Pulsed EPR in the Study of Drug Binding in Cytochrome P450 and NOS.

Pulsed EPR methods for the study of drug binding to heme-thiolate enzymes such as cytochrome P450 and nitric oxide synthase are discussed. HYSCORE and ENDOR methods to measure (1)H of axial ligands of the heme group are described with illustrations of water serving as the axial ligand in the drug-free enzyme and ligands coordinating directly to the heme or through one or more bridging water molecules. Some practical aspects of measurement and data processing are discussed along with prospects for use with other nuclei and at other EPR bands.