This award is a Career Advancement Award under the Research Opportunities for Women Program. The award will be used to gain mastery of biochemical techniques necessary for protein manipulation in a project concerned with the mechanisms of biological electron transfer. Electron transfer is one of the most fundamental biological processes. It is an integral part of many metabolic pathways and plays a vital role in the utilization of oxygen by biological systems. The focus of the research project is electron transfer between cytochromes, a family of metalloproteins which undergo electron transfer during the utilization of oxygen. The study will focus on the three factors which are expected to be the primary determinants of cytochrome electron transfer: electrostatics, the distance between the two hemes, and protein motion. Electron self-exchange rate constants will be measured for: a) cytochromes from various species, b) cytochromes with derivatized residues, c) cytochromes in which the native heme has been replaced with a synthetic heme, d) cytochromes in which there is a break in the polypeptide chain, and e) cytochromes synthesized via site-directed mutagenesis. Self-exchange rate constants will be measured by NMR spectroscopy.