Cholate-interspersed porphyrin-anthraquinone conjugates: photonuclease activity of large sized, 'tweezer-like' molecules

In a new approach towards the development of a 'dual-wavelength dual-mechanism' type of photosensitizer for use in photodynamic therapy (PDT), covalently linked bichromophoric systems comprising of porphyrin (P) and anthraquinone (AnQ) subunits have been synthesized and fully characterized by FAB-MS, IR, UV-Visible and 1H NMR methods. The porphyrin donor and the anthraquinone acceptor subunits of these mono- or bis-intercalating hybrid molecules are interspersed with either cholate or polymethylene spacers. There exists minimal ground- and singlet-state interaction between the porphyrin and anthraquinone subunits in the giant-sized, cholate-interspersed P-AnQ systems as revealed by a comparison of their spectroscopic and electrochemical properties with those of the corresponding individual reference compounds. On the other hand, quenching of fluorescence observed for the P-AnQ systems endowed with polymethylene spacers has been interpreted in terms of a possible intramolecular electron transfer between the singlet porphyrin and the anthraquinone acceptor. When excited into their porphyrin absorption band maxima, each new P-AnQ system could generate singlet molecular oxygen in good-to-moderate yield. Wavelength-dependent photonuclease activity of these new bis-intercalating species has been examined

Cobalt(III), nickel(II) and ruthenium(II) complexes of 1,10-phenanthroline family of ligands: DNA binding and photocleavage studies

DNA binding and photocleavage characteristics of a series of mixed-ligand complexes of the type [M(phen)2LL]n+ (where M = Co(III), Ni(II) or Ru(II), LL = 1,10-phenanthroline (phen), phenanthroline-dione (phen-dione) or dipyridophenazine (dppz) andn = 3 or 2) have been investigated in detail. Various physico-chemical and biochemical techniques including UV/Visible, fluorescence and viscometric titration, thermal denaturation, and differential pulse voltammetry have been employed to probe the details of DNA binding by these complexes; intrinsic binding constants (Kb) have been estimated under a similar set of experimental conditions. Analysis of the results suggests that intercalative ability of the coordinated ligands varies as dppz>phen>phen-dione in this series of complexes. While the Co(II) and Ru(II) complexes investigated in this study effect photocleavage of the supercoiled pBR 322 DNA, the corresponding Ni(II) complexes are found to be inactive under similar experimental conditions. Results of detailed investigations carried out inquiring into the mechanistic aspects of DNA photocleavage by [Co(phen)2(dppz)]3+ have also been reported

Dipyridophenazine complexes of cobalt(III) and nickel(II): DNA-binding and photocleavage studies

Results of absorption titration, thermal denaturation, and differential pulse voltammetric experiments suggest that [Co(phen)2DPPZ]3+ and [Ni(phen)2DPPZ]2+ (phen = 1, 10-phenanthroline and DPPZ = dipyrido[3,2-a:2',3'-c]phenazine) are both avid binders of calf thymus DNA. On the other hand, while the cobalt(III) complex has been found to effect the photocleavage of the supercoiled pBR 322 DNA, the nickel(II) complex is ineffective under similar experimental conditions

"Electro-photo switch" and "molecular light switch" devices based on ruthenium(II) complexes of modified dipyridophenazine ligands: modulation of the photochemical function through ligand design

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Redox-activated luminescence and light-induced nuclease activity of a new mixed-ligand ruthenium(II) complex

The new metallointercalator 1̲, a mixed-ligand ruthenium(II) complex incorporating a quinone-fused dipyridophenazine ligand, effects an efficient cleavage of the supercoiled plasmid DNA upon activation with visible light. In addition, the quinone/hydroquinone redox couple 1̲/2̲ represents a molecular light-switching device displaying interconversion between non-luminescent state 1̲ and luminescent state 2̲

Porphyrin-anthraquinone hybrids: wavelength dependent DNA photonucleases

Covalently-linked, bichromophoric systems comprising of a porphyrin donor and an anthraquinone acceptor are shown to exhibit wavelength dependent photonuclease activity

DNA cleavage by photoexcited diazoarenes

Photolysis of simple, readily available arene diazo compounds leads to the cleavage of DNA

Dipyridophenazine complexes of cobalt(III): DNA photocleavage and ohotobiology

The UV-visible spectroscopy and photochemistry of [Co(en)2(DPPZ)](ClO4)3 (DPPZ = dipyrido[3,2-a:2´,3´-c]-phenazine) in the presence of plasmid DNA and the nucleoside 2´-deoxygaunosine have been investigated. Evidence for the intercalation of the complex with DNA and photoinduced DNA strand breakage is found. The structurally related complexes [Co(en)2(DPPN)]Cl3 and [Co(en)2(DPPA)]Cl2, where DPPN = benzo[i]dipyrido[3,2-a:2´,3´-c]phenazine and DPPA = dipyrido[3,2-a:2´,3´-c] phenazine-11-carboxylic acid, have also been synthesized and characterized. In vitro cytotoxicity studies and photocytotoxicity studies of the complexes using the C6 rat glioma cell line are reported and indicate significant increases in toxicity following irradation