Abstract
In extension of previous in vivo experiments, the effects of X irradiation on DPN were studied in vitro. No correlation between the effects on the ultraviolet absorption spectrum and on the coenzyme function of DPN was evident after irradiation at different pH values. However, the loss of coenzyme function could be correlated with the destruction of ribose and of riboside linkages. Catalase did not provide greater protection than did other proteins. It was concluded that the observed loss of DPN from irradiated cells is not due to the radiosensitivity of the DPN molecule itself.