title: 2,3-butanedione as a photosensitizing agent: application to alpha-amino acids and alpha-chymotrypsin.
abstract: 2,3-Butanedione sensitized the rapid photodestruction of free alpha-amino acids, and the photoinactivation of alpha-chymotrypsin, in the presence of ultraviolet light and oxygen. These reactions showed "pseudo-first-order" kinetics at 2,3-butanedione concentrations approximating those employed for the chemical modification of arginine residues in proteins. The photoreactions were inhibited in anoxic media or in the presence of azide; findings were consistent with a singlet oxygen mechanism for these reactions. No enhancement in the rate of reaction was observed in D2O. The rate of 2,3-butanedione-sensitized photodestruction of free amino acids increased with increasing pH. However, the rate constants for the photosensitized inactivation of alpha-chymotrypsin, as well as those for the photodestruction of the tryptophan residues of this enzyme, decreased linearly with increasing pH.
mesh_terms: D000596:Amino Acids / Q000528:radiation effects*; D001386:Azides / Q000494:pharmacology; D002074:Butanones / Q000494:pharmacology*; D002918:Chymotrypsin / Q000528:radiation effects*; D003903:Deuterium / Q000494:pharmacology; D003931:Diacetyl / Q000494:pharmacology*; D007700:Kinetics; D010777:Photochemistry; D014466:Ultraviolet Rays
chemical_list: D000596:Amino Acids; D001386:Azides; D002074:Butanones; D003903:Deuterium; D002918:Chymotrypsin; D003931:Diacetyl