Fluorescent whitening agents. IX.The effect of proteins on the photodecomposition of pyrazolines

Abstract

Ultraviolet irradiation of the diaryl-2-pyrazoline (1) in water gives the corresponding pyrazole (3), the 4-hydroxypyrazole (4) and several unidentified products. Irradiation of the tetraaryl-2-pyrazoline (2) gives the pyrazole (6) as the major product. The rates of photodegradation are increased if lysozyme is present and the corresponding pyrazoles are formed preferentially. Pyrazoles are also the major products when wool containing (1) or (2) is irradiated. Both pyrazolines photosensitize the degradation of lysozyme, the tryptophan, histidine and methionine residues being the main sites of attack.