title: Effects of N,N-dimethyl-N-alkylamine-N-oxides on DOPC bilayers in unilamellar vesicles: small-angle neutron scattering study.
abstract: Small-angle neutron scattering data were collected from aqueous dispersions of unilamellar vesicles (ULVs) consisting of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine and a homologous series of N,N-dimethyl-N-alkylamine-N-oxides (CnNO, n = 12, 14, 16, and 18, where n is the number of carbon atoms in the alkyl chain). A modeling approach was applied to the neutron scattering curves to obtain the bilayer structural parameters. Particularly, the external (2)H2O/H2O contrast variation technique was carried out on pure dioleoylphosphatidylcholine (DOPC) ULVs to determine the hydrophilic region thickness [Formula: see text] = 9.8 ± 0.6 Å. Consequently, the hydrocarbon region thickness [Formula: see text], the lateral bilayer area per one lipid molecule [Formula: see text], and the number of water molecules located in the hydrophilic region per one lipid molecule [Formula: see text] were obtained from single-contrast neutron scattering curves using the previously determined [Formula: see text]. The structural parameters were extracted as functions of [Formula: see text] (the CnNO:DOPC molar ratio) and n. The dependences [Formula: see text] provided the partial lateral areas of CnNOs ([Formula: see text]) and DOPC ([Formula: see text]) in bilayers. It was observed that the [Formula: see text]'s were constant in the investigated interval of [Formula: see text] and for n = 12, 14, and 16 equal to 36.6 ± 0.4 Å(2), while [Formula: see text] increased to 39.4 ± 0.4 Å(2). The bilayer hydrocarbon region thickness [Formula: see text] decreased with intercalation of each CnNO. This effect increased with [Formula: see text] and decreased with increasing CnNO alkyl chain length. The intercalation of C18NO changed the [Formula: see text] only slightly. To quantify the effect of CnNO intercalation into DOPC bilayers we fit the [Formula: see text] dependences with weighted linear approximations and acquired their slopes [Formula: see text].
authors.affiliation: Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, 842 48, Bratislava, Slovakia, belicka.michal@gmail.com.
authors.forename: Michal
authors.initials: M
authors.lastname: Belička
authors.forename: Norbert
authors.initials: N
authors.lastname: Kučerka
authors.forename: Daniela
authors.initials: D
authors.lastname: Uhríková
authors.forename: Akhmed Kh
authors.initials: AKh
authors.lastname: Islamov
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Kuklin
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Devínsky
authors.forename: Pavol
authors.initials: P
authors.lastname: Balgavý
mesh_terms: D004123:Dimethylamines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008051:Lipid Bilayers / Q000737:chemistry*; D033363:Neutron Diffraction; D010713:Phosphatidylcholines; D053838:Scattering, Small Angle; D053835:Unilamellar Liposomes / Q000737:chemistry*
chemical_list: D004123:Dimethylamines; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D053835:Unilamellar Liposomes; C017251:1,2-oleoylphosphatidylcholine