Phase transitions in hard-core Yukawa fluids: toward a theory of phase stability in protein solutions

Thermodynamically self-consistent integral equation theories (TC-IETs) supplemented by a one-phase freezing criterion, and Monte Carlo simulations, are used to investigate the thermodynamic and structural properties, as well as the phase diagram, of the hard-core Yukawa fluid (HCYF). The attention is focused on rapidly decaying Yukawa tails, a potential regime suited to model in an approximate manner the interaction between globular proteins in protein solutions. TC-IETs are found to give a reasonably accurate description of the physical properties of the HCYF in this limit. The position of the sublimation line relative to the liquid-vapour binodal line, known to play a crucial role in the onset of crystallization in protein solutions, seems qualitatively reproducible. We suggest on this basis the possibility of extending the use of TC-IET to more realistic models of protein solutions, so as to take into account the true multicomponent nature of these fluids, a physical situation whose description still challenges the currently available computer simulation capabilities.