MOLECULAR-DYNAMICS STUDY OF HYALURONIC-ACID IN WATER

Molecular dynamics (MD) simulations on hyaluronic acid (HA)-water syst ems were carried out to study the HA-water interactions, Employing the GROMOS force field and the SPC water model, HA dimer and trimer subun its surrounded by 490 water molecules were investigated. For each syst em pair distribution functions, diffusion coefficients and reorientati on correlation times of the water molecules were calculated from 450 p s 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 Ramacha ndran plots. The self-diffusion coefficients of the water molecules va ry from 1.5 x 10(-9) m(2) s(-1) to 2.3 x 10(-9) m(2) s(-1) dependent o n the distance between the water molecules and the atoms of the HA mol ecule. The reorientation correlation times of the water molecules were estimated to be about 2 ps at a polymer concentration of 7 wt.% HA. O n the basis of energy and geometry criteria, the number of hydrogen bo nds between the water molecules and the acceptor atoms of HA was deter mined to be between IO and 15 per dimer unit indicating the high hydra tion ability of hyaluronic acid in comparison to other di-and oligosac charides. (C) 1998 Elsevier Science B.V.