Quantitative fractionation of casein mixtures by fast protein liquid chromatography

Summary Alkylation of whole casein samples by reaction with cysteamine and cystamine in a bis-tris-propane–urea buffer (pH 7·0) followed by fast protein liquid chromatography (FPLC) at 20°C on a Mono Q HR5/5 column in the same buffer and using a NaCl gradient led to good resolution of the whole casein into fractions representing (i) γ 2 - plus γ 3 -caseins, (ii) κ-caseins, (iii) β-casein, (iv) α s2 -caseins and (v) α sl -caseins, together with small amounts of unidentified materials. Quantitatively the FPLC values agreed well with those for α s1 -, β-, α s2 - and γ 2 - plus γ 3 -caseins obtained by ion-exchange chromatography on DEAE cellulose, Whatman DE52 and with those for º-caseins obtained by gel-permeation chromatography on Sephadex G–150.