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

Abstract

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.