Interaction of All-trans-Retinal with Bilayer Lipid Membranes

摘要

The interaction of all-trans-retinal (hereinafter referred to as retinal) with planar bilayer lipidmembranes has been studied. Addition of retinal into aqueous solutions on both sides of the membraneformed from diphytanoilphosphatidylcholine (DPhPC) or its mixture with diphytanoilphosphatidylethanolamine(DPhPC/DPhPE in w/w proportion of 3 : 5) led to a change of conductance induced by ionophores nonactin(increase of conductance) or pentachlorophenol (decrease). Increase of nonactin-induced conductance wasdependent on the membrane lipid composition and was two times higher in the case of DPhPC/DPhPE mixture.The change of conductance caused by ionophores of different signs (plus or minus) had different direction sug-gesting the influence of the retinal on the dipole potential upon its incorporation into BLM. The boundarypotentials difference measured by the intramembrane field compensation method (IFC) after the retinal additionon one side of the membrane did not exceed 2.5 mV suggesting that its distribution in the bilayer is almost sym-metrical. The illumination of the retinal-containing BLM caused a decrease in its lifetime when the membraneswere formed from unsaturated lipids. Retinal incorporated into BLM led also to photoinactivation of the gram-icidin channels. The process was completely inhibited by a singlet oxygen quencher (sodium azide). Theseresults indicate that retinal accumulated in the membrane can affect both membrane proteins and the unsatur-ated lipids by their oxidation by the singlet oxygen.