Department of Chemistry and Biochemistry Seminars
Summer Graduate Student Seminar Series
Thursday, May 19 at 3:00 pm
Graduate Student: Lu Wang
Seminar Title: NMR Metabolomics Analyses of Escherichia coli Strains W3110 and AW3110 Reveal Distinct Metabolic Adaptations in the Presence and Absence of Arsenic Stress.
Abstract: Arsenic is classified as a Group-A carcinogen and tops the US EPA Priority List of Hazardous Substances. In nature, its mobility and toxicity is largely governed by bacterial redox transformations that are encoded by arsenic resistance (ars) operons which are widespread in both gram-negative and gram-positive bacteria. Generally, the simplest ars operon encodes the transcriptional regulator ArsR, the As(III) efflux protein ArsB, and arsenate reductase, ArsC. Our recent transcriptomics studies revealed the hierarchical relationship among multiple ArsRs in the genome of a single strain of Agrobacterium tumefaciens, showing how ArsR exerts global repression and activation effects on gene regulation that extends well beyond the current ars operon model. The goal of this project is to use nuclear magnetic resonance (NMR) to examine the metabolome variations that result from such transcriptome changes, and in particular to extend our understanding to microorganisms relevant to the gut microbiome. Escherichia coli strain W3110 is a wild type strain which contains the arsRBC operon, whereas strain AW3110 is an arsRBC deletion mutant, making these strains ideal candidates to study how the ars operon influences metabolism under normal growth conditions as well as under arsenic stress. Growth of AW3110 was significantly weaker than strain W3110 regardless of arsenic, indicating that the loss of the ars genes results in significant cellular changes. NMR verified this to be the case; multivariate statistical analysis of profiled metabolites reveals fundamental metabolomic differences between W3110 and AW3110 in both control cells as well as arsenate treated cells. This study provides insights into the metabolic adaptations of E. coli strains W3110 and AW3110 following arsenic stress and demonstrates the global effects of ars operon on bacterial metabolism.
Research Advisors: Professor Valérie Copié and Professor Tim McDermott
Thursday, May 26 at 3:00 pm
Graduate Student: Skyler Hollinbeck
Seminar Title: Leveraging Ultrafast Microscopies to Explore Excited State Dynamics and the Structure-Function Relationship of Organic and Hybrid Systems.
Abstract: It is well known that molecular energetics and optoelectronic properties are strongly affected by local chemical environments. This phenomenon is well studied in the effect of solvation on single molecules and to a lesser degree suspended molecular aggregates. However, within the growing application of organic molecules and chromophores to optoelectronic devices such as photovoltaics, LEDs, and photocatalysts, they are often most effective when deposited into solid thin films. Additionally, because these devices employ energy from light to do work, it is important to characterize not only the ground state but also how the excited state behaves in solid-state assemblies. We are uniquely positioned to explore this lively research area because of our development of ultrafast broadband microscopies with high spectral, spatial, and temporal resolution.
We have two interests in this field: to investigate the optoelectronic effect of directed molecular aggregation on a perylene-3,4,9,10-bis(dicarboxyimide) (PDI) organic semiconductor system, and to investigate how organic ligand character affects nanoparticle properties in suspension and solid-state assembly. Within the PDI investigation we compare equilibrium assembled thin film structures to kinetically trapped samples obtained from our collaborator Jean-Hubert Olivier. We have observed differences in morphology, relaxation kinetics, and polarization responsivity between these samples as well as obtained preliminary Femtosecond Stimulated Raman Microscopy measurements. Our goal is to elucidate what these observations mean regarding the nature of excited state relaxation and how it may affect device efficiency. The perovskite nanoparticle study will focus on how different ligand environments manifest changes in thin film excited state behavior. By illuminating the intricate interactions described by these two systems we will build knowledge that is very useful in material selection, fabrication and understanding of organic semiconductor and hybrid devices.
Research Advisor: Professor Erik Grumstrup
Thursday, June 2 at 3:00 pm
Research Advisor: Professor Tom Livinghouse
Thursday, June 9 at 3:00 pm
Research Advisor: Professor Valérie Copié
Thursday, June 16 at 3:00 pm
Research Advisor: Professor Rob Walker
Thursday, June 23 at 3:00 pm
Research Advisor: Professor Sharon Neufeldt
Thursday, June 30 at 3:00 pm
Research Advisor: Professor Sharon Neufeldt
Friday, August 26
Isabelle Gordon 4th year Graduate Student seminar
Izzy is a graduate student in the PhD Materials Science program.
Host: Prof. Nick Stadie
Friday, September 2
Asst. Prof. Martin Mosquera
Friday, September 9
Patrick Anderson Graduate Student Seminar
Research Advisor: Prof Mary Cloninger
Friday, September 16
Prof. Jennifer Bridwell-Rabb of U Michigan
Host: Prof. Jen DuBois
Friday, September 23
Asst. Prof. Sharon Neufeldt
Friday, September 30-open
Friday, October 7 -
Prof. Edwin Antony (Dept. of Biochemistry and Molecular Biology) Saint Louis University School of Medicine
Host: Prof. Brian Bothner
Friday, October 14
Asst. Prof. Nick Stadie
Friday, October 21
Saia Afrin - Materials Science PhD student seminiar
Host: Prof. Erik Grumstrup
Friday, October 28
Asst. Prof. Roland Hatzenpichler