Photodecomposition of Ergosterol by Near-UV irradiation in the Plasma Membrane of the Yeast Rhodotorula minuta

In search for primary photochemical reaction related to photoinduced carotenogenesis and photoinactivivation in yeast Rhodotorula minuta, the influence of near-UV radiation (300-400 nm) on ergosterol in the plasma membrane of the yeast. Irradiation by near-UV of intact cells and the plasma membrane preparation from the yeast caused changes in their absorption spectra. For the plasma membrane, difference spectra measured after irradiation of near-UV suggested the decomposition of ergosterol and the suggestion was proved by HPLC analysis. Experiments in model systems revealed that ergosterol itself was the photoreceptor in the photochemical reaction, and that there was not any other photoreceptor or photosensitizer which was related to photochemical reaction of ergosterol decomposition in the plasma membrane.