represents the first chemical assessment of water and soil at the site since the restoration and adds to the growing body of work aimed at understanding the requirements of sustainable Bunched Arrowhead populations. Water samples were analyzed for major ions, pH, and temperature. Soil texture was similar throughout the study area, consisting of sandy loams and loamy sands. Cation Exchange Capacity ranged from 19.5 to 38.8 Cmolc kg-1. Areas of the restoration site that had top soil removed in order to form topological depressions were found to have lower soil organic content (>4.01% SOC) than undisturbed areas (6.02% to 12.66% SOC). Soils were acidic, with pH ranging from 4.45 to 4.93. These data from Hyder Pasture were then compared to established bunched arrowhead populations at other sites.
The natural product pestalone has been shown to have antibiotic activity against resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). However, pestalone is not readily isolated from its natural source, and its total synthesis has proven to be challenging due to low yielding reactions. Presented is the synthesis of 16 pestalone analogs, as well as the main carbon backbone. Attempts to synthesize the core structure of pestalone have proved difficult and are still in progress. The analogs were synthesized from either substituted benzaldehydes or phthalic anhydride using a Grignard reaction as the key step, with most yields between 65 and 85% for both reactions. The analogs were tested in bacterial assays against Gram-positive S. aureus and B. subtilis, as well as Gram-negative E. coli and P. aeruginosa, with 6 compounds showing antibiotic activity.
Ethanol dehydrogenation is a process that has a high potential to provide a carbon neutral source of hydrogen gas for use in fuel cells. This process involves the use of high temperatures and a catalytic metal to decompose the molecule into hydrogen gas and basic chemical precursors. However, the reactants and catalysts utilized by this process are not as cost efficient as obtaining hydrogen gas from carbon positive sources, mainly due to the high temperatures needed to carry out the catalysis and rare metals as catalysts. If the energy of reaction for creating hydrogen gas is lowered, the temperatures needed to carry out the reactions and thus the cost of production also go down. The Wasileski research group has computationally elucidated energy of reaction trends for dehydrogenation using periodic density functional theory when the reactants and catalyst makeup are altered, such as the type of primary alcohol fuel or the surface structure of the catalyst. From this data, the most favorable structure for ethanol dehydrogenation over a rhodium surface was the stepped 211 Miller index surface as compared to a planar 111 Miller index surface. In this research, a kinked 653 Miller index surface was tested and found to be in between the reaction energies for the 211 and 111 surfaces. From this finding, the current research project sets out to test additional kinked rhodium surfaces to elucidate how the overall and local surface structures affect trends in ethanol dehydrogenation catalysis.
Trichloroethylene (TCE), a volatile industrial solvent used for degreasing metal prior to electroplating has been identified as a human carcinogen and contaminant by the US EPA. Estimated to be in 34% of the nation’s drinking supply, with a maximum contaminant level set at 5ppb. The photodegradation of TCE coupled with pure 15 nm Anatase Titanium Dioxide (TiO2) and pure 15 nm Rutile TiO2 Nanoparticles (NPs) was investigated. Gas Chromatography and Mass Spectrometry (GC-MS) was used to analyze aqueous samples of known TCE concentrations and TiO2 NPs pre and post treatment with UV-light at 254 nm using Rayonet Photochemical Reactor. The results from this study agree with previous studies in the field that TCE degradation is achievable only when UV light is coupled with TiO2 NPs. Final degraded results from both, 15 nm Anatase Titanium Dioxide and 15 nm Rutile TiO2 NPs, achieved were under the US EPA limit of 5ppb.
In order to treat the growing number of antibiotic resistant pathogens, the isolation and production of new antibiotics is necessary. The need to discover novel antibiotics is increased by the lack of interest of large pharmaceutical companies. The two strains being studied were isolated from the phytotelma of Serracenia pitcher plants found in Western North Carolina. Pseudomonas CM/CP G1 was grown in a 25 mMol sodium succinate minimal media, and Streptomyces SS568 was grown in both glucose and acetate minimal medias (12.5mMol). Antibiotic activity of crude extractions were tested against Gram positive Staphylococcus aureus (grown on 10% Triptic Soy Agarose plates). The presence of antibiotic compounds has been confirmed for both strains in crude extracts, and compounds isolated from SS568 are currently under test for antibiotic activity against S. aureus. Characterization of active compounds will be completed upon results of activity. Techniques of liquid-liquid extraction and column chromatography are used to purify the active metabolites, which are then characterized by 1D and 2D NMR, IR, and LC-MSMS.
