Preferential solvation of bovine serum albumin in aqueous guanidine hydrochloride.

Bovine serum albumin, in aqueous guanidine hydrochloride, interacts preferentially with the solvent components, as was shown by techniques in which refractometry and light scattering and equilibrium dialysis were used. If constant salt molality after dialysis is taken as the reference state for zero binding, then 0.08 f 0.03 and 0.18 f 0.05 g of salt per g of protein is bound at 3 M and 6 M salt, respectively, with similar values at 4 and 5 M salt. These results indicate that (E)T,,+~ (obtained by measuring the difference in density between a protein solution and its dialysate) is 2 to 3 % less than the value obtained at constant molality of salt.