Interaction of DNA with DPPC in presence of zinc: the ionic strength effect

Zinc plays a fundamental role in several critical cellular functions such as protein metabolism, gene expression, structural and functional integrity of biomembranes, and in metabolic processes [1]. Concentration of zinc in animals systems range from <10 M in cytoplasm to >10 M in some membrane vesicles [2]. Like all metal cations, zinc interacts electrostatically with anionic groups. In contrast to other divalent metal cations with similar ionic radius such as Mg, zinc ions possess a higher affinity to electronegative groups and obviously binds more tightly. It forms a stable complex with the zwitterionic phospholipid headgroup. Zinc cations are among the strong inducers of DNA conformational changes. They influence denaturation and renaturation of DNA by stabilizing its double helix structure [3]. Generally, in a system DNA, dipalmitoylphosphatidylcholine (DPPC) and ZnCl2 one must consider the following binding events (schematic):