The use of p-toluene sulfonate to dissolve synaptosomal membrane proteins into organic solvents

A method is described by which a large proportion of membrane proteins may be dissolved in organic solvents by the use of p-toluene sulfonate. Synaptosomal membrane fractions from rat cerebral cortex were used as test material. Chloroform-methanol extraction dissolved 7% of proteins, 89% of lipid phosphorus, and 35% of reducing sugars. Further extraction of the residue with 2.5 mm p-toluene sulfonate in chloroform-methanol allowed the dissolution of 45% of the proteins. The final residue contained the rest of the protein and 60% of reducing sugars. The polypeptides in the three fractions showed marked differences in molecular weight and several glycoprotein bands were found in the final residue. The amino acid content of these three protein fractions was also different. It is concluded that p-toluene sulfonate, by lowering the pH and binding to the positive charges in the protein, is able to transfer about half of the synaptosomal membrane proteins into a hydrophobic medium.