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

We studied the effect of divalent alkaline earth metal cations Ca2+, Mg2+ and transition metals Co2+, Ni2+, Cu2+ and Zn2+ on DNA condensation and its protection against thermal denaturation in presence of dioleoylphosphatidylcholine liposomes (DOPC). Experimental results have shown that Ca2+ and Mg2+ as well as Zn2+ mediate DNA condensation. Cu2+ causes DNA double helix destabilization, and does not mediate binding between DNA and DOPC liposomes. Co2+ and Ni2+ 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 Ca2+ and Zn2+, whereas in presence of either Co2+ or Ni2+ some volume fraction of DNA is denatured.