Sedimentation equilibrium in macromolecular solutions of arbitrary concentration. I. Self‐associating proteins

Publisher Website
Google Scholar
Abstract
Relations describing sedimentation equilibrium in solutions of self‐associating macromolecules at arbitrary concentration are presented. These relations are obtained by using scaled‐particle theory to calculate the thermodynamic activity of each species present at a given radial distance. The results are expected to be valid for solutions of globular proteins under conditions such that interactions between individual solute molecules may be approximated by a hard‐particle potential. Sedimentation equilibria in solutions containing either a nonassociating solute or a solute that self‐associates according to several different schemes are simulated using the derived relations. The results of these simulations are presented in terms of the dependence of apparent weight‐average molecular weight upon solute concentration. Simple empirical relations are presented for estimating the true weight‐average molecular weight from the apparent weight‐average molecular weight, without reference to any particular self‐association scheme. The weight‐average molecular weight estimated in this fashion is within a few percent of the true weight‐average molecular weight at all experimentally realizable solute concentrations ( < 400 g/L).