One-electron transfer reactions of the couple NAD. /NADH. [Pulse radiolysis]

Journal Article · Thu Aug 04 00:00:00 EDT 1983 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100239a035· OSTI ID:5779709

Grodkowski, J ^[1]; Neta, P; Carlson, B W; Miller, L

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1. Univ. of Notre Dame, IN

One-electron transfer reactions involving nicotinamide-adenine dinucleotide in its oxidized and reducd forms (NAD./NADH) were studied by pulse radiolysis in aqueous solutions. One-electron oxidation of NADH by various phenoxyl radicals and phenothiazine cation radicals was found to take place with rate constants in the range of 10/sup 5/ to 10/sup 8/ M/sup -1/ s/sup -1/, depending on the redox potential of the oxidizing species. In all cases, NAD. is formed quantitatively with no indication for the existence of the protonated form (NADH/sup +/.). The spectrum of NAD., as well as the rates of oxidation of NADH by phenoxyl and by (chlorpromazine)/sup +/. were independent of pH between pH 4.5 and 13.5. Reaction of deuterated NADH indicated only a small kinetic isotope effect. All these findings point to an electron transfer mechanism. On the other hand, attempts to observe the reverse electron transfer, i.e., one-electron reduction of NAD. to NADH by radicals such as semiquinones, showed that k was less than 10/sup 4/ to 10/sup 5/ M/sup -1/ s/sup -1/, so that it was unobservable. Consequently, it was not possible to achieve equilibrium conditions which would have permitted the direct measurement of the redox potential for NAD./NADH. One-electron reduction of NAD. appears to be an unlikely process. 1 table.

• OSTI ID: 5779709
• Journal Information: J. Phys. Chem.; (United States), Vol. 87:16
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHLORPROMAZINE
RADIOLYSIS
DEUTERIUM
ISOTOPIC EXCHANGE
NAD
LABELLING
PHENOL
WATER
AQUEOUS SOLUTIONS
CATIONS
CHEMICAL REACTION KINETICS
DEUTERIUM COMPOUNDS
ELECTRON TRANSFER
EXPERIMENTAL DATA
OXIDATION
PH VALUE
PHENOXY RADICALS
PULSED IRRADIATION
REDUCTION
AMINES
AROMATICS
AZINES
CENTRAL NERVOUS SYSTEM AGENTS
CENTRAL NERVOUS SYSTEM DEPRESSANTS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COENZYMES
DATA
DECOMPOSITION
DISPERSIONS
DRUGS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
HYPNOTICS AND SEDATIVES
INFORMATION
IONS
IRRADIATION
ISOTOPES
KINETICS
LIGHT NUCLEI
MIXTURES
NUCLEI
NUCLEOTIDES
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PHENOLS
PHENOTHIAZINES
PSYCHOTROPIC DRUGS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
REACTION KINETICS
SOLUTIONS
STABLE ISOTOPES
TRANQUILIZERS
400600* - Radiation Chemistry
400303 - Organic Chemistry- Isotope Exchange & Isotope Separation- (-1987)
400302 - Organic Chemistry- Isotope Effects- (-1987)