scispace - formally typeset
Search or ask a question

Showing papers on "Porphyrin published in 1983"


Journal ArticleDOI
TL;DR: These results corroborate previous static studies, utilizing visible spectroscopy and circular dichroism, which indicate that the formation of an intercalated complex occurs only at GC base pair sites with porphyrins which do not possess axial ligands.
Abstract: The interactions of tetrakis(4-N-methylpyridyl)-porphine (H2TMpyP-4) and its copper(II), nickel(II), zinc(II), cobalt(III), iron(III), and manganese(III) derivatives with several nucleic acids have been investigated. Spectrophotometric titrations of H2TMpyP-4 and Cu(II)TMpyP-4 with the synthetic polymer poly(dG-dC) could be analyzed by a nearest-neighbor exclusion model leading to n approximately equal to two base pairs and equilibrium constants of 7.7 X 10(5) M-1 and 8.0 X 10(5) M-1, respectively. The other metal derivatives [except for the nickel(II) porphyrin] do not provide sufficiently large color changes with poly(dG-dC) to allow analysis. In contrast, all of these porphyrins interact with poly(dA-dT) and DNA. For those porphyrins investigated, the binding profiles are not adequately fit by a nearest-neighbor exclusion model but have profiles suggesting that cooperativity effects are important. Spectral and circular dichroic experiments both suggest base specificity. With calf thymus DNA, the copper(II) and nickel(II) derivatives show prominent negative circular dichroism (CD) features and large red shifts and hypochromicity of the Soret absorption band characteristic of GC specificity, as demonstrated with the synthetic polymer. The other metal derivatives show prominent positive induced visible CD features with small red shifts and hypochromicity of the absorption bands in the Soret region characteristic of AT specificity. Only the metal-free derivative has a conservative CD spectrum suggesting distribution among GC and AT sites.

769 citations





Journal ArticleDOI
TL;DR: The results from these studies indicate that sequence selective binding occurs within a small aperture of solution conditions, and the impact that porphyrins' binding has upon the structure of DNA is discussed.
Abstract: The large meso-substituted porphine, meso-tetra(4-N-methylpyridyl)porphine has been identified as a DNA-interactive ligand with a capacity for intercalation (1,2). Subsequently, the 2-N-methyl, 3-N-methyl and N-trimethylanilinium analogues of this porphyrin intercalator have been obtained for physico-chemical analyses (absorption spectroscopy, viscometry, circular dichroism, unwinding of supercoiled DNA). In this paper we discuss the factors affecting the character of porphyrin binding (intercalative, as is the case for the 4-N-methyl and 3-N-methyl porphines, versus non-intercalative, as is the case for the 2-N-methyl and N-trimethylanilinium porphines) and the impact that porphyrins' binding has upon the structure of DNA. The molecular conformation of the porphyrin ligand varies slightly within this series so that the ability of a given porphyrin to intercalate may be correlated with the arrangement of charged groups, the planarity of the porphine ring and the effective width of the individual molecules. The results from these studies indicate that sequence selective binding occurs within a small aperture of solution conditions.

174 citations


Journal ArticleDOI
TL;DR: Findings lead to a sequential Bi Bi kinetic model for ferrochelatase with iron binding occurring prior to porphyrin binding and heme being released prior to the release of two protons, and Heme, one of the products, is a noncompetitive inhibitor with respect to iron.

149 citations


Journal ArticleDOI
TL;DR: A new, specific, quantitative method for fecal blood, based on conversion of nonfluorescing heme to fluorescing porphyrins, that obviates serious deficiencies inherent in currently used tests is described.
Abstract: We describe a new, specific, quantitative method for fecal blood, based on conversion of nonfluorescing heme to fluorescing porphyrins, that obviates serious deficiencies inherent in currently used tests. A two-reagent system is used to determine the two hemoglobin-related fractions that are found in feces. The hot citric acid extract includes only the variable fraction of porphyrins that have been preformed from heme in the intestinal tract; this often is the major fraction. Total hemoglobin is indirectly determined by reaction with heated oxalic acid:FeSO4 reagent, which converts the remaining heme to porphyrin without loss of the preformed porphyrins. A three-step purification procedure eliminates interfering materials. Analytical recovery of added hemoglobin is linearly related to concentration over a several-thousand-fold range. The assay is equally applicable to whole blood or to sub-microgram amounts of hemoglobin in the 8-mg (wet weight) fecal sample tested. Quality control by liquid chromatographic and fluorometric analysis documents fluorescence specificity of the heme-derived porphyrins.

