Crowding effects on water-mediated hydrophobic interactions

Area of Science:

• Biophysics
• Computational Chemistry
• Molecular Dynamics

Background:

• Understanding intracellular crowding is key to protein folding and biomolecular assembly.
• The entropic depletion model of crowding overlooks soft crowder-biomolecule interactions.
• Hydrophobic interactions are fundamental to biological processes.

Purpose of the Study:

• To investigate how crowder chemical nature and soft interactions affect water-mediated hydrophobic interactions.
• To model crowded environments using dipeptides of varying sizes and polarities.
• To elucidate the thermodynamic driving forces behind crowder-mediated hydrophobic association.

Main Methods:

• Molecular dynamics simulations were employed.
• Two non-polar neopentane solutes were used to study hydrophobic interactions.
• Crowded environments were simulated using dipeptides of polar and non-polar amino acids.

Main Results:

• Bulky non-polar crowders (Leu2) significantly strengthen hydrophobic interactions.
• Small crowders and polar crowders showed less significant strengthening effects.
• A crossover from energy-stabilized to entropy-stabilized states was observed with bulky crowders.

Conclusions:

• Both entropic (size) and energetic (chemical nature) effects are crucial for hydrophobic association.
• Crowder-solute energy influences dehydration penalty and neopentane association.
• Findings have implications for understanding protein crowding effects on free energy landscapes.