Differential stability of DNA based on salt concentration.

Intracellular positive ions neutralize negative charges on the phosphates of a DNA strand, conferring greater strength on the hydrogen bonds that connect complementary strands into a double helix and so confer enhanced stability. Beyond a certain value of salt concentration, the DNA molecule displays an unstable nature in vivo as well as in vitro. We consider a wide range of salt concentrations and study the stability of the DNA double helix using a statistical model. Through numerical calculations, we attempt to explain the different behavior exhibited by DNA molecules in this range. We compare our results with experimental data and find a close agreement.