Chlorine dioxide oxidation of dihydronicotinamide adenine dinucleotide (NADH)

摘要

The oxidation of dihydronicotinamide adenine dinucleotide (NADH) by chlorine dioxide in phosphate buffered solutions (pH 6-8) is very rapid with a second-order rate constant of 3.9 x 10(6) M-1 s(-1) at 24.6 degrees C. The overall reaction stoichiometry is 2ClO(2)(center dot) per NADH. In contrast to many oxidants where NADH reacts by hydricle transfer, the proposed mechanism is a rate-limiting transfer of an electron from NADH to ClO2 center dot Subsequent sequential fast reactions with H+ transfer to H2O and transfer of an electron to a second ClO2 center dot give 2ClO(2)(-), H3O+, and NAD(+) as products. The electrode potential of 0.936 V for the ClO2 center dot/ClO2- couple is so large that even 0.1 M of added ClO2- (a 10(3) excess over the initial ClO2 center dot concentration) fails to suppress the reaction rate.