Preparation and isolation of dityrosine

A new procedure for the 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).