One-electron oxidation of flavins. A flash photolysis and pulse radiolysis study

One-electron oxidation of flavins in aqueous solution has been studied by using the reactions of the sulfate radical (SO/sub 4//sup .-/) and tetranitromethane with three different flavin derivatives in their ground and triplet excited states, respectively. The resulting spectra are compared and the results discussed in terms of the site of electron removal and the state of protonation of the resulting oxidized flavin radicals. It is concluded that electron loss occurs from the main ..pi..-electron system rather than a specific site and may be followed by deprotonation (pK/sub a/ approx. 6) in flavins unsubstituted at the N(3) position.