Studies on casein. III.—Preparation of a carbohydraterich fraction and a calcium‐sensitive fraction from α‐casein

Abstract α‐Casein was fractionated by the addition of calcium chloride to an α‐Casein solution (pH 7) which had previously been kept for 45 min. at pH 12. One fraction (Fraction A) accounted for 13.4% and another (α‐Casein — Fraction A) for 56.7% of the original α‐Casein. The sugar contents (anthrone) of Fraction A, and α‐Casein — Fraction A, were 3.94 and 0.68 mg./g., respectively, and the hexosamine contents were 4.58 and 0.68 mg./g., respectively. The product α‐Casein — Fraction A was precipitated from aqueous solution (pH 7) by the addition of calcium ion whereas Fraction A was not precipitated under the same conditions. No precipitate was formed on addition of o.IM‐calcium chloride solution to a solution containing 3 parts of α‐Casein — Fraction A to one part of Fraction A but a precipitate was formed if Fraction A was pretreated with rennin.