The Action of Diazomethane on Caseinogen: Preliminary Communication.

Skraup and Krause [1909] methylated caseinogen with methyl iodide and boiling alcoholic potash with the object of showing which of the constituent amino-acids of the protein chain contained free aminoor hydroxylgroups. Since their product on hydrolysis yielded no tyrosine or lysine and but little histidine and arginine they concluded that such free groups were present in the nuclei of these amino-acids. It is evident that such a vigorous methylation as they employed may be accompanied by an essential hydrolysis of the protein molecule. We have therefore methylated caseinogen with diazomethane in the hope that by this method results of a more conclusive character may be obtained. By the employment of such a mild reagent the possibility of decomposition is reduced to a minimum and it is therefore practically certain that the product obtained is a direct substitution product of caseinogen. By a comparison between the behaviour, on the one hand, of amino-acids and simple polypeptides and, on the other hand, of caseinogen, it is hoped that a direct view may be obtained into the protein molecule as it actually exists. Results have already been obtained which indicate clearly that the presence of carboxyll groups may be proved and their number estimated. It may also be possible to estimate the number of free hydroxyl groups. It is to be expected that our product, like that of Skraup and Krause, will on hydrolysis fail to give those amino-acids which when combined in the protein chain still contain free groups capable of methylation. It is further hoped that it may be possible to isolate in the form of their methyl