Pairwise-additive hydrophobic effect for alkanes in water

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Chemical Physics

Background:

• The hydrophobic effect is a key phenomenon in aqueous solutions, influencing molecular interactions and self-assembly.
• Understanding the nature of hydrophobic interactions is crucial for fields ranging from drug design to materials science.

Purpose of the Study:

• To investigate the pairwise additivity of the hydrophobic effect for alkanes in water.
• To determine if the hydrophobic interaction can be represented by a semiempirical force field.
• To compare hydrophobic potential calculations using different simulation methods.

Main Methods:

• Analysis of experimental Henry's constants for various linear and branched alkanes.
• Development of a semiempirical model for hydrophobic potential based on hydration layer overlap volume.
• Comparison of calculated hydrophobic potential values with those from quantum mechanics and classical molecular dynamics simulations.

Main Results:

• Experimental Henry's constants indicate pairwise additivity of the hydrophobic effect for alkanes.
• The hydrophobic effect is primarily a local phenomenon, supporting the use of a semiempirical force field.
• The calculated contact value of the hydrophobic potential between methane molecules (-0.72 kcal/mol) aligns well with classical molecular dynamics results (-0.5 to -0.9 kcal/mol).

Conclusions:

• The hydrophobic effect for alkanes in water exhibits pairwise additivity.
• Hydrophobic interactions can be effectively modeled as a local phenomenon using semiempirical force fields.
• The semiempirical model provides a valuable and computationally efficient approach to studying hydrophobic interactions, complementing more computationally intensive methods.