Extended law of corresponding states for protein solutions

TL;DR

This paper extends the law of corresponding states to protein solutions, demonstrating that their phase behavior can be mapped onto short-range fluid models, enabling predictions of thermodynamic properties from limited experimental data.

Contribution

It applies the extended law of corresponding states to complex protein solutions, linking experimental phase data to simulation models through effective scaling and virial coefficients.

Findings

Protein solution binodals map onto short-range fluid models.

Scaled second virial coefficients follow a master curve.

Second virial coefficients estimated from cloud points agree with other methods.

Abstract

The so-called extended law of corresponding states, as proposed by Noro and Frenkel [J. Chem. Phys. 113, 2941 (2000)], involves a mapping of the phase behaviors of systems with short-range attractive interactions. While it has already extensively been applied to various model potentials, here we test its applicability to protein solutions with their complex interactions. We successfully map their experimentally determined metastable gas--liquid binodals, as available in the literature, to the binodals of short-range square-well fluids, as determined by previous as well as new Monte Carlo simulations. This is achieved by representing the binodals as a function of the temperature scaled with the critical temperature (or as a function of the reduced second virial coefficient) and the concentration scaled by the cube of an effective particle diameter, where the scalings take into account the attractive and repulsive contributions to the interaction potential, respectively. The scaled binodals of the protein solutions coincide with simulation data of the adhesive hard-sphere fluid. Furthermore, once the repulsive contributions are taken into account by the effective particle diameter, the temperature dependence of the reduced second virial coefficients follows a master curve that corresponds to a linear temperature dependence of the depth of the square-well potential. We moreover demonstrate that, based on this approach and cloud-point measurements only, second virial coefficients can be estimated, which we show to agree with values determined by light scattering or by DLVO-based calculations.