Showing papers on "Porphyrin published in 1984"
TL;DR: No and nitroso compounds may react with enzyme-bound heme to generate a modified porphyrin which structurally resembles protoporphyr in IX in its interaction with guanylate cyclase.
239 citations
TL;DR: It can be concluded that hydrophobic porphyrins bind to blood proteins in patients suffering from protoporphyria.
Abstract: The incorporation of proto-, uro- and hematoporphyrin in low density lipoproteins (LDL) of human blood has been studied by equilibrium dialysis, fluorescence and absorption spectroscopy. The lipoproteins may efficiently compete with albumin in the binding of protoporphyrin to human blood proteins in patients suffering from protoporphyria. It can be concluded that hydrophobic porphyrins bind to blood proteins.
The complexation of hydrophobic porphyrins in LDL is responsible not only for efficient photodynamic effect at the lipoprotein level, but also for photoinduced lipid peroxidation and for consumption of β-carotene incorporated into LDL which are one of their natural carriers. The water-soluble uroporphyrin, although an efficient photosensitizer for the LDL apoprotein photoinactivation, is much less efficient for lipid peroxidation and β-carotene bleaching. The 353 nm laser flash photolysis shows that porphyrin triplet states are not affected by the physiological β-carotene content of LDL but are fully accessible to oxygen.
148 citations
147 citations
TL;DR: In this paper, the authors report the synthesis of three rigidly linked side-by-side porphyrinone molecules 2-4 whose edge-to-edge distances are fixed at 6, 10, and 14 A (Figure 1).
Abstract: We report the syntheses of three rigidly linked side-by-side porphyrinquinone molecules 2-4 whose edge-to-edge distances are fixed at 6, 10, and 14 A (Figure 1). The spacer units bicyclo[2.2.2]octane and bibicyclo[2.2.2]octane prevent translational
displacement and only allow rotational freedom. Our preliminary studies of the fluorescence yields of both the free base PLQ 2a-4a and Zn PLQ 2b-4b systems, relative to 1, a similar porphyrin not equipped with a quinone, reveal a distance dependence. This suggests that 2-4 will be useful systems for studying the incremental effect of distance on photochemical electron transfer from excited-state porphyrins to quinones.
136 citations
TL;DR: The results suggest that the mechanism(s) of the photobleaching of porphyrin photosensitizers in cells and tissues during PDT may be complex.
Abstract: Porphyrins used as sensitizers for the photodynamic therapy (PDT) of tumors are progressively destroyed (photobleached) during illumination. If the porphyrin bleaches too rapidly, tumor destruction will not be complete. However, with appropriate sensitizer dosages and bleaching rates, irreversible photodynamic injury to the normal tissues surrounding the tumor, which retain less sensitizer, may be significantly decreased. This paper surveys the quantum yields and kinetics of the photobleaching of four porphyrins: hematoporphyrin (HP), Photofrin II (PF II), tetra(4-sulfonatophenyl)porphine (TSPP) and uroporphyrin I (URO). The initial quantum yields of photobleaching, as measured in pH 7.4 phosphate buffer in air, were: 4.7 x 10(-5), 5.4 x 10(-5), 9.8 x 10(-6), and 2.8 x 10(-5) for HP, PF II, TSPP and URO respectively; thus, the rates of photobleaching are rather slow. Low oxygen concentration (2 microM) significantly reduced the photobleaching yields. However, D2O increased the yields only slightly, and the singlet oxygen quencher, azide, had no effect, even at 0.1 M. Photosensitizing porphyrins in body fluids, cells and tissues may be closely associated with various photooxidizable molecules and electron acceptors and donors. Therefore, selected model compounds in these categories were examined for their effects on porphyrin photobleaching. A number inhibited and/or accelerated photobleaching, depending on the compound, the porphyrin and the reaction conditions. For example, 1.0 mM furfuryl alcohol increased the photobleaching yields of HP and URO more than 5-fold, with little effect on PF II or TSPP. In contrast, the electron acceptor, methyl viologen, increased the photobleaching yield of TSPP more than 10-fold, with little accelerating effect on the other porphyrins. These results suggest that the mechanism(s) of the photobleaching of porphyrin photosensitizers in cells and tissues during PDT may be complex.
