Constitution of the Keratin Molecule

Abstract

OF the two comments which Dr. Rimington¹ has to make on our recent note² regarding the constitution of the keratin molecule, one is erroneous and the other misleading. In our original communication, we claim to have shown that the amount of free amino nitrogen in wool is precisely equivalent to the amount of hydrochloric acid absorbed from solution at pH 1.0 and to the arginine and lysine content of the fibre as determined by Marston.³ In Rimington's opinion, the significance of these identities is lost because “the guanidine group of arginine does not yield nitrogen with nitrous acid under the usual conditions”. Van Slyke and Birchard⁴ are quoted in support of the contention, a more recent paper by Plimmer⁵ being overlooked. The latter has shown that the guanidine group of arginine is attacked slowly by nitrous acid under the usual conditions, and his data indicate that, in twenty-four hours, reaction with the second amino group is almost complete. The determinations which we made of the free amino nitrogen in wool were all allowed to proceed for twenty-four hours, and there is, in consequence, no necessity to follow Rimington in his speculation “that wool probably contains hydroxylysine or other diamino acid in addition to lysine’. The “other diamino acid” is undoubtedly arginine.