Nirmalendu Datta-Gupta

Circular dichroism spectroscopy of a cationic porphyrin bound to DNA

Recently, the porphyrin photosensitizer meso-tetra(4-N-methyl-pyridyl)-porphine was identified as a DNA-reactive agent demonstrating both electrostatic and intercalative binding. A series of porphyrin derivatives were synthesized and studied to see if similar compounds manifested identical behavior. One derivative, meso-tetra(p-N-trimethylanilinium) porphine did not exhibit intercalation behavior but did show avid binding and novel circular dichroic features when bound to B-form DNA. At an ionic strength of 1.02, the binding constant was found to be on the order of 104 and higher at lower ionic strength. The large binding constants and induced optical activity suggest that at large porphyrin/DNA ratios the final porphyrin · DNA complex may take the form of a suprahelical helix.

DNA strand scission activity of metalloporphyrins.

Abstract The iron porphyrin derivatives, iron (III) meso-tetra(4-N-methylpyridyl)-porphine (Fe(III)T4MPyP), aceto-iron (III) meso-tetra(3-N-methylpyridyl)porporphine (AcO-Fe(III)T3MPyP), and iron (III) meso-tetra(p-sulfonatophenyl)-porphine (Fe(III)TSPP), have been shown to induce strand scissions in DNA. Incubation of these porphyrins with PM2 DNA results in the conversion of circular supercoiled DNA to the nicked circular duplex form. The presence of dithiothreitol increases the extent of the nicking reaction. Fe(III)TSPP, which, unlike Fe(III)T4MPyP and AcO-Fe(III)T3MPyP, does not bind to DNA, is the least effective of the three porphyrins in inducing strand scissions in PM2. Both Fe(III)T4MPyP and AcO-Fe(III)T3MPyP induce strand scissions in cellular DNA of pre-labeled HeLa S 3 cells while Fe(III)TSPP has a very limited effect.

Inhibition of DNA dependent RNA synthesis by porphyrin photosensitizers

Abstract Select porphyrin photosensitizers were studied to determine their effects on DNA-dependent RNA synthesis in the presence and absence of visible light. All of the porphyrins were found to inhibit wheat germ polymerase II to some degree in the dark. In the presence of light, the inhibitory effects of the porphyrins was found to result from both inactivation of the enzyme and impairment of the ability of DNA to serve as a template.

SOME METAL COMPLEXES OF α, β, γ, δ-TETRA-(4-PYRIDYL) PORPHINE

Abstract The zinc (II), copper (II), nickel (II), cobalt (II), chloromanganese (III), and chloroiron (III) complexes of α, β, γ, δ-tetra-(4-pyridyl)-porphine (4-TPyP) were prepared. The magnetic susceptibilities from near 0° to 90° K and at room temperature were measured for solid Cu(4-TPyp), Ni(4-TPyP), Co-(4-TPyP), ClMn(4-TPyP) · H2 O and ClFe(4-TPyP). The Mossbauer spectra of ClFe(4-TPyP) were obtained at several temperatures. The infrared spectra and d-spacings were obtained for all of the solids. Electronic spectra of the complexes in pyridine and, where possible, in 0.1 N HCl solution were recorded. Evidence of intermolecular interaction was found for Co(4-TPyP), Ni(4-TPyP), and ClFe(4-TPyP).

Preparation and spectra of some cobaltic complexes of meso-tetra-p-tolylporphin

Abstract A series of cobaltic complexes of meso -tetra- p -tolylporphin have been synthesized as potential vitamin B 12 analog and/or antagonists. Their near u.v., visible and i.r. absorption spectral data have been studied.

Binding of pyridine to a zinc porphyrin in aromatic solvents[1]

Abstract The 1:1 adduct formation between the zinc complex of meso -tetra-4-benzyloxyphenylporphine and pyridine have been studied in benzene, chlorobenzene, bromobenzene, toluene, acetophenone, methylbenzoate, anisole and nitrobenzene using absorption spectroscopy and water-jacketed cells. The binding equilibria were measured at 20, 30 and 40°C. K eq values of binding decrease with increasing temperature. The thermodynamic parameters have been calculated. Attempts have been made to explain the thermodynamic parameters.

The halo(aquo)-α, β, γ, δ-tetra- (p-carbomethoxy)phenolporphine manganese(III) complexes☆

Abstract Four Mn(III) complexes of the type, PCMTPPMnX·H2O, where PCMTPP is the (p-carbomethoxy)-phenylporphine anion and X is either the fluoro, chloro, bromo, or iodo ion, have been prepared and characterized. The magnetic susceptibility and infrared spectra have been obtained. The ultraviolet-visible spectra were measured in a variety of coordinating and non-coordinating solvents. The spectral changes observed, as the solvent is varied, give an indication of the nature of the axial ligands bound to the Mn(III) ion.

Reaction of dinitrogen tetroxide with octaethylhemin in dichloromethane: a meso-substitution reaction

Octaethylhemin(I) reacts rapidly with N2O4 in CHCl2 to produce meso-tetranitromethyloctaethylhemin(II), a high-spin iron(III) complex with a porphyrin lignad fully substituted in all β- and meso-positions.