General Description of the Volume: The role of low molecular weight cofactors (often vitamins) in enzyme catalysis has been discussed in many earlier volumes of Methods in Enzymology. Exciting new results indicate that redox-active prosthetic groups can also arise from pre-existing amino acid side chains in proteins. In this volume, methods are described for the detection and characterization of such prosthetic groups in a range of enzyme systems. General Description of the Series: The critically acclaimed laboratory standard for more than forty years, Methods in Enzymology is one of the most highly respected publications in the field of biochemistry. Since 1955, each volume has been eagerly awaited, frequently consulted, and praised by researchers and reviewers alike. Now with more than 300 volumes (all of them still in print), the series contains much material still relevant today--truly an essential publication for researchers in all fields of life sciences.