Determination of fluid--solid transitions in model protein solutions using the histogram reweighting method and...

Area of Science:

• Computational physics
• Biophysics
• Materials science

Background:

• Protein crystallization is complex and typically relies on empirical screening.
• Understanding crystallization is crucial for protein structure determination and drug development.
• Nonequilibrium phases and polymorphism complicate predicting crystal formation.

Purpose of the Study:

• To investigate protein crystallization using a computational model.
• To explore the influence of anisotropic interactions on crystal structure.
• To construct a phase diagram for a model protein system.

Main Methods:

• Utilized a model protein composed of spheres with isotropic and anisotropic interactions.
• Employed expanded ensemble simulations of the Einstein crystal to calculate free energy.
• Applied NpT-Monte Carlo simulations with histogram reweighting for fluid-solid coexistence determination.

Main Results:

• Identified a stable simple cubic structure near room temperature and a disordered face-centered-cubic structure at higher temperatures.
• Observed a metastable first-order transition between disordered and ordered face-centered-cubic structures at low temperatures.
• Generated a complete phase diagram for a six-patch protein model, including fluid, three solid phases, and two triple points.

Conclusions:

• Anisotropic interactions significantly influence protein crystal structure and stability.
• The computational model successfully predicts multiple crystal phases and phase transitions.
• The study provides a framework for understanding and potentially controlling protein crystallization through molecular design.