Showing papers on "Porphyrin published in 1977"
TL;DR: The initial site of photoactivated porphyrin toxicity is at or near the cell surface, and this mode of action is confirmed in murine leukemia L1210 cells.
Abstract: When murine leukemia L1210 cells are exposed to certain porphyrins, in the presence of light, a rapid loss of cell viability occurs. We have examined structure-activity relationships, using a series of porphyrins, and have studied early effects of these agents, to elucidate their mode of action. In the system employed here, only water-soluble porphyrins were cytotoxic. The first step in cytotoxicity involved binding of porphyrin to the cell surface. Porphyrins unable to bind were inactive. An important determinant of drug binding was the partition coefficient of a porphyrin between octanol and water. In the presence of light, presumably via a singlet oxygen intermediate, a variety of effects on the cell surface and cell membrane were then produced. These included inhibition of nucleoside and amino acid transport, perturbation of permeability barriers to actinomycin D uptake, enhanced binding of the fluorescent probe 8-anilino-1-naphthalenesulfonate, inhibition of activity of 5′-nucleotidase, an ectoenzyme, and altered cell-surface properties, measured with a two-phase aqueous polymer system. In the L1210 cell line, the most potent compound tested was deuteroporphyrin IX which produced the effects mentioned above at a 5 × 10−6 level; this drug level also prevented subsequent cell division. A tenfold higher drug level caused inhibition of intracellular nucleoside kinase activity, along with inhibition of sugar transport and of the fluorogenic interaction between 8-anilino-1-naphthalenesulfonic acid and cell companents. We conclude that the initial site of photoactivated porphyrin toxicity is at or near the cell surface.
194 citations
105 citations
TL;DR: It is found that the out-of-plane metal displacement in pentacoordinate heme systems is due to both the restricted size of the porphyrin hole and the "1-3" steric interaction between the axial ligand and the heme nitrogens.
Abstract: The contribution of the porphyrin skeleton to the potential energy surface metalloporphyrins is calculated by the semiempirical method of quantum mechanical extension of the consistent force field to eta electron molecules. This calculation makes it possible to correlate the observed structure of metalloporphyrins with the strain energy of the porphyrin skeleton. It is found that the out-of-plane metal displacement in pentacoordinate heme systems is due to both the restricted size of the porphyrin hole and the "1-3" steric interaction between the axial ligand and the heme nitrogens. The main components of the active site of hemoglobin are simulated by a histidine-heme-oxygen system. The energy surface of this system provides a quantitative explanation for the control of ligand binding by hemoglobin. It is shown that the heme acts as a diaphragm, designed to provide simultaneous binding to the histidine and the sixth ligand under the steric requirements of the 1-3 interactions. The dependence of the hemoglobin potential surface on the distance between the proximal histidine and the heme plane is evaluated for the R and T states, using the calculated heme potential and the observed energy of heme-heme interaction.
94 citations
TL;DR: In this paper, a network model of the ring current effect in the porphyrin system is described, using the double-dipole approximation, to give a calculation of ring current shifts in the PPHY system; this agrees with the observed shifts of protons both in the ring plane and above it.
Abstract: The equivalent dipole model of the ring current shift in benzene is shown to be equivalent to that of the well-known two current loop calculation. A network model of the ring current effect in the porphyrin system is described, using the double–dipole approximation, to give a calculation of the ring current shifts in the porphyrin system; this agrees with the observed shifts of protons both in the ring-plane and above it. A simple modification of the model enables treatment of ring current shifts in the chlorin ring. These models may be used to provide, very simply, good estimates of the ring current shifts of the porphyrin and chlorin rings at points above and outside the current loops; the agreement is sufficiently good to allow assignments of peripheral substituents to be made, and to provide information on their orientation. The model is consistent with a peripheral ring current loop in both the free-base porphyrins and their metal complexes. The relationship of these results to calculations in polycyclic aromatics and to protonation shifts in porphyrins is discussed.
91 citations
87 citations
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71 citations
TL;DR: A reaction mechanism involving 1O2 as the oxidizing agent is proposed and an enhancement of the non‐radiative decay of the first excited singlet state as well as to a reduction of the triplet lifetime is proposed.
Abstract: — A kinetic investigation was performed on the photooxidation of methionine sensitized by various porphyrins at different oxygen concentrations. The rate of photooxidation was found to be strongly dependent on the nature of the sensitizer. In the case of hematoporphyrin, chelation of Mg2+ and Zn2+ and especially of Cu2+ and Fe2+ caused a significant decrease of the photosensitizing efficiency. Fluorescence and/or flash photolysis studies showed that such a decrease is ascribed to an enhancement of the non-radiative decay of the first excited singlet state as well as to a reduction of the triplet lifetime. The sensitizing efficiency is also dependent on the nature of the porphyrin side chains. A reaction mechanism involving 1O2 as the oxidizing agent is proposed.
