An ultrasensitive tool exploiting hydration dynamics to decipher weak lipid membrane-polymer interactions.

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Macromolecular interactions at interfaces are vital for biological and material functions.
• Understanding these interactions, especially weak ones, is challenging due to the presence of bulk water.
• Hydration water plays a critical role in interfacial phenomena but its dynamics are often overlooked.

Purpose of the Study:

• To introduce and validate a novel tool, (1)H Overhauser Dynamic Nuclear Polarization (ODNP), for studying weak macromolecular interactions.
• To investigate the role of hydration water dynamics at polymer-membrane interfaces.
• To demonstrate ODNP's capability in detecting subtle changes in interfacial water under ambient conditions.

Main Methods:

• Development and application of (1)H Overhauser Dynamic Nuclear Polarization (ODNP) spectroscopy.
• Site-specific probing of translational dynamics of hydration water.
• Utilizing a model system of poloxamer 188 (P188) interacting with lipid vesicles.

Main Results:

• ODNP detected distinct changes in the translational dynamics of hydration water at the lipid membrane surface and bilayer interior upon P188 addition.
• No significant changes were observed in the dynamics or structure of the lipid membranes themselves.
• The study highlights the sensitivity of hydration water diffusivity to weak polymer-membrane interactions.

Conclusions:

• Hydration water is an integral component of lipid membrane systems.
• Modulation of hydration water's translational diffusivity serves as a sensitive indicator of weak polymer-membrane interactions.
• ODNP is a powerful tool for unraveling molecular interactions at interfaces, even in the presence of bulk water.