Singlet oxygen production and photobiological effects of pinacyanol chloride on yeast Saccharomyces cerevisiae.

Photobiological activities of pinacyanol chloride (PC), which is known as a non-intercalating dye, were investigated. Irradiation of PC-sensitized yeast cells in the dark brought about marked decrease of survival and induction of "petites" which are respiration-deficient mutants caused by partial loss of mitochondrial deoxyribonucleic acid. Nuclear mutation represented by reversion from Trp- to Trp+ was also induced by photodynamic action of PC. This fact suggested photoactive dyes are not necessarily intercalated for inducing mitochondrial and nuclear mutation. Singlet oxygen production was determined in the photoirradiated PC solution by electron spin resonance spectrometry. Photobiological effects of PC might be brought about mainly by a type II photodynamic mechanism.