The current technological push for nanoscopic devices has led to interest in the behavior of confined fluids. Colloidal and protein solutions garner particular interest, aside from their ubiquity in biology, due to the ability to “tune” the nature of molecular interactions by altering variables such as pH, salt concentration, and temperature. These tunable molecular interactions lead to rich macroscopic phase behavior, both in bulk and under confinement. Currently, knowledge of how to predict colloidal and protein phase behavior a priori is largely empirical, thus detailed understanding of the underlying physics that causes macroscopic properties is needed. This study looks at a model for the protein lysozyme, previously introduced by Carlsson et al.¹, under confinement of a slit pore. The model describes lysozyme as a spherical protein with a hard core, a single spherically-symmetric hydrophobic interaction, and a collection of embedded charge residues. Charge locations are based on information from the protein data bank and the charge values are pH dependent. We will present results indicating how protein phase behavior evolves with changing pore height as well as changing solution conditions. We will also compare confined protein phase behavior to simulations of bulk solution.

¹ F. Carlsson, M. Malmsten, and P. Linse, Journal of Physical Chemistry B 105 (48), 12189 (2001).