Multiple pathways in the oxidation of a NADH analogue.
Oxidation of the NADH analogue, N-benzyl-1,4-dihydronicotinamide (BNAH), by the 1e(-) acceptor, [Os(dmb)3](3+), and 2e(-)/2H(+) acceptor, benzoquinone (Q), has been investigated in aqueous solutions over extended pH and buffer concentration ranges by application of a double-mixing stopped-flow technique in order to explore the redox pathways available to this important redox cofactor. Our results indicate that oxidation by quinone is dominated by hydride transfer, and a pathway appears with added acids involving concerted hydride-proton transfer (HPT) in which synchronous transfer of hydride to one O-atom at Q and proton transfer to the second occurs driven by the formation of the stable H2Q product. Oxidation by [Os(dmb)3](3+) occurs by outer-sphere electron transfer including a pathway involving ion-pair preassociation of HPO4(2-) with the complex that may also involve a concerted proton transfer.
Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-3290, United States.
Na
N
Song
Ming-Tian
MT
Zhang
Robert A
RA
Binstead
Zhen
Z
Fang
Thomas J
TJ
Meyer
D016227:Benzoquinones / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D009243:NAD / Q000031:analogs & derivatives* / Q000737:chemistry; D010084:Oxidation-Reduction
C445701:1-benzyl-1,4-dihydronicotinamide; D016227:Benzoquinones; D056831:Coordination Complexes; C000596850:tris(4,4'-dimethyl-bipyridine)osmium(II) dichloride; D009243:NAD; C004532:quinone