A contribution to the chemistry of proteids: Part I. A preliminary study of a hitherto undescribed product of tryptic digestion.

I. IN a recent paper' we showed that the colour reaction of proteids described by Adamkiewicz is obtained only when glyoxylic acid is present in the acetic acid employed. From the observations described in the paper referred to it follows that the Adamkiewicz reaction is in no sense a furfurol reaction, and therefore that there is no evidence for the current conception of its dependence upon carbohydrate aroups in the proteid molecule. It becomes of interest therefore to know the nature of the molecular groups actually responsible for the colour reaction2. That such groups are present intact in some substance or substances to be found among the simpler products of proteid hydrolysis, is suggested by the fact that a glyoxylic reaction may be obtained during the progress of an acid hydrolysis long after the biuret reaction ceases to be given. It may also be displayed with great intensity after the influence of strong trypsin has reduced the biuret-yielding substances to a minimumn. The reaction, too, may be obtained in acid alcohol extracts from the products of tryptic digestion which show no biuret reaction whatever. We endeavoured therefore to separate suich a substance from the products of proteolysis, and have finally succeeded in preparing a beautifully