Life Sciences Commons^™

Towards The Total Synthesis Of Thioviridamide: Thiyl Radical Approach To The Beta-Thioenamide Linkage Formation, Jung-Hoon Kang

Theses and Dissertations

We developed an approach to the β-thioenamide linkage contained in the S-(2-aminovinyl)cysteine (avCys) residue of thioviridamide.1,2 Kinetic and thermodynamic control of radical additions of thiols to ynamides were studied for the formation of β-thioenamide linkage. Thiyl radicals are electrophilic and ynamides are electron-rich alkynes. This complementary polarity of the radical and acceptor increases the likelihood of a successful radical addition reaction. Because little is known about these types of compounds (β-thioenamides), we were unsure what kinds of yields and stereoselectivities (cis vs. trans) to expect. The adduct stability is another issue to consider. Fortunately, under typical radical addition conditions, the …

Molecular Mechanisms Involved In Oligodendrocyte Development, Rochelle Coelho

Theses and Dissertations

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) characterized by demyelination and loss of oligodendrocytes (OLGs), the CNS myelin-producing cells. Thus, understanding the mechanisms that control OLG development can provide valuable knowledge regarding remyelination therapies for MS. This disease is thought to result from an autoimmune attack towards myelin. FTY720, an immunomodulator under evaluation for MS treatment is a sphingosine-1-phosphate (S1P) analog. We found before that S1P plays a crucial role in the NT-3-mediated survival of OLGs, an observation that led us to investigate whether FTY720 could have any effect on these cells. Our studies …

Regulation Of Mdm2 Mediated Nfκb2 Pathway In Human Lung Cancer, Lathika Mohanraj

Theses and Dissertations

Overexpression of oncoprotein MDM2 and mutations of tumor suppressor p53 are frequently observed in human cancers. The NFκB pathway is one of the deregulated pathways in oncogenesis. The overall goal of the project was to study the regulation of NFκB pathway by MDM2 in lung cancer. Our first effort was to determine the frequency of MDM2 overexpression in human lung tumor samples and to identify co-occurring abnormal gene expression by studying the levels of MDM2 and members of NFκB pathway with respect to p53 status. Higher than normal levels of MDM2 were found in approximately 30% of the cancer samples …

Crosstalk Between Mdm2 And Akt Signaling Pathway In Oncogenesis., Mahesh Ramamoorthy

Theses and Dissertations

MDM2, the human homologue of the Mouse Double Minute 2 gene product, has been shown to be over-expressed in many cancers and to induce tumorigenesis. The role of MDM2 in oncogenesis was thought to be p53 dependent. However recent years have shown MDM2 to be a key player in a complex network of interactions that affect cell cycle, apoptosis, and tumorigenesis in a p53 independent manner. Here we report a novel p53 independent role for the multidimensional protein MDM2; its ability to induce phosphorylation of Akt at serine 473 residue. Transient and stable over-expression of MDM2 in cultured cell lines …

Novel Xanthine And Oxanine Dna Glycosylase Activities In Yeast And Mammalian Systems, Liang Dong

All Dissertations

DNA that stores genetic information is frequently damaged in cells. The DNA bases carrying an exocyclic amino group [adenine (A), guanine (G), cytosine (C)] encounter deamination even under physiological conditions. Xanthine (X) and the newly discovered oxanine (O) are derived from deamination of guanine; they are potentially cytotoxic and mutagenic lesions. However, in yeast and eukaryotes, studies on the enzymatic repair of these lesions are limited.
In the yeast, Schizosaccharomyces pombe thymine-DNA glycosylase (Spo TDG) is homologous to human thymine-DNA glycosylase (hTDG), an enzyme that removes thymine from T/G pair. It was reported that Spo TDG contains uracil DNA glycosylase …

Dna Deamination Repair Enzymes In Bacterial And Human Systems, Rongjuan Mi

All Dissertations

DNA repair enzymes and pathways are diverse and critical for living cells to maintain correct genetic information. Single-strand-selective monofunctional uracil DNA glycosylase (SMUG1) belongs to Family 3 of the uracil DNA glycosylase superfamily. We report that a bacterial SMUG1 ortholog in Geobacter metallireducens (Gme) and the human SMUG1 enzyme are not only uracil DNA glycosylases (UDG), but also xanthine DNA glycosylases (XDG). Mutations at M57 (M57L) and H210 (H210G, H210M, H210N) can cause substantial reductions in XDG and UDG activities. Increased selectivity is achieved in the A214R mutant of Gme SMUG1 and G60Y completely abolishes XDG and UDG activity. Most …

Biochemical Characterization Of Two Yeast Paralogous Proteins Mth1 And Std1, Satish Pasula

