Comparison of free-energy methods using a tripeptide-water model system

Area of Science:

• Computational chemistry
• Molecular modeling
• Biophysics

Background:

• Accurately calculating binding affinities is crucial for drug design.
• Modeling the displacement of structural water molecules in protein active sites presents a significant challenge.
• Free-energy calculation methods are essential for predicting molecular interactions.

Purpose of the Study:

• To evaluate the performance of various free-energy calculation methods for combining two alchemical changes.
• To compare pairwise and two-dimensional approaches for perturbing a water molecule and an amino acid simultaneously.
• To assess the feasibility, efficiency, and usability of these methods in a model system mimicking protein residue mutation.

Main Methods:

• Bennett acceptance ratio (BAR)
• Thermodynamic integration (TI)
• Extended TI (X-TI)
• Enveloping distribution sampling (EDS)
• Two-dimensional TI (2D-TI)
• EDS-TI

Main Results:

• Pairwise methods like BAR and X-TI were found to be most suitable for the investigated problem.
• Two-dimensional methods (EDS-TI, 2D-TI) were also presented and compared.
• The model system simulated the displacement of a water molecule in a protein active site during residue mutation.

Conclusions:

• BAR and X-TI are currently the most practical methods for handling problems involving few end states, such as modeling structural water displacement.
• Accurate treatment of structural water is vital for successful binding affinity calculations in computational drug design.
• Further development of computational methods is needed for more complex systems.