Corresponding-states laws for protein solutions.
The solvent around protein molecules in solutions is structured and this structuring introduces a repulsion in the intermolecular interaction potential at intermediate separations. We use Monte Carlo simulations with isotropic, pair-additive systems interacting with such potentials. We test if the liquid-liquid and liquid-solid phase lines in model protein solutions can be predicted from universal curves and a pair of experimentally determined parameters, as done for atomic and colloid materials using several laws of corresponding states. As predictors, we test three properties at the critical point for liquid-liquid separation: temperature, as in the original van der Waals law, the second virial coefficient, and a modified second virial coefficient, all paired with the critical volume fraction. We find that the van der Waals law is best obeyed and appears more general than its original formulation: A single universal curve describes all tested nonconformal isotropic pair-additive systems. Published experimental data for the liquid-liquid equilibrium for several proteins at various conditions follow a single van der Waals curve. For the solid-liquid equilibrium, we find that no single system property serves as its predictor. We go beyond corresponding-states correlations and put forth semiempirical laws, which allow prediction of the critical temperature and volume fraction solely based on the range of attraction of the intermolecular interaction potential.
Katsonis
Panagiotis
P
Departments of Chemical Engineering and Chemistry, University of Houston, Houston, Texas 77204, USA.
Brandon
Simon
S
Vekilov
Peter G
PG
D001703:Biophysics / Q000379:methods*; D002627:Chemistry, Physical / Q000379:methods*; D003198:Computer Simulation; D006860:Hydrogen Bonding; D007477:Ions; D015233:Models, Statistical; D008968:Molecular Conformation; D009010:Monte Carlo Method; D011506:Proteins / Q000737:chemistry*; D012997:Solvents; D013696:Temperature; D013816:Thermodynamics
D007477:Ions; D011506:Proteins; D012997:Solvents