Electron Paramagnetic Resonance Spectroscopy of Metalloproteins

Electron paramagnetic resonance (EPR), or electron spin resonance (ESR) spectroscopy, is a technique for studying paramagnetic materials, the molecules of which contain unpaired electrons. These comprise organic free radicals and transition metal ions. The biological significance of these rare species is that they often occur at the active sites of enzymes and the electron-transfer systems of bioenergetics. Manganese ions are of special significance in molecular biology, because they can often bind to nucleotides and nucleic acids in a similar way to magnesium, and serve as probes of their environment.