title: Supramolecular organization in self-assembly of chromatin and cationic lipid bilayers is controlled by membrane charge density.
abstract: In this work we have investigated the structures of aggregates formed in model systems of dilute aqueous mixtures of "model chromatin" consisting of either recombinant nucleosome core particles (NCPs) or nucleosome arrays consisting of 12 NCPs connected with 30 bp linker DNA, and liposomes made from different mixtures of cationic and zwitterionic lipids, 1,2-dioleoyl-3-trimethylammonium-propane chloride salt (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The aggregates formed were characterized using different optical microscopy methods and small-angle X-ray scattering (SAXS), and the results are discussed in terms of the competing intermolecular interactions among the components. For a majority of the samples, the presence of lamellar structures could be identified. In samples with high fractions of DOTAP in the liposomes, well-defined lamellar structures very similar to those formed by the corresponding lipid mixtures and DNA alone (i.e., without histone proteins) were observed; in these aggregates, the histones are expelled from the model chromatin. The findings suggest that, with liposomes containing large fractions of cationic lipid, the dominating driving force for aggregation is the increase in translational entropy from the release of counterions, whereas with lower fractions of the cationic lipid, the entropy of mixing of the lipids within the bilayers results in a decreased DNA-lipid attraction.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
authors.forename: Nikolay V
authors.initials: NV
authors.lastname: Berezhnoy
authors.forename: Dan
authors.initials: D
authors.lastname: Lundberg
authors.forename: Nikolay
authors.initials: N
authors.lastname: Korolev
authors.forename: Chenning
authors.initials: C
authors.lastname: Lu
authors.forename: Jiang
authors.initials: J
authors.lastname: Yan
authors.forename: Maria
authors.initials: M
authors.lastname: Miguel
authors.forename: Björn
authors.initials: B
authors.lastname: Lindman
authors.forename: Lars
authors.initials: L
authors.lastname: Nordenskiöld
mesh_terms: D002412:Cations / Q000737:chemistry*; D002843:Chromatin / Q000737:chemistry*; D042002:Chromatin Assembly and Disassembly; D004247:DNA / Q000737:chemistry*; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D006657:Histones / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D036103:Nanotechnology / Q000379:methods; D009707:Nucleosomes / Q000737:chemistry; D010713:Phosphatidylcholines / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D053838:Scattering, Small Angle; D014965:X-Rays
chemical_list: D002412:Cations; D002843:Chromatin; D005229:Fatty Acids, Monounsaturated; D006657:Histones; D008051:Lipid Bilayers; D008081:Liposomes; D009707:Nucleosomes; D010713:Phosphatidylcholines; D000644:Quaternary Ammonium Compounds; D011994:Recombinant Proteins; D004247:DNA; C017251:1,2-oleoylphosphatidylcholine; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane