Life Sciences Commons^™

Structure-Function Relationships In Bacterial Regulatory Proteins And An Enzyme Involved In Antibiotic Biosynthesis, Lanlan Han

Theses and Dissertations

The first part of my thesis is focused on a new family of two-component response regulator proteins: Aspartate-Less Regulators (ALR). They lack the catalytic aspartate residue required for the phosphorylation mechanism of typical two component response regulators. We are using biophysical tools to characterize two proteins with redox-sensitive ALR domains: repressor of iron transport regulator (RitR) from Streptococcus pneumonia R6 and diguanylate cyclase Q15Z91 from Pseudoalteromonas atalantica. The structure of inactive RitRC128S monomer showed that the ALR domain and the DNA-binding domain are linked by an α-helix that runs the length of the entire protein, with C128 near the C-terminal …

Sex Differences In Differential Fear Conditioning During The Acquisition And Consolidation Of Learned Safety, David Sylvan Reis

Theses and Dissertations

The ability to distinguish between threatening and non-threatening situations requires careful regulation of behavioral and physiological responses to stress and fear. Deficits in fear regulation are maladaptive and can lead to the development of anxiety disorders such as PTSD. Women are nearly twice as likely to develop PTSD as are men and laboratory animal studies have shown facilitated fear acquisition, resistance to fear extinction, deficits in extinction retention and impaired discrimination between danger and safety cues in females. Taken together this suggests a propensity for reduced inhibitory control over fear responding in females. Here we investigate the mechanisms underlying fear …

An Inducible Fluorescent Reporter System To Measure Lux Operon Promoter Activity, Nicole Thunes

Theses and Dissertations

Bioluminescence is the enzymatic production of light by a living organism. Many species of marine bacteria produce light with varying degrees of brightness. The lux operon is responsible for bioluminescence and is well studied, however it is currently unknown why different species of bacteria display different brightness levels. A dual-plasmid system designed to mimic the quorum-sensing induction of the lux operon was created and successfully implemented in E. coli. This was accomplished through the use of an arabinose-inducible plasmid containing a luxR gene from Vibrio harveyi, and then using the resulting LuxR protein to activate the lux promoter in a …

Interaction With Nitric Oxide Of The Nitrosomonas Europaea Tetraheme Protein Cytochrome C554, And Two Of Its Variants, In Increasingly Reducing Environments, Jennifer M. Mcgarry

Theses and Dissertations

A re-investigation of the interaction with NO of the small tetraheme protein cytochrome c554 (C554) from Nitrosomonas europaea has shown that the 5-coordinate heme II of the 2-electron or 4-electron reduced protein will nitrosylate reversibly. The nitrosylation process was found to be first order in C554, first-order in NO, and second-order overall. The rate constant for NO binding to the heme was determined to be 3000 ± 140 M-1s-1, while the rate constant for dissociation was 0.034 ± 0.009 s-1; the degree of protein reduction does not appear to significantly influence the nitrosylation rate. In contrast to a previous report, …

Part – I: Development Of A Two-Step Regiospecific Synthetic Route For Multigram Scale Synthesis Of Β-Carboline Analogs For Studies In Primates As Anti-Alcohol Agents,Part – Ii: Design And Synthesis Of Novel Antimicrobials For The Treatment Of Drug Resistant Bacterial Infections Part – Iii: A Novel Synthetic Method For The Synthesis Of The Key Quinine Metabolite (3s)-3-Hydroxyquinine, Veera Venkata Naga Phani Babu Tiruveedhula

Theses and Dissertations

PART – I

Development of a Two-Step Regiospecifc Synthetic Route for Multigram-Scale Synthesis of β-Carboline Analogs for Studies in Primates as Anti-Alcohol Agents

β-Carboline and their derivatives are important structural motifs in synthetic organic and medicinal chemistry because of their novel biological activity, especially in regard to the reduction of alcohol self-administration [binge drinking (BD)], a major problem increasing day by day in modern society. This anti-alcohol effect is proposed to be due to the activity of ligands at the benzodiazepine site of the GABAA receptor in the central nervous system acting as antagonists at the α1 subunit. The past …

New Insights Into The Role Of Antimicrobials Of Xenorhabdus In Interspecies Competition, Kristin Jean Ciezki

Theses and Dissertations

Xenorhabdus spp. are symbionts of entomopathogenic nematodes and pathogens of susceptible insects. The nematodes penetrate the insect midgut to enter the hemocoel where Xenorhabdus bacteria are released, transitioning to their pathogenic stage. During nematode invasion microbes from the insect gut translocate into the hemocoel. In addition, different species of nematodes carrying specific strains of Xenorhabdus can invade a single insect. Xenorhabdus spp thereby engage in competition with both related strains and nonrelated gut microbes. In complex media Xenorhabdus spp produce diverse antimicrobial compounds whose functions in biological systems remain poorly understood. R-type bacteriocins are contractile phage-tail-like structures that are bactericidal …

