Dynamics of protein and peptide hydration

Area of Science:

• Biophysics
• Structural Biology
• Physical Chemistry

Background:

• Biological processes are influenced by the unique properties of water at protein surfaces.
• Understanding protein hydration dynamics is crucial for deciphering biomolecular interactions.
• Magnetic Relaxation Dispersion (MRD) and Nuclear Overhauser Effect (NOE) are key techniques for studying water dynamics.

Purpose of the Study:

• To investigate the dynamics of water molecules in the hydration layer of biomolecules.
• To characterize the influence of cyclic peptides (oxytocin) and globular proteins (BPTI) on water dynamics.
• To reconcile MRD and NOE data using a novel dipolar relaxation theory.

Main Methods:

• Magnetic Relaxation Dispersion (MRD) measurements on 2H and 17O nuclei of water.
• Analysis of Nuclear Overhauser Effect (NOE) data between water and protein protons.
• Study of deeply supercooled solutions of oxytocin and BPTI.

Main Results:

• Over 95% of water molecules at biomolecular surfaces exhibit motion only up to two times slower than bulk water.
• The hydration layer of BPTI shows minimal temperature dependence, unlike small nonpolar molecules.
• Exposed nonpolar residues on BPTI do not appear to form clathrate-like structures.

Conclusions:

• Protein hydration layers exhibit surprisingly fast water dynamics.
• The behavior of water around BPTI suggests a lack of clathrate-like hydrophobic hydration.
• A new theory of intermolecular dipolar relaxation successfully integrates MRD and NOE findings, clarifying water-protein interactions.