Binding of quadruplex DNA to nickel and zinc complexes monitored by surface-enhanced raman and fluorescence spectroscopy

Abstract

The interactions between quadruplex DNA and various transition metal complexes were studied using Surface-Enhanced Raman Spectroscopy (SERS) and fluorescence spectroscopy. Using gold nanoparticles as the SERS substrate and Raman signal enhancer, intensity changes in the Raman peaks of the metal complexes were used as a measure of these interactions. Water-soluble zinc and nickel metal complexes with a N,N'- bis (2-pyridylmethylene)-1,3-diaminopropyl ligand in octahedral geometry were used. The Raman intensities of these complexes decreased in the presence of various quadruplex DNA sequences and similar trends were observed using fluorescence spectroscopy. The DNA sequences studied were the thrombin-binding aptamer or 15mer (5′-GGTTGGTGTGGTTGG-3′), 8mer (5′-TTTTGGGG-3′), 16mer (5′-TTTTGGGG GGGGTTTT-3′), and 17mer (5′-GGTATGGTGTGGATTGG-3′) DNA sequences, and the changes in SERS and fluorescence signal intensities indicate that the metal complexes were binding to the DNA.