Changes in Amino-nitrogen Content of Solutions of γ-Keratose from Wool Keratin

NUMEROUS workers 1–3 have fractionated wool keratin after oxidation of disulphide bonds with performic or peracetic acids into three fractions, α, β and γ-keratose (β-keratose is insoluble in water, α-keratose is that fraction precipitating at p H 4 and γ-keratose the remaining fraction). While these fractions vary somewhat in the amounts of terminal amino-acids 4 , no comments have yet been made on any changes in constitution of the isolated fraction of γ-keratose on re-dissolution in water. As an introduction to some work on the hydrolysis of γ-keratose (prepared by the method of Corfield, Robson and Skinner 2 ), the free amino-nitrogen value was determined by reaction with nitrous acid, the method of Van Slyke 5,6 , and it was found that reproducible results were not obtained on samples until the solution had been standing for some time. Accordingly the determination of amino-nitrogen of γ-keratose (10 mg/ml.) at various periods of time after dissolution was carried out and plotted as a function of time in acid (0.2 M potassium hydrogen phthalate buffer, p H 4), alkaline (0.2 M boric acid in 0.2 M potassium chloride buffer, p H 10), salt (0.2 M potassium chloride) and simple aqueous solution. The results are shown in Fig. 1.