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Self-assembly of tetracationic porphyrin TMPyP(4+) onto polyanionic matrix of inorganic polyphosphate (PPS) in aqueous solutions has been studied in a wide range of molar phosphate-to-dye ratios using techniques of polarized fluorescence, absorption, resonance Raman spectroscopy and static light scattering. The binding of TMPyP(4+) to PPS is characterized by the binding constant of 3 x 10(5) M(-1) and the cooperativity parameter of about 150. The fluorescence quenching of the bound TMPyP(4+) evidences the stacking of the porphyrine chromophores. Under the stoichiometric binding ratio TMPyP(4+) forms extended continuous face-to-face aggregates (so-called H-aggregates) which manifest themselves by a blue shift (12 nm) and a large hypochromisity (51%) of the Soret absorption band. Each face-to-face TMPyP(4+) stack is formed with participation of four PPS chains. Formation of such columnar aggregates is promoted by the ability of PPS chains to take a helix conformation where negative charges are arranged along two oppositely situated rows with intercharge distance of 0.36 nm which corresponds to the thickness of the porphyrin pi-electronic system. The ability of each PPS strand to be template for formation of two porphyrin stacks results in the integration of the adjacent stacks into higher-order aggregates which dimension was estimated from the fluorescence polarization data.

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The cooperative binding of a novel water-soluble cationic derivative of pheophorbide-a (CatPheo-a) to inorganic polyphosphate (PPS) in buffered aqueous solutions was studied by means of polarized fluorescence spectroscopy in a wide range of molar phosphate-to-dye ratios (P/D). Under low P/D values, CatPheo-a forms extended stacking associates on the PPS matrix, while under high P/D the dye binds to PPS in the dimer form. The CatPheo-a self-association is accompanied by 40-fold dye fluorescence quenching and a substantial increase in the fluorescence polarization degree. The fluorescent titration data were used for determination of cooperative binding parameters by Schwarz's method.

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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.

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