140 citations


Journal ArticleDOI
TL;DR: In this paper, the photophysical behavior and some photochemical processes for nickel (II) porphyrins have been examined with picosecond transient absorption techniques, and detailed results are reported for Ni-OEP and Ni-protoporphyrin IX dimethylester (NiPPDME) in toluene, pyridine and piperidine.

140 citations


Journal ArticleDOI
TL;DR: In this article, the Mn-Porphyrin-Komplexe (I) and (II) reagieren with prim., sek. and tert. Alkanen in relativ inerten Losungsmitteln wie CH2Cl" Chlor- oder Brombenzol bei 25°C zu funktionalisierten Produkten in guten Ausbeuten
Abstract: Die Mn- Porphyrin-Komplexe (I) und (II) reagieren mit prim., sek. und tert. Alkanen in relativ inerten Losungsmitteln wie CH2Cl" Chlor- oder Brombenzol bei 25°C zu funktionalisierten Produkten in guten Ausbeuten.

139 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of the heat treatment at 850°C on this catalyst has been examined with emission Mossbauer spectroscopy using Co-57 enriched Co-TMPP.

133 citations


Journal Article
TL;DR: It is concluded that localization is mediated by hematoporphyrin derivative components which are among the most hydrophobic in the preparation, and apparent hydrophobicity may derive from hydrogen-bonding phenomena, rather than from absence of hydrophilic functional groups.
Abstract: Synthetic and analytical approaches were used to characterize the tumor-localizing components of the porphyrin preparation, hematoporphyrin derivative. From studies involving aqueous and nonaqueous gel exclusion and reverse-phase chromatography, we conclude that localization is mediated by hematoporphyrin derivative components which are among the most hydrophobic in the preparation. This apparent hydrophobicity may derive from hydrogen-bonding phenomena, rather than from absence of hydrophilic functional groups.

Journal ArticleDOI
TL;DR: These results implicate an active site that is sterically encumbered in the region over pyrrole ring B and has a lipophilic binding site that accommodates chains of at least six carbon atoms over p Pyrrole ring C.

Journal ArticleDOI
TL;DR: In this article, a series of meso-tetratolylporphyrin-quinone molecules with diamide linkages with the two amides being separated by n methylene groups (n=2, 3, or 4) were studied.
Abstract: Systematic studies of absorption spectra and fluorescence spectra and lifetimes have been carried out on a series of meso-tetratolylporphyrins to which various molecular entities have been covalently attached via diamide linkages with the two amides being separated by n methylene groups (n=2, 3, or 4). The attached end groups include p-benzoquinone, hydroquinone, and dimethoxybenzene. These studies reveal the existence of at least two more or less distinct forms: a family of ''complexed'' conformers in which the end group is likely folded so as to interact with the porphyrin, and one or more ''extended'' conformers in which the porphyrin moiety is relatively unperturbed by the end group. The complexed conformers exhibit perturbations of spectra and diminished fluorescence lifetimes and quantum yields as compared with the extended conformer(s). Oxidation of the porphyrin-linked hydroquinone form to the quinone form does not significantly affect the absorption or fluorescence spectra but causes strong quenching of fluorescence and diminution of the fluorescence lifetimes. This quenching is interpreted primarily in terms of electron transfer from the lowest excited singlet state of the porphyrin to the quinone moiety. On the basis of the assumption that these shorter fluorescence lifetimes of the quinone relative to the hydroquinone are duemore » entirely to electron transfer, apparent electron-transfer rate constants k/sup et/ at room temperature range from <1 x 10/sup 8/ to <7 x 10/sup 9/ s-/sup 1/, depending on solvent and probably the specific geometry of the conformers. Quenching in both sets of conformers appears to be thermally activated and is strongly inhibited in frozen matrices. Parallel studies of porphyrin-quinone molecules with various methylene chains (n=2, 3, and 4) indicate that the geometry of the linkage is critical to the rate of electron transfer. A methylene chain with n = 3 appears to be optimum. 4 figures, 6 tables.« less

