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Sedimentation equilibrium in macromolecular solutions of arbitrary concentration. II. Two protein components
Author(s) -
Chatelier Ronald C.,
Minton Allen P.
Publication year - 1987
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360260709
Subject(s) - chemistry , sedimentation equilibrium , macromolecule , work (physics) , thermodynamics , sedimentation , range (aeronautics) , inert , composition (language) , centrifuge , molecular mass , chromatography , physics , ultracentrifuge , materials science , organic chemistry , biochemistry , biology , nuclear physics , composite material , enzyme , paleontology , linguistics , philosophy , sediment
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) Biopolymers , 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 weight‐average 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.