The solubilities of denatured proteins in different organic solvents

The solubilities of heat-denatured and reduced, S-carboxymethylated proteins have been investigated in various organic solvents. Polar, protic solvents (formic acid, trifluoroacetic acid, 3-mercaptopropionic acid) were found to be good solvents for the denatured proteins (20-40 mg ml-1), and the solubilities of the reduced, S-carboxymethylated proteins were generally higher than those of the heat-denatured forms. Most other organic solvents were less effective in solubilizing the denatured proteins. Apolar solvents did not solubilise denatured proteins, but low solubilizing powers were observed for polar, aprotic solvents. Heat-denaturation was observed to result in the formation of large intermolecular aggregates, which, for ovalbumin and lysozyme, were formed by intermolecular S-S bonds, but for bovine serum albumin involved intermolecular isopeptide bonds.