The quantitative partition of the albumin fraction of milk serum proteins by gel chromatography.

Abstract

SummaryA method for the quantitative partition of the albumin fraction of milk serum proteins is described. The partition, which is carried out by chromatography on a column of Sephadex G-100 (2·5×90cm) at 4°C in the presence of 0·02 m-sodium phosphate buffer (pH 6·7) containing 0·1 m-NaCl, yields 4 fractions. By gel electrophoresis it was shown that the fractions represent, in order of elution from the Sephadex, the following: fraction 1, a mixture of the largest proteins present, probably comprising γ-globulins, proteose-peptones and lactoferrin; fraction 2, bovine serum albumin and bovine serum transferrins; fraction 3, β-lactoglobulins; and fraction 4, α-lactalbumins. The protein contents of the various fractions were determined by nitrogen analysis and the results showed that good agreement was obtained between values from duplicate fractionations, and also that the recovery of material was satisfactory. The partition of the albumin fraction was not complete, but at least 90% of the material was found in fractions which represent essentially single proteins. The influences of some aspects of the pretreatment of samples, buffer composition and column preparation are described.