Dissertations

Glucose is the most abundant monosaccharide and preferred carbon and energy source for most cells. Many organisms have evolved sophisticated means to sense glucose and respond to it appropriately. The budding yeast, Saccharomyces cerevisiae senses glucose through two transmembrane proteins, Snf3 and Rgt2. In the presence of extracellular glucose Snf3 and Rgt2 generate an intracellular signal that leads to the degradation of Mthl and Stdl, thereby inducing the expression of hexose transporter genes (EXT) by inhibiting the function of Rgtl, a transcriptional repressor of HXT genes. Mthl and Stdl are degraded via the Yckl/2 Kinase-SCFGrrl-26S proteasome pathway triggered by the …

Ceramide Kinase And Ceramide-1-Phosphate, Dayanjan Wijesinghe

Theses and Dissertations

Ceramide-1-phosphate (C1P) is a bioactive lipid that has been implicated in many biological processes. Our laboratory has conclusively demonstrated its role in inflammation via activation of cPLA2α. The only known enzyme to date responsible for direct synthesis of C1P is ceramide kinase. Very little was known about this enzyme in terms of its enzyme kinetics and substrate specificity. As CERK is an enzyme that acts on membrane lipids, its kinetics cannot be studied using standard bulk dilutions methods. Thus we developed a surface dilution approach using Triton X 100 mixed micelles for studying the kinetics of CERK. We discovered that …

Photocycloaddition Of Allenes, Crystal Ward

Theses and Dissertations

For the past ten years the Fleming research group has been involved in the research of allene compounds. We have explored the synthesis of allenes as well as several reactions involving allenes, such as oxidation and nitrene addition. Recently, we have explored the synthesis and photochemistry of allenic alcohols tethered to silicon. There are literature examples using allenes in synthesis, but very few examples exist using allenes in photochemical cycloaddition reactions. We have found that a diisopropylallenyloxy(cinnamyloxy)silane derivative undergoes [2+2] photochemical cycloaddition to produce a cyclobutylsilane product when irradiated for 60-75 minutes.

Polymer Supported Optical Biosensors, Ignacio Joseph Garcia

Electronic Theses and Dissertations

The use of various polymer supports adhering phospholipid multibilayers to an internal reflection element have been investigated. The polymer supports studied range from polystyrene (PS), and 100 nm wide PS nanospheres to triethylaminated poly(vinyl benzyl chloride) (PVBC). The PS nanospheres showed the most promise as an adhesion layer since they appear to be the most robust with repeated washings. They also appear to stabilize their adjacent phospholipid multibilayer by increasing the lipid melting temperature. The triethylaminated DVBC also provided an increase of lipid melting temperature, but not quite to the same degree as the PS nanospheres. The cooperativity of such …

I. Thermodynamics And Magnetism Of Cu2ocl2 Ii. Repairs To Microcalorimeter The "2"S Are Subscripts, And The Second 2 Is Preceded By A Lower Case L, Not A One, Thomas J. Parry

Theses and Dissertations

Adiabatic calorimetry provides accurate and precise specific heat (Cp) data. From this data, thermodynamic functions may be calculated. Cu2OCl2, melanothallite, became of interest as part of a study of a particular thermochemical cycle. The experimental specific heat data and the calculated thermodynamic functions are reported here. Free energies of formation, calculated from the thermodynamic functions, suggest the particular cycle of interest with this compound as an intermediate is not feasible; uncertainty as to the accuracy of CuO and CuCl2 data used in the calculations indicate further study may be necessary. Upon collection of the specific heat data, an antiferromagnetic transition …

Characterization Of Heat Shock Protein A12b As A Novel Angiogenesis Regulator., Rebecca J. Steagall

Electronic Theses and Dissertations

Previously, we cloned Heat shock protein A12B (HspA12B), the newest member of a recently defined subfamily of proteins distantly related to the Hsp70 family that are enriched in atherosclerotic lesions. We have found that HspA12B is predominantly expressed in vascular endothelium, and that it is involved in angiogenesis which we probed by in vitro angiogenesis assays (Matrigel), migration assays and Directed In Vivo Angiogenesis Assay (DIVAA). Hsp70s are molecular chaperones that are inducible by stress and have been found to be anti-apoptotic (Li et al. 2000; Nylandsted et al. 2000; Garrido et al. 2001). Because of its homology to Hsp70, …

A Radical Conjugate Addition Approach To The Total Synthesis Of Celogentin C, Steven G. Capps

