Molecular dynamics study of hyaluronic acid in water

Molecular dynamics (MD) simulations on hyaluronic acid (HA)-water systems were carried out to study the HA-water interactions, Employing the GROMOS force field and the SPC water model, HA dimer and trimer subunits surrounded by 490 water molecules were investigated. For each system pair distribution functions, diffusion coefficients and reorientation correlation times of the water molecules were calculated from 450 ps trajectories. The average values of the interglycosidic angles found in the simulations are phi(13)=52 degrees, psi(13)=25 degrees for the beta(1,3) linkage, and phi(14)=40 degrees, psi(14)=3 degrees for the beta(1,4) linkage well corresponding to the minimum regions in Ramachandran plots. The self-diffusion coefficients of the water molecules vary from 1.5 x 10(-9) m(2) s(-1) to 2.3 x 10(-9) m(2) s(-1) dependent on the distance between the water molecules and the atoms of the HA molecule. The reorientation correlation times of the water molecules were estimated to be about 2 ps at a polymer concentration of 7 wt.% HA. On the basis of energy and geometry criteria, the number of hydrogen bonds between the water molecules and the acceptor atoms of HA was determined to be between IO and 15 per dimer unit indicating the high hydration ability of hyaluronic acid in comparison to other di-and oligosaccharides. (C) 1998 Elsevier Science B.V.