Flavianates of lysine

Whilst investigating the separation of the bases of protein hydrolysates, it seemed necessary to ascer- tain whether lysine is precipitated by flavianic acid (2:4-dinitro-1-naphthol-7-sulphonic acid) in the pro- portions (4 equivalents) recommended by Kossel & Gross (1924) and later by Cox (1928) for the precipitation of arginine as monoflavianate. Should lysine be precipitated under these conditions, the use of flavianic acid for the removal of arginine and histidine from hydrolysates of proteins must also involve some loss of lysine. This would inevitably affect the conclusions to be drawn from experiments such as, for example, those described by Bunney & Rose (1928) who endeavoured to prepare in this manner an arginine-free diet. According to Schmidt (1944) flavianates of lysine have not yet been isolated, although the preparation of a very soluble mono-salt was claimed by Kossel & Gross (1924). The experiments which follow show clearly that lysine is precipitated quantitatively in the presence of excess flavianic acid. The preparation and pro- perties of both a mono-and a di-flavianate of lysine are also described in detail. A preliminary report on this work has already been made EXPERIMENTAL Unless otherwise stated, melting points throughout are un- corrected.