ABSTRACT
Electron paramagnetic resonance (EPR), also known as electron spin resonance or electronic magnetic resonance spectroscopy, is a means of investigating paramagnetic molecules (i.e., those containing unpaired electrons) [1]. The majority of molecules are diamagnetic, having all their electrons paired in atomic or molecular orbitals. As a result, EPR is a selective technique capable of yielding specific molecular information. EPR spectroscopy has many different applications in
biochemistry and molecular biology. These include the observation of transient free radicals by spin trapping and the observation of molecular motion and environment by spin labeling-methods that involve the introduction of a paramagnet to the biological system. However, this chapter will focus principally on the application of EPR spectroscopy to observe naturally occurring stable paramagnetic complexes of transition metals, such as iron, copper, molybdenum, or nickel. Examples of these are found in the active sites of metalloenzymes and metalloproteins [2-5].
