Water Librations in the Hydration Shell of Phospholipids

Area of Science:

• Biophysics
• Physical Chemistry

Background:

• Phospholipid headgroups feature hydrophilic phosphate moieties crucial for water interactions.
• Understanding water's behavior near polar surfaces is vital in biological systems.

Purpose of the Study:

• To investigate the influence of phospholipid headgroups on water molecule rotations.
• To characterize water nanopools within phospholipid reverse micelles using spectroscopy.

Main Methods:

• Time-domain terahertz spectroscopy was employed to measure librational absorption spectra.
• Molecular dynamics simulations were used to model water behavior in reverse micelles.

Main Results:

• A distinct absorption feature at 830 cm^-1 indicates water molecules forming strong hydrogen bonds with phosphate groups.
• A broad absorption band (300-1000 cm^-1) corresponds to bulk-like water environments.
• Spectra differ significantly from water interacting with less polar surfaces.

Conclusions:

• The phosphate group strongly influences water's rotational dynamics, creating a distinct hydration layer.
• This study provides insights into the interfacial water structure at phospholipid-water interfaces.