Dye-sensitized Photo-reactivation of X-ray Damage in Diploid Yeast

Abstract

IN an investigation of the binding of aminoacridine dyes to deoxyribonucleic acid in living cells we have shown that the nucleic acid fluorochrome, acridine orange (3,6,-bis-dimethylaminoacridine), sensitizes both haploid and diploid yeast (Saccharomyces cerevisiae) to visible light¹. The significance of the survival curves obtained for this acridine orange-sensitized photo-inactivation was further examined by experiments involving additivity of X-rays, ultra-violet and visible light. In the course of these additivity studies² a new effect appeared : dye-sensitized visible-light reactivation of X-ray damage in diploid cells. This effect is of special interest because, although ultra-violet damage having a nucleic-acid action spectrum is partially reversible by visible light, previous attempts at reactivation of X-ray damage with visible light have not been successful³.