Showing papers on "Porphyrin published in 1979"
TL;DR: The porphyrin photosensitizer, meso-Tetra (4-N-methylpyridyl) porphine tetraperchlorate binds to calf thymus DNA by intercalation and by external electrostatic association.
Abstract: The porphyrin photosensitizer, meso-Tetra (4-N-methylpyridyl) porphine tetraperchlorate binds to calf thymus DNA by intercalation and by external electrostatic association. This was concluded from the results of measruements involving Scatchard analysis, viscometry, thermal denaturation, and circular dichroism.
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TL;DR: In this article, a series of acid/base transitions in alkaline solution due to axially coordinated water molecules were identified for manganese(III) porphyrins, and electrophoresis has identified the total electronic charge of each of the acid or base forms.
Abstract: Manganese(III) forms many high spin d4 porphyrins, for which pyridyl, N-methylpyridyl, sulphonic acid and carboxylic acid and carboxylic acid functions act as water solubilising groups. Reduction with dithionite yields the corresponding manganese(II) porphyrin. Both oxidation states have been clearly identified by e.p.r. and magnetic susceptibility measurements. On the other hand, oxidation with persulphate gives an unstable manganese(III) porphyrin π-radical cation which appears to form a dimer in aqueous solution at pH ≈ 10. All the porphyrins undergo a series of acid/base transitions in alkaline solution due to axially coordinated water molecules. For manganese(III) porphyrins, there are two pK transitions, around 8.0 and 10.5, and electrophoresis has identified the total electronic charge of each of the acid/base forms.
125 citations
TL;DR: In this paper, the lifetimes of the excited singlet state of Ni, Pd, and Zn porphyrins as 10±2ps, 19±3ps, and 2.6±0.5 ps, respectively, and <8 ps for Pt porphrin.
Abstract: —Picosecond absorption spectroscopy was used to determine the intramolecular energy relaxation processes occurring in Ni(II). Pd(II), Pt(II), and Zn(II) protoporphyrin IX dimethyl ester. Picosecond data on the rate of ground state repopulation and the kinetics of a transient intermediate made it possible to determine the lifetimes of the excited singlet state of Ni, Pd, and Zn porphyrins as 10±2ps, 19±3ps, and 2.6±0.5 ps, respectively, and<8 ps for Pt porphyrin. On the basis of these data. the nonfluorescent and nonphosphorescent property of Ni porphyrin can be interpreted in terms of internal conversion to a lower lying singlet d-d level which is not the case for the strongly phosphorescent Pd and Pt porphyrins.
94 citations
TL;DR: The nuclear modulation pattern in the envelope of electron spin echoes for various low spin paramagnetic heme proteins, using the three-pulse-stimulated echo method, is observed and the heme of low spin ferric cytochrome P-450 is coordinated to a nitrogenous ligand, probably imidazole.
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TL;DR: The hepatic pigment accumulated as a consequence of the self-catalyzed destruction of cytochrome P-450 by norethisterone, after acidic methylation and purification, consists of two virtually identical, probably isomeric, porphyrins.
Abstract: The hepatic pigment accumulated as a consequence of the self-catalyzed destruction of cytochrome P-450 by norethisterone (17-hydroxy-19-nor-17 alpha-pregn-4-en-20-yn-3-one), after acidic methylation and purification, consists of two virtually identical, probably isomeric, porphyrins. Radiolabeled norethisterone is incorporated into both porphyrin products. The major of the two porphyrins exhibits a mass spectrometric molecular ion exactly equivalent to the sum of norethisterone and dimethylprotoporphyrin IX, less two hydrogen atoms: unequivocably demonstrating covalent association of the sterol with this porphyrin in a 1:1 ratio. Cytochrome P-450 is therefore destroyed by self-catalyzed addition of norethisterone to its heme prosthetic group. Cytochrome P-450 is also destroyed by norgestrel (13-ethyl-17-hydroxyl-18, 19-dinor-17 alpha-pregn-4-en-20-yn-3-one) and by 1-ethynylcyclohexanol but not by 17-hydroxy-19-nor-17alpha-pregn-4,20-dien-3-one. The destructive potential is thus clearly a property of the propargylic alcohol function. A mechanism involving enzymatic oxidation of the triple bond is postulated.
TL;DR: In this paper, a.k. f konstanten der Komplexierung von N-Methyltetraphenylporphyrin with Cum)′, N Zn(II)-, Co(II), Mn(II) and Ni (II)-Perchloratsalzen in Dimethylformamid werden.
Abstract: Die Geschwindigkeit? f konstanten der Komplexierung von N-Methyltetraphenylporphyrin mit Cum)′, N Zn(II)-, Co(II)-, Mn(II)- und Ni(II)-Perchloratsalzen in Dimethylformamid werden.
TL;DR: Raman difference spectroscopy measurements on native and chemically modified human deoxyhemoglobins stabilized in either the R or the T quaternary structure revealed frequency differences in the oxidation state marker lines that indicate that the R structure has an effective increase in the electron density of the antibonding pi* orbitals of the porphyrin rings.
Abstract: Raman difference spectroscopy measurements on native and chemically modified human deoxyhemoglobins stabilized in either the R or the T quaternary structure revealed frequency differences in the oxidation state marker lines. The differences indicate that the R structure has an effective increase in the electron density of the antibonding pi* orbitals of the porphyrin rings. This increase is explained by a charge transfer interaction between donor orbitals and the pi* orbitals of the porphyrins. The relative amount of charge transferred, which is inferred from the Raman difference measurements, correlates with some but not all factors that influence the energetics of the quaternary structure equilibrium. In addition, the free energy of cooperativity for a variety of ligated proteins follows the same order as that of the degree of charge depletion of the pi* orbitals upon ligation as determined from the frequency of a Raman mode. The proposed electronic interaction between the protein and heme could result in energies large enough to provide a significant contribution to the energetics of hemoglobin cooperativity.