Journal ArticleDOI
TL;DR: All four porphyrins were found to bind to the polynucleotides as shown by the induction of circular dichroism in their Soret bands, and the sign of the induced ellipticity reflects selective occupation of binding sites by the p Morphyrin ligands.
Abstract: The interactions of two positional isomers and one analogue of meso-tetra (4-N-methylpyridyl) porphine, with the synthetic polynucleotides poly[d(A-T)] poly[d(A-T)] and poly[d(G-C)] poly[d(G-C)] have been investigated by circular dichroism All four porphyrins were found to bind to the polynucleotides as shown by the induction of circular dichroism in their Soret bands Furthermore, the sign of the induced ellipticity reflects selective occupation of binding sites by the porphyrin ligands The conformational lability of poly[d(A-T)] X poly[d(A-T)] was found to be appreciable as micromolar amounts of meso-substituted 4-N-methylpyridyl, 3-N-methylpyridyl, and p-N-trimethylanilinium porphines induced a CD spectrum similar but not identical to that of DNA in the Z-form, ie a negative band at 280 nm and a positive band at 259 nm The effect of porphyrin binding to poly[d(G-C)] X poly[d(G-C)] was less pronounced and dissimilar to that seen in the AT polymer

Journal ArticleDOI
TL;DR: Meso-tetrakis (3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin (1a) undergoes rapid, non-photosensitised, aerial oxidation in basic solutions as discussed by the authors.



Journal ArticleDOI
TL;DR: In this article, a spin Hamiltonian model was employed to interpret the data of a polycrystalline form of oxidized chloro-5,10,15,20,tetra(mesityl)porphyrin• atoiron(III)•[Fe(TMP)Cl], compound A, which is similar to the others in comprising a Fe(IV) complex within a porphyrin cation radical.
Abstract: Mossbauer spectra of a polycrystalline form of oxidized chloro‐5,10,15,20‐tetra(mesityl)porphyrin‐ atoiron(III) [Fe(TMP)Cl], compound A, were recorded over a range of temperatures (4.2–195 K) and magnetic fields (0–6 T). These spectra of compound A exhibit magnetic features which are markedly different from those of the analogous protein complexes, horse radish peroxidase compound I (HRP‐I) and compound ES of cytochrome c peroxidase, even though chemical evidence and optical spectroscopy indicate that compound A is similar to the others in comprising a Fe(IV) complex within a porphyrin cation radical. We interpret the data by employing a spin Hamiltonian model in which the central Fe(IV) complex, with S=1, is tightly coupled to a S=1/2 system of the oxidized porphyrin to yield a net S=3/2 system as suggested by the susceptibility measurements. The theoretical treatment yields information on the d‐electron energies which is similar to that more directly available in the peroxidase spectra. The strength of ...

Journal ArticleDOI
TL;DR: A reversed-phase gradient elution system is described, adaptable for isocratic and stepwise separation of individual groups of isomers, which is also suitable for preparative isolation of pure porphyrins.
Abstract: A reversed-phase gradient elution system is described for the simultaneous separation of the type I and type III isomers of 8-, 7-, 6-, 5- and 4-carboxylated porphyrins and isocoproporphyrins. The method, adaptable for isocratic and stepwise separation of individual groups of isomers, is also suitable for preparative isolation of pure porphyrins. The analyses of porphyrin isomers in the urine and faeces of porphyric patients are examples of applications.

Journal ArticleDOI
TL;DR: The bis-pocket porphyrin with sterically protected pockets on both faces is described in this article, where the authors show that the protected pockets do not sterically interfere with axial ligation.
Abstract: The synthesis, characterization, and ligand-binding properties of a porphyrin with sterically protected pockets on both faces is described. 5,10,15,20-Tetrakis(2,4,6-triphenylphenyl)porphyrin, or the “bis-pocket” porphyrin, is synthesized by the condensation of 2,4,6-triphenylbenzaldehyde with pyrrole in refluxing propionic acid. Metalation of this porphyrin with Fe(CO)S/12 in toluene and reduction with (CH3)4NBH4 yields the four-coordinate Fe(I1) complex. Upon addition of 1,2-dimethylimidazole, the five-coordinate adduct is produced which is capable of completely reversible oxygenation. The equilibrium constant for imidazole binding indicates that the protected pockets do not sterically interfere with axial ligation, while still providing the spacing necessary to prevent bimolecular irreversible oxidation of the Fe(I1) complex. In contrast, the 0, affinity shown by this porphyrin complex is dramatically reduced compared to other synthetic analogues or to most heme proteins. This is attributed in part to the completely nonpolar binding site present in this bis-pocket porphyrin, compared to the relatively polar and hydrogen-bonding environment of other systems. Confirmation of this interpretation comes from the effect of solvent polarity on dioxygen affinities: a s the solvent is changed from mesitylene to toluene to chlorobenzene to o-dichlorobenzene, the PI for O2 binding decreased from 640 torr to 508 to 299 to 227 torr, in good correlation with empirical

