Two-dimensional structure in a generic model of triangular proteins and protein trimers

Area of Science:

• Condensed matter physics
• Biophysics
• Materials science

Background:

• Two-dimensional (2D) crystals formed by triangular proteins and protein trimers exhibit complex structures.
• Understanding the self-assembly principles of such 2D systems is crucial for designing novel materials and understanding biological structures.

Purpose of the Study:

• To investigate the structures and phase behavior of hard-disk trimers with attractive interactions.
• To mimic specific binding interactions found in biological systems using a simplified model.
• To explore the formation of different aggregate structures and their transition into ordered phases.

Main Methods:

• Computer simulations of hard-disk trimers with an attractive square-well potential.
• Analysis of fluid and solid phases at varying densities and temperatures.
• Identification of structural motifs like tetramers, pentamers, and hexamers.

Main Results:

• At low density and temperature, fluid phases consist of various aggregates (tetramers to hexamers).
• Hexamers form the primary structural motif for a high-density, low-temperature periodic solid phase.
• A metastable periodic structure based on a tetramer motif was identified.
• A transition between orientationally ordered and disordered solid phases occurs at high density.

Conclusions:

• The study reveals the rich phase behavior of hard-disk trimers, including the formation of hexamer-based and tetramer-based crystalline structures.
• Simulation results provide insights into the self-assembly mechanisms relevant to 2D protein crystals observed in electron microscopy.
• The model demonstrates how simple attractive interactions can lead to complex ordered structures.