Lii. Separation of Serum Albumin into Two Fractions Ii. Observations on the Nature of the Glycoprotein Fraction by Leslie Frank

EXPERIMENTS recently reported led to the conclusion that serum albumin, even when obtained in the crystalline condition, contains considerable amounts of another protein which is removable only with difficulty [Hewitt, 1936]. It would thus appear that material regarded as being reasonably pure and used as the starting point of many investigations was a mixture of different proteins. A clear-cut separation of the albumin fraction of horse serum into two distinct fractions of widely different chemical and physical properties was described in the former paper. One of the fractions was crystalline serum albumin in a purer state than that usually attained and was virtually free from polysaccharide. Since the total albumin fraction of serum contains considerable amounts of polysaccharide it is not surprising that the second fraction isolated contained a glycoprotein, the identity of which was not established. In view of the possible importance of these observations the experiments now described were carried out in order to obtain further evidence in support of the conclusions reached and to collect more information about the glycoprotein present in the second fraction of serum albumin.