title: Binding of the alkaloid coralyne to parallel G-quadruplex DNA [d(TTGGGGT)]4studied by multi-spectroscopic techniques.
abstract: Binding of coralyne to tetra-molecular parallel G-quadruplex DNA [d(TTGGGGT)]4was evaluated for the first time using biophysical techniques. Absorbance titrations show hypo/hyper-chromism accompanied by 12nm red shift with binding constant Kb=0.2-4.0×106M-1. Binding induces a negative circular dichroism band of coralyne at 315nm. Quenching of fluorescence (~64%) along with 10nm blue shift in emission maxima indicates proximity of coralyne to guanine bases. Job plot indicates existence of multiple complexes. The observed two fluorescence life times, 6 and 12ns, with relative abundance 33% and 63%, respectively suggest two binding sites/conformations in complex. 1D1H NMR spectra reveal significant broadening and upfield shift of G3NH, G6NH and G3H8 proton signals upon binding. The NOESY spectra reveal sequence specific non-intercalative interaction of coralyne in monomeric form at two sites close to A3/G3 and G6 bases of [d(TTGGGGT)]4and [d(TTAGGGT)]4, which has implications in anti-cancer drug action.
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India.
authors.forename: Kumar
authors.initials: K
authors.lastname: Padmapriya
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India. Electronic address: ritubfbs@iitr.ac.in.
authors.forename: Ritu
authors.initials: R
authors.lastname: Barthwal
mesh_terms: D000225:Adenine; D000970:Antineoplastic Agents; D001600:Berberine Alkaloids / Q000737:chemistry*; D001665:Binding Sites; D002942:Circular Dichroism; D054856:G-Quadruplexes; D006147:Guanine; D066244:Proton Magnetic Resonance Spectroscopy; D013050:Spectrometry, Fluorescence; D013057:Spectrum Analysis
chemical_list: D000970:Antineoplastic Agents; D001600:Berberine Alkaloids; D006147:Guanine; C000666:coralyne; D000225:Adenine
keywords: Absorbance and fluorescence; Alkaloid coralyne; Circular dichroism; Non-intercalative binding; Nuclear magnetic resonance; Parallel G-quadruplex DNA