Phase behavior of mixtures of intrinsic disordered proteins and rod-like colloidal particles*

We report on studies of the phase behavior of aqueous dispersions composed of intrinsic disordered proteins (IDPs) [1] and submicrometer-sized rod-like colloidal particles such as fd-virus particles [2]. Here we focus on results with fd. In isolation, IDPs form condensates through spontaneous liquid-liquid phase separation in solutions with low ion concentration; in IDP-fd mixtures, the IDPs interact with the fd via hard-core and Coulomb interactions. Using fluorescence microscopy we have found that at low fd concentration, condensates form and have a core-shell structure with the fd aggregated on the surface. On the other hand, at high colloidal particle concentration, phase separation of IDPs is suppressed, with substantially fewer and smaller condensates observed. Notably, at intermediate fd concentration, the fd and the IDPs form well-mixed condensates in which the fd are highly concentrated (i.e., compared to the background liquid phase). We will describe the experiments and offer some analysis of the phase behavior of these mixtures and the microscopic structure of the condensates.

 

[1] Garabedian, M V., et al. Biochemistry 61.22 (2022): 2470-2481.

[2] Dogic, Z. and Fraden, S. Current opinion in colloid & interface science 11.1 (2006): 47-55.