The calculation of partial specific volumes of proteins in guanidine hydrochloride

A method is presented for calculating the number of guanidine hydrochloride and water molecules bound to proteins in 6 m guanidine hydrochloride solution. By correct combination of these quantities, the preferential interaction parameter of solvent components with proteins can be calculated, and, in turn, accurate values of the apparent partial specific volumes of proteins in 6 m guanidine hydrochloride can be predicted. This method requires only the knowledge of the amino acid composition of the protein. Application of this method to literature data shows that the predicted values of the partial specific volumes of proteins render possible an accurate estimation of their subunit molecular weights from sedimentation equilibrium experiments in 6 m guanidine hydrochloride.