Effect of NO• on the adhesion-spreading of DMPC and DOPC liposomes on electrodes, and the partition of NO• between an aqueous phase and DMPC liposomes

The effect of NO center dot radicals on the adhesion and spreading of unilamellar DMPC and DOPC liposomes on mercury electrodes were studied by chronoamperometry. NO center dot was either generated in situ from NOC-18 or supplied as an admixture of nitrogen gas. These measurements reveal details of the kinetics of the adhesion and spreading process and provide access to information on the membrane fluidity of lipid bilayer membranes. The results indicate that NO center dot stabilizes the membranes of DMPC liposomes. The effect of NO center dot radicals is most probably caused by their physical association with the polar head groups of DMPC, as indicated by 31-P NMR spectroscopy. This interaction also explains the partition coefficient K-DMPC H2O(NO) of NO center dot between water and DMPC liposomes of 10.0 +/- 2.1. (C) 2012 Elsevier B.V. All rights reserved.