Sterically Driven Current Reversal in a Model Molecular Motor

TL;DR

This study uses molecular simulations to demonstrate that slight structural modifications in a synthetic molecular motor can reverse its direction of motion, revealing a steric mechanism behind current reversal.

Contribution

It introduces a minimal model showing how adjusting site spacing can reverse motor direction, advancing understanding of molecular motor control mechanisms.

Findings

Direction of the motor can be reversed by changing site spacing.

Steric interactions are key to current reversal.

Simulation results support a steric mechanism for reversal.

Abstract

Simulations can help unravel the complicated ways in which molecular structure determines function. Here, we use molecular simulations to show how slight alterations of a molecular motor's structure can cause the motor's typical dynamical behavior to reverse directions. Inspired by autonomous synthetic catenane motors, we study the molecular dynamics of a minimal motor model, consisting of a shuttling ring that moves along a track containing interspersed binding sites and catalytic sites. The binding sites attract the shuttling ring while the catalytic sites speed up a reaction between molecular species, which can be thought of as fuel and waste. When that fuel and waste are held in a nonequilibrium steady-state concentration, the free energy from the reaction drives directed motion of the shuttling ring along the track. Using this model and nonequilibrium molecular dynamics, we show that the shuttling ring's direction can be reversed by simply adjusting the spacing between binding and catalytic sites on the track. We present a steric mechanism behind the current reversal, supported by kinetic measurements from the simulations. These results demonstrate how molecular simulation can guide future development of artificial molecular motors.