5% in Petrolatum. Applied 30 to 60 minutes before irradiation

Two strains of yeast were used for activity evaluation. Cells were grown m the dark m squad YEPD medium, harvested in exponential phase from an overnight culture or m stationary phase from a 48-h culture, washed twice with water and illuminated at 2 x 10^7 colony-forming units per ml m 20 mM sodium phosphate, pH 7 4, with gentle bubbling with sterile air to keep them suspended. The solubility of Padtmate was estimated at 50 mkM by comparing the peak absorbance (290 nm) of a saturated solution in buffer with the peak absorbance (312 nm) of standard solutions in methanol. To add chemicals, 10 mk1 of a solution methanol was added to IO ml of yeast suspension: controls received ethanol alone.