Solid-State NMR Validation of OPLS4: Structure of PC-Lipid Bilayers and Its Modulation by Dehydration

Area of Science:

• Computational biophysics
• Molecular modeling of biomembranes

Background:

• Atomistic molecular dynamics (MD) simulations are crucial for studying biomembrane structure and dynamics.
• The accuracy of MD simulations depends heavily on the chosen force field.
• Independent validation of force fields against experimental data is essential for reliable biomembrane modeling.

Purpose of the Study:

• To evaluate the OPLS4 force field's performance in simulating phosphatidylcholine (PC) lipid bilayers.
• To compare OPLS4 against the CHARMM36 force field using experimental data.
• To assess the accuracy of these force fields in capturing lipid bilayer behavior under varying hydration conditions.

Main Methods:

• Atomistic molecular dynamics (MD) simulations were performed using OPLS4 and CHARMM36 force fields.
• Nuclear magnetic resonance (NMR) order parameters for C-H bonds were used as a benchmark.
• Simulations were compared against experimental data for saturated (DMPC) and unsaturated (POPC) lipid bilayers under dehydration.

Main Results:

• The OPLS4 force field demonstrated good reproduction of PC lipid bilayer structure and dehydration response.
• OPLS4 slightly outperformed CHARMM36 in describing the dehydration response of lipid bilayers.
• Both force fields exhibited inaccuracies in the glycerol backbone, unsaturated carbon segments, and PC headgroup response to dehydration.

Conclusions:

• The OPLS4 force field is a viable option for biomembrane simulations, showing competitive performance with CHARMM36.
• Independent validation of force fields, especially proprietary ones like OPLS4, is critical.
• Nuanced differences and similarities between OPLS4 and CHARMM36 highlight areas for future force field development in biomembrane modeling.