Thermal stability of human serum albumin by sodium halide salts.

The influence of sodium halide salts at low concentration (above 0.3 M) on the thermal stability of human serum albumin was studied by differential scanning calorimetry. It was found that the sodium halides increase the "melting temperature" and the enthalpy of unfolding of albumin in the following order: F- < Cl- < Br- < I-. It is suggested that the sodium halides do not change the number of solvophobic residues of the protein exposed to the solvent, while an increase of the surface accessible area of the protein to the solvent was found. The increase in the thermal stability of albumin may be due to the preferential hydration of the protein, produced by the structure breaking halides on the water of the bulk solvent.