Time-resolved resonance Raman, time-resolved UV–visible absorption and DFT calculation study on photo-oxidation of the reduced form of nicotinamide adenine dinucleotide

✍ Scribed by Noriko Takahashi; Takaaki Shinno; Masanori Tachikawa; Tetsuro Yuzawa; Hiroaki Takahashi

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 256 KB
• Volume: 37
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/jrs.1472

✦ Synopsis

Abstract

Photochemical reaction of the reduced form of nicotinamide adenine dinucleotide (NADH) was studied in aqueous solutions using nanosecond time‐resolved resonance Raman and UV–visible absorption spectroscopies combined with DFT/B3LYP calculations. Four transients were detected. A transient exhibiting absorption bands at 370 and 560 nm was assigned to the cation radical NADH^+•^. A transient having an absorption band at 394 nm was assigned to the deprotonated neutral radical NAD^•^. A transient exhibiting an absorption band at 493 nm was considered to be attributable to the anion radical NADH^−•^. The broad and strong band at about 700 nm was assigned to hydrated electrons. It was concluded that the photo‐oxidation of NADH to NAD^+^ proceeded stepwise via NADH^+•^ and NAD^•^. The Raman band at 1627 cm^−1^ of NADH^+•^ was assigned to the CC symmetric stretch of the protonated pyridyl ring of the dihydronicotinamide moiety. It was shown that the CC symmetric stretch of the protonated pyridyl ring exhibited a low‐wavenumber shift from 1688 cm^−1^ to 1627 cm^−1^ on going from the ground state to NADH^+•^. This implies that the protonated pyridyl ring is weakened considerably on ionization in good accord with the DFT calculations. Copyright © 2006 John Wiley & Sons, Ltd.