Award Abstract #0820965
MRI: Acquisition of a Spectropolarimeter for Circular Dichroism and Magnetic Circular Dichroism Experiments

NSF Org:	CHE Division of Chemistry
Initial Amendment Date:	August 14, 2008
Latest Amendment Date:	August 14, 2008
Award Number:	0820965
Award Instrument:	Standard Grant
Program Manager:	Carlos A. Murillo CHE Division of Chemistry MPS Directorate for Mathematical & Physical Sciences
Start Date:	August 15, 2008
Expires:	July 31, 2011 (Estimated)
Awarded Amount to Date:	$76748
Investigator(s):	James Larrabee larrabee@middlebury.edu (Principal Investigator)
Sponsor:	Middlebury College 9 OLD CHAPEL ROAD MIDDLEBURY, VT 05753 802/443-5000
NSF Program(s):	MAJOR RESEARCH INSTRUMENTATION
Field Application(s):
Program Reference Code(s):	othr, biot, OTHR, 9184, 9183, 9150, 0000
Program Element Code(s):	1189

ABSTRACT

The Department of Chemistry at Middlebury College will acquire a spectropolarimeter with this award from the Major Research Instrumentation (MRI) program. It will be coupled to a variable field magnet to enable magnetic circular dichroism (MCD) as well as circular dichroism (CD) measurements. Studies by the principal investigator (PI) will utilize variable temperature, variable field magnetic circular dichroism to determine the strength of the magnetic coupling in a series of carboxylate-bridged Co(II) dimer complexes and enzyme active sites which contain dinuclear Co(II). This will provide a more detailed picture of the electronic ground state structure of this active site motif commonly found in nature. MCD will be used by the co-PI to perform exploratory experiments on the interactions of Ru(III) complexes with DNA analogues. Two additional Middlebury biochemistry professors will use the instrument to collect CD data for protein secondary structure analysis.

A circular dichroism spectropolarimeter will produce circular dichroism spectral data that provides information on molecular structure and especially the conformations of biomolecules such as proteins, enzymes and nucleic acids. In magnetic circular dichroism, chirality is induced by a strong magnetic field applied parallel to the direction of light propagation, a phenomenon known as the Faraday effect. The behavior of MCD intensity with temperature and field strength is dependent on the electronic ground state of the metal. Thus MCD is a sensitive probe of the electronic structure associated with paramagnetic metals ions in small complexes and protein active sites. The instrument will be used in research by undergraduate students. This training will prepare students to utilize this sophisticated technique in various careers, especially in chemical, biological and health related fields.

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