Sedimentation equilibrium in macromolecular solutions of arbitrary concentration. II. Two protein components

✍ Scribed by Ronald C. Chatelier; Allen P. Minton

• Publisher: Wiley (John Wiley & Sons)
• Year: 1987
• Tongue: English
• Weight: 894 KB
• Volume: 26
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360260709

✦ Synopsis

Synopsis

Relations describing sedimentation equilibrium in solutions containing two macromolecular solute components are derived for the following cases: (1) two nonassociating proteins at arbitrary concentration, (2) one dilute self-associating protein in the presence of a second inert protein at arbitrary concentration, and (3) two proteins at arbitrary concentration that can associate to form a single heterocomplex of arbitrary composition. As in earlier work (R. C. Chatelier and A. P. Minton (1987) Bwpolymers, 26,507-524), the relations are obtained by using scaled particle theory to calculate the thermodynamic activity of each species present at a given radial distance in the centrifuge. The results of numerical simulations of sedimentation equilibrium are presented as the dependence of apparent molecular weights, or apparent weight-average molecular weights, upon solution composition. Semiempirical methods are presented, by means of which the weightaverage molecular weights of self-and heteroassociating proteins in highly nonideal solutions may be estimated from experimental data. It is found that the semiempirical methods yield reasonably accurate estimates of the true weight-average molecular weight over a broad range of experimental conditions, providing that the partial specific volumes of two components in a heteroassociating system do not differ by more than about 0.05 mL/g.