Application of Electron Spin Resonance (ESR) for Detection and Characterization of Flavoprotein Semiquinones

Flavoproteins are involved in a variety of biological electron transfer processes, from energy accumulation in respiratory and photosynthetic electron transfer chains to oxidation of toxic compounds by cytochrome P450-dependent systems. The structure and function of free and protein bound flavins have been a subject of extensive studies. This effort has resulted in our current understanding of the chemistry and significance of flavins in living cells, as summarized in a number of reviews (, , , ).