Studies of the Effects of Zn2+on the Stability of DNA by Using Raman Spectroscopy

Raman spectroscopic technique has been used to study the effect of Zn2 + on the stability of calf thymus DNA macromolecule at different Zn2 + / PO2- ratios in solution. The experimental results show that when Zn2 + / PO2-’2. 0，Zn2 + will be bound to the chelate position of guanine（G）at N7 sites and - PO2- ?Zn2 + ?N7（G）chelates will be formed. The chelation strengthens the energy of the H-bond between GC pairs. Simultaneously，Zn2 + will be also bound to adenine（A）at N3 sites and this binding causes a slight destabilization of the AT pairs. When Zn2 + / PO2 > 2. 0，a number of Zn2 + will be bound to Cytosine at N3 - O2 sites and disrupt the Hbonds between GC pairs. At the same time，Zn2 + will be bound to A at N1 sites and disrupt the AT hydrogen bonds. So it can be concluded that at low concentrations，Zn2 + can stabilize the double strand structure of DNA，whereas at higher concentrations unwinding of the double strand is facilitated. At higher concentrations，the damage of GC pairs is larger than that of AT，even some C is displaced by T by missing an amidogen，base pairs become unpaired，and the geometry and second structure of DNA have changed and it is not a normal B-DNA but a modified B'-DNA.