On certain colour reactions of proteid due to tryptophane

Abstract

IT has been shown by Dr F. G. Hopkins and myself that the Adamkiewcz reaction for proteids is due to an interaction between tryptophane and glyoxylic acid'. We have therefore named the reaction the glyoxylic reactioln, and have introduced a reagent ('reduced oxalic acid') which contains an abundance of glyoxylic acid, for testing for proteids. In our work on the separation and constitution of tryptophane we found that this substance is remarkably chromogenic, and it seemed desirable to determine whether certain other colour reactions were due to this substance. Liebermann's reaction. Liebermann2 stated that if proteids are precipitated by alcohol and washed with ether they give an intense blue colour when heated with concentrated hydrochloric acid. The purpose of the washing with alcohol and ether is, according to Liebermann, the complete removal of adheretit fat, and so important did he consider this that he treated the proteid four times with hot alcohol and four times with cold ether before performinog the test. Krukenberg3 states that the coloured product shows a band between E and b with a certain amount of absorption on either side of this. E. Salkowski4 and Pickering' agree that the reaction is not due to any of the aromatic decomposition products of proteids. Rimini6 drew attention to the fact that the quality of the ether