Calendar

Calendar

Seminar Series: Spring 2009

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 6, 2009
Jennifer Krumper, Visiting Assistant Professor of Chemistry, Bowdoin College
Continuum of Mechanisms for Nucleophilic Substitution Reactions of Cyclic Acetals
The effect of nucleophile strength on diastereoselectivity in the nucleophilic substitution of cyclic acetals was explored. Stereoselectivity remained constant and high as nucleophilicity increased until a threshold value was reached. Beyond this point, however, selection of Lewis acid determined whether stereochemical inversion or erosion was observed.  These findings were attributed to transitions between SN1-type and SN2-type reaction mechanisms.  Erosion of stereoselectivity was attributed to diffusion-limited reaction rates.  Data supporting these hypotheses and stereochemical models will be presented.


Friday, February 13, 2009Susan Soloman, Head of the Chemistry and Climate Processes Group of the National Oceanic and Atmospheric Administration Chemical Sciences Division. - Searles 315
Susan Solomon, Head of the Chemistry and Climate Processes Group of the National Oceanic and Atmospheric Administration Chemical Sciences Division.
Ozone Depletion From Pole to Pole







Friday, February 20, 2009Barkley C. Sive, University of New Hampshire Research Associate Professor, Climate Change Research Center
Barkley C. Sive, University of New Hampshire
Research Associate Professor, Climate Change Research Center
Atmospheric Volatile Organic Compound Measurements:  New Insight on Sources and Distributions of Methyl Iodide
Methyl iodide (CH3I) is the most abundant organoiodine compound in the atmosphere and it can influence ozone chemistry, aerosol formation, and ultimately the atmosphere's oxidizing capacity. We have identified terrestrial sources of CH3I and assessed their importance in its atmospheric budget using a synthesis of field observations. Measurements include those from NASA DC-8 research flights over the United States and the North Atlantic, the AIRMAP long-term ground-observing network in New England, and a field campaign at Duke Forest, North Carolina. We found an average CH3I flux of ~2,700 ng m-2 d-1 to the atmosphere from mid-latitude vegetation and soils, a value similar in magnitude to previous estimates of the oceanic source strength. The large-scale aircraft measurements of vertical profiles over the continental U.S. showed CH3I-mixing ratios comparable to and greater than those observed over the North Atlantic. Overall, mid-latitude terrestrial biomes appear to contribute 33 Gg yr-1 to the CH3I global budget.



Friday, April 3, 2009Gary R. Weisman, Universtiy of New Hampshire Gloria G. & Robert E. Lyle Professor of Chemistry
Gary R. Weisman, Universtiy of New Hampshire
Gloria G. & Robert E. Lyle Professor of Chemistry
Cross-Bridged Tetraamines:  Synthesis, Coordination Chemistry, Biomedical Utility, and Conformational Contortions
Short, efficient syntheses of medium-ring bicyclo[5.5.2], [6.5.2], and [6.6.2.] tetraamine ligands, the "cross-bridged" tetraamines and derivatives will be described.  These versatile tetraamines are proton sponges and form strong coordination complexes with a variety of metal ions.  Biomedical utility of these ligands, including application of 64Cu complexes in radiodiagnostic medicine, will be discussed.


Friday, April 17, 2009Vernon N. Reinhold, University of New Hampshire Research Professor in Analytical Chemistry
Vernon N. Reinhold, University of New Hampshire
Research Professor in Analytical Chemistry
The Ion Trap Reigns Supreme as a Carbohydrate Sequenator
For resolving molecular complexity in the field of mass spectrometry, the analytical cu de gras has persistently focused on higher resolution and/or chromatographic interfacing.  This talk demonstrates that such attributes have little influence when considering the utmost challenges of a carbohydrate polymer.  Here the brilliant technology of the ion trap reigns supreme for having a solution long before it could connect to the problem.  This contemporary application now exemplifies the cleaver development by providing component resolution exceeding the best attempts of chormatography and coupled with structural understanding of linkage, branching, stereo-and structural isomers.  Who would have dreamed, and all in the gas phase.

Friday, April 24, 2009 - CANCELLEDLinda McGown, Rensselaer Polytechnic Institute William Weightman Walker Professor and Head Department of Chemistry and Chemical Biology
Linda McGown, Rensselaer Polytechnic Institute
William Weightman Walker Professor and Head
Department of Chemistry and Chemical Biology
Teasing Apart DNA Fragments in Capillary Gel Elecrtophoresis
A major challenge in DNA profiling has been the resolution of single-stranded DNA fragments of similar or identical length based on differences in sequence.  Examples include mutations, polymorphisms and DNA from different organisms in microbial communities. Existing techniques such as single-stranded conformation polymorphism (SSCP) or heteroduplex analysis (HA) rely upon differential migration through a sieving gel due to small differences in conformation of single-stranded DNA fragments or of exact vs. slightly mismatched duplex DNA formed with a complementary strand; however, these small conformational differences become increasingly insignificant with increasing strand size and the high density gels also limit the size of the fragments that can be accommodated. We are working to overcome these limitations through the use of gels formed by guanosine compounds alone or in combination with sieving gels in capillary gel electrophoresis (CGE). Guanosine gels (G-gels) are reversible, self-assembled aggregates of hydrogen-bonded guanine tetrads formed by guanosine nucleosides and their derivatives. They allow unprecedented separation of DNA fragments based solely on sequence rather than strand length or conformation.  Applications include forensic DNA profiling and metagenomic profiling of microbial communities such as biofilms.


Friday, May 1, 2009Wayne E. Steinmetz, Ponoma College Carnegie Professor of Chemistry
Wayne E. Steinmetz, Ponoma College
Carnegie Professor of Chemistry
The NMR Structure of DX600, a Bioactive Peptide with a Random-Coil Conformation
DX600, a small peptide with 26 residents, is a potent, highly selective inhibitor of angiotensin converting enzyme 2.  A range of NMR methods including TOCSY and ROESY yielded constraints on its three-dimensional structure in water.  Modeling calculations-an exhaustive search of conformational space via molecular dynamics and a constrained minimization with the Merck Molecular Force Field - show that the peptide adopts a random-coil conformation which is stabilized by a disulfide bond.  Its backbone defines an overhand knot with frayed ends.