Level-Set Variational Implicit-Solvent Modeling of Biomolecules with the Coulomb-Field Approximation

Area of Science:

• Computational chemistry
• Molecular modeling
• Biophysics

Background:

• The variational implicit-solvent model (VISM) uses a mean-field free-energy functional to model molecular solvation.
• Level-set VISM effectively handles nonpolar systems, predicting phenomena like capillary evaporation in hydrophobic confinement.

Purpose of the Study:

• To incorporate an electrostatic free energy approximation into VISM.
• To enhance VISM's capability in modeling complex solvation phenomena, particularly for molecules with both polar and nonpolar regions.

Main Methods:

• Introduced the Coulomb-field approximation for electrostatic free energy within VISM.
• Utilized the effective boundary force as "normal velocity" in level-set relaxation.
• Calculated solvation free energies and potentials of mean force for various molecules, including the protein BphC.

Main Results:

• The enhanced VISM accurately couples polar and nonpolar interactions.
• Demonstrated sensitivity of protein dehydration to local electrostatic potentials, consistent with molecular dynamics simulations.
• Successfully calculated solvation free energies and potentials of mean force for diverse molecular systems.

Conclusions:

• The integrated VISM provides a more comprehensive approach to molecular solvation.
• This work represents a significant step towards modeling complex protein dehydration using implicit-solvent methods.
• The findings highlight the critical interplay between electrostatics and hydrophobic effects in biological systems.