title: Binding of Metallated Porphyrin-Imidazophenazine Conjugate to Tetramolecular Quadruplex Formed by Poly(G): a Spectroscopic Investigation.
abstract: The binding of telomerase inhibitor ZnTMPyP(3+)-ImPzn, Zn(II) derivative of tricationic porphyrin-imidazophenazine conjugate, to tetramolecular quadruplex structure formed by poly(G) was studied in aqueous solutions at neutral pH and near physiological ionic strength using absorption and polarized fluorescent spectroscopy techniques. Three binding modes were determined from the dependences of the fluorescence intensity and polarization degree for the porphyrin and phenazine moieties of the conjugate on molar polymer-to-dye ratio (P/D). The first one is outside electrostatic binding of positively charged porphyrin fragments to anionic phosphate groups of the polymer which prevails only at very low P/D values and manifests itself by substantial fluorescence quenching. It is suggested that the formation of externally bound porphyrin dimers occurs. The other two binding modes observed at high P/D are embedding of the ZnTMPyP(3+) moiety into the groove of poly(G) quadruplex accompanied by more than 3-fold enhancement of the conjugate emission, and simultaneous intercalation of the phenazine fragment between the guanine bases accompanied by the increase of its fluorescence polarization degree up to 0.25. Thus Zn(II) conjugate seems to be promising ligand for the stabilization of G-quadruplex structures since porphyrin binding to poly(G) is strengthened by additional intercalation of phenazine moiety.
authors.affiliation: Department of Molecular Biophysics, B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin ave, 61103, Kharkov, Ukraine. ryazanova@ilt.kharkov.ua.
authors.forename: Olga
authors.initials: O
authors.lastname: Ryazanova
authors.affiliation: Department of Molecular Biophysics, B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin ave, 61103, Kharkov, Ukraine.
authors.forename: Victor
authors.initials: V
authors.lastname: Zozulya
authors.affiliation: Department of Molecular Biophysics, B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin ave, 61103, Kharkov, Ukraine.
authors.forename: Igor
authors.initials: I
authors.lastname: Voloshin
authors.affiliation: Department of Synthetic Bioregulators, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnogo str, 03680, Kyiv, Ukraine.
authors.forename: Larysa
authors.initials: L
authors.lastname: Dubey
authors.affiliation: Department of Synthetic Bioregulators, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnogo str, 03680, Kyiv, Ukraine.
authors.forename: Igor
authors.initials: I
authors.lastname: Dubey
authors.affiliation: Department of Molecular Biophysics, B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin ave, 61103, Kharkov, Ukraine.
authors.forename: Victor
authors.initials: V
authors.lastname: Karachevtsev
mesh_terms: D001483:Base Sequence; D054856:G-Quadruplexes; D008665:Metalloporphyrins / Q000737:chemistry*; D010619:Phenazines / Q000737:chemistry*; D011068:Poly G / Q000737:chemistry* / Q000235:genetics; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000737:chemistry*
chemical_list: D008665:Metalloporphyrins; D010619:Phenazines; D011068:Poly G; D015032:Zinc
keywords: Absorption; Fluorescence; G-quadruplex; Poly(G); Porphyrin–imidazophenazine conjugate