Rapid and Specific Effects of Bromine on the System Keratin/Formic Acid

Abstract

FORMIC acid interacts strongly with many fibrous proteins, polypeptides and polyamides; it produces either complete dissolution or considerable swelling together with a marked contraction of the fibre resulting from melting of the crystalline material¹. Fibres of α-keratin, however, show considerable radial swelling (about 50–60 per cent) in concentrated formic acid, but virtually no change of length. The swelling will tend to lengthen the fibre while the melting of α-helices will tend to contract it, but the major cause for the constant length must be sought in the stability of a residual proportion of the crystallites which have been shown by X-ray measurements to remain in the α form in 98 per cent formic acid². This residual stability has been shown to persist even in dilute solutions of the helix-forming protein extracted from wool³.