THERMODYNAMICS OF DENATURATION OF RIBONUCLEASE-A IN AQUEOUS AMINO-ACID SOLUTIONS

Differential scanning calorimetry has been used to investigate the effects of amino acids (osmoregulatory solutes) on the thermodynamics of denaturation of ribonuclease A. The transition temperature, heat capacity and the enthalpy of denaturation of RNase A in aqueous amino acids solutions at pH 6.00 has been determined by the least squares fit of the excess heat capacity data to the two state model. The amino acids increase the thermal stability of RNase A in the order:leucine < valine < proline < alpha-alanine < serine < gamma aminobutyric acid < beta-alanine < glycine. The results have been explained on the basis of the cosphere overlap model.