F. Gowland Hopkins

A contribution to the chemistry of proteids: Part II. The constitution of tryptophane, and the action of bacteria upon it1

IN the first part of this communication we described the separation from the tryptic digestion products of casein of a substance capable of giving the glyoxylic (Adamkiewicz) reaction. This substance was found to yield also the tryptophane reaction with halogens. Since Tiedemann and Gmelin2 in 1831 first described the colour reaction given by pancreatic juice when treated with chlorine water, and Claude Bernard3 in 1856 showed that the same reaction could be obtained from the tryptic digestion products of casein and from the products of putrefaction, many workers, beginning with Kiihne4, have concerned themselves with the phenomenon. The literature of the subject comprises, however, chiefly accounts of work upon the coloured halogen derivatives themselves. As regards isolating the parent substance most observers have contented themselves with reporting their failure in the attempt. Neumeister5, though he did not follow up the matter, suggested that amyl alcohol might prove a solvent capable of extracting the suibstance from digestion mixtures, but Stadelmann6 immediately afterwards showed that success was not to be attained by the use of this solvent. So far as we know no other suggestion had been made until we described the use of mercuric sulphate as a precipitant. [Reference must be made however to the observations of Ferd. Klug published in 1901. This author isolated from the products of the self-digestion of the pancreas an amorphous pigment, and his analyses of the product correspond with the formula C4H8NO2. This pigment

A study of Bence‐Jones protein, and of the metabolism in three cases of Bence‐Jones proteinuria

THE condition known as Bence-Jones proteinuria should not fail to interest the physiologist as well as the pathologist. The appearance, in the course of a disordered metabolism, of protein material which escapes breakdown, and passes the kidneys in such amount that the nitrogen contained in it may amount to a third or more of the total nitrogen excreted; the peculiar characters of the protein, and the fact that, though a highly complex suibstance forming colloid solutions, it nmay be passed in large quantities and for long periods by kidneys which remain impervious to plasma proteins, and which are-to all appearance at least-histologically intact: these are aspects of the condition of significance for all concerned with the processes of metabolism and excretion. A proper understanding of the disturbances involved couild hardly fail to throw light on normnal protein metabolism. The physicochemical properties of the excreted product deserve, too, the attention of all concerned with the study of colloid solution. Considerably more than a hundred cases of the condition have now been recorded, and there is every reason to suppose that it is much

On the separation of a pure albumin from egg-white.

TEIE chemical study of animal proteids made one of its greatest advances when Hofmeister showed that under special conditions egg-albumins could be crystallised. When to this discover*y was added the observation of Gurber showing that Hofineisters method of crystallization could be extended to certain serum-albumins, there became available for research representative proteid material obtainable in practicable quantities, and possessing some guarantee of purity. The work of the decade which has elapsed since these crystalline albumiius became available for study cannot be said however to have defined the conditions necessary for obtaining a product with a just claim to actual chemical individuality. It is quite certain that more than one proteid in egg-white remains unprecipitated after half-saturation with ammonium sulphate; and it is at least highly probable that on continued evaporation of the ammoniumsulphate-albumin mixture, in accordance with the original description of Hofmeisters process, more than one crystalline albumin eventually separates. The well-known research of Bondzynski and Zoj al published in 1894 offered strong grounds for believing this to be the case; these observers finding wide differences in the specific rotatory powers of different crystalline fractions-an indication of great significance where proteids are concerned.