Surfactancy in a tadpole model of proteins

TL;DR

This paper models proteins with mixed globular and disordered regions as 'tadpoles' to study phase separation and surfactant behaviors in nuclear environments, revealing entropy-driven effects that are biologically limited.

Contribution

Introduces a novel 'tadpole' model combining polymers and colloids to simulate protein behavior and surfactant properties in nuclear phase separation.

Findings

Tadpoles support phase separation via depletion flocculation.

They exhibit surfactant behaviors like interface preference and micelle formation.

Entropy alone is insufficient to drive these behaviors at biological concentrations.

Abstract

We model the environment of eukaryotic nuclei by representing macromolecules by only their entropic properties, with globular molecules represented by spherical colloids and flexible molecules by polymers. We put particular focus on proteins with both globular and intrinsically disordered regions, which we represent with `tadpole' constructed by grafting single polymers and colloids together. In Monte Carlo simulations we find these tadpoles support phase separation via depletion flocculation, and demonstrate several surfactant behaviours, including being found preferentially at interfaces and forming micelles in single phase solution. Furthermore, the model parameters can be tuned to give a tadpole a preference for either bulk phase. However, we find entropy too weak to drive these behaviours by itself at likely biological concentrations.