title: Spectroscopic Studies on Binding of Porphyrin-Phenazine Conjugate to Four-Stranded Poly(G).
abstract: Binding of a novel cationic porphyrin-imidazophenazine conjugate, TMPyP(3+)-ImPzn, to four-stranded poly(G) was investigated in aqueous solutions of neutral pH under near physiological ionic conditions using absorption, polarized fluorescent spectroscopy and fluorescence titration techniques. In absence of the polymer the conjugate folds into stable internal heterodimer with stacking between the porphyrin and phenazine chromophores. Binding of TMPyP(3+)-ImPzn to poly(G) is realized by two competing ways. At low polymer-to-dye ratio (P/D < 6) outside electrostatic binding of the cationic porphyrin moieties of the conjugate to anionic polynucleotide backbone with their self-stacking is predominant. It is accompanied by heterodimer dissociation and distancing of phenazine moieties from the polymer. This binding mode is characterized by strong quenching of the conjugate fluorescence. Increase of P/D results in the disintegration of the porphyrin stacks and redistribution of the bound conjugate molecules along the polymer chain. At P/D > 10 another binding mode becomes dominant, embedding of TMPyP(3+)-ImPzn heterodimers into poly(G) groove as a whole is occurred.
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.forename: Victor
authors.initials: V
authors.lastname: Zozulya
authors.forename: Igor
authors.initials: I
authors.lastname: Voloshin
authors.forename: Larysa
authors.initials: L
authors.lastname: Dubey
authors.forename: Igor
authors.initials: I
authors.lastname: Dubey
authors.forename: Victor
authors.initials: V
authors.lastname: Karachevtsev
mesh_terms: D001665:Binding Sites; D002942:Circular Dichroism; D005453:Fluorescence; D009025:Morpholines / Q000737:chemistry* / Q000378:metabolism; D010619:Phenazines / Q000737:chemistry* / Q000378:metabolism; D011068:Poly G / Q000737:chemistry* / Q000378:metabolism; D011108:Polymers / Q000737:chemistry* / Q000378:metabolism; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D009025:Morpholines; D010619:Phenazines; D011108:Polymers; D011166:Porphyrins; D011068:Poly G; C021096:tetra(4-N-methylpyridyl)porphine; C100294:phendimetrazine