Solubility of Proteins in Dextran Solutions

excluded volume of a linear polysaccharide is therefore expected to be larger. That the excluded volume decreases with increased dextran concentration is expected because of the increased overlapping of the neighbouring molecules. There may be other explanations for the effect of dextran on the solubility of proteins. Formation of a complex between the protein and the polysaccharide, which had a lower solubility than its constituents, could account for some of the results that have been observed. A charge interaction is unlikely because the dextran is essentially uncharged, and, further, the effect persists even at very high concentrations of electrolytes and is independent of the electrolyte concentration and pH over a wide range. Other types of chemical interaction are equally improbable, for the effect seems to vary only with the dextran concentration while being independent of the albumin concentration even at very low concentrations. In addition to the importance of this phenomenon in biological systems, it may have practical application in the fractionation of high-molecularweight compounds.