Theses and Dissertations

The synthesis of five chiral DBFOX (dibenzofuran-oxazoline) ligands with either aryl or benzyl substituents will be presented. The requisite amino alcohols were obtained with high enantioselectivity either commercially (DBFOX/Bn), via Sharpless asymmetric aminohydroxylation (DBFOX/Nap, DBFOX/t-BuPh, DBFOX/Pip), or via phase-transfer catalyzed asymmetric alkylation (DBFOX/MeNap). These ligands, complexed with Mg(NTf2)2, were used as Lewis acid promoters of enantioselective radical conjugate additions to α/β-unsaturated nitro-amides/esters. A summary of these results is presented and discussed. These findings led us to believe that our initial binding model between metal, ligand, and substrate was flawed. Thus, we figured that if we started with a functionality known …

Regulators Of G-Protein Signaling, Rgs13 And Rgs16, Are Associated With Cxcl12-Mediated Cd4+ T Cell Migration, Lijin Xia

Theses and Dissertations

Chemokines are important chemical signals that guide lymphocyte movement within the immune system and promote the organization and functions of germinal centers (GCs) in the secondary lymphoid tissues. Previous studies have shown that GC T cells exhibit high expression of chemokine receptor 4, CXCR4, but that these cells are unable to migrate to the ligand for this receptor, the chemokine CXCL12. This “migratory paralysis” to CXCL12 was found to be correlated with the expression of two Regulators of G-protein Signaling, RGS13 and RGS16 in the GC T cells. The objective of my research was to determine whether RGS13 and RGS16 …

The Identification, Functional Characterization And Phylogeny Of The Nodulin-Like Anion Transporter (Nlat) Family In Plants, Eric Daniel Vincill

Doctoral Dissertations

A cDNA was isolated from soybean (Glycine max) nodules that encodes a putative transporter (GmN70). GmN70 is expressed predominantly in mature nitrogenfixing root nodules. By western-blot and immunocytochemical analyses, GmN70 was localized to the symbiosome membrane of infected root nodule cells, suggesting a transport role in symbiosis. To investigate its transport function, cRNA encoding GmN70 was expressed in Xenopus laevis oocytes, and two-electrode voltage clamp analysis was performed. Ooctyes expressing GmN70 showed outward currents that are carried by anions with a selectivity of nitrate > nitrite >> chloride. These currents showed little sensitivity to pH or the nature …

Quantum Mechanical/Molecular Mechanical Molecular Dynamics Simulations On Enzymes, Qin Xu

Doctoral Dissertations

The dynamic nature of proteins in solution is often an indispensable factor in biological function such as enzymatic catalysis. Complementary to the conventional structural analysis, computational simulations have the advantage to reflect the dynamic nature of proteins or enzymes. One of the computational simulation methods, the quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations, has been widely applied to the research in structural analysis, ligand-receptor binding and enzymatic catalysis.

In this dissertation, QM/MM MD simulations were applied to the studies on cytidine deaminase (CDA), yeast cytosine deaminase (yCD), and kumamolisin-As, as well as two protein lysine methyltransferases (PKMTs), DIM-5 and …

A Fluorescent Photoinduced Electron Transfer (Pet) Sensor For Cations With A Separate Pet Channel To Suppress Proton Signals, Supun Pathirana

Theses, Dissertations and Culminating Projects

This thesis presents A-((10-((2-methoxy-4-methylphenoxy)methyl)anthracen-9- yl)methyl)(pyridin-2-yl)-A-((pyridin-2-yl)methyl)methanamine, 1, a photoinduced electron transfer (PET) sensor that acts as a fluorescent ‘Off-On’ switch in the presence of Zn ions and not sensitive to protons.

Spectroscopic Study Of Compressible Mobile Phase And Stationary Phase Behavior In Chromatography, Lawrence R. Baker

Theses and Dissertations

Raman spectroscopy, laser-induced fluorescence, and sum-frequency generation (SFG) spectroscopy are used to investigate the behavior of compressible mobile phases and stationary phases under a variety of chromatographic conditions. Efforts to understand and optimize separations employing compressible mobile phases have been limited by a lack of understanding of the mobile phase density gradient. Mobile phase compressibility leads to gradients in linear velocity and solute retention and affects separation speed and efficiency, especially in packed columns. This work describes on-column density measurement of CO2, a common carrier fluid for SFC and SGC, in packed capillary columns using Raman microspectroscopy. On-column detection by …

Dendrimer Supramolecular Assembly For Gene Delivery, Karthikeyan Pasupathy

All Theses

Dendrimers have found many applications in the fields of polymer science, biophysics, nanomedicine and the petroleum industry. Poly(amidoamine) (PAMAM) was studied as a model dendrimer and squalane as a model hydrocarbon. The interaction between PAMAM and squalane is pH dependent. Specifically, at low or neutral pH the squalane is found on the periphery of the PAMAM while at high pH the hydrocarbon is entrapped inside the PAMAM molecules.

