THERMODYNAMIC STABILITY OF RIBONUCLEASE A AT 25 °C IN AQUEOUS SOLUTIONS OF GUANIDINE HYDROCHLORIDE, UREA AND ALKYLUREAS

Nataša Poklar, Nina Lah, Miha Oblak and Gorazd Vesnaver
Department of Chemistry, University of Ljubljana, Aškerèeva 5, 1000 Ljubljana, Slovenia

ABSTRACT

The previously published results of the effect of pH, guanidinium hydrochloride (GuHCl), urea, methylurea, N,N'-dimethylurea, ethylurea and butylurea on the thermal stability of ribonuclease A (RNase A) studied by differential scanning calorimetry (DSC) (N. Poklar, N. Petroveie, M. Oblak, G. Vesnaver, Protein Sci. 1999, 8, 832-840) were used to calculate the RNase A thermodynamic stability at 25°C. It has been shown that thermodynamic stability of RNase A at 25 °C decreases with increasing concentration of denaturants and the size of the hydrophobic group substituted on the urea molecule