Hyaluronan orders water molecules in its nanoscale extended hydration shells

Area of Science:

• Biophysics
• Polymer Science
• Physical Chemistry

Background:

• Hyaluronan (HA) is a crucial extracellular matrix component, particularly in synovial fluid.
• Understanding HA's interaction with water is vital for biological and material science applications.
• Previous studies have focused on HA's structural properties but less on its hydration dynamics.

Purpose of the Study:

• To investigate the extended hydration shell structure of hyaluronan (HA) in water.
• To quantify the influence of HA on water molecule orientation and correlation.
• To determine the concentration-dependent size and shape of HA in aqueous solutions.

Main Methods:

• Femtosecond elastic second-harmonic scattering (fs-ESHS) for probing water structure around HA.
• Angle-resolved fs-ESHS measurements combined with nonlinear optical modeling.
• Temperature-dependent measurements to determine hydration shell extent.
• Isotope effect studies using heavy water (D2O) to probe nuclear quantum effects.

Main Results:

• HA acts as a flexible chain surrounded by orientationally correlated water shells.
• The spatial extent of the hydration shell can reach up to 475 nm (1600 water molecules).
• A significant isotope effect (factor of 4.3) was observed between H2O and D2O, indicating nuclear quantum effects.

Conclusions:

• HA significantly influences water structure, creating extended hydration shells.
• fs-ESHS is a powerful technique for characterizing polyelectrolyte hydration and size.
• Nuclear quantum effects play a notable role in HA-water interactions.