Single-molecule fluorescence revealed that the interaction between PAMAM and squalane is reversible. At a pH value of 8, the time constants for the approaching, binding and dissociation of single PAMAM to squalane …

Genetic Analysis Of The Role Of Smpb In Establishing The Reading Frame On Tmrna, Talina Christensen Watts

Theses and Dissertations

Ribosomes translate the genetic information encoded by mRNA into proteins. Defective mRNAs can cause stalling of translating ribosomes. The molecule tmRNA (transfer-messenger RNA) rescues stalled ribosomes in eubacteria. Together with its protein partner SmpB, tmRNA mimics a tRNA by entering the ribosomal A site and linking an alanine residue to the growing polypeptide chain. The ribosome then abandons the defective mRNA template and resumes translation on tmRNA, adding ten more amino acids to the nascent polypeptide. As a result of tmRNA action, stalled ribosomes are released and recycled, the defective mRNA is destroyed, and the aborted protein product is tagged …

Ion Permeation Through Membrane Channels: Molecular Dynamics Simulations Studies, Morad Mustafa

Theses and Dissertations

Molecular dynamics simulation was used to study ion permeation through different membrane proteins embedded in a lipid bilayer (DMPC) with different saline solutions. The potential of mean force (PMF) for ion transport was obtained by umbrella sampling simulations. A revised MacKerell force field for tryptophan residues was studied using gramicidin A (gA) channel as a test model. The revised force field contribution to the Na+ PMF was consonant with the prediction from the experimental results, but in stark contrast to the prediction of the CHARMM force field, version 22, for the tryptophan side-chain. A new grid-based correction map algorithm by …

Pge2 Receptor Subsets Mediate Hcg Regulation Of The Plasminogen Activator/Plasmin System In Primate Periovulatory Follicles, Nune Markosyan

Theses and Dissertations in Biomedical Sciences

Elevated follicular prostaglandin E2 (PGE2) levels are necessary for follicle rupture during ovulation. As the degradation of the follicle wall requires proteolysis, it was hypothesized that regulation of proteolysis by gonadotropins is PGE2 mediated.

There are four PGE2 receptors: EP1, EP2, EP3 and EP4. To determine which PGE2 receptors are present in monkey periovulatory follicles, granulosa cells and whole ovaries were collected 0, 12, 24, and 36 hours after administration of an ovulatory dose of human chorionic gonadotropin (hCG), or 36 hours after hCG from monkeys that received the prostaglandin (PG) synthesis inhibitor celecoxib. All EP receptor mRNAs were present …

Nanosecond Pulsed Electric Fields Induce A Mitochondria-Independent Apoptosis In B16f10 Melanoma Cells In Vitro, Wentia Elissa Ford

Theses and Dissertations in Biomedical Sciences

Nanosecond pulsed electric fields (nsPEFs) are ultra-short pulses that induce direct electric field and biological effects that initiate apoptosis. Here the application of ten 300ns pulses ranging in electric fields from 12kV/cm-60kV/cm was administered to determine the effects on B16F10 melanoma cells evaluated by in vitro studies. Initial application of nsPEFs demonstrated apoptosis induction in an electric field- and pulse number-dependent manner measured by caspase activation that correlated with decrease in cell viability 24hr post pulse. In addition caspase activity was shown to be independent of calcium mobilization though ions may play a part in other aspects of apoptosis. The …

In Vivo Murine Melanoma Tumor Responses To Nanosecond Pulsed Electric Field Treatment, Xinhua Chen

Theses and Dissertations in Biomedical Sciences

High intensity nanosecond pulsed electric fields (nsPEF) were applied to melanoma tumors to observe functional and structural biological changes and to investigate the possible molecular mechanisms responsible. An animal model was set up by injecting B16F10 mouse melanoma cells into SKH-1 mice. A treatment (Tx) of 100 pulses: 300 nanosecond duration; 40 kV/cm field strength; at 0.5 Hz rate were delivered to melanoma tumors in 120 mice. The nsPEF Txcaused tumor self-destruction with sharply decreased cell volumes and shrunken nuclei. The apoptotic biochemical tests confirmed nsPEF Tx induced apoptosis in a time-dependent manner. Examination of gross vessel and micro-vessel density …

