The Unidentified Base in Gelatin

Abstract

Van Slyke and Hiller 1 reported evidence that the phosphotungstate precipitate obtained from hydrolyzed gelatin contained amino acid material other than the hexone bases usually found in this precipitate. Other problems prevented continuance of work on the isolation of the material. It was taken up by Van Slyke and Robson 2 but after preparation of a copper salt, since found to be contaminated with proline, the work was again discontinued by Robson's return to England.

The unidentified base has now been isolated and recrystallized, both as the picrate and as the hydrochloride, and has the composition of a hydroxylysine. After removal of arginine and histidine as silver salts the residual “lysine fraction” is freed of adherent mono-amino acids by repeated precipitation in very dilute solution as phosphotungstate. The greater part of the lysine is removed by addition of enough picric acid to the hot aqueous solution to combine with 3/4 of the amino nitrogen present. To the mother liquors enough more picric acid is then added to combine with the rest of the amino nitrogen. A picrate of the composition C₆H₁₄N₂O₃. C₆H₃N₃O₇ is crystallized, from a dilution of about 1 to 10, and is purified by recrystallization. It is more soluble than the picrate of lysine, and when heated at the rate of a degree every 3 seconds shows a melting point at 225°. Both the nitrogens of the amino acid react completely with nitrous acid in 10 minutes. There is a marked difference from lysine in speed of reaction; in 3 minutes at 25 under the conditions of the manometric analysis 3 lysine evolves only 83% of its total nitrogen, while the new base in the same time evolves 95%.