| Abstract: | The reversible thermal denaturation of lysozyme and ribonuclease was investigated in aqueous solutions of mono- and polyvalent alcohols. The polyvalent alcohols show a stabilizing influence whereas the monovalent alcohols destabilize the native conformation. The concentration of the monovalent alcohol proportionally lowers the transition temperature Tm with concentration. The increments of Tm of lysozyme and of ribonuclease, excerted by a polyvalent alcohol, are of the same magnitude. This was also found for chymotrypsinogen A (1). It is reasoned that these stabilizing effects may find their origin in the intensification of the intra-hydrophobic interactions of the protein. The effects of the monovalent alcohols on the Tm of lysozyme as well as on the Tm of ribonuclease are enhanced with the increase of the hydrophobic character of the alcohol. These increments of Tm for lysozyme are slightly larger than those obtained for ribonuclease at 50–60°C, as could be expected from their amino acid compositions. |
