On generalizing the induced surface charge method to heterogeneous Poisson-Boltzmann models for electrostatic free...

Area of Science:

• Computational chemistry
• Biophysics
• Electrostatics

Background:

• The induced surface charges (ISC) method is a robust approach for electrostatic analysis using the Poisson-Boltzmann (PB) model.
• However, the ISC method has limitations in generalizing to heterogeneous dielectric PB models.

Purpose of the Study:

• To propose a novel far-field (FF) method for calculating polar solvation free energy.
• To address the limitations of the ISC method, particularly with heterogeneous dielectric models.

Main Methods:

• The FF method reformulates energy functionals of nonlinear PB potential in solvent and vacuum states.
• It reconstructs free energies using far-field solutions, avoiding self-energy terms from singular charges.
• The method is validated for sharp-interface and heterogeneous PB models, including diffuse interface, Gaussian, and super-Gaussian PB models.

Main Results:

• The FF method demonstrates validity for both sharp-interface and heterogeneous PB models.
• Performance was validated on Kirkwood spheres and protein systems.
• The FF method shows robustness for non-rigid biomolecules and is insensitive to charge location perturbations.

Conclusions:

• The proposed FF method offers a physically intuitive and mathematically rigorous approach to calculating polar solvation free energy.
• It overcomes the limitations of the ISC method, enabling broader applicability in electrostatic analysis of biomolecules.