Self-Propulsion Enhances Polymerization.

Maximino Aldana,Miguel Fuentes-Cabrera,Martín Zumaya

doi:10.3390/e22020251

Abstract

Self-assembly is a spontaneous process through which macroscopic structures are formed from basic microscopic constituents (e.g., molecules or colloids). By contrast, the formation of large biological molecules inside the cell (such as proteins or nucleic acids) is a process more akin to self-organization than to self-assembly, as it requires a constant supply of external energy. Recent studies have tried to merge self-assembly with self-organization by analyzing the assembly of self-propelled (or active) colloid-like particles whose motion is driven by a permanent source of energy. Here we present evidence that points to the fact that self-propulsion considerably enhances the assembly of polymers: self-propelled molecules are found to assemble faster into polymer-like structures than non self-propelled ones. The average polymer length increases towards a maximum as the self-propulsion force increases. Beyond this maximum, the average polymer length decreases due to the competition between bonding energy and disruptive forces that result from collisions. The assembly of active molecules might have promoted the formation of large pre-biotic polymers that could be the precursors of the informational polymers we observe nowadays.

Highlights

The formation of long biological polymers inside the cell is an out of equilibrium process that is carried out by a molecular machinery which, nowadays, is extremely complex
All the the results results presented presented in this figure were computed at constant temperature in this figure were computed at constant temperature T = 0.1. (a) Probability P( L)) that that aa chain chain of of 7 time steps, for different values of the self-propulsion force F in a channel length is formed after length L is formed after 107 time steps, for different values of the self-propulsion force Fsp in a channel sp with with an an aspect-ratio aspect-ratio R
7 we focused on the longest polymers in each realization instead of instead of just computing average polymer length over all the polymers

Summary

Introduction

The formation of long biological polymers inside the cell (e.g., proteins and nucleic acids) is an out of equilibrium process that is carried out by a molecular machinery which, nowadays, is extremely complex. An area of intense research in the last two decades has been the study of the self-assembly of patchy colloids [22,23,24] These are molecules which have different attraction and repulsion zones (patches) around them and, depending on the geometry of the molecule and the distribution of its patches, these molecules can self-assemble in a variety of different structures, from linear chains to two-dimensional triangles to three-dimensional icosahedra [22]. The formation of protein domains on the cell membrane is observed, these domains are considerably larger (about four hundred times fold) than those formed via equilibrium processes These results show that the external input of energy, via self-propulsion or other sources (such as ATP), can considerably enhance the assembly of structures. We show how a model that borrows some of these ideas can be used to study polymer formation from a collection of self-propelled monomers

Model Definition

Results

Snapshots

5.5.Conclusions