The Response Of Hn4 Cells To Porphyromonas Gingivalis Dna, Cheyanne Warren

Theses and Dissertations

Periodontal disease is one of the most common human diseases. Bacteria trigger the onset and progression of the disease and among them Porphyromonas gingivalis has been demonstrated to be a major etiologic agent. Although the interaction of the bacterium with the host is of major importance for the understanding of the disease mechanisms, both the host as well as the pathogen components involved in the interaction remain poorly understood. One of the bacterial components capable of eliciting a host response is unmethylated CpG DNA motifs found in bacteria. Thus, the first aim was to determine the response of oral epithelial …

Structural And Biochemical Investigation Of The Molecular Mechanisms Of Dna Response And Repair In Humans And Escherichia Coli., Steven Michael Shell

Electronic Theses and Dissertations

The genomes of all living cells are under constant attack from both endogenous and exogenous agents that damage DNA. In order to maintain genetic integrity a variety of response pathways have evolved to recognize and eliminate DNA damage. Replication protein A (RPA), the eukaryotic single-stranded DNA (ssDNA) binding protein, is a required factor for all major DNA metabolisms. Although much work has been done to elucidate the nature of the interaction between RPA and ssDNA currently there is no structural information on how the full-length protein binds to ssDNA. This study presents a novel examination of the full nucleoprotein complex …

Contribution Of Water And Energetics Of Ligand Binding In The Catalytic Mechanism Of R67 Dihydrofolate Reductase, Shaileja Chopra

Doctoral Dissertations

R67 dihydrofolate reductase (DHFR) catalyzes the transfer of a hydride ion from NADPH to dihydrofolate (DHF) to produce tetrahydrofolate (THF). The enzyme is a homotetramer and its 222 symmetry allows for binding of both ligands to a single active site pore. A productive ternary complex is formed by the binding of one molecule of DHF and NADPH and inter-ligand cooperativity has been suggested to be essential for binding and catalysis. To gain further insight into the thermodynamics involved in the ground state and the transition state, temperature dependent studies on DHF binding and catalysis were performed. It was observed that …

The Ttc7Fsn/Fsn Mutation Results In Hyperactivation Of Lymphocytes And Overproduction Of Il-4 Leading To The Development Of Systemic Autoimmunity, Beth Lindroth Hill

Electronic Theses and Dissertations

Ttc7^fsn/fsn mice exhibit systemic autoimmunity characterized by hyperactivated B cells, increased interleukin-4, autoantibodies, kidney disease and reduced lifespan. Because the pathology is similar to systemic lupus erythematosus, Ttc7^fsn/fsn mice are a useful model with which to study early events that lead to autoimmune disease. Although the Ttc7^fsn mutation has been identified the gene function is unknown. The phenotype of Ttc7^fsn/fsn mice mimics the Th2 autoimmunity of the IL-4 transgenic (Erb et al 1997). It was previously unknown whether the over-production of IL-4 was an intrinsic defect of Ttc7^fsn/fsn lymphocytes that led to autoimmunity, or, whether …

Expression Analysis Of Plant Defense Responses During The Establishment Of Biotrophy And Role Of Abiotic Stress In The Infection Of Dyer’S Woad (Isatis Tinctoria) By Puccinia Thlaspeos, Elizabeth Thomas

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The kinetics and amplitude of the salicylic acid-responsive pathogenesis-related (PR) genes and the cytochrome P450 gene ItCYP79B2 in the compatible interaction between Puccinia thlaspeos and dyer’s woad (Isatis tinctoria) during the first 72 hours of inoculation were examined. Immediately following penetration of the host by the rust pathogen, there was a modest up-regulation of PR genes but a significant down-regulation of ItCYP79B2 expression. During haustoria formation, a significant pathogen-mediated suppression of PR genes was observed with a corresponding up-regulation of ItCYP79B2. This potentially facilitates haustoria formation by P. thlaspeos. After haustoria formation, a more …

Optimization Of Expression And Purification Of Acetoacetyl-Coa Thiolase From Sunflower, Anthony Muriithi Maina

Theses, Dissertations and Culminating Projects

The [beta]-oxidation system in sunflower (Helianthus annuus L.) cotyledons is distinguished by the existence of two different thiolase isoforms, Thiolase I (acetoacetyl-CoA thiolase, EC 2.3.1.9 AACT) and Thiolase II (3-oxoacyl-CoA thiolase, EC 2.3.1.16 OACT). Glyoxysomal AACT is the last enzyme in the p-oxidation of fatty acids in plant glyoxysomes. Glyoxysomal AACT has been successfully cloned, expressed and purified from sunflower cotyledons (Dyer et al., 2006). In this paper we investigate the optimal conditions for both expression and purification. These include the choice of vector, the growth conditions and the purification parameters for the maximum possible yield of AACT protein.