DNA Denaturation Curve

         The melting temperatur of DNA is a characteristc of each DNA that is determined by the G:C content of the DNA and the ionic of the solution. The higher the percent of G:C base pairs in the DNA , the higher the melting point.

DNA Denaturation Curve.

        Likewise,  the salt concentration of the solution greater the temperature at which the DNA denatures. G:C base pairs contribute more to the stability of DNA than do A:T base pairs because of the greater number of hydrogen bonds for the former but also importantly because the stacking interactions of G:C base pairs with adjacent base pairs are favorable than the corresponding interactions of A:T base pairs with their neighboring base pairs. The effect of ionic strength reflects another fundamental feature of the double helix. The backbones of the two DNA strands contain phosphoryl groups, which carry a negative charge. These negative charges are close enough across the two strands that if not shielded they tend to cause the strands to repel each other, facilitating their separation. At high ionic strength, the negative charges are shielded by cations, thereby stabilizing the helix. Conversely, at low ionic strength the unshielded negative charges render the helix less stable.