Quantifying the Extent of Hydration of a Surface-Bound Peptide Using Neutron Reflectometry

Area of Science:

• Biophysics
• Surface Chemistry
• Materials Science

Background:

• Protein immobilization on inorganic surfaces is crucial for applications.
• Water's role in protein structure, dynamics, and function at interfaces is not fully understood.
• Hydrophobic interfaces present unique challenges for protein hydration.

Purpose of the Study:

• Quantify water associated with peptides on hydrophobic surfaces.
• Determine the location of water molecules relative to the peptide and surface.
• Investigate the effect of water on surface-bound peptide structure.

Main Methods:

• Neutron reflectometry (NR) to measure water quantity.
• Covalent attachment of helical peptides to self-assembled monolayers (SAMs) on gold.
• Comparison with molecular dynamics (MD) simulations.

Main Results:

• Peptide attachment increased water in the SAM layer, indicating SAM disruption.
• Significant hydration of peptides was observed (75-111 water molecules per peptide).
• Approximately 50% of nearby water molecules were directly hydrogen-bound to the peptide.
• Water immersion compressed the peptide structure towards the surface.

Conclusions:

• Surface-bound peptides are sufficiently hydrated even at hydrophobic interfaces.
• Water plays a critical role in the structure and hydration of peptides at bio/abio interfaces.
• Findings inform protein immobilization strategies and biomaterial design.