Efficient Multistate Free-Energy Calculations with QM/MM Accuracy Using Replica-Exchange Enveloping Distribution...

Area of Science:

• Computational Chemistry
• Molecular Dynamics Simulations
• Quantum Chemistry

Background:

• Calculating free-energy differences is crucial in computational chemistry.
• Current methods face limitations in accuracy due to model approximations and insufficient phase-space sampling from limited computational resources.

Purpose of the Study:

• To develop a computationally efficient, multistate, and multiscale free-energy method by integrating QM/MM with RE-EDS.
• To assess the performance of the QM/MM RE-EDS approach for calculating hydration free energies.

Main Methods:

• Integration of quantum-mechanical/molecular-mechanical (QM/MM) scheme with replica-exchange enveloping distribution sampling (RE-EDS).
• Calculation of hydration free energies for three datasets using semiempirical methods for the QM zone.

Main Results:

• The QM/MM RE-EDS method demonstrates high computational efficiency.
• The choice of QM Hamiltonian (specifically semiempirical methods) significantly impacts accuracy.
• Compatibility between QM and MM models, and the selection of the MM water model, are also non-negligible factors affecting results.

Conclusions:

• RE-EDS is an efficient approach for free-energy calculations within a QM/MM framework.
• The study provides a foundation for future advancements and applications of this multiscale, multistate method.