Diphotonic one-electron oxidation of NADH on laser excitation at 353 nm

The primary steps in one-electron oxidation of NADH (the reduced form of nicotinamide adenine dinucleotide) were studied by means of nanosecond laser photolysis combined with kinetic spectrophotometry. High-intensity excitation at 353 nm of NADH in aqueous solution (pH 10.0) was found to produce two-photon ionization at the nicotinamide group. The absorption spectrum of the -NADH⁺ radical cation formed in this reaction was determined. This species disappeared by deprotonation at a rate of 3.6 × 10⁶ s^?1 at pH 10 forming -NAD.