Biomolecular association

Hyaluronic acid, also known as hyaluronan, is an anionic polysaccharide that fulfils many important functions in our body. For instance, it plays a major role in lubricating our joints. The current understanding is that hyaluronan associates with phospholipids in the synovial fluid, and it is these complexes that facilitate lubrication rather than hyaluronic acid alone. The present diploma work aims at increasing our understanding of the association between hyaluronan on the one hand and phospholipids and cationic surfactants on the other hand. The following studies are planned:

• Turbidity measurements for mixtures of hyaluronic acid and cationic surfactants in absence and presence of calcium ions. These studies will allow us to understand:
o How the surfactant chain length affects the association
o How the association differs depending on if the surfactant has one or two hydrocarbon chains
o How the presence of divalent calcium ions inhibits the electrostatically driven association between hyaluronic acid and the surfactant
• Mobility measurements for the same systems as studied with turbidity. This would allow us to determine the net charge of the complexes formed.
• Surface tension measurements for the same systems as above. This will allow determination of the onset of binding and the amount of surfactants bound to hyaluronic acid
• Langmuir trough experiments to determine the surface pressure vs. area isotherms and the area relaxation isotherms of three phospholipids, DPPE, DPPC and POPC, in absence and presence of hyaluronan. This will provide information on the association between hyaluronan and phospholipids present in the synovial fluid and how this is affected by the nature of the phospholipid headgroup and the presence of unsaturation in the hydrophobic region.