133 citations
TL;DR: Synthese de [Ru(OEP)] 2 and [Ru (TPP)] 2 par pyrolyse sous vide de Ru (OEP) 2 and Ru(TPP) 2. Structure moleculaire de ces complexes as discussed by the authors.
Abstract: Synthese de [Ru(OEP)] 2 et de [Ru(TPP)] 2 par pyrolyse sous vide de Ru(OEP)(py) 2 et Ru(TPP)(py) 2 . Structure moleculaire de ces complexes. Structure cristalline du complexe avec (OEP). OEP=octaethylporphyrine, TPP=tetraphenylporphyrine, py=pyridine
119 citations
TL;DR: In this paper, a porphyrin pyrrole has been ringexpanded to a morpholine derivative, ring-contracted to an azetine derivative, and converted into the oxazolone derivatives.
Abstract: Novel heterocyclic systems in which a porphyrin pyrrole has been ring-expanded to a morpholine derivative (5), ring-contracted to an azetine derivative (6), and converted into the oxazolone derivatives (4) and (9) result from selective oxidation of 2-amino-5,10,15,20-tetraphenylporphyrin (1).
113 citations
TL;DR: In human skin there are local variations in the pH; therefore the findings may be of importance for porphyrin production in acne.
Abstract: Propionibacterium acnes was grown on Eagle's medium for 4–15 days at pH 5.3–7.2 The porphyrin production was measured both by direct fluorometry and by high pressure liquid chromatography (HPLC). The greatest concentration of porphyrins was produced at pH 6.1. Protoporphyrin was the dominant porphyrin species present in the bacteria in all samples. The relative amount of coproporphyrin was greatest at pH 6.7 after 4 days of incubation. In human skin there are local variations in the pH; therefore our findings may be of importance for porphyrin production in acne.
79 citations
TL;DR: In this article, the effect of dimerization on the optical spectra of the title compound TPPS and the ESR spectra for its photoexcited triplet state were investigated.
Abstract: The effect of dimerization on the optical spectra of the title compound TPPS and the ESR spectra of its photoexcited triplet state were investigated. Dimerization can be promoted by addition of cations and cation-crown ether complexes. Two distinct dimer species could be identified with ESR. Dimerization produces red shifts of the optical absorption (Q) bands and fluorescence peaks. In addition, the fluorescence intensity is strongly quenched. These results parallel finding reported for a variety of cofacial covalently linked chlorophylls and porphyrins. However, a striking difference exists between the triplet characteristics of the TPPS dimers on the one hand and covalently linked dimers. The former exhibit a pronounced dimerization-induced reduction in zero-field splitting values. The values of the latter are very similar to those of their monomer precursors. In this respect, the TPPS system mimics changes found in the triplet ESR spectra associated with the transition from chlorophyll monomers (in vitro) to chlorophyll dimers in reaction centers of
73 citations
01 Jan 1984
TL;DR: Mesure des rendements quantiques de formation de 10 2 en solutions aqueuses pour plusieurs porphyrines par: 1) blanchiment de la p-nitrodimethylaniline a 440 nm en presence d'imidazole and mesures de consommation de O 2 en presence of accepteur de 1 O 2 as mentioned in this paper.
Abstract: Mesure des rendements quantiques de formation de 10 2 en solutions aqueuses pour plusieurs porphyrines par: 1) blanchiment de la p-nitrodimethylaniline a 440 nm en presence d'imidazole et mesures de consommation de O 2 en presence d'accepteur de 1 O 2 . Les porphyrines cationiques (meso-tetra(4N-methylpyridyl-4) et porphyrine, meso-tetra(N,N',N''-trimethylamino-4phenyl) porphyrine) et anioniques (meso-tetra(carboxy-4phenyl)porphyrine et mesotetra(sulfonato-4phenyl) porphyrine ont des rendements quantiques eleves pour 1 O 2 (>0,6). Les porphyrines metalliques (metal diamagnetique) ont des rendements non nuls
68 citations
TL;DR: Preparation et proprietes (susceptibilite magnetique, spectres RPE, Mossbauer) d'un compose modele pour l'enzyme citee dans le titre as mentioned in this paper.
