EFFECT OF GUANIDINIUM, CARBAMOYLGUANIDINIUM, AND GUANYLGUANIDINIUM SALTS ON SOLUBILITY OF BENZOYL-L-TYROSINE ETHYL ESTER AND ACETYLTETRAGLYCINE ETHYL ESTER IN WATER

The effects of the chloride, bromide, iodide, and thiocyanate salts of guanidinium, carbamoylguanidinium, and guanylguanidinium cations on the water solubility of benzoyl-L-tyrosine ethyl ester, a model hydrophobic compound, and acetyltetraglycine ethyl ester, a model peptide and amide compound, have been examined. Regardless of the cation used, the solubility of both model compounds increases progressively through the series chloride < bromide < iodide < thiocyanate. This anion series parallels the effectiveness of these anions as denaturants of several proteins. When the anion is held conslant, the cation effect on the solubility of benzoyl-L-tyrosine ethyl ester is guanidinium < guanylguanidinium < carbamoylguanidinium and the cation effect on the solubility of acetyltetraglycine ethyl ester is guanidinium < carbamoylguanidinium < guanylguanidinium. It is concluded that the protein denaturing effectiveness of these guanidinium, carbamoylguanidinium, and guanylguanidinium salts is due to their ability to increase the solubility of protein hydrophobic and peptide amide groups. © 1969, American Chemical Society. All rights reserved.