title: Accurate standard hydrogen electrode potential and applications to the redox potentials of vitamin C and NAD/NADH.
abstract: We computationally evaluated the standard hydrogen electrode (SHE) potential in aqueous phase and the Gibbs energy of a proton from the experimental pKa values of alcohol molecules. From the "golden standard" CCSD(T)/aug-cc-pVTZ level calculation, we estimated the SHE potential as 4.48 V, which is very close to the IUPAC-recommended experimental value of 4.44 V. As applications to the Gaussian-3 (G3) methods, which also reproduce the "golden standard" level calculations, we computed various pKa values and redox potentials for a vitamin series. For vitamin C, we support the experimental result of +0.35 V and predict the pKa value of d-ascorbic acid to be 3.7-3.9. Using a model molecule for nicotinamide adenine dinucleotide (NAD), we reproduced the redox potential and determined the order of the proton/electron addition, based on both the proton affinity and redox potential.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Matsui
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kitagawa
authors.forename: Mitsutaka
authors.initials: M
authors.lastname: Okumura
authors.forename: Yasuteru
authors.initials: Y
authors.lastname: Shigeta
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D003198:Computer Simulation; D004566:Electrodes; D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D009243:NAD / Q000737:chemistry*; D010084:Oxidation-Reduction; D011522:Protons; D014867:Water / Q000737:chemistry
chemical_list: D011522:Protons; D014867:Water; D009243:NAD; D006859:Hydrogen; D001205:Ascorbic Acid