Identification of the End-Amino Groups of Wool by Means of their 2 : 4-Dinitrophenyl Derivatives

Abstract

THE amino-acids with free α-amino groups in wool have been identified using Dr. F. Sanger's technique1. Considerable use was made of buffered, as well as unbuffered, silica gel columns, using Sanger's original solvents. The gel was buffered at pH 6.0 with 0.5 ml. buffer solution (9.36 gm. NaH2PO4.2H2O + 14.32 gm. Na2HPO4.12H2O per 100 ml. solution) per gm. silica. This was used in conjunction with (a) ether, (b) 1 per cent butanol–chloroform, (c) 30 per cent butanol–chloroform, (d) 5 per cent propanol–eyclohexane, (e) 33 per cent ether-ligroin as solvents. The ether was freed from peroxides by shaking with an acid solution of ferrous ammonium sulphate, followed by several changes of distilled water, and stored in a dark bottle. In agreement with other workers2,3, leucine could not be separated from valine on unbuffered columns, but this was easily achieved by using 0·5 ml. solution (7·16 gm. Na2HPO4.12H2O + 7·60 gm. Na3PO4.12H2O per 100 ml. solution) per gm. silica with ether as solvent. The acids were identified as (a) valine, (b) alanine, (c) glycine, (d) threonine, (e) serine, (f) glutamic acid, (g) aspartio acid.