Mean Molecular Weights of Synthetic Mixtures of Bovine Plasma Albumin and Globulin

Abstract

Albumin and globulin, though generally considered to be separate entities, show sedimentation anomalies when they are studied in mixtures with the ultracentrifuge (Pederson1). The data of McFarlane2 suggest that globulin may dissociate in such mixtures. We have studied purified bovine plasma albumin and globulin, alone and in synthetic mixtures, by osmometric methods.Sterile bovine plasma was carefully fractionated with ammonium sulfate at 0°C by a technic similar to that used by McMeekin.3 The albumin and globulin fractions were reprecipitated, freed of ammonia by dialysis and then dialyzed to equilibrium with phosphate buffer of pH 7.4, μ = 0.16. Osmotic pressures were measured at 0°C by the method to be described by Keys. Protein concentrations were determined with the Pulfrich refractometer in every sample and checked by the micro-Kjeldahl method of Keys4 in about every third sample. Mean molecular weights were determined by the method of Adair and Robinson5 in which the pressure-concentration ratio i...