Detailed spectroscopic investigations to reveal the nature of interaction of anionic porphyrin with calf thymus DNA.

The interaction between anionic form of meso-tetrakis(4-carboxyphenyl) porphyrin (TCPP) and calf thymus deoxyribonucleic acid (CT DNA) is investigated by measuring UV-vis absorption, steady-state fluorescence, steady-state fluorescence anisotropy, time-resolved fluorescence, resonance light scattering (RLS), FT-IR and circular dichroism (CD) spectra along with the help of atomic force microscopy (AFM) under Tris-Borate-EDTA (TBE) buffer solution of pH 8.3. The static mode of fluorescence quenching of porphyrin by calf thymus deoxyribonucleic acid indicates the formation of a ground-state complex. The formation of ground-state complex is a spontaneous molecular interaction procedure in which outside groove binding through hydrogen bond or van der Waals force plays a major role. For biomedical application this investigation is very important as here TCPP, i.e. the anionic porphyrin does not bring any changes in the original structure of the CT DNA to selectively cleaving the nucleic acid to destroy the cancer or tumor cells whereas cationic porphyrin makes change in the protein structure significantly during the same process.