Sedimentation equilibrium in a solution containing an arbitrary number of solute species at arbitrary concentrations: theory and application to concentrated solutions of ribonuclease.
Simple expressions are derived describing the equilibrium concentration gradient of each species in a solution containing an arbitrary number of solute species at arbitrary concentration, as a function of the concentration of all species. Quantitative relationships between the species gradients and experimentally observable signal gradients are presented. The expressions are model-free and take into account both attractive and repulsive interactions between all species. In order to analyze data obtained from strongly nonideal solutions, a statistical thermodynamic model for repulsive solute-solute interactions is required. The relations obtained are utilized to analyze the dependence of the equilibrium gradient of ribonuclease A in phosphate-buffered saline, pH 7.4, upon total protein concentration. Experimental results are interpreted in the context of a model for weak self-association leading to the formation of significant amounts of oligomers at total protein concentrations exceeding 25 g/l.
Zorrilla
Silvia
S
Instituto de Química Física Rocasolano, CSIC, Madrid, Spain.
Jiménez
Mercedes
M
Lillo
Pilar
P
Rivas
Germán
G
Minton
Allen P
AP
D001288:Attention; D019281:Dimerization; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D008970:Molecular Weight; D011506:Proteins / Q000737:chemistry; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013816:Thermodynamics; D014461:Ultracentrifugation / Q000379:methods
D011506:Proteins; D012996:Solutions; D012259:Ribonuclease, Pancreatic