Journal ArticleDOI
TL;DR: In this article, the Raman difference spectroscopy was used to investigate the acceptor ability of copper and nickel-II uroporphyrin I complexes with a variety of aromatic heterocycles in aqueous alkaline solution.
Abstract: Copper(II) and nickel(II) uroporphyrin I form molecular complexes with a variety of aromatic heterocycles in aqueous alkaline solution. The molecular complexes have been examined with Raman difference spectroscopy. As a result of complex formation, small shifts in the frequencies of vibrational modes of the porphyrin ring occur. For the phenanthroline derivatives and methyl viologen, the shifts are similar but not identical with those observed in iron porphyrins and heme proteins when the par. delta-electron density in the ring is modified. Shifts to higher frequencies in the Raman lines of CuURO-phenanthroline complexes indicate that the porphyrin acts as a donor. In the viologen dication complex CuURO is found to be an acceptor in the ground state. A correlation exits between charge donation by copper uroporphyrin (as measured by the increase in frequencies of ''electron-density-sensitive'' Raman lines) and the acceptor ability of the phenanthroline derivatives (as expressed by the Hammett sigma's of the substituents). Consideration of the steric properties of some derivatives indicates that the structures of these complexes are such that the plane of the phenanthroline is parallel to that of the porphyrin and interactions of nitrogen lone pairs with the metal ion are not involved. A good correlation between themore » free energy of association and the Raman shifts is evidence that the charge-transfer interaction stabilizes the complex by up to approx.3 kcal/mol.« less

Journal ArticleDOI
TL;DR: A biphasic H2O-C6H6 system with phase transfer agents as catalysts and ascorbate as a reducing agent was shown to activate dioxygen leading to selective epoxidation of olefins and hydroxylation of alkanes as mentioned in this paper.
Abstract: A biphasic H2O–C6H6 system, which has MnIII(tetraphenylporphyrin)(Cl) and a phase transfer agent as catalysts and ascorbate as a reducing agent, activates dioxygen leading to selective epoxidation of olefins and hydroxylation of alkanes under mild conditions.

Journal ArticleDOI
TL;DR: The absorption spectrum of serum samples from infants with bronze baby syndrome (BBS) showed spectral features typical of bilirubin, as well as an intense band peaking around 400 nm and a generalized broad absorbance in the near-UV and in the 600–700 nm spectral region.
Abstract: Summary: The absorption spectrum of serum samples from infants with bronze baby syndrome (BBS) showed spectral features typical of bilirubin (i.e., λ max at approximately 460 nm), as well as an intense band peaking around 400 nm and a generalized broad absorbance in the near-UV and in the 600–700 nm spectral region. The two latter features were not observed in the absorption spectra of control sera; moreover, the BBS sera exhibited multiband emission spectra with maxima at 585, 619, and 670 nm. This finding indicates that the 400-nm absorption band does not reflect the presence of residual hemoglobin in the sera because hemoproteins are known to be nonfluorescent in the red region. Instead the observed emission spectra are characteristic of porphyrin compounds. The porphyrins extracted from BBS sera were analyzed chromatographically. The results of paper chromatography led to the conclusion that the two porphyrins present in the ether fraction are Cu2+-proto and Cu2+-coproporphyrin, whereas the porphyrin in the aqueous phase is Cu2+-uroporphyrin. Visible light-irradiation of diluted sera from BBS newborn infants caused an increase of the brown color of the solution corresponding with a disappearance of the typical porphyrin fluorescence and an increase of the absorbance in the near-UV and red spectral regions. Extraction of porphyrins from 15-min irradiated BBS sera showed that an essentially total destruction had occurred. In order to verify the responsibility of Cu2+-porphyrins in inducing the BBS discoloration, we irradiated 8-ml samples of serum obtained from normal cord blood in presence of Cu2+-proto, Cu2+-copro, and Cu2+-uroporphyrin, which were added at a concentration of 3.28 μg/ml. Cu2+-porphyrins were slowly destroyed and the consequent spectral changes closely resembled those observed from BBS sera from phototreated patients. The addition of equimolar bilirubin to the aqueous solution of Cu2+-porphyrins bound to albumin enhanced the first order rate constant for porphyrin photodestruction from 0.12 sec-1 to 0.49 sec-1.

