Amino Acids as Protective Compounds in Ultraviolet-irradiated Hansenula Wingei.

Hunt, D. E. (Charles V. Chapin Hospital, Providence, R.I.). Amino acids as protective compounds in ultraviolet-irradiated Hansenula wingei. J. Bacteriol. 88:893-895. 1964.-"Prefeeding" Hansenula wingei with small concentrations of either tryptophan, cystine, tyrosine, phenylalanine, leucine, cysteine, threonine, isoleucine, ethionine, norvaline, or histidine protected this yeast against inactivating ultraviolet treatment. "Prefeeding" with methionine, proline, or alanine conferred little if any protection, and valine or serine caused this organism to be more sensitive to ultraviolet inactivation. A direct relation exists between the concentration of the protective amino acids and the number of surviving cells. The heterocyclic and aromatic amino acids are generally more protective than the corresponding aliphatic compounds. The diversity of the compounds as well as quantitative differences in the protection afforded by them suggest that they have different modes of action.