PREPARATION AND ISOLATION OF DITYROSINE

has been developed. Tyrosine was oxidized by means of incubation both with hydrogen peroxide and horse-radish peroxidase. The reaction mixture was separated by permeation chromatography on Sephadex G-10 being monitored at 280 and 310 nm spectrophotometrically. The dityrosine fraction was freeze-dried and purified on a cation-exchange column (in acidic citrate buffer). The purified fraction was desalted and freeze-dried. The yield was 96 mg of homogenous dityrosine per 1 g of D, L-tyrosine. Some physico-chemical constants of the preparation were measured (optical characteristics with U.V. and I.R. spectra, fluorescence spectra, chromatography on an amino acid analyzer). A new procedure for the isolation of dityrosine mixture obtained from tyrosine oxidized with hydrogen peroxide and peroxidase has been reported (1). Hitherto, dityrosine wap isolated only from acid hydrolysates of resilin by means of chromatography on a column of DEAE-cellulofie (2).More recently, in 1976, an alternate procedure was proposed by Xeachbach et al. (3). The authors isolated dityrosine from the reaction mixture of N-acetyltyroaine oxidized by hydrogen peroxide and peroxidase by means of preceding chromatography on Sephadex C-10, preparative thin-layer chromatography on silica gel, and chromatography on a column of silica gel. The present procedure, independent from that of Aeschbach, gives comparable yields, is shorter and less Laborious. © 1979, Taylor & Francis Group, LLC. All rights reserved.