New Photoproducts from Irradiation of NADH with Near-UV Light

Adenosine 5′‐diphosphoribose (ADPR) and a second compound, which may be nicotinamide, are the newly discovered photoproducts resulting from irradiation of β‐nicotinamide adenine dinucleotide (β‐NADH) in the wavelength range of 300–400 nm under oxygen‐poor conditions. Both products emerge there even exclusively, whereas, at higher oxygen concentrations, the oxidized form of nicotinamide adenine dinucleotide (NAD+) is additionally formed, although still as a minor product. The development of ADPR and NAD+ is clearly oxygen‐dependent, while, for the formation of the second photoproduct, small quantities of oxygen appear to be sufficient.