Abstract: Preparation et proprietes (susceptibilite magnetique, spectres RPE, Mossbauer) d'un compose modele pour l'enzyme citee dans le titre. Etude comparative avec les cytochromes oxydases bovines et bacteriennes
TL;DR: The results of this study suggest that the porphyrins sensitize Singlet oxygen efficiently but that the singlet oxygen is rapidly scavenged by substrates such as methionine and other amino acids.
TL;DR: The site of nitration by nitrogen dioxide on a range of metalloporphyrins has been found to be dependent on the co-ordinated metal; copper(II), nickel (II), and palladium(II) complexes are nitrated specifically on the porphyrin β-pyrrolic position while magnesium(II, zinc, zinc-II), chloroiron(III), and cobalt-II complexes also give products which result from reaction at the meso-position as discussed by the authors.
Abstract: The site of nitration by nitrogen dioxide on a range of metalloporphyrins has been found to be dependent on the co-ordinated metal; copper(II), nickel(II), and palladium(II) complexes are nitrated specifically on the porphyrin β-pyrrolic position while magnesium(II), zinc(II), chloroiron(III), and cobalt(II) complexes also give products which result from reaction at the meso-position.
TL;DR: The mechanism of the Mn(III) porphyrin-catalyzed epoxidation of olefins by lithium hypochlorite by showing that a relatively stable intermediate is reversibly formed upon interaction of the olefin and the oxo complex.
Abstract: The mechanism of the Mn(III) porphyrin-catalyzed epoxidation of olefins by lithium hypochlorite is examined. The active oxidant is thought to be a high-valent manganese-oxo complex. It is shown that a relatively stable intermediate is reversibly formed upon interaction of the olefin and the oxo complex. The decomposition of this intermediate to Mn(III) porphyrin and epoxide is the rate-determining step of the catalytic cycle. Some analogies to the biochemical epoxidation of olefins catalyzed by cytochrome P-450 are discussed.
Journal Article•
TL;DR: A series of porphyrins and catalysts have been used to test the hypotheses that the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis and the proto‐photosynthetic function of biogenetic p Morphyrins was the oxidation of organic molecules by photoexcited porphyrs with the attendant emission of molecular hydrogen.
Abstract: A series of porphyrins and catalysts has been prepared as a model for the origin of photosynthesis on the primordial earth. These compounds have been used to test the hypotheses that (1) the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis, and (2) the proto-photosythetic function of biogenetic porphyrins (biosynthetic chlorophyll precursors) was the oxidation of organic molecules by photoexcited porphyrins with the attendant emission of molecular hydrogen. This paper describes experiments in which photoexcited biogenetic porphyrins oxidize ethylenediamine tetraacetic acid (EDTA). The concomitant reduction of protons to hydrogen gas occurs in the presence of a colloidal platinum catalyst. The addition of methyl viologen, a one-electron shuttle, increases the amount of molecular hydrogen generated during long irradiations and the quantum yield of hydrogen production. When the porphyrin and catalyst are held in association by molecular complexes, the increased efficiency of electron transfer produces higher yields of hydrogen gas.
TL;DR: In this paper, it is suggested that oxidation proceeds via nucleophilic attack of H 2 O on the Zn II PP + radical cations, leading eventually to the six-electron product dioxoporphomethene.
TL;DR: In this paper, reaction de SO 2 avec (TPP)Fe-O 2 -Fe(TPP) avec TiPO 2 ou P=TPP, ou OEP et avec FeP(O 2 )-TPP=la tetraphenylporphyrine et OEP=l'octaethylporphyreine
Abstract: Reaction de SO 2 avec (TPP)Fe-O 2 -Fe(TPP) avec TiPO 2 ou P=TPP, ou OEP et avec FeP(O 2 )-TPP=la tetraphenylporphyrine et OEP=l'octaethylporphyrine
TL;DR: The ground state complexation between zinc porphyrins and viologens in aqueous solution, and in cases where there is strong electrostatic attraction between the reactants the stability constants are high as mentioned in this paper.
