Calendar
Calendar
Seminar Series: Spring 2008
All seminars are Fridays, 3-4pm Druckenmiller room 20 and a student reception in Druckenmiller 26 prior to the seminar, unless otherwise noted.
Chemistry Faculty & Student Lunch
When: Every Friday at 12:30pm
Where: Pinette Dining Room, Thorne Dining Hall
Why: Get to know the chemistry faculty and other students interested in chemistry
Friday, February 15, 2008 CANCELLED
Roy P. Planalp
Associate Professor of Inorganic Chemistry
Department of Chemistry
University of New Hampshire
Iron Chelation for Health: Synthetic Tripods and Ways to Spice it Up
Abstract:
The biometals iron, copper and zinc are necessary for life yet toxic when in excess. The diseases of iron overload or copper overload have serious consequences, which have led to more or less successful treatment regimens, in which metal chelators are used to motivate excretion of the excess metal. This lecture presents work to selectively chelate iron with synthetic ligands and studies of plant-based medicines (curcuminoids, derived from turmeric et. al.) for which we believe iron chelation is a contributor to the therapeutic value.
Friday, February 22, 2008
Shizuka Hsieh
Assistant Professor
Department of Chemistry
Smith College
Making radicals from vibrationally-excited organic hydroperoxides
Abstract:
An active and important oxidant in the atmosphere is the OH radical. An unusual source of these OH radicals is visible-light photodissociation via highly vibrationally-excited molecules. We investigate the vibrational states of two organic hydroperoxides, CH3OOH and CH3CH2OOH, which are secondary pollutants formed from hydrocarbon emissions. A combination of laser photoacoustic spectroscopy and quantum mechanical calculations indicates that excitation involves both O-H stretch and torsional motion aboth the peroxide O-O bond. Laser-induced fluorescence reveals which of these vibrationally-excited states preferentially dissociate to form OH radicals.
Friday, February 29, 2008
Anthony Bishop
Assistant Professor
Department of Chemistry
Amherst College
Ligand-sensitive protein tyrosine phosphates
Abstract:
Protein tyrosine phosphates (PTPs) catalyze the dephosphorylation of phosphotyrosine, a central signal-transduction control element. Small-molecule inhibitors that are specific for individual PTPs would be valuable tools for dissecting protein-phosphorylation networks. However, the common architecture of PTP active sites impedes the discovery of selective PTP ligands. We have utilized a combination of chemical and biochemical approaches to target engineered PTPs with highly selective small-molecule ligands. The crux of these strategies resides in the design of "ligand-sensitized" PTPs through protein specificity inhibitors with bulky chemical groups that are designed to fit a novel, rationally redigned, PTP active site. In a complementary approach, we have generated allosterically controllable PTPs through insertion of ligand-binding motifs in PTP catalytic domains. The insertions were designed to confer novel ligand-sensitivity to a small molecule that has little to no effect on all wild-type PTP catalytic domains. Successful identification of ligand-sensitive PTP/small molecule pairs should greatly facilitate the chemical-genetic analysis of PTP function, and may have applications in the validation of PTPs as viable therapeutic targets.
Thursday, March 27, 2008
Garry Buettner
Professor & Assistant Director
Free Radical and Radiation Biology Graduate Program
University of Iowa
Superoxide and H2O2in Health and Disease: Superoxide dismutase and ascorbate in cancer and cancer treatment
Friday, April 4, 2008
Ming Chen Hammond
Burroughs Wellcome Fund CASI Post-Doctoral Fellow
Molecular, Cellular, Developmental Biology
Yale University
Riboswitches and Beyond: Deciphering the Regulatory Logic of Natural RNA Sensors
Abstract:
It is increasingly apparent that messenger RNAs are active rather than passive agents in the process of converting the instructions dictated by our genomic DNA to translated proteins. This regulatory activity is due to portions of mRNA that were previously considered “junk”, the untranslated regions (UTRs) at the ends of protein coding sequences and the introns in between. For example, some UTRs contain sequences that directly bind to specific small molecule metabolites and alter production of the downstream encoded proteins in response. These natural chemical sensors made of RNA are called “riboswitches” and are very common in bacteria. In this lecture I will present our discovery of a tandem riboswitch architecture that acts as two chemical input logic gate in bacteria. More recently, we have expanded our search for novel regulatory RNAs to eukaryotes, and I will present our latest discovery of a plant RNA that utilizes structural mimicry of a ribosomal RNA to control alternative splicing of an rRNA-related gene. These natural RNA-based regulatory circuits hint at an even greater repertoire for RNA in the cell, and may elucidate starting paradigms for building synthetic biological systems.
Friday, April 11, 2008
Ephraim Woods III
Associate Professor
Department of Chemistry
Colgate University
What Its Like to Be Sea Spray Abstract:
We use probe molecule spectroscopy to characterize the surface model marine aerosol particles. In some cases, we can generate empirical polarity parameters that provide measures of dipolarity/polarizability and hydrogen bond acidity on the particle surfaces. These experiments show that both composition and morphology are important in determining the character of the surface. We also measure the photoelectric charging efficiency of these model aerosols, which is a sensitive indicator of the amount of water on the particle's surface. These complementary measurements provide a clear picture of the particle morphology over a wide range of relative humidity and highlight important considerations for the heterogeneous chemistry of marine particles.
Friday, April 18, 2008
Patricia Matrai
Senior Research Scientist
Bigelow Laboratory for Ocean Sciences
Microlayer Organic Composition in the High Arctic: Marine Biogenic Precursors of Atmospheric Primary Particles?
Abstract
Particulate organic matter, including microorganisms, small water-insoluble particles and microaggregates, can form a substantial part of the summer aerosol over the open leads of the central Atlantic Ocean. The increased presence of leads during the summer melt increases the biological activity of the region possibly resulting in accumulation of organic material, especially in the surface microlayer. Preferential microlayer enrichment of particulate and dissolved organic matter and gases might be reflected in derived aerosols. The subsurface seawater and microlayer concentrations were determined for dimethyl sulfide (DMS) and its biogenic precursor dimethylsulfoniopropionate (DMSP), dissolved combined amino acids (DCAA) and individual aminoacids, proteins, chlorophyll a (chl a) and bacterial cells as well as bacterial production. Enrichment factors and surface excess concentrations in the surface microlayer were calculated. Concentrations of particulate and dissolved DMSP, chl a -containing material, and bacterial cells were consistently enriched in arctic lead microlayers at 89 °N in August 2001. DMS, protein and DCAA concentrations, however, were not in excess in surface microlayers, although proteins were occasionally enriched. Co-occurences of enrichment and atmospheric nucleation events will be discussed.
May 2, 2008
Amy Gehring
Assistant Professor
Department of Chemistry
Williams College
Stressing Out Streptomyces: Proteomic Consequences of Sigma Factor Activity Abstract Bacteria of the genus Streptomyces are famous as producers of a diverse array of antibiotic molecules. Antibiotic production is intimately linked to the organism's complex life cycle, which culminates in sporulation. This talk will focus on the proteomic consequences of SigU activity, a protein involved in gene transcription whose unregulated activity leads to defects in both the sporulation and antibiotic production pathways. We have used MALDI-TOF mass spectrometry to identify a large number of unique proteins secreted by Streptomyces coelicolor as a result of SigU activity, a likely response to environmental stress conditions.