Abstract
We are extending the work of Gascoigne and Radda on the aqueous reaction of flavins which cannot undergo ionization at N(3) with thiols. We confirm that the reaction is first order in flavin and dithiol. Linear buffer catalysis is observed between pH 7 and 11 and a change in rate determining step occurs below pH 7 and above pH 11. Our results support the mechanism depicted in Scheme 1, in which a C(4a) adduct is formed. This scheme may be compared with mechanisms suggested previously by others.