Effect of glycosaminoglycans and divalent cations on the thermal properties of dipalmitoylphosphatidylcholine

The effect of glycosaminoglycans (GAG) and divalent cations on the thermal properties of dipalmitoyl-phosphatidylcholine (DPPC)-water systems was examined in order to model some interactions taking place on low density lipoprotein (LDL) surfaces. The thermal properties of these systems were measured by differential scanning calorimetry (DSC). According to the results, all three glycosaminoglycans used (chondroitin-4-sulfate, chondroitin-6-sulfate and heparin) were effective but to a different extent. Calcium ions enhance the interaction more than magnesium ions, probably because divalent cations form bridges between the negatively charged groups of GAGs and the headgroups of lipids. It is conceivable that similar processes might occur in the case of LDL.