title: Molecular dynamics simulations and Kelvin probe force microscopy to study of cholesterol-induced electrostatic nanodomains in complex lipid mixtures.
abstract: The molecular arrangement of lipids and proteins within biomembranes and monolayers gives rise to complex film morphologies as well as regions of distinct electrical surface potential, topographical and electrostatic nanoscale domains. To probe these nanodomains in soft matter is a challenging task both experimentally and theoretically. This work addresses the effects of cholesterol, lipid composition, lipid charge, and lipid phase on the monolayer structure and the electrical surface potential distribution. Atomic force microscopy (AFM) was used to resolve topographical nanodomains and Kelvin probe force microscopy (KPFM) to resolve electrical surface potential of these nanodomains in lipid monolayers. Model monolayers composed of dipalmitoylphosphatidylcholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(3-lysyl(1-glycerol))] (DOPG), and cholesterol were studied. It is shown that cholesterol changes nanoscale domain formation, affecting both topography and electrical surface potential. The molecular basis for differences in electrical surface potential was addressed with atomistic molecular dynamics (MD). MD simulations are compared the experimental results, with 100 s of mV difference in electrostatic potential between liquid-disordered bilayer (Ld, less cholesterol and lower chain order) and a liquid-ordered bilayer (Lo, more cholesterol and higher chain order). Importantly, the difference in electrostatic properties between Loand Ldphases suggests a new mechanism by which membrane composition couples to membrane function.
authors.affiliation: Department of Biology, University of Waterloo, Canada. zleonenk@uwaterloo.ca and Waterloo Institute of Nanotechnology, University of Waterloo, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Drolle
authors.affiliation: Department of Physics and Astronomy and Department of Chemistry and Biochemistry, University of California, Santa Barbara, USA.
authors.forename: W F D
authors.initials: WF
authors.lastname: Bennett
authors.affiliation: Department of Physics and Astronomy, University of Waterloo, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Hammond
authors.affiliation: Department of Physics and Astronomy, 217 Sharp Lab, Newark, USA.
authors.forename: E
authors.initials: E
authors.lastname: Lyman
authors.affiliation: Department of Mathematics and Computer Science & Institute for Complex Molecular Systems, Eindhoven University of Technology, MetaForum, 5600 MB Eindhoven, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Karttunen
authors.affiliation: Department of Biology, University of Waterloo, Canada. zleonenk@uwaterloo.ca and Waterloo Institute of Nanotechnology, University of Waterloo, Canada and Department of Physics and Astronomy, University of Waterloo, Canada.
authors.forename: Z
authors.initials: Z
authors.lastname: Leonenko