Abstract: Ground-state complexation occurs between zinc porphyrins and viologens in aqueous solution, and in cases where there is strong electrostatic attraction between the reactants the stability constants are high. This complexation ensures that static effects far outweigh dynamic effects in fluorescence quenching experiments, but direct excitation of the complexes does not result in the formation of redox-ion products.Both singlet and triplet excited states of the porphyrin are quenched when the viologen is covalently linked to the chromophore by a short, flexible chain. The quenching efficiencies depend upon chain length and solvent. In alcohol solvents, redox-ion products are observed by flash-photolysis techniques but there is no real evidence to show that the singlet excited state is capable of charge separation under such conditions.
TL;DR: Isolement et caracterisation d'un complexe porphyrinique de fer(III) renfermant un (SH − ) comme coordinat axial.
Abstract: Isolement et caracterisation d'un complexe porphyrinique de fer(III) renfermant un (SH − ) comme coordinat axial
TL;DR: A C32 and a C31 alkyl porphyrin, each present in Serpiano oil shale as the vanadyl complex, have been -isolated as the demetallated compounds and their structures determined by 1H NMR spectroscopic analysis of the zinc complexes, using selective decoupling and nuclear Overhauser effects.
TL;DR: Synthese, proprietes electrochimiques et etude par luminescence d'un nouveau complexe dinucleaire renfermant un complexe Ru(bpy) 3 2+ lie covalentiellement a une porphyrine a une distance d'environ 4 A.
Abstract: Synthese, proprietes electrochimiques et etude par luminescence d'un nouveau complexe dinucleaire renfermant un complexe Ru(bpy) 3 2+ lie covalentiellement a une porphyrine a une distance d'environ 4 A. Ru=Ruthenium(II), bpy=bipyridyle 2,2p
TL;DR: In this paper, the steric effects arising from steric factors cause significant differences in the absorption and emission spectra and triplet lifetimes of the title porphyrin systems as compared to their non-methyl-substituted analogs.
TL;DR: Differences observed among resonance Raman spectra show that the proteins of these two classes of hemoprotein impose two distinct heme structures which are likely related to their biological functions, and provides a new understanding of structure-function relationships of protoheme in hemoproteins.
TL;DR: In this paper, the resonance Raman spectra of the alkaline forms of horseradish peroxidase isoenzymes are indicative of six-coordinate low-spin hemes.
TL;DR: Results tend to associate the well-known phenomenon of photoreduction of Fe( III) and Mn(III) porphyrins with the formation of OH radicals.
Abstract: Radical production during the photolysis of deaerated aqueous alkaline solutions (pH 11) of some water-soluble porphyrins was investigated. Metal-free and metallo complexes of tetrakis (4-N-methylpyridyl)porphyrin (TMPyP) and tetra (4-sulphonatophenyl)porphyrin (TPPS4) were studied. Evidence for the formation of OH radicals during photolysis at 615, 545, 435, 408 and 335 nm of Fe(III) TPPS4 is presented. Fe(III) TMPyP, Mn(III) TPPS4 and Mn(III) TMPyP also gave OH radicals but only during photolysis at 335 nm. The method of spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and 4-pyridyl-1-oxide-N-tert-butylnitrone (POBN) combined with e.s.r. was used for the detection of OH, H and hydrated electrons. With the spin trap DMPO, photolysis generated DMPO-OH adducts under certain conditions but no DMPO-H adducts could be observed. With POBN, no POBN-H adducts were found. The formation of OH was confirmed by studying competition reactions for OH between the spin traps and OH scavengers (formate, isopropanol) and the concomitant formation of the CO-2 adduct and the (CH3)2COH adduct with both DMPO and POBN. The photochemical generation of OH radicals was pH dependent; at pH 7.5 no OH radicals could be detected. Photolysis (615-335 nm) of dicyanocomplexes of the Fe(III) porphyrins did not produce OH radicals. When corresponding Cu(II), Ni(II), Zn(II) and metal-free porphyrins were photolysed at 615 and 335 nm, no OH radicals could be spin trapped. These results tend to associate the well-known phenomenon of photoreduction of Fe(III) and Mn(III) porphyrins with the formation of OH radicals. This process is described mainly as the photoreduction of the metal ion by the ligand-bound hydroxyl ion via an intramolecular process.