The effect of phospholipid structure on the thermal stability of rhodopsin

The effect of the major headgroup classes of phospholipids on the conformational stability of rhodopsin is investigated. This is accomplished by measuring the effect of L-alpha-dimyristylphosphatidic acid (DMPA), L-alpha-dimyristylphosphatidylcholine (DMPC), L-alpha-dimyristylphosphatidylethanolamine (DMPE) and L-alpha-dimyristylphosphatidylserine (DMPS) on the thermal decay rate of rhodopsin in dodecyltrimethylammonium bromide (DTAB) and octylglucoside detergent systems. In the DTAB system the relative stabilization by these phospholipids is DMPA less than DMPS greater than DMPC greater than DMPE. In the octylglucoside system, the relative stabilization ability is DMPA greater than DMPS congruent to DMPC greater than DMPE. The relative stabilization ability in a series of lecithin derivatives that differ in fatty acid chain structure is also reported. This series of experiments demonstrate that the structure of the fatty acid chains is as important as the headgroup structure in determining the stabilization ability of a phospholipid.