Question

Describe two modes of DNA cleavage by metal ions, using Fe2+ and Zn2+ as examples. Briefly describe the chemistry involved in each case. Other than H-bonding, briefly describe two important factors that contribute to the overall stability of the DNA double-helix under normal physiological conditions.

Answer 1

If we see the basic property of metal ion in solution then we see that, In aquaous solution most metal ion exist as a cationic aquo-complex, which trend to form aqua hydroxo complex according to their Pka value.

A) OXIDATION CLEAVAGE OF NUCLEIC ACID BY METAL- ION

This process occurred through two processes.

a) electrophilic attack of guanine residue.

b) oxidation of pyrimidine nucleotide.

Here, a transfer of +ve charge from the metal ion to the guanine residue result in the formation of Absaisc acid, DNA cleve by beta elimination.

B) HYDROLYTIC CLEAVAGE BY METAL ION

Metal ion directly cleaved DNA by hydrolysis of NTPs and dNTPs.

Q2) Two important factor for the stability of DNA is

a) base stacking interaction

b) van der walls forces.