title: Corresponding-states laws for protein solutions.
abstract: 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.
authors.affiliation: Departments of Chemical Engineering and Chemistry, University of Houston, Houston, Texas 77204, USA.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Katsonis
authors.forename: Simon
authors.initials: S
authors.lastname: Brandon
authors.forename: Peter G
authors.initials: PG
authors.lastname: Vekilov
mesh_terms: 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
chemical_list: D007477:Ions; D011506:Proteins; D012997:Solvents