The precise spatiotemporal control of nanoscale membrane shape and composition is the result of a complex interplay of individual and collective molecular behaviors. Here, we employed single-molecule localization microscopy and computational simulations to observe single-lipid diffusion and sorting in model membranes with varying compositions, phases, temperatures, and curvatures. Supported lipid bilayers were created over 50-nm-radius nanoparticles to mimic the size of naturally occurring membrane buds, such as endocytic pits and the formation of viral envelopes. The curved membranes recruited liquid-disordered lipid phases while altering the diffusion and sorting of tracer lipids. Disorder-preferring fluorescent lipids sorted to and experienced faster diffusion on the nanoscale curvature only when embedded in a membrane capable of sustaining lipid phase separation at low temperatures. The curvature-induced sorting and faster diffusion even occurred when the sample temperature was above the miscibility temperature of the planar membrane, implying that the nanoscale curvature could induce phase separation in otherwise homogeneous membranes. Further confirmation and understanding of these results are provided by continuum and coarse-grained molecular dynamics simulations with explicit and spontaneous curvature-phase coupling, respectively. The curvature-induced membrane compositional heterogeneity and altered dynamics were achieved only with a coupling of the curvature with a lipid phase separation. These cross-validating results demonstrate the complex interplay of lipid phases, molecular diffusion, and nanoscale membrane curvature that are critical for membrane functionality.

• MeSH
• Cell Membrane MeSH
• Diffusion MeSH
• Lipid Bilayers * MeSH
• Molecular Dynamics Simulation * MeSH
• Temperature MeSH
• Protein Transport MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Names of Substances
• Lipid Bilayers * MeSH

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.

• MeSH
• Anti-Bacterial Agents chemistry   isolation & purification   pharmacology   MeSH
• Cell Membrane chemistry   drug effects   MeSH
• Ethanolamines chemistry   MeSH
• Drug Combinations MeSH
• Fluorescent Dyes chemistry   MeSH
• Spectrometry, Fluorescence MeSH
• Phosphatidylcholines chemistry   MeSH
• Phosphatidylethanolamines chemistry   MeSH
• Phosphatidylglycerols chemistry   MeSH
• Antimicrobial Cationic Peptides chemistry   isolation & purification   pharmacology   MeSH
• Skin chemistry   MeSH
• Lipid Bilayers chemistry   MeSH
• Magainins chemistry   isolation & purification   pharmacology   MeSH
• Xenopus Proteins chemistry   isolation & purification   pharmacology   MeSH
• Boron Compounds chemistry   MeSH
• Drug Synergism MeSH
• Protein Binding MeSH
• Xenopus laevis MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 1-palmitoyl-2-oleoylglycero-3-phosphoglycerol MeSH Browser
• 1-palmitoyl-2-oleoylphosphatidylethanolamine MeSH Browser
• 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene MeSH Browser
• Anti-Bacterial Agents MeSH
• Ethanolamines MeSH
• Drug Combinations MeSH
• Fluorescent Dyes MeSH
• Phosphatidylcholines MeSH
• Phosphatidylethanolamines MeSH
• Phosphatidylglycerols MeSH
• Antimicrobial Cationic Peptides MeSH
• Lipid Bilayers MeSH
• magainin 2 peptide, Xenopus MeSH Browser
• Magainins MeSH
• PGLa-H peptide, Xenopus MeSH Browser
• phosphorylethanolamine MeSH Browser
• Xenopus Proteins MeSH
• Boron Compounds MeSH

β-Amyloid (Aβ) oligomers are neurotoxic and implicated in Alzheimer's disease. Neuronal plasma membranes may mediate formation of Aβ oligomers in vivo. Membrane components sphingomyelin and GM1 have been shown to promote aggregation of Aβ; however, these studies were performed under extreme, non-physiological conditions. We demonstrate that physiological levels of GM1 , organized in nanodomains do not seed oligomerization of Aβ40 monomers. We show that sphingomyelin triggers oligomerization of Aβ40 and that GM1 is counteractive thus preventing oligomerization. We propose a molecular explanation that is supported by all-atom molecular dynamics simulations. The preventive role of GM1 in the oligomerization of Aβ40 suggests that decreasing levels of GM1 in the brain, for example, due to aging, could reduce protection against Aβ oligomerization and contribute to the onset of Alzheimer's disease.

• Keywords
• Alzheimer's disease, amyloid beta-peptides, diffusion coefficients, fluorescence spectroscopy, neuroprotectives,
• MeSH
• Amyloid beta-Peptides antagonists & inhibitors   metabolism   MeSH
• G(M1) Ganglioside chemistry   pharmacology   MeSH
• Sphingomyelins chemistry   pharmacology   MeSH
• Molecular Dynamics Simulation MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Amyloid beta-Peptides MeSH
• G(M1) Ganglioside MeSH
• Sphingomyelins MeSH