Tryptophan Content of Wool

Abstract

PREVIOUS results for the tryptophan content of wool have given results varying from 0.5 to 2.3 gm. per 100 gm. of wool^1–7. In the majority of cases the tryptophan has been determined after alkaline hydrolysis of the wool. Spies and Chambers⁸ have shown that the determination of tryptophan in casein, after alkaline hydrolysis, is unreliable unless special precautions, such as the use of an atmosphere of hydrogen, are taken. They found that there is reaction of tryptophan with serine, threonine and cystine during hydrolysis, and, since wool contains larger amounts of these amino-acids than casein, the results are likely to be less reliable than those for casein. They developed a method for the estimation of tryptophan in intact proteins by reaction with p-dimethylamino-benzaldehyde in 19 N sulphuric acid which avoided these side reactions.