Binding mode and conformational status of DNA via interaction with [Cu 3 (ATP) 2· 6H 2O] 2−: Spectroscopic and thermal denaturation studies

Abstract

The interaction of DNA with [Cu 3(ATP) 2·6H 2O] 2− has been investigated using various physicochemical tools like fluorescence (both steady state and dynamical), IR, CD spectroscopy, and thermal denaturation studies. Fluorescence spectroscopic data indicate that both the intensity and life-time of DNA bound Ethidium Bromide (EB) are quenched in the presence of [Cu 3(ATP) 2· 6H 2O] 2− thereby indicating an intercalative mode of interaction of copper-ATP complex with DNA. This binding mechanism 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 Cup 2+ ion binds phosphates of DNA. The solution CD spectra of DNA, DNA-[Cu 3(ATP) 2·6H 2O], and DNA-Cu are all characteristic of typical B-families of conformers. The thin film CD and IR data also suggest that DNA retains the B-family of conformations after its interaction with the CuATP complex while the slight perturbation of the CD spectra is suggestive of intercalative binding mechanisms. It has been found that DNA generates ψ − CD spectrum when bound with Cu 2+ and assumes compact (B) n types of conformation, however, still belonging to the same B-family.