Organic Analysis of Hevea Latex. IV. Amino Acids

Abstract

Abstract The presence of amino acids in fresh latex was reported by Belgrave in 1925. On the basis of certain considerations, he considered it improbable that his experiments involved any profound changes in the original state of the nitrogen compounds. Accordingly the amino acids which he isolated must have been present in the free state in latex. It may be noted here that Belgrave's experiments did not completely exclude either chemical or enzymatic hydrolysis of proteins. Indeed, his amino acids were separated from a serum which was prepared by acidifying fresh latex with acetic acid (20 cc. of 10 per cent acid per liter of latex) and heating gently, with no precautions whatever for inactivating any proteolytic enzymes which may have been present. Aside from Belgrave's paper, there have been only two published references to the presence of amino acids in rubber or latex. Whereas Whitby, Dolid, and Yorston reported the isolation of valine from the acetone extract of crepe rubber, McGavack and Rumbold were able to isolate d-alanine from the serum of old ammoniated latex. There is no reason whatever for assuming from these observations that valine and alanine also occur free in latex. Indeed it would be impossible to give any guaranty that there was no hydrolytic degradation of proteins in the sample. In view of this situation it seemed highly desirable, as part of a systematic organic analysis of latex, to investigate more exactly the free amino acids which are present in latex. In addition to Belgrave's observation a preliminary analysis of fresh bottom latex which had been prepared for other purposes indicated that free amino acids actually do occur in latex. The object of the present paper is to identify the amino acids occurring in latex and, so far as is feasible, to determine the quantity also.