The selectivity of nucleobases in DNA binding by Ru(phenanthroline) 3 complex

Interaction ability of Ru(phenanthroline) 3 with various sites of nucleobases like guanine, adenine, cytosine and thymine has been investigated by ab initio quantum mechanical calculations. While the N7 of guanine is found to be a susceptible site for binding with Ru metal, the other sites of nucleobases can also bind with this metal centre. The 06 of guanine and 02 of cytosine can form more stable Ru coordinated complexes than N7 of guanine. Formation of bridged hydrogen bonds between polarized atomic sites of this complex and all the nucleobases (except thymine) has been observed. Such hydrogen bonds may also stabilize the complex better than the direct Ru coordinated complexes inside DNA.