The Role Of Pilj And Its Structural Domains In The Localization And Function Of The Chp Chemosensory System In Pseudomonas Aeruginosa, Vibhuti Hemantkumar Jansari

Theses and Dissertations

Bacteria detect environmental signals using membrane-bound methyl-accepting chemotaxis proteins (MCPs), which are part of a larger complex of chemosensory proteins. Pseudomonas aeruginosa has four functionally distinct chemosensory protein complexes. The Chp chemosensory system regulates type IV pili mediated twitching motility and intracellular levels of cAMP by modulating the activity of an adenylate cyclase, CyaB. The Chp system is also proposed to be involved in type IV pili mediated directional twitching motility towards phosphatidylethanolamine (PE). PilJ is the only MCP predicted to be associated with the Chp system. In this study we investigated different domains of PilJ in order to decipher …

Biomedical Applications Of Mid-Infrared Spectroscopic Imaging And Multivariate Data Analysis: Contribution To The Understanding Of Diabetes Pathogenesis, Ebrahim Aboualizadeh

Theses and Dissertations

Diabetic retinopathy (DR) is a microvascular complication of diabetes and a leading cause of adult vision loss. Although a great deal of progress has been made in ophthalmological examinations and clinical approaches to detect the signs of retinopathy in patients with diabetes, there still remain outstanding questions regarding the molecular and biochemical changes involved. To discover the biochemical mechanisms underlying the development and progression of changes in the retina as a result of diabetes, a more comprehensive understanding of the bio-molecular processes, in individual retinal cells subjected to hyperglycemia, is required. Animal models provide a suitable resource for temporal detection …

Microbial Communities And The Diverse Ecology Of Fecal Indicators At Lake Michigan Beaches, Danielle Cloutier

Theses and Dissertations

Fecal indicator bacteria (FIB) such as Escherichia coli (E. coli) and enterococci are used to assess microbiological water quality in recreational waters. The use of FIB follows the assumption that their presence correlates with that of fecal-associated pathogens in recreational waters. The beach ecosystem is complex however and multiple factors can influence the concentration of E. coli and enterococci in the beach environment. Microbial communities within beach sand play a key role in nutrient cycling and are important to the nearshore ecosystem function. E. coli and enterococci, two common indicators of fecal pollution, have been shown to persist in the …

Towards Autonomous Microcystin Detection: Investigating Methods For Automation, Maureen Anne Schneider

Theses and Dissertations

Due to increased anthropogenic activity, severe eutrophication is occurring in bodies of water around the world. Effects include decreased water quality, decreased value of surrounding land and recreational use (estimated loss in revenue of 0.67 and 3.96 U.S. billion dollars per year), and increased occurrence of toxin producing Harmful Algal Blooms (HABs). Microcystins are cyclic peptides made up of 7 amino acids and 800-1100 Daltons in size. They are one of the most predominantly produced of these toxins, and therefore was the focus of this study. Numerous structural variants of microcystin (referred to as congeners) exist, but microcystin-LR is one …

Investigation Of Membrane Receptors’ Oligomers Using Fluorescence Resonance Energy Transfer And Multiphoton Microscopy In Living Cells, Ashish K. Mishra

Theses and Dissertations

Investigating quaternary structure (oligomerization) of macromolecules (such as proteins and nucleic acids) in living systems (in vivo) has been a great challenge in biophysics, due to molecular diffusion, fluctuations in several biochemical parameters such as pH, quenching of fluorescence by oxygen (when fluorescence methods are used), etc.

We studied oligomerization of membrane receptors in living cells by means of Fluorescence (Förster) Resonance Energy Transfer (FRET) using fluorescent markers and two photon excitation fluorescence micro-spectroscopy. Using suitable FRET models, we determined the stoichiometry and quaternary structure of various macromolecular complexes. The proteins of interest for this work are : (1) sigma-1 …

A Novel Link Between The Chemotaxis And Biofilm Dispersion Systems Of Pseudomonas Aeruginosa, Jesse Michael Reinhardt

Theses and Dissertations

Bacterial chemotaxis is the movement of a cell towards an attractant or away from a repellent. This controlled movement is possible due to the chemotaxis system, which is typically made up of several proteins that collectively sense the stimuli and transduce the signal within the cell to mediate a motility response. The chemotaxis proteins of Pseudomonas aeruginosa are encoded in two clusters, which are located at different regions of the chromosome: che I and che V. These gene clusters are known to control chemotaxis via swimming, or flagellar-based, motility. When expressed, these chemotaxis proteins associate with each other to form …