Simulating force-induced conformational transitions in polysaccharides with the SMD replica exchange method

Area of Science:

• Biophysics
• Computational Chemistry
• Materials Science

Background:

• Conventional steered molecular dynamics (SMD) simulations struggle to replicate equilibrium conditions observed in atomic force microscopy (AFM) measurements.
• A significant timescale gap exists between typical SMD simulations (microseconds) and AFM experiments (seconds), hindering direct comparison of force-induced conformational transitions in polysaccharides.

Purpose of the Study:

• To introduce and validate the replica exchange method (REM) combined with SMD (REM SMD) for enhanced sampling in molecular dynamics simulations.
• To assess the ability of REM SMD to accurately reproduce experimental results from AFM stretching and release measurements of polysaccharides.

Main Methods:

• Application of replica exchange method (REM) to steered molecular dynamics (SMD) simulations.
• Comparative analysis of REM SMD simulation results against experimental data from atomic force microscopy (AFM) stretching experiments on a small polysaccharide system.

Main Results:

• REM SMD successfully reproduces both qualitative and quantitative aspects of AFM experimental results for polysaccharide conformational transitions.
• The REM SMD approach significantly reduces hysteresis and computational time compared to conventional SMD simulations.
• The method effectively bridges the timescale gap, approaching near-equilibrium conditions relevant to AFM measurements.

Conclusions:

• REM SMD is a powerful and efficient computational tool for studying force-induced conformational transitions in small biopolymer systems.
• This enhanced sampling technique provides a more accurate and computationally feasible method for investigating biopolymer mechanics at near-equilibrium conditions.
• REM SMD offers a valuable alternative for researchers seeking to bridge the gap between simulation and experimental biophysics.