The structural variety of DNA-DPPC-divalent metal cation aggregates: SAXD and SANS study
Faculty of Pharmacy, Comenius University, Odbojárov 10, 832 32 Bratislava, Slovakia
2 Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, K0J 1P0, Canada
3 HASYLAB, DESY, Notkestr. 85, 22603 Hamburg, Germany
4 Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
We examine the structure of aggregates formed due to DNA interaction with dipalmitoylphosphatidylcholine (DPPC) in presence of Ca2 + and Zn2 + using small-angle synchrotron X-ray diffraction (SAXD) and neutron scattering (SANS). SAXD shows structural heterogeneity as a function of the cation concentration and temperature: At low cation concentration (∼1 mM), aggregates show two DPPC phases, one with a lateral segregation of DNA and cation, while higher cation concentration improves the DNA packing and the condensed lamellar phase is observed in DNA+DPPC+20mMion2 + aggregates. The SANS detected the dissolution of the condensed lamellar phase into unilamellar DPPC+Zn2 + vesicles due to gel ↦ liquid-crystal phase transition in DNA+DPPC+20mM Zn2 + aggregates with the short fragmented salmon sperm DNA.
© EDP Sciences, Springer-Verlag, 2009