Optimized Radii for Poisson-Boltzmann Calculations with the AMBER Force Field.

Area of Science:

• Computational chemistry
• Biophysics
• Molecular modeling

Background:

• Implicit solvent models are crucial for biomolecular electrostatics.
• Accurate predictions of pKa, binding, and solvation energies depend on continuum parameters like radii.
• Benchmarking against explicit solvent simulations is key for parameter accuracy.

Purpose of the Study:

• To develop and validate optimized radii for Poisson-Boltzmann (PB) calculations.
• To improve the accuracy of electrostatic predictions in biomolecular systems using AMBER (parm99) charges.
• To enable more reliable continuum force calculations through stabilized electrostatic potentials.

Main Methods:

• Optimized radii were developed for abrupt and cubic-spline smoothed dielectric boundaries in PB calculations.
• Initial radii were approximated from solvent radial charge distributions.
• A genetic algorithm fine-tuned radii using charging free energies from explicit solvent simulations.
• The optimized radii were tested on four protein-like polypeptides.

Main Results:

• The optimized radii significantly increased the accuracy of molecular solvation energies and atomic forces.
• Spline smoothing of the dielectric boundary stabilized the electrostatic potential.
• Results showed improved performance compared to commonly used continuum parameter sets.
• The developed radii offer energetic congruence for combined molecular mechanics and PB solvation models.

Conclusions:

• The optimized radii provide a more accurate and reliable method for PB calculations in protein systems.
• These parameters enhance the quantitative prediction of various biomolecular properties.
• The findings are applicable to models combining molecular mechanics with PB solvation energies.