5] Calculation of the partial specific volume of proteins in concentrated salt and amino acid solutions

Abstract

Publisher Summary This chapter illustrates that the physicochemical characterization of proteins, requires working in solvents which contain high concentrations of low-molecular-weight compounds. Parameters which play an important role in sedimentation equilibrium and sedimentation velocity experiments, density gradient sedimentation, and in X-ray scattering, X-ray diffraction, and some column techniques are the preferential hydration of the proteins and the apparent partial specific volume, φ ' 2 °, of the protein measured at dialysis equilibrium, i.e., under conditions where the chemical potentials of the additive are identical in the protein solution and the bulk solvent. This procedure, requires relatively large amounts of protein and extensive dialysis, which may not be practical for many proteins because of stability problems. The chapter explains that as the patterns of preferential interaction for salts and amino acids with proteins are completely different from those for the denaturants, that method cannot be applied. However, in these systems there exists a correlation between the preferential interaction and the protein surface area which renders possible the calculation of the preferential interactions for various proteins from the data obtained with other proteins. This method is addressed in the present chapter.