Interactions of hyaluronan (hyaluronic acid) with phospholipids as determined by gel permeation chromatography, multi-angle laser-light-scattering photometry and 1H-NMR spectroscopy.

The chain flexibility of solutions of hyaluronan (HA) of different molecular weights was determined by 1H-NMR spectroscopy in the absence and presence of the phospholipid dipalmitoyl-D,L-alpha-phosphatidylcholine (DPC). Sonication of high- or low-molecular-weight HA with DPC for periods of up to 120 min markedly increased HA chain flexibility as determined by observing the half-peak linewidths (delta V1/2) for the methyl protons of the acetamidodeoxyglucose residues of the HA molecules. Gel permeation chromatography of mixtures of purified high-molecular-weight HA (Healon) with 3H-DPC or 3H-platelet activating factor (PAF) showed exclusion of these radioactively labelled molecules from the gel in the presence of HA but not in its absence. Studies using multi-angle laser-light-scattering (MALLS) photometry of sonicates of DPC and Healon after Superose 6 chromatography revealed increases in HA Mw, Mn, Mz and their corresponding root mean square radii relative to control sonicates of HA without DPC. From these data, we have deduced that DPC binds to HA by competing for those hydrophobic centres along the HA chain which are normally responsible for the inter- and intra-chain interactions and which confer stiffness to the HA molecule. It is proposed that such interactions in arthritic joints could reduce synovial fluid viscoelasticity thereby diminishing the ability of this medium to protect articular cartilage from mechanical injury.