Effect of aminophospholipid glycation on order parameter and hydration of phospholipid bilayer

The effect of aminophospholipid glycation on lipid order and lipid bilayer hydration was investigated using time-resolved fluorescence spectroscopy. T he changes of lipid bilayer hydration were estimated both from its effect o n the fluorescence lifetime of the l-[4-(trimethylammonium)-phenyl]-6-pheny lhexa-1,3,5-triene (TMA-DPH) and 1,6-diphenylhexa-1,3,5-triene (DPH) and us ing solvatochromic shift studies with 1-anilinonaphthalene-8-sulfonic acid. The head-group and acyl chain order were determined from time-resolved flu orescence anisotropy measurements of the TMA-DPH and DPH. The suspensions o f small unilamellar vesicles (with phosphatidylethanolamine/phosphatidylcho line molar ratio 1:2.33) were incubated with glyceraldehyde and it was foun d that aminophospholipids react with glyceraldehyde to form products with t he absorbance and the fluorescence properties typical for protein advanced glycation end products. The lipid glycation was accompanied by the progress ive oxidative modification of unsaturated fatty acid residues. It was found that aminophospholipid glycation increased the head-group hydration and li pid:order in both regions of the membrane. The lipid oxidation accompanying the lipid glycation affected mainly the lipid order, while the effect on t he lipid hydration was small. The increase in the lipid order was presumabl y the result of two effects: (1) the modification of head-groups of phospha tidylethanolamine by glycation; and (2) the degradation of unsaturated fatt y acid residues by oxidation. (C) 1999 Elsevier Science B.V. All rights res erved.