Cooperative effects in water-biomolecule crystal systems

Area of Science:

• Computational chemistry
• Biomolecular simulations
• Water-protein interactions

Background:

• Traditional water models assume pair-additive potentials, neglecting cooperative effects.
• Quantum mechanics and experimental data suggest non-negligible cooperative effects in hydrogen-bonded water.
• Understanding these effects is crucial for accurate biomolecular simulations.

Purpose of the Study:

• To model non-pair-additive (cooperative) effects in water organization around biomolecules using Monte Carlo simulations.
• To investigate the extent and consequences of cooperative water behavior in biomolecule hydrate crystals.
• To develop computationally feasible methods for simulating large systems with cooperative effects.

Main Methods:

• Utilized Monte Carlo computer simulation techniques.
• Employed the many-body polarizable electropole (PE) model for water.
• Examined cooperative effects in several biomolecule hydrate crystals.

Main Results:

• Predicted increases in water molecule dipole moments, up to 50% higher than the monomer value.
• Demonstrated that the average dipole moment is a system-specific property, not an intrinsic water property.
• Observed discrepancies when using a fixed average dipole moment compared to unfixed simulations.

Conclusions:

• Cooperative effects significantly influence water organization around biomolecules.
• The PE model captures these non-pair-additive interactions, predicting substantial dipole moment increases.
• A new simulation procedure allowing for a spread of dipole moments makes large-scale simulations feasible.