The bleaching of the bacteriorhodopsin chromophore by ionizing radiation.

The visible chromophore of bacteriorhodopsin, BR(570), undergoes progressive bleaching when subjected to 60CO gamma-irradiation. The low G-value for bleaching confirms that the site of the chromophore is highly protected. Positive and negative circular dichroic (CD) bands associated with the chromosphone undergo concomitant decrease in a manner which is consistent with two independent chromophores rather than exciton coupling between neighbouring chromophoric site.