Dehydration of carbonyls and phosphates of phosphatidylcholines determines the lytic action of lysoderivatives

The purpose of this study was to correlate the effectiveness of the lysoPC to disrupt bilayers with the effects of trehalose and sucrose on the hydration sites of a lipid bilayer. The vibration frequencies of carbonyls and phosphates was measured at 18 °C for different ratios of monomyristoylphosphatidylcholine and dimyristoylphosphatidylcholine vesicles prepared in water, sucrose and trehalose. The disruption point of the bilayer, evaluated by following the changes in the turbidity of the suspension of unilamellar vesicles, was decreased when the vesicles were prepared in 100 mM sucrose. The increase of the lytic action is directly related to the extent of hydration of the carbonyl populations. It is interpreted that the insertion of the sucrose molecule in the interface causes local changes in interfacial structure, such as the dehydration of the second population of the carbonyls that may be identified as defects of packing. In contrast, the insertion of trehalose by replacing water simultaneously at the carbonyls and the phosphates does not cause defects of packing. For this reason, the lytic action is produced at a concentration very similar to that found in water.