Eur. Phys. J. Special Topics 167, 191-197 (2009)
https://doi.org/10.1140/epjst/e2009-00957-0

The structural variety of DNA-DPPC-divalent metal cation aggregates: SAXD and SANS study

¹ 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

Abstract

We examine the structure of aggregates formed due to DNA interaction with dipalmitoylphosphatidylcholine (DPPC) in presence of Ca^{2 +} and Zn^{2 +} 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+20mMion^{2 +} aggregates. The SANS detected the dissolution of the condensed lamellar phase into unilamellar DPPC+Zn^{2 +} vesicles due to gel ↦ liquid-crystal phase transition in DNA+DPPC+20mM Zn^{2 +} aggregates with the short fragmented salmon sperm DNA.