Polarizable water model for the coarse-grained MARTINI force field

Area of Science:

• Computational chemistry
• Biophysics
• Molecular dynamics

Background:

• Coarse-grained (CG) simulations offer access to larger temporal and spatial scales than atomistic models for biomolecular processes.
• Current CG models often lack accurate representation of solvent polarization, crucial for understanding biological systems.
• The MARTINI force field is a widely used CG model, but its water model does not account for polarization effects.

Purpose of the Study:

• To parameterize a novel polarizable coarse-grained water model for use with the MARTINI force field.
• To improve the representation of solvent effects, specifically dielectric screening, in CG simulations.
• To enhance the accuracy of CG simulations for phenomena influenced by electrostatic interactions and local dielectric environments.

Main Methods:

• Developed a three-bead model to represent four water molecules, capturing orientational polarizability.
• Parameterized the model to reproduce bulk water dielectric screening, density, and oil/water partitioning.
• Applied the new model to simulate ion transport across lipid membranes and electroporation of lipid bilayers.

Main Results:

• The new polarizable CG water model effectively reproduces the dielectric screening of bulk water.
• The model maintains the accuracy of bulk water density and partitioning properties compared to the standard MARTINI force field.
• Simulations show improved accuracy in modeling ion transport across membranes and electroporation, consistent with atomistic results.

Conclusions:

• The developed polarizable CG water model significantly enhances the accuracy of CG simulations for electrostatic phenomena.
• This model provides a more realistic representation of water's role in biomolecular processes, particularly concerning dielectric effects.
• The improved model enables more reliable studies of ion permeation and membrane electroporation at CG scales.