title: Interaction of short-fragmented DNA with dipalmitoylphosphatidylcholine bilayers in presence of zinc.
abstract: The structure and temperature behaviour of the DNA+dipalmitoylphosphatidylcholine (DPPC) bilayer as a function of ZnCl2 concentration were examined using differential scanning calorimetry (DSC), small-angle neutron scattering (SANS) and small-angle X-ray diffraction (SAXD). Experiments revealed the coexistence of two lamellar phases in the mixture: the L(PC) phase, formed due to Zn(2+) binding to the DPPC bilayers, and the condensed lamellar phase L(DNA+PC) with DNA strands packed between the DPPC bilayers. With increasing concentration of zinc, the temperature of the gel - liquid-crystal phase transition of DPPC increases in both phases, and the volume fraction of L(DNA+PC) phase decreases. In the gel state (at 20 degrees C), the repeat distance of L(DNA+PC) phase is constant, d(DNA+PC) approximately 8.3 nm, up to 20 mmol/l of ZnCl2, and increases for higher concentrations of the salt. The periodicity of the L(PC) lamellar phase decreases substantially with the increasing concentration of the salt in the mixture. In the liquid-crystalline state, concentrations above 20 mmol/l ZnCl2 promote the dissolution of the L(DNA+PC) phase into DPPC + Zn(2+) unilamellar vesicles and DNA is neutralized by Zn(2+) ions. The screening of Zn(2+) charge and the formation of a diffuse double layer due to increasing ionic strength of solution are responsible for the observed changes.
authors: Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, 832 32 Bratislava, Slovakia. daniela.uhrikova@fpharm.uniba.sk
authors: Daniela
authors: D
authors: Uhríková
authors: Petra
authors: P
authors: Pullmannová
authors: Margarida
authors: M
authors: Bastos
authors: Sérgio S
authors: SS
authors: Funari
authors: José
authors: J
authors: Teixeira
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000465:Algorithms; D000818:Animals; D002152:Calorimetry, Differential Scanning; D002712:Chlorides / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D009502:Neutrons; D010507:Periodicity; D012474:Salmon; D053838:Scattering, Small Angle; D044366:Transition Temperature; D053835:Unilamellar Liposomes / Q000737:chemistry; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D002712:Chlorides; D008051:Lipid Bilayers; D053835:Unilamellar Liposomes; D017967:Zinc Compounds; D015060:1,2-Dipalmitoylphosphatidylcholine; C016837:zinc chloride; D004247:DNA; D015032:Zinc