ABSTRACT
Electron paramagnetic resonance (EPR) spectroscopy, also less frequently called electron spin resonance (ESR) spectroscopy, or occasionally electron magnetic resonance (EMR) spectroscopy, is the resonance spectroscopy of molecular systems with unpaired electrons. Although there are more molecules without unpaired electrons (diamagnets) than with unpaired electrons (paramagnets), the latter are usually of particular interest. For example, biomolecules with unpaired electrons are transition ion complexes or radicals, and these structures are frequently found where the biological action is in the active center of enzymes, for example. This book is about the EPR spectroscopy of biomolecules and of several classes of biochemically relevant synthetic molecules, notably models or mimics, probes, and traps. Biomolecular EPR spectroscopy, or bio-EPR for short, has a long and imposing history as a tool in the life sciences. The technique has been instrumental in the discovery of biological metal clusters, an area of research that in its turn has greatly stimulated the still expanding field of synthetic metal cluster chemistry. Also, bio-EPR has been a key technique in the initial characterization of copper, nickel, molybdenum sites, to name a few, as the hearts of metalloenzymes. And studying radical biochemistry is not easily envisioned without the resource of an EPR machine.
