title: Calcium and Zinc Differentially Affect the Structure of Lipid Membranes.
abstract: Interactions of calcium (Ca2+) and zinc (Zn2+) cations with biomimetic membranes made of dipalmitoylphosphatidylcholine (DPPC) were studied by small angle neutron diffraction (SAND). Experiments show that the structure of these lipid bilayers is differentially affected by the two divalent cations. Initially, both Ca2+and Zn2+cause DPPC bilayers to thicken, while further increases in Ca2+concentration result in the bilayer thinning, eventually reverting to having the same thickness as pure DPPC. The binding of Zn2+, on the other hand, causes the bilayers to swell to a maximum thickness, and the addition of more Zn2+does not result in a further thickening of the membrane. Agreement between our results obtained using oriented planar membranes and those from vesicular samples implies that the effect of cations on bilayer thickness is the result of electrostatic interactions, rather than geometrical constraints due to bilayer curvature. This notion is further reinforced by MD simulations. Finally, the radial distribution functions reveal a strong interaction between Ca2+and the phosphate oxygens, while Zn2+shows a much weaker binding specificity.
authors.affiliation: Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University in Bratislava , 83232 Bratislava, Slovakia.
authors.forename: Norbert
authors.identifier: 0000-0002-1075-6640
authors.initials: N
authors.lastname: Kučerka
authors.forename: Ermuhammad
authors.initials: E
authors.lastname: Dushanov
authors.affiliation: Dubna State University , 141980 Dubna - Moscow Region, Russia.
authors.forename: Kholmirzo T
authors.initials: KT
authors.lastname: Kholmurodov
authors.affiliation: Department of Physics and Astronomy, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: John
authors.initials: J
authors.lastname: Katsaras
authors.affiliation: Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University in Bratislava , 83232 Bratislava, Slovakia.
authors.forename: Daniela
authors.initials: D
authors.lastname: Uhríková
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D040761:Biomimetic Materials / Q000737:chemistry; D002118:Calcium / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D015032:Zinc / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine; D015032:Zinc; D002118:Calcium