Paramagnetic transition metal ions provide the opportunity for application of a wide variety of spectroscopic techniques. Although spectroscopic techniques are not as well known as conventional nuclear magnetic resonance (NMR), they provide detailed information centered on the active site itself. This book describes the application of paramagnetic resonance techniques to a number of important systems in metallobiochemistry. Simultaneously, this volume provides information on novel experimantal methods and theoretical approaches to understanding the structure and function of metalloenzymes and other metallobiomolecules. The specific techniques described include electron paramagnetic resonance (EPR) spectroscopy, and its derivative techniques, electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM). These latter two techniques directly probe the nuclear environment of the paramagnetic active site, without interference from magnetically active nuclei that are not involved in the active site. Magnetic circular dichroism (MCD), which links magnetic resonance and oprical spectrospoy, is also described. The application of MCD to problems in metallobiochemistry is growing rapidly, yet uhere are few sources that clearly describe this complex technique. This volume provides several approaches involving MCD. Finally, this book also includes a wide variety of biological systems including heme proteins, iron-sulfur proteins, molybdopterins, manganese proteins, and copper proteins, as well as non-protein biological molecules, such as ribozymes.