On the mechanism of the cold ethanol precipitation method of plasma protein fractionation

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Abstract
Given the negligible difference in the value of the dielectric constant of water at 20°C and that of ethanol solutions at low temperatures, the often advanced expanation for the precipitation of plasma proteins by the cold ethanol process, as being due to a reduction of the dielectric constant and the resulting increase in interprotein charge interactions, is not tenable. It is shown by a surface-thermodynamic approach that, upon dehydration by ethanol, isoelectric serum albumin molecules as well as isoelectric serum gamma globulin molecules will attract each other to a sufficient degree by van der Waals forces to become insoluble in the ethanol-water mixtures used.