title: The organization of melatonin in lipid membranes.
abstract: Melatonin is a hormone that has been shown to have protective effects in several diseases that are associated with cholesterol dysregulation, including cardiovascular disease, Alzheimer's disease, and certain types of cancers. We studied the interaction of melatonin with model membranes made of dimyristoylphosphatidylcholine (DMPC) at melatonin concentrations ranging from 0.5mol% to 30mol%. From 2-dimensional X-ray diffraction measurements, we find that melatonin induces a re-ordering of the lipid membrane that is strongly dependent on the melatonin concentration. At low melatonin concentrations, we observe the presence of melatonin-enriched patches in the membrane, which are significantly thinner than the lipid bilayer. The melatonin molecules were found to align parallel to the lipid tails in these patches. At high melatonin concentrations of 30mol%, we observe a highly ordered melatonin structure that is uniform throughout the membrane, where the melatonin molecules align parallel to the bilayers and one melatonin molecule associates with 2 lipid molecules. Understanding the organization and interactions of melatonin in membranes, and how these are dependent on the concentration, may shed light into its anti-amyloidogenic, antioxidative and photoprotective properties and help develop a structural basis for these properties.
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario Canada. Electronic address: dieshe@mcmaster.ca.
authors.forename: Hannah
authors.initials: H
authors.lastname: Dies
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario Canada.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Cheung
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tang
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario Canada. Electronic address: rheinstadter@mcmaster.ca.
authors.forename: Maikel C
authors.initials: MC
authors.lastname: Rheinstädter
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008550:Melatonin / Q000737:chemistry* / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D008563:Membrane Lipids; D008550:Melatonin; D004134:Dimyristoylphosphatidylcholine
keywords: Lipid membrane; Melatonin; Melatonin-enriched domain; Molecular organization; Molecular structure; X-ray diffraction