Looped liquid-liquid coexistence in protein crystallization

In view of the notorious complexity of protein–protein interactions, simplified models of proteins treated as patchy particles offer a promising strategy to obtain insight into the mechanism of crystallization. Here we report liquid–liquid phase separation (LLPS) with a highly asymmetric coexistence region in a computational model of rubredoxin with real molecular shape. The coexistence region terminates in both an upper (UCST) and a lower (LCST) critical solution temperature, and the complex molecular shape explains the closed-loop behavior of the LLPS.