[The role of the complex formation between cytochrome c and NAD in the manifestation of the photoprotective effect of the dinucleotide in relation to hemeprotein].

UV irradiation of free ferricytochrome solutions, pH 8, induces photorecovery of protein molecules. Hemoproteide photorecovery does not occur after irradiation of the ferricytochrome c/NAD mixture, pH 6 and 8: dinucleotide exerts a photoprotective effect with respect to ferricytochrome. This NAD effect is not observed after exposure of the ferricytochrome c/NAD system, pH 4. With this pH value, each component of the above mixture is eluted from a gel chromatographic column by its peak, whereas with pH 6 and 8, NAD and ferricytochrome c leave the column as one fraction. This indicates that the photoprotective effect of the coenzyme manifests itself upon formation of complex with hemoprotein.