63 citations
TL;DR: Reduced hemin in detergent solution, unexpectedly, gave the Raman spectrum of ferric low spin type.
46 citations
TL;DR: Vilsmeier formylation of the nickel dimer yields mono- and di-substitution products.
Abstract: Treatment of the nickel(II) or copper(II) derivative of octaethyl-meso-hydroxymethylporphyrin with sulphuric acid in dimethyl-formamide or -acetamide gives mainly the meso,meso′-ethylenebis(porphyrinatometal) derivative by reactions involving electron transfer from the metal, In the absence of metal, only disproportionation reactions occur. Vilsmeier formylation of the nickel dimer yields mono- and di-substitution products.
45 citations
TL;DR: A monobenzoporphyrin has been described in this article, which is a rhodo-type series of porphyrins which have been isolated from some petroleum deposits.
Abstract: A monobenzoporphyrin has been prepared from porphyrin derivatives containing a fused cyclo-hexanone ring. The cyclohexanone system can be constructed either before or after the porphyrin macrocycle has been synthesized. The spectroscopic properties of the monobenzoporphyrin are described and these support the proposal that such a species constitutes the rhodo-type series of porphyrins which have been isolated from some petroleum deposits.
TL;DR: In this article, the transition energies, the oscillator strengths, and the A/D values of porphin, protoporphyrin, and porphyn a were calculated within the framework of the Pariser-Parr-Pople approximation.
TL;DR: Its excitation profile suggests that the Raman intensity of this axial vibration originates in delocalization of the II electrons of the porphyrin ring toward the Fe-NO moiety.
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TL;DR: A new endocrine abnormality in AIP patients is defined and the possibility that endogenously derived 5β steroids may contribute by an induction mechanism to the increased levels of hepatic δ-aminolevulinate synthetase activity found in Aip patients is raised.
TL;DR: The results indicate that the major interaction between bound ligands and substituents around the porphyrin is that transmitted electronically from substituent to ligand.
Abstract: The effects of changes in the groups attached to
the periphery of the porphyrin ring of the heme of various hemoglobins
and myoglobins on the environment experienced
by the ligand, carbon monoxide, have been studied by observation
of the chemical shift of the bound ^(13)CO. The results
indicate that the major interaction between bound ligand and
substituents around the porphyrin is that transmitted electronically
from substituent to ligand. The nature of the protein
environment around the ligand and the interaction between the proximal histidine (F8) and the ligand (through the iron
atom) impose differences between subunits of hemoglobin and
between myoglobins and hemoglobins which are largely, but
not entirely, independent of these substituent effects. To assess
the influence of protein structure on the chemical shifts of
bound ligand, the shifts of ^(13)CO bound to myoglobin and hemoglobins
from a wide range of species have also been measured.
TL;DR: The excited state lifetime in ferrocytochromes c and b5 is longer than that in cytochrome b5 and the relaxation of the pi-pi* excited state configuration of the porphyrin ring is different in the x direction than in the y direction.
Abstract: Resonance Raman scattering excitation profile data have been obtained on ferrocytochromes c and b5 in the alpha absorption band region. We observe in cytochrome c that the shape of the excitation profile agrees with the absorption band shape, while in cytochrome b5 it does not. In addition, we observe in cytochrome b5 a linewidth substantially larger than that in cytochrome c. From our data we conclude that the excited state lifetime in cytochrome c is longer than that in cytochrome b5 and that in cytochrome b5 the relaxation of the pi-pi* excited state configuration of the porphyrin ring is different in the x direction than in the y direction. Possible origins of these effects due to coupling to the d-d transitions of the iron atom are discussed.
TL;DR: A new class of dimeric porphyrin ligands and their metal complexes have been prepared by an unambiguous and high-yield synthetic scheme as mentioned in this paper, which is used in this paper.
TL;DR: Although the reported failure of the Co3+HRP to catalyze peroxide-dependent oxidations of classical peroxidase substrates is confirmed, the oxy-CoHRP does undergo oxidation-reduction reactions analogous to those exhibited in the cytochrome P-450 catalytic cycle.
TL;DR: Grim et al. as mentioned in this paper investigated the adsorption of hemin, protoporphyrin and hemato-porphrin by kaolinite and a Ca-montmorillonite in aqueous solutions buffered at pH 4 and 9.
Abstract: A study was undertaken to investigate the adsorption of hemin, protoporphyrin and hemato- porphyrin by kaolinite and a Ca-montmorillonite in aqueous solutions buffered at pH 4 and 9. Although experimental restrictions at pH 4 prevented the complete characterization of the adsorption isotherms, kaolinite did exhibit a saturation of exchange sites by