Calendar of Events

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Chemistry Department Seminar. Carolyn Bertozzi Univeristy of California Berkeley. "Bioorthogonal Chemistry"

January 23, 2015 3:00 PM  – 4:00 PM
Druckenmiller Hall, Room 020

The molecular details of biological processes can be most accurately understood by probing biomolecules within their native habitats – in cells, or even better, live organisms.  To interrogate biomolecules in such complex settings requires the means to selectively modify them with imaging probes, affinity reagents, or moieties that perturb function.  Toward this end, we have focused on the development of chemical reactions that have such exquisite selectivity that they can be employed to modify biomolecules even within the environs of live organisms.  Such “bioorthogonal” chemical transformations include C-C bond forming reactions with aldehydes, which we employ for site-specific protein chemical modification, as well as reactions of azides that enable in vivo imaging of metabolically labeled glycoconjugates.  Progress toward the development of chemically modified protein therapeutics and methods for imaging disease-related glycans will be discussed in this presentation.

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Chemistry Department Seminar. Jennifer Koviah-Cote. Bates College. "Synthesis and Anti-Oxidant Activity of Phenylpropanoid Glycosides"

February 13, 2015 3:00 PM  – 4:00 PM
Druckenmiller Hall, Room 020

Phenylpropanoid glycosides, isolated from plants, show significant activity as radical scavengers and antioxidants. As part of a study to better understand the mechanism by which these compounds scavenge free radicals, we have synthesized a library of compounds containing 1-4 phenylpropanoid groups on a glucose core. We then measured the radical scavenging activity of each compound in both a protic and aprotic solvent using a well established assay. We found that anti-oxidant activity is most dependent on the number of phenol groups present in the compound, but preliminary data suggests that proximity of two groups may also play a role.

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Peter Woodruff, Chemistry Seminar: "Harnessing Enzymes to Synthesize Probes Against Pathogenic Mycobacteria"

April 3, 2015 3:00 PM  – 4:00 PM
Druckenmiller Hall, Room 020

Mycobacteria, including the pathogenic Mycobacterium tuberculosis, require the sugar trehalose for construction of their cell wall. Trehalose analogs are emerging as valuable tools for inhibiting Mycobacterium tuberculosis, but progress in this area is slow due to the difficulty in synthesizing these compounds using traditional organic synthesis. 

In this chemistry seminar, Peter Woodruff discusses the invention of a chemoenzymatic method for the synthesis of trehalose analogs that employs the heat-stable enzyme trehalose synthase (TreT) from the hyperthermophile Thermoproteus tenax. He examines how, by using TreT, various trehalose analogues were prepared quickly (one hour) in high yield in a single step from readily available glucose analogues. In addition, he explains data that reveals how several of these analogs are incorporated into the mycobacterial cell wall used to detect the bacteria, laying the groundwork for imaging tuberculosis infections in live patients.

Woodruff is assistant professor of chemistry at the University of Southern Maine. 

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Michael Ardolino: "Catalyst Design, Methodology Development and Mechanistic Studies in Asymmetric Organo-Organometallic Catalysts."

April 10, 2015 3:00 PM  – 4:00 PM
Druckenmiller Hall, Room 020

Carbon- and heteroatom-bearing stereocenters are common in natural products and have become increasingly prevalent in many of today's leading pharmaceutical compounds. As a result, enantioselective methods to build chiral molecules are of central importance to fields within organic chemistry ranging from total synthesis to the design and production of therapeutic drugs.

Michael Ardolino will discuss how, in that context, his graduate and post-doctoral research has focused on the development of highly selective, efficient, and robust catalytic asymmetric methodologies that utilize both organic- and organometallic-based catalysts. Specifically, his work in the Morken laboratory at Boston College focused on the development of palladium-catalyzed asymmetric allyl-allyl and allyl-propargyl cross-couplings. These methods allowed for the synthesis of synthetically useful branched 1,5-dienes and 1,5-enynes with previously unprecedented enantio- and regioselectivity.

Ardolino's ongoing work at Harvard University in the Jacobsen lab is focused on the development of silicon- and tin-based catalysts for anion-binding. These catalysts provide an attractive alternative to current urea- and thiourea-based anion-binding catalysts as they engage hard anions such as hydroxide and alkoxides through sigma-hole interactions rather than hydrogen-bonding.