Journal ArticleDOI
TL;DR: Protoporphyrin IX dimethyl ester and tetra(4-carbomethoxyphenyl) porphyrin form condensed Langmuir films which can be transferred at 20-30 mN m −1 to quartz or aluminized substrates by an unusual Z deposition process as mentioned in this paper.


Journal ArticleDOI
TL;DR: In this paper, the synthesis of tetra-aryl porphyrins for studies in solar energy conversion is described, which are derived from 5,10,15,20-meso-tetrakis(4-hydroxyphenyl)porphyrin, which, in basic media, forms a green intermediate that is probably the tetraphenoxide.
Abstract: The synthesis of tetra-arylporphyrins, for studies in solar energy conversion, is described. They are derived from 5,10,15,20-meso-tetrakis(4-hydroxyphenyl)porphyrin (4) which, in basic media, forms a green intermediate that is probably the tetraphenoxide (6). The porphyrins (10) and (13), were synthesised as prospective sensitisers for catalysed microheterogenous water photo-oxidation. U.v./visible spectroscopy demonstrates that the porphyrin (10) aggregates in aqueous solution. Cyclic voltammetry shows that the porphyrin (13) behaves as a typical viologen with bulky substituents. A pentameric porphyrin (15) was synthesised and characterised in order to model energy transfer in photosynthetic chlorophyll antennae. There is some evidence that weak singlet-energy transfer occurs between the porphyrin sub-units of the pentamer.

Journal ArticleDOI
TL;DR: Proprietes chimiques des composes cites dans le titre. as discussed by the authors as discussed by the authors ) describe reactions suivies spectroscopiquement to spectroscopy.
Abstract: Proprietes chimiques des composes cites dans le titre. Reactions suivies spectroscopiquement

Journal ArticleDOI
TL;DR: The zinc porphyrin ZnTAPP undergoes facile photoredox reactions and also sensitizes H2 evolution upon visible-light photolysis in ‘sacrificial’ systems as discussed by the authors.
Abstract: Photophysical properties (fluorescence spectra, lifetimes, triplet–triplet absorption spectra, triplet lifetimes and quantum yields) and redox potentials have been measured for the free-base, Zn2+ derivatives of a cationic water-soluble porphyrin, tetrakis(trimethyl-aminophenyl)porphyrin [TAPP(4+)]; the values are similar to those of tetrakis(sulphonatophenyl)porphyrin, TPPS(4 –). The zinc porphyrin ZnTAPP undergoes facile photoredox reactions and also sensitizes H2 evolution upon visible-light photolysis in ‘sacrificial’ systems, albeit with a lower efficiency in comparison with tetrakis(4-methylpyridyl)porphyrin, ZnTMPyP.

Journal ArticleDOI
TL;DR: In this article, a combination of model studies, theoretical calculations, and in vivo experiments has recently shown that ferryl porphyrin x cations provide viable models for the two-electron oxidation intermediates (compounds I) observed in the catalytic cycles of peroxidases and catalases.
Abstract: A combination of model studies, theoretical calculations, and “in vivo” experiments has recently shown that ferryl porphyrin x cations provide viable models for the two-electron oxidation intermediates (compounds I) observed in the catalytic cycles of peroxidases and catalases. Extended Hiickel calculations predict significant spin delocalization on the axial ligand, if an electron is abstracted from the a2, orbital of the ferryl porphyrin. Similar profiles are computed for zinc porphyrins. Redox, optical, and ESR data are presented that probe the effect of bound pyridine on zinc cation radicals. The ESR results support the trend predicted by the calculations and provide evidence of spin density delocalization on the axial pyridine in azu radicals. Such axial delocalization in vivo may provide a conduit for electron exchange between the oxidized transients and neighboring protein residues. A mechanism is therefore proposed for the formation of compound ES of cytochrome