Charge transfer between tryptophan and tyrosine in casein: a pulse radiolysis study

Charge transfer from tyrosine to tryptophan radicals in bovine milk casein, as observed using pulse radiolysis technique, is reported. The reactions of casein with hydroxyl, azide, Br-2(.-) and CCl3O2. radicals have also been studied. Radical transformation was found to take place at a rate of 1.5 x 10(4) s(-1). The effect of pH, oxidising radical and the proximity of tyrosine and tryptophan on this radical transformation, as well as repair of the casein radical by ascorbate, have also been studied. (C) 2002 Elsevier Science B.V. All rights reserved.