His talk will summarize each of these areas of research, with a focus on the laboratory and computational-based mechanistic studies that have been utilized to probe elements of reactivity and selectivity and guide further development.

Michael Ardolino is a Post-doctoral Research Fellow at Harvard University. He graduated from Bowdoin in 2008.

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Joseph Dinnocenzo: "Revised View of Electron Transfer Dependence on Free Energy"

April 17, 2015 12:00 PM  – 1:00 PM
Druckenmiller Hall, Room 020

In a landmark publication over forty years ago, Rehm and Weller
used a comprehensive set of data to show that photoinduced
electron transfer (PET) rate constants correlate with excited state energies and ground state redox potentials. The Rehm Weller paper has been cited more than 3000 times and the data contained in it interpreted by a variety of theoretical models. 

In this talk, Joseph Dinnocenzo will show that the widely accepted Rehm Weller equation and plot have serious flaws. He explains that revised measurements obtained in the lab differ significantly from those of Rehm and Weller and are interpreted in terms of a simple Boltzmann type equation that takes into account not only Coulombic stabilization of contact ion radical pairs produced by PET, but also solvation and desolvation processes. In addition, he will speak to finding that the mechanism for the PET reactions studied by Rehm and Weller does not involve simple, one electron transfer, but instead occurs by two partial electron transfers via exciplex intermediates. 

The general implications of the results and a variety of lessons learned will be discussed.

Joseph Dinnocenzo is a professor of chemistry at the University of Rochester in Rochester, New York. He received his Ph.D. from Cornell University in 1983. 



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Reception for Admitted Students: Introduction to the Bowdoin Science Experience

April 17, 2015 3:45 PM  – 4:45 PM
Druckenmiller Hall, Atrium

Congratulations! Admission to Bowdoin is a first step in a successful college career. The Bowdoin Science Experience offers incoming first-year students a unique alternative to the orientation trips. BSE is committed to developing the talents of all students interested in science and mathematics-particularity those underrepresented in the sciences, including students of color, women and first generation college students. This is an opportunity to speak with the director of Bowdoin Science Experience Michael Danahy and meet current BSE members and mentors. We hope to see you there!

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Robert Hettich: "Development of a Proteogenomic Approach for the Characterization of the Functions and Metabolic Activities of the Human Gut Microbiome"

April 24, 2015 3:00 PM  – 4:00 PM
Druckenmiller Hall, Room 020

The human gastrointestinal tract is a complex ecosystem containing a delicate balance of human and microbial cells involved in an intricate symbiotic relationship. In general, the microbial constituency helps maintain a healthy environment and aids in efficient digestion. However, environmental and/or genetic factors may result in an altered bacterial composition that manifests in a diseased condition, such as Crohn's disease. 

 In his talk, Robert Hettich will discuss how the recent availability of whole community genome sequencing and whole community proteomics has provided unique capabilities of profiling the compositions and activities of this microbiome without having to cultivate its membership. He describes the development of a non-targeted, mass spectrometry-based proteomics approach to identify the microbial proteins in human fecal samples; how proteome samples were characterized via a multidimensional LC tandem mass spectrometric approach on a hybrid linear ion trap-Orbitrap, yielding greater than four thousand proteins per sample; how amongst the microbial membership, the Bacteroides and Bifidobacterium spoecies were the abundant, as expected since these are known to be common in the human gut. The majority of the microbial proteins that were identified were classified into functional categories for translation, energy generation, and carbohydrate metabolism. Surprisingly, a number of innate human immunity proteins were also observed, suggesting a level of human regulation of microbial abundance. Finally, he explains how the results of his study demonstrate that it is possible to obtain high quality, extensive protein identifications by integrating metagenomic and metaproteomic information from human gut micro biomes. 

Hettich is a scientist on the senior research staff with the organic and biological mass spectrometry group in the chemical sciences division at the Oak Ridge National Laboratory. He holds a Ph.D. analytical chemistry from Purdue University, a B.S. in chemistry from South Dakota School of Mines and Technology,? and is an adjunct faculty member for genome sciences and technology at the University of Tennessee graduate school in Knoxville.

Chemistry Seminars

May 1, 2015 3:00 PM  – 4:00 PM
Druckenmiller Hall, Room 020