Drugs that target tubulin polymerization have largely been focused on in the field of cancer research. Combretastatin A-4 (CA-4) binds to the colchicine site of ß-tubulin, inhibiting polymerization and thus inducing the subsequent anti-cancer effects. Structural modifications of CA-4 have been made as an attempt to increase the solubility and binding affinity of the compound to the colchicine site. CA-4 analogs that possess indole and chalcone moiety have demonstrated improved anti-cancer effects when compared to the unmodified CA-4 lead compound. This research focuses on synthesizing an analog of CA-4 that incorporates indole-chalcone functional groups, and assessing the efficacy of various reactions in the target molecule synthetic scheme. One of the halogenated acetophenones, α-bromo-3,4,5-trimethoxy acetophenone, has been synthesized and purified via column chromatography. The first step of the indole synthesis was completed, in which a protecting group was added to the hydroxyl of the substituted benzaldehyde starting material. Synthesis of ethyl azidoacetate, the second step of the indole synthesis, has been attempted in two trials. The ethyl azidoacetate product needs to be purified, so that it can be reacted with the protected benzaldehyde to yield the vinyl azide product. The vinyl azide reaction has been attempted using ethyl azidoacetate synthesized by a previous research student, and the two trials were completed using different reagents. Completing the indole synthesis and reacting the substituted indole product with the brominated acetophenone will allow formation of the CA-4 chalcone target molecule through an aldol-condensation reaction.
A previous study characterized the soil of four Southern Appalachian wetland sites where endangered pitcher plants of the Sarracenia genus are currently growing. Pitcher plants are known to thrive in weakly acidic, nutrient-poor environments and are susceptible to competition from woody species when soils undergo nutrient shifts. The pitcher plant soils were found to have a pH range of 3.52 - 5.08 and cation exchange capacity (CEC) of between 7.3 - 99.8 cmol/kg. Base cation saturation ranged from 0.4 - 20.1 % and organic carbon from 4.9 - 32.9 % across the four sites. The project was then expanded to include soils collected from four sites where pitcher plants are not growing. Soil pH, CEC, exchangeable cations, and organic carbon were again used as methods to characterize non-pitcher plants soils so that direct comparisons could be made to pitcher plant soils. The non-pitcher plant soils will be evaluated as to whether they have higher concentrations of base cations (Ca2+, Mg2+, K+ and Na+) and/or higher pH than do the soils of pitcher plant sites. This presentation will focus on determining if the soil of Southern Appalachian wetlands is consistent across sites or if pitcher plant sites have a unique chemical signature.
Octahedral mixed ligand cobalt(III) complexes derived from bidentate nitrogenous ligands such as ethylenediamine (en), 2,2’-bipyridine (bpy), and 1,10-phenanthroline (phen) have garnered interest for their usage in diverse applications such as bacterial inhibition (biochemistry) and increased photocathode efficiency in dye-sensitized solar cells (materials science). While much research has been undertaken on unmixed ligand complexes of Co(III), relatively little has been reported on the mixed complexes. The goal of this project is to investigate more efficient synthesis schemes for higher yields of these complexes, and to also record information via ultraviolet-visible (UV-vis) spectroscopy for determining and comparing the complexes’ structural properties. Two experiments are presented from this project. In the first experiment, the synthesis of [Co(bpy)2(phen)]Cl3 is discussed. This complex was obtained in very low yield, calling into question the quality of the synthesis and demanding a revised reaction scheme. In the second experiment, the synthesis of trans-[Co(en)2Cl2]Cl is presented. Comparisons of the UV-vis spectra of the synthesized complex, its CoCl2·6H2O starting material, and a commercially purchased sample of complex are presented. The findings from these experiments will be used for further developments and characterization of these cobalt complexes and their utilities in other fields of science.
Depsidone natural products are potent inhibitors of Gram-positive bacteria, with MIC values ranging from 0.1–8.0 μg/mL. By synthesising various heterocyclic depsidone analogs and testing them on antibacterial assays, the antibiotic activity against Staphylococcus aureus will be observed as well as its correlation with the electronic profile of the analog. Synthesis and optimization of pyridine, furan, and thiophene depsidone analogs has been accomplished through an optimized 4-step synthetic sequence beginning from the corresponding 2-carboxyphenylboronic acid heterocycles. After the methyl protection of the heterocycle is achieved, the central 7 membered ring of each depsidone analog is produced by first coupling to catechol through a Cu(OAc)2 catalyzed reaction (12-25% yield), deprotection of the methyl ester (57% yield), and closing the ring through an intramolecular esterification. Each analog will be tested in an antibacterial bioassay against Staphylococcus aureus to reveal how the changes in the electronic profile affect antibiotic activity.
