DNA condensation and its thermal stability influenced by phospholipid bilayer and divalent cations.

Abstract We studied the effect of divalent alkaline earth metal cations Ca 2+ , Mg 2+ and transition metals Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ on DNA condensation and its protection against thermal denaturation in presence of dioleoylphosphatidylcholine liposomes (DOPC). Experimental results have shown that Ca 2+ and Mg 2+ as well as Zn 2+ mediate DNA condensation. Cu 2+ causes DNA double helix destabilization, and does not mediate binding between DNA and DOPC liposomes. Co 2+ and Ni 2+ can interact with DNA on both ways mentioned above. Static light scattering was use to follow the size of aggregates in DNA condensation process. Phospholipid bilayer and divalent cations protect condensed DNA against thermal destabilization. The highest stabilization effect was found in aggregates with Ca 2+ and Zn 2+ , whereas in presence of either Co 2+ or Ni 2+ some volume fraction of DNA is denatured.