Role of anisotropic interactions for proteins and patchy nanoparticles

Area of Science:

• Biophysics
• Physical Chemistry
• Protein Science

Background:

• Protein-protein interactions exhibit inherent anisotropy due to specific regions or "patches."
• The influence of these anisotropic interactions on the thermodynamics of dilute protein solutions, particularly the osmotic second virial coefficient (B22), is not fully understood.

Purpose of the Study:

• To investigate the conditions under which anisotropic patch-patch interactions dominate protein solution thermodynamics.
• To elucidate the balance between attractive/repulsive patch interactions, patch size, and entropic contributions to B22.

Main Methods:

• Utilized exactly solvable models to analyze orientation-dependent protein interactions.
• Reformulated B22 in terms of the density of states for interaction energy and particle distance, avoiding approximations.

Main Results:

• A balance between attractive patch-patch interaction strength and patch size is crucial for dominance.
• Repulsive patch interactions significantly affect B22 only when long-ranged.
• Anisotropic interactions dominate B22 only if entropic penalties are overcome, which requires sufficiently large patches.

Conclusions:

• The dominance of anisotropic interactions in dilute protein solutions depends on a delicate balance of energetic and entropic factors.
• Patch size is a critical determinant; small patches hinder the dominance of anisotropic interactions.
• Temperature dependence of B22 offers a potential experimental method to assess the contribution of dominant attractive configurations.