TL;DR: Upon photoactivation, porphyrins accumulated by tumor cells catalyze cross-linking of membrane protein but not of glycoprotein, which is associated with a decrease in cell-surface hydrophobicity and with other alterations in vital membrane propeprties.
TL;DR: Results clearly establish that the carbonyl groups of the two destructive substrates are intimately involved in formation of the isolated porphyrin adducts, and exclude participation of the corresponding epoxide metabolites in the destruction of cytochrome P-450.
TL;DR: In this paper, a small reverse wave at ca. −0.4 V vs. NaSCE in CH3CN and DMSO solvent is interpreted as reoxidation of diprotonated surface bound porphyrin.
TL;DR: The carbon monoxide affinities of iron complexes of meso-tetra and of a "picket fence" porphyrin derivative with an appended axial base have been measured in solution and compared with the CO affinITIES of various hemoproteins and mutant hemoglobins lacking distal residues that sterically inhibit the binding of CO are presented.
Abstract: The carbon monoxide affinities of iron complexes of meso-tetra (alpha, alpha, alpha, alpha-o-pivalamidophenyl)porphyrin (the "picket fence" porphyrin) and of a "picket fence" porphyrin derivative with an appended axial base have been measured in solution and compared with the CO affinities of various hemoproteins. The model complexes bind CO with much greater affinity than normal hemoproteins; the role of the steric bulk of distal residues in lowering the CO affinities of the hemoproteins is discussed. The significance of this lowered CO affinity is described with regard to endogenous CO. A discussion of mutant hemoglobins lacking distal residues that sterically inhibit the binding of CO is presented. The use of pressure units versus concentration units in equilibrium expressions is analyzed.
TL;DR: Porphyrin synthesis and iron accumulation was stimulated by exogenous 5-aminolevulinic acid (ALA) in uninduced Friend erythroleukemic cells (FELC), indicating an inhibitory effect of hemin on ALA dehydrase and urosynthetase activities.
TL;DR: The Raman spectra of native chloroperoxidase are found to be sensitive to temperature and imply that a high leads to low spin transition of the heme iron atom takes place as the temperature is lowered.
Abstract: Resonance Raman spectra of the heme protein chloroperoxidase in its native and reduced forms and complexed with various small ions are obtained by using laser excitation in the Soret region (350-450 nm). Additionally, Raman spectra of horseradish peroxidase, cytochrome P-450cam, and cytochrome c, taken with Soret excitation, are presented and discussed. The data support previous findings that indicate a strong analogy between the active site environments of chloroperoxidase and cytochrome P-450cam. The Raman spectra of native chloroperoxidase are found to be sensitive to temperature and imply that a high leads to low spin transition of the heme iron atom takes place as the temperature is lowered. Unusual peak positions are also found for native and reduced chloroperoxidase and indicate a weakening of porphyrin ring bond strengths due to the presence of a strongly electron-donating axial ligand. Enormous selective enhancements of vibrational modes at 1360 and 674 cm-1 are also observed in some low-spin ferrous forms of the enzyme. These vibrational frequencies are assigned to primary normal modes of expansion of the prophyrin macrocycle upon electronic excitation.
TL;DR: A spectral study was carried out of the green pigments produced by allyl-containing drugs and a comparison made with N-methylated octaethylporphyrin and 2,4-diformyldeuteroporphyrin.
Abstract: A spectral study was carried out of the green pigments produced by allyl-containing drugs and a comparison made with N-methylated octaethylporphyrin and 2,4-diformyldeuteroporphyrin. The green pigments resemble the former (and markedly differ from the latter) in the intensity of the bathochromic shifts, titration curves with trifluoroacetic acid and rate of incorporation of metal ions in vitro.
TL;DR: A spectroscopic method to chlorophyll-containing vesicles was developed and the orientation of the porphyrin ring appears to be orientated in the polar head group region of the lipid layer, but not to be protruding out into the water phase.
TL;DR: In this paper, an investigation of the quenching of porphyrin and metalloporphrin excited states by oxygen in protic and aprotic organic solvents is reported.
TL;DR: In this paper, the authors showed that the chemical environment around the oxygen-binding site plays an important role on the stability of an oxygenated complex as in the case of the tetraamide groups on the porphyrin plane.
Abstract: Construction of artificial oxygen carriers by use of iron or cobalt complexes bound to synthetic polymers was attempted Radical copolymerization of porphyrin vinyl monomers with styrene gave the metalloporphyrins covalently bonded to a polymer chain at low concentration For these metalloporphyrin polymers, irreversible oxidation via dimerization was prevented in aprotic solvents and reversible oxygenation was observed The chemical environment around the oxygen-binding site was presumed to play an important role on the stability of oxygenated complex as in the case of the tetraamide groups on the porphyrin plane When ethylenebis(salicylideniminato)cobalt chelate coordinated to a polymer-ligand, it formed a stable oxygenated complex at room temperature Rotational motion of the chelate was decreased markedly by the polymer chain to enhance the coordinate bond between the metal ion and the bound oxygen molecule Furthermore, the iron porphyrin with bulky substituents was oxygenated even in homog
TL;DR: In this article, the reaction between Zn(II) ion and the peripherally positively charged tetra-(p-trimethylammoniumphenyl)porphyrin (H2TAPP) was investigated at 30°C and 0.5°F ionic strength (NaNO3).