Heterogeneous water dynamics in hyaluronan-DPPC interfaces

The synergistic interactions between hyaluronic acid (HA) and other cellular components, particularly lipids and water, play a vital role in maintaining cellular structure and function. Variations in HA concentration and chain length lead to changes in the mechanical and viscoelastic properties of diseased cells, such as those in colon cancer and osteoarthritis. Despite its biological significance, the microscopic dynamics at the HA-water and lipid bilayer interface remain poorly understood. In this study, we investigate the dynamic properties of water molecules at the interface between HA and a dipalmitoylphosphatidylcholine (DPPC) lipid bilayer using molecular dynamics simulations. The interfacial and hydration water exhibit non-Gaussian self van Hove functions, indicating dynamic heterogeneity. The diffusivity distributions reveal contrasts in the underlying translational and rotational dynamics between the two regions. In the diffusive interface, while the diffusion coefficients decrease with increasing HA concentration, they show only a weak dependence on HA chain length. However, the water dynamics in the subdiffusive hydration layer are largely unaffected by the presence of HA chains.