Water dynamics at protein interfaces: ultrafast optical Kerr effect study.

Area of Science:

• Biophysics
• Physical Chemistry
• Structural Biology

Background:

• Protein hydration shells influence protein structure and function.
• Understanding water dynamics at protein surfaces is crucial for molecular biology.
• Previous studies have focused on water relaxation dynamics near proteins.

Purpose of the Study:

• To investigate the H-bond structure and dynamics of water in aqueous protein solutions.
• To quantify the changes in water dynamics at the protein surface using ultrafast optical Kerr effect.
• To correlate water dynamics with protein properties like hydrophilicity.

Main Methods:

• Ultrafast optical Kerr effect spectroscopy.
• Analysis of aqueous solutions of three different proteins at varying concentrations.
• Terahertz Raman spectroscopy.

Main Results:

• Water dynamics in the first solvation layer of proteins are slowed by up to a factor of 8 compared to bulk water.
• The most significant slowdown was observed for hydrophilic bovine serum albumin.
• A new spectral feature at ~80 cm(-1) appears above 5 wt % protein, attributed to protein amide chain bending.

Conclusions:

• Protein hydration significantly alters water molecule dynamics in the immediate vicinity of the protein.
• The degree of water dynamics slowdown correlates with protein hydrophilicity.
• Terahertz Raman spectroscopy can reveal structural changes in proteins at higher concentrations.