Phthalates are excreted after glucuronidation. However other possible metabolic pathways have not been examined. One possible route, amino acid conjugation, has been observed in compounds with structural similarity to phthalate monoesters. An amino acid conjugate of monoethyl phthalate (MEP) was synthesized in the lab with a low yield (
Multidrug resistant bacterial infections, which arise due to misuse and overuse of antibiotics, are responsible for many nosocomial infections and are a threat to human health. Derivatization of known antibiotic compounds via total or semisynthesis can be time consuming and ineffective at targeting specific bacteria. This investigation focuses on bacteria found in the phytotelmata of Sarracenia pitcher plants and the natural antibiotic compounds they secrete under varying conditions. The aim of the project is to find single-producer and co-culture producing bacteria that secrete secondary metabolites effective a broad spectrum of Gram-positive and -negative pathogens. A Pseudomonas (CMCP E3) and Chromobacterium (CP2 SSIV) isolated in this study have been found to be effective against Gram-positive bacteria Staphylococcus aureus and the fungi Fusarium solani. The bacteria strains were cultured in minimal media containing either succinate or citrate that showed the densest growth after 72 hours. Final characterization of the CMCP E3 antibacterial compound was inconclusive. A 6 L succinate culture of the CP2 SSIV bacterium yielded on average 16 mg of crude product and 0.5 mg of antibacterial compound. Optimization of antibacterial isolation and characterization of CP2 SSIV secondary metabolite using column chromatography, NMR, and mass spectrometry is ongoing.
The purpose for this project is to evaluate a qualitative analysis experiment of the general chemistry laboratory course, CHEM 111, in order to determine the extent of student success and to improve this experiment, for future cohorts of students. Qualitative analysis is the identification of unknown elements in a sample through a series of tests and is an important part in general chemistry education, it also aids in developing students critical thinking ability. In this experiment, an unknown solution of anions is identified through a series of chemical tests executed in a particular order via a student-generated qualitative analysis (“qual”) scheme. The “qual” scheme is created by the CHEM 111 student using their interpretation of observations obtained through chemical tests on single-anion solutions of known identity. Historically, there has been a sense among the CHEM 111 faculty that students have difficulty designing and understanding the role of the “qual” scheme in the analysis of the unknown. Furthermore, anecdotal evidence has suggested the nitrate anion (NO3-) is incorrectly identified substantially more often than the other anions used in this experiment. Survey data gathered from CHEM 111 students in Spring 2016, Fall 2016, and Spring 2017 does indeed indicate that many students encountered problems creating a “qual” scheme, and the anion most often incorrectly identified was NO3-. The survey results suggest the test for NO3- either needs to be explained more clearly to the students or substantially altered to reduce barriers to its success. A few chemical alterations of this test will be presented, as will information about how modification of the “qual” scheme can impact students’ success in identifying their unknowns.
Amendments to The Montreal Protocol have called for a phase out of all hydrochlorofluorocarbons (HCFC’s) and hydrofluorocarbons (HFC’s). These common gases are found in many household appliances such as refrigerators and air conditioners. Little is known about the 1,1-HX (X=halogen) elimination channel of HFCs; thus, we have designed a number of model compounds to learn more about the kinetics and mechanism of 1,1-HX elimination reactions. Here we present experimental and computational results for chemically activated CHF2CHF2 (HFC-134) and CHF2CF3 (HFC-125). The carbene from CHF2CHF2 has previously been reported to isomerize to CHF=CF2, but our calculations show that the isomerization barrier is too high. The carbene yield was measured by trapping with trans-2-butene. The 1,2-HF and 1,1-HF elimination rate constants were experimentally determined to be 4.6 x 105 s-1 and 1.3 x 105 s-1, respectively. The same method has been used to measure the 1,1 HF and 1,2 HF elimination rate constants of CHF2CF3. A variety of computational methods and basis sets were explored to find the 1,1 HF and 1,2 HF transition states and threshold energies for both compounds. A CF2 expulsion reaction pathway to yield fluoroform has also been identified in CHF2CF3.
Microtubulin targeting agents have increased in popularity due to non-invasive methods of destroying cancer cells. Molecules like phenstatin have been studied heavily due to its reversible binding ability to the colchicine binding site and its toxicity towards cancer cells. The goal of this research is to produce four phenstatin derivatives with phenothiazine in location of the A-ring and non-aromatic attachments (3-, 4-, 7-, 8-membered rings) in location of the B-ring. The focus is to observe if size and torsional strain of the phenstatin derivatives will affect the binding affinity towards the colchicine binding site. Currently, the synthesis of a peptide coupling reaction utilizing N,N’-Dicyclohexylcarbodiimide (DCC)/4-Dimethylaminopyridine (DMAP) is being examined as a method to produce the desired phenstatin derivatives with a cyclopropane and cyclobutane in place of the B-ring. A Grignard synthesis will be performed to synthesize the phenstatin derivatives with a cycloheptane and cyclooctane in place of the B-ring. Progress towards the synthesis of the four new phenstatin derivatives will be discussed.
Multidrug resistant bacterial infections are one of the top three threats to global public health. Nearly all clinical antibiotics have lost their effectiveness due to the rapid onset of bacterial resistance. Unfortunately, there is not a robust and efficient method that allows researchers to study bioactive antibiotic compounds that come from novel secondary metabolites produced by bacteria and other microorganisms. This research will develop a high throughput liquid culture method, which can screen both single and multi-culture mixtures of bacteria for antibiotic product. This method is a quick five-day process, compared to the current agar overlay method, which takes about two weeks. This new method includes four basic steps: growing bacteria overnight, developing a liquid well assay which shakes for 48 hours, filtering the bacteria’s excreted secondary metabolites to a new well assay plate which shakes for 24 hours, and then finally testing for antibiotic activity against Gram-positive and Gram-negative pathogens.
The French Broad River (FBR) serves as the home to several endangered species, raising concern due to the possible presence of endocrine-active compounds (EAC). Research shows that exposure to EACs in wastewater treatment plant (WWTP) effluent, namely phthalates, induces complications in reproductive physiology of fish and animals. Quantification of EAC concentration in WWTP effluent was conducted in Asheville, NC. Multiple phthalate monoester concentrations have been successfully detected in WWTP effluent above the LOD and LOQ, though the use of solid-phase extraction and a Shimadzu Liquid Chromatograph Mass Spectrometer-8040 (LCMS). Moving forward, metabolite concentrations acquired in WWTP influent will be compared to concentrations located in the effluent. This comparison will describe the effectiveness of WWTP removal of EACs, and increase awareness in the community for environmental sustainability. We hypothesize that processes within the WWTP might promote an increase in monoester concentration due to the cleaving of the glucuronide bond on phthalate glucuronide metabolites. Considering the WWTP makes use of a rotating biological contactor, the biofilm located on the surface of the contactors could be a prime location for glucuronide cleaving.
Multidrug resistant bacteria pose a huge threat to human health due to overprescription and misuse of antibiotics, an industry of agriculture reliance, and the decline of novel antibiotic discovery. According to the CDC at least two million people in the United States each year are infected with multidrug resistant bacteria and more than 23,000 succumb to those infections. Natural product (NP) isolation is a robust source of potential antibiotics even though recent random selection of organisms which undergo novel NP biosynthesis is rare. Understanding how ecological and evolutionary pressures drive NP synthesis may lead to new discoveries in novel NP production and isolation. This research involves the isolation and purification of 101 bacterial soil samples from the Southwestern United States and subsequent screening of those bacteria for antibiosis induction through coculture and quadculture agar overlay and lawn inhibition assays. Bacteria found to be strong antibiotic producers were then characterized by 16S ribosomal polymerase chain reactions and subjected to scale up and extraction to isolate the produced antibiotic. Currently antibiotics produced by three bacteria, a Bacillus strain (SS729) and two Streptomyces strains (SS735 and SS746) are being isolated and characterized. SS735 was found to have antibiotic activity against Gram-positive Staphylococcus aureus while the other two strains, SS729 and SS746 were found to have antibiotic activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli in agar overlay inhibition assays.
Combretastatin A-4, an anti-tumor agent isolated from the Combretum caffrum bush, along with some synthetic derivatives, have been found to be effective in combating tumors by initiating vasculature collapse. While investigations into increasing combretastatins’ activity have focused mainly on utilizing a central ring to gain conformational locking have been performed, these modifications can have the undesired effect of creating a molecule too large or planar to attach to the corresponding binding site. This research focuses on bridge and b-ring fluorine substituted CA-4 derivatives to obtain the same desirable outcomes desired with CA-4, with the avoidance of steric hindrance. A total synthesis of an alpha, 3’-difluoro CA-4 analog was attempted with the use of diazonium salts in a Balz-Schiemann reaction using fluoride nucleophiles. However, a new pathway, using Duff formylation and the Wittig reaction to generate the B-ring, a Grignard reaction to synthesize the A-ring, and a final Suzuki coupling is being explored. The versatility of the diazonium salts are also being investigating for creating interesting heterocyclic molecules, namely tetrazoles, as well.