QUANTUM YIELDS OF PHOTOCHEMICAL REACTIONS OF TYROSINE AND TRYPTOPHANE IN SOLUTIONS

An investigation has been made of absolute quantum yields of photochemical decolorization of tryptophane, glycyltryptophane, and tyrosine in the presence and in a vacuum. The quantum yield of decolorization of tryptophane in air type I reaction did not depend on wavelength of the effective radiation and increased in the alkaline medium the quantum yield of decolorization of glycyltryptophane in vacuum type II reaction in an alkaline medium was reduced. In glycyltryptophane reactions I and II occurred evidently independently of each other. The quantum yield of tyrosine was constant upon change in pH from 2 to 12. Glycine, NaCl, and alcohol did not affect the rate of decolorization of tryptophane, although during the lifetime of the excited state the tryptophane molecule is able to collide with molecules of these compounds several dozens of times. Upon evacuation of air from the solution, a decrease in the rate of photo-oxidation of tryptophane was observed only at pressures or 0.1 mm Hg. This signifies that in the reaction of interaction with oxygen metastable tryptophane products take part possibly, of the free radical type with lifetimes of the order of 0.0001 second.