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Density Functional Studies of Coenzyme NADPH and Its Oxidized Form NADP + : Structures, UV–Vis Spectra, and the Oxidation Mechanism of NADPH
Author(s) -
Cao Xiaoyan,
Wu Liangliang,
Zhang Jun,
Dolg Michael
Publication year - 2020
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.26103
Subject(s) - chemistry , singlet oxygen , density functional theory , aqueous solution , reaction mechanism , gibbs free energy , oxygen , molecule , redox , yield (engineering) , photochemistry , crystallography , stereochemistry , catalysis , computational chemistry , inorganic chemistry , organic chemistry , materials science , thermodynamics , physics , metallurgy
Density functional theory has been used to study the biologically important coenzyme NADPH and its oxidized form NADP + . It was found that free NADPH prefers a compact structure in gas phase and exists in more extended geometries in aqueous solution. Ultraviolet–visible absorption spectra in aqueous solution were calculated for NADPH with an explicit treatment of 100 surrounding water molecules in combination with the COSMO solvation model for bulk hydration effects. The obtained spectra using the B3LYP hybrid density functional agree quite well with experimental data. The changes of Gibbs free energies Δ G in reactions of NADPH with O 2 observed experimentally in cardiovascular and in chemical systems, that is, NADPH + 2 3 O 2 → NADP + + 2 O 2 − + H + and NADPH + 1 O 2 + H + → NADP + + H 2 O 2 , respectively, were calculated. The NADPH oxidation reaction in the cardiovascular system cannot proceed without activation since the obtained Δ G is positive. The reaction of NADPH in the chemical system with singlet oxygen was found to proceed in two ways, each consisting of two steps, that is, NADPH firstly reacts with 1 O 2 barrierlessly to form NADP + and HO 2 − , from which H 2 O 2 is formed in a spontaneous reaction with H + , or 1 O 2 and H + initially form 1 HO 2 + , which further reacts with NADPH to yield NADP + and H 2 O 2 . © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.