BINDING MODE AND CONFORMATIONAL STATUS OF DNA VIA INTERACTION WITH [CU3(ATP)(2).6H2O](2-) - SPECTROSCOPIC AND THERMAL-DENATURATION STUDIES

The interaction of DNA with [Cu3(ATP)2 . 6H2O]2 - has been investigate d using various physicochemical tools like fluorescence (both steady s tate and dynamical), IR, CD spectroscopy, and thermal denaturation stu dies. Fluorescence spectroscopic data indicate that both the intensity and life-time of DNA bound Ethidium Bromide (EB) are quenched in the presence of [Cu3(ATP)2. 6H2O]2- thereby indicating an intercalative mo de of interaction of copper-ATP complex with DNA. This binding mechani sm has further been supported by thermal denaturation studies. From IR data it becomes evident that the CuATP system neither binds bases nor phosphates of DNA although aquo Cu2+ ion binds phosphates of DNA. The solution CD spectra of DNA, DNA-[Cu3(ATP)2.6H2O], and DNA-Cu are all characteristic of typical B-families of conformers. The thin film CD a nd IR data also suggest that DNA retains the B-family of conformations after its interaction with the CuATP complex while the slight perturb ation of the CD spectra is suggestive of intercalative binding mechani sms. It has been found that DNA generates psi- CD spectrum when bound with Cu2+ and assumes compact (B)n types of conformation, however, sti ll belonging to the same B-family.