title: Does fluoride disrupt hydrogen bond network in cationic lipid bilayer? Time-dependent fluorescence shift of Laurdan and molecular dynamics simulations.
abstract: Time-dependent fluorescence shift (TDFS) of Laurdan embedded in phospholipid bilayers reports on hydration and mobility of the phospholipid acylgroups. Exchange of H2O with D2O prolongs the lifetime of lipid-water and lipid-water-lipid interactions, which is reflected in a significantly slower TDFS kinetics. Combining TDFS measurements in H2O and D2O hydrated bilayers with atomistic molecular dynamics (MD) simulations provides a unique tool for characterization of the hydrogen bonding at the acylgroup level of lipid bilayers. In this work, we use this approach to study the influence of fluoride anions on the properties of cationic bilayers composed of trimethylammonium-propane (DOTAP). The results obtained for DOTAP are confronted with those for neutral phosphatidylcholine (DOPC) bilayers. Both in DOTAP and DOPC H2O/D2O exchange prolongs hydrogen-bonding lifetime and does not disturb bilayer structure. These results are confirmed by MD simulations. TDFS experiments show, however, that for DOTAP this effect is cancelled in the presence of fluoride ions. We interpret these results as evidence that strongly hydrated fluoride is able to steal water molecules that bridge lipid carbonyls. Consequently, when attracted to DOTAP bilayer, fluoride disrupts the local hydrogen-bonding network, and the differences in TDFS kinetics between H2O and D2O hydrated bilayers are no longer observed. A distinct behavior of fluoride is also evidenced by MD simulations, which show different lipid-ion binding for Cl(-) and F(-).
authors.affiliation: J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic.
authors.forename: Sarka
authors.initials: S
authors.lastname: Pokorna
authors.affiliation: J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic.
authors.forename: Piotr
authors.initials: P
authors.lastname: Jurkiewicz
authors.affiliation: Division of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, P.O.B. 180, HR-10002 Zagreb, Croatia.
authors.forename: Mario
authors.initials: M
authors.lastname: Vazdar
authors.affiliation: J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Cwiklik
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
authors.affiliation: J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Hof
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives / Q000032:analysis; D005229:Fatty Acids, Monounsaturated / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000032:analysis; D005459:Fluorides / Q000737:chemistry*; D006860:Hydrogen Bonding; D007848:Laurates / Q000032:analysis; D008051:Lipid Bilayers / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D010713:Phosphatidylcholines / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D005229:Fatty Acids, Monounsaturated; D005456:Fluorescent Dyes; D007848:Laurates; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D000644:Quaternary Ammonium Compounds; D014867:Water; D015081:2-Naphthylamine; C017251:1,2-oleoylphosphatidylcholine; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane; D005459:Fluorides; C065580:laurdan