Enhanced Sensitivity Biological EPR

University Of Denver, Denver CO

Investigators

Abstract

ABSTRACT 9986942 Gareth R. Eaton University of Denver Enhanced Sensitivity Biological EPR Electron paramagnetic resonance (EPR) is a spectroscopic method for studying unpaired electrons. Unpaired electrons are often found in naturally occurring proteins that are important in chemistry and biology. Unpaired electrons are also produced by radiation damage and by pyrolysis in foodstuffs and in other materials. Modern EPR methods can determine the detailed environment of unpaired electrons, their lifetimes, and their interactions. For example, interactions between discrete pairs of free radicals can be used to measure distances in proteins. The special features of EPR that provide unique power for biological characterization are that (1) the method detects only unpaired electrons, and thus can literally see the needle in the haystack; (2) EPR can see unpaired electrons in solids or in liquid solution phase and over a wide range of temperatures; and (3) the large electron magnetic dipole results in very-long-range effects on EPR line shapes and relaxation times. EPR spectra can be observed for proteins in membranes and even in whole cells and tissues, environments that can confound other physical methods. Unfortunately, these advantages of EPR sometimes cannot be exploited in biological systems because of a severe signal-to-noise problem. This award will support improvement in the signal-to-noise level attainable by EPR. The award will make it possible to combine newly invented types of EPR resonators, cryogenically coolable limiters, and low noise cryogenically coolable microwave amplifiers into application-specific modules. The resulting spectrometer will be used to study proteins whose EPR signals are too weak to be effectively studied by current commercial EPR spectrometers. The technology developed will be transferable and could be used to upgrade existing EPR spectrometers in other laboratories. Students, and visitors to the University of Denver, will be trained in the new technology. Through collaborations with researchers at many other schools the new technology will be applied to a wide variety of biological problems and will be iteratively refined to give the best signal-to-noise possible for biological samples.