Multiscale Water Dynamics on Protein Surfaces: Protein-Specific Response to Surface Ions

Area of Science:

• Biophysical Chemistry
• Protein Dynamics
• Solution Chemistry

Background:

• Proteins interact with ions in aqueous solutions, with water mediating these interactions.
• Understanding ion-protein-water dynamics is crucial for biological processes.

Purpose of the Study:

• To investigate ion-specific water dynamics on protein surfaces using Nuclear Magnetic Resonance Dispersion (NMRD) and theory.
• To explore how different ions (NaCl, NaI) influence water relaxation rates around hen egg-white lysozyme (LZM) and bovine serum albumin (BSA).

Main Methods:

• Field-dependent Nuclear Magnetic Resonance Relaxation (NMRD) experiments.
• Theoretical modeling accounting for non-Lorentzian NMRD profiles and protein surface properties.
• Analysis of water dynamics on protein surfaces in concentrated solutions.

Main Results:

• Salt addition caused opposite effects on water relaxation rates for LZM (increase) and BSA (decrease).
• Ion identity influenced the magnitude of these changes.
• The developed model successfully reproduced experimental data and explained ion-specific effects through protein surface fractal dimension and water residence times.

Conclusions:

• Water dynamics at protein surfaces are protein-specific and influenced by ion identity.
• These effects are linked to the unique geometrical features of protein surfaces.
• The findings extend beyond simple Hofmeister-style ion ordering.