Comparison of Cellulose Iβ Simulations with Three Carbohydrate Force Fields

Area of Science:

• Biomolecular simulation
• Renewable energy materials science
• Computational chemistry

Background:

• Molecular dynamics (MD) simulations of cellulose are crucial for renewable energy applications.
• Numerous atomistic and coarse-grained force fields exist for cellulose, but a systematic comparison is lacking.

Purpose of the Study:

• To systematically compare the performance of three prominent carbohydrate force fields (CHARMM35, GLYCAM06, Gromos 45a4) for cellulose Iβ microfibrils.
• To evaluate the structural stability and divergence of hydrated cellulose microfibrils under near-microsecond timescales using MD simulations.

Main Methods:

• Performed molecular dynamics simulations of 36-chain cellulose Iβ microfibrils at room temperature.
• Utilized three distinct carbohydrate force fields: CHARMM35, GLYCAM06, and Gromos 45a4.
• Simulated systems up to the near-microsecond timescale to assess long-term structural behavior.

Main Results:

• All tested force fields showed divergence from the native cellulose Iβ crystal structure.
• CHARMM35 and GLYCAM06 force fields produced structures mimicking high-temperature experimental behavior.
• Gromos 45a4 exhibited significant deviations from experimental data and other force fields, differing from previous shorter simulations.

Conclusions:

• The choice of force field significantly impacts cellulose microfibril structural dynamics and convergence timescales.
• Initial conditions and electrostatic parameters within the GLYCAM06 force field influence the rate of structural divergence.
• Further experimental and theoretical studies are needed to accurately model small-diameter cellulose microfibrils relevant to plant cellulose.