1-palmitoyl-2-oleoylphosphatidylethanolamine and phosphorylethanolamine

Magainin 2 and PGLa are cationic, amphipathic antimicrobial peptides which when added as equimolar mixture exhibit a pronounced synergism in both their antibacterial and pore-forming activities. Here we show for the first time that the peptides assemble into defined supramolecular structures along the membrane interface. The resulting mesophases are quantitatively described by state-of-the art fluorescence self-quenching and correlation spectroscopies. Notably, the synergistic behavior of magainin 2 and PGLa correlates with the formation of hetero-domains and an order-of-magnitude increased membrane affinity of both peptides. Enhanced membrane association of the peptide mixture is only observed in the presence of phophatidylethanolamines but not of phosphatidylcholines, lipids that dominate bacterial and eukaryotic membranes, respectively. Thereby the increased membrane-affinity of the peptide mixtures not only explains their synergistic antimicrobial activity, but at the same time provides a new concept to increase the therapeutic window of combinatorial drugs.

Topics: Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Boron Compounds; Cell Membrane; Drug Combinations; Drug Synergism; Ethanolamines; Fluorescent Dyes; Lipid Bilayers; Magainins; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylglycerols; Protein Binding; Skin; Spectrometry, Fluorescence; Xenopus laevis; Xenopus Proteins

The identification of phosphocholine and phosphoethanolamine lipids by MALDI TOF/TOF, including characterisation of the headgroup and delineation of the acyl chain at each position of the glycerol backbone, has been explored using lipids representative of each type. The relative intensities of fragments involving the neutral loss of one or other of the acyl chains from ion adducts of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC) were compared. For POPC and POPE, a statistical preference for the loss of the chain from the sn-1 position was observed in the presence of lithium. For OPPC this selectivity was reversed for one of the fragments. In the absence of lithium, fragmentation was favoured at the sn-2 position for all lipids. In all cases, spectra obtained in the presence of lithium yielded more intense product ion peaks. Although Collision Induced Dissociation (CID) could be used for complete lipid characterisation, LIFT™ was found to be a better method due to the presence of a greater number of distinguishing product ion peaks and a better shot-to-shot reproducibility of peak intensities.

Topics: Ethanolamines; Lithium; Phosphatidylcholines; Phosphatidylethanolamines; Phospholipid Ethers; Phosphorylcholine; Reproducibility of Results; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The nanomechanical response of supported lipid bilayers has been studied by force spectroscopy with atomic force microscopy. We have experimentally proved that the amount of ions present in the measuring system has a strong effect on the force needed to puncture a 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer with an atomic force microscope tip, thus highlighting the role that monovalent cations (so far underestimated, e.g., Na(+)) play upon membrane stability. The increase in the yield threshold force has been related to the increase in lateral interactions (higher phospholipid-phospholipid interaction, decrease in area per lipid) promoted by ions bound into the membrane. The same tendency has also been observed for other phosphatidylcholine bilayers, namely, 2-dilauroyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, and 1,2-dioleoyl-sn-3-phosphocholine, and also for phosphatidylethanolamine bilayers such as 1-palmitoyl-2-oleoyl-sn-3-phosphoethanolamine. Finally, this effect has been also tested on a natural lipid bilayer (Escherichia coli lipid extract), showing the same overall tendency. The kinetics of the process has also been studied, together with the role of water upon membrane stability and its effect on membrane nanomechanics. Finally, the effect of the chemical structure of the phospholipid molecule on the nanomechanical response of the membrane has also been discussed.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Biophysical Phenomena; Biophysics; Dimyristoylphosphatidylcholine; Dose-Response Relationship, Drug; Escherichia coli; Ethanolamines; Ions; Kinetics; Lipid Bilayers; Lipids; Microscopy, Atomic Force; Nanotechnology; Phosphatidylcholines; Phosphatidylethanolamines; Phospholipids; Phosphorylcholine; Silicon Compounds; Sodium; Sodium Chloride; Spectrophotometry