2,3-Butanedione as a photosensitizing agents: application to α-amino acids and α-chymotrypsin

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Abstract
2,3-Butanedione sensitized the rapid photodestruction of free .alpha.-amino acids and the photoinactivation of .alpha.-chymotrypsin in the presence of UV light and O2. These reactions showed pseudo-1st-order kinetics at 2,3-butanedione concentrations approximating those for the chemical modification of arginine residues in proteins. The photoreactions were inhibited in anoxic media or the presence of azide; findings were consistent with a singlet O2-mechanism for these reactions. No rate of reaction enhancement occurred in D2O. The rate of 2,3-butanedione-sensitized photodestruction of free amino acids increased with increasing pH. The rate constants for the photosensitized inactivation of .alpha.-chymotrypsin and the photodestruction of the tryptophan residues of this enzyme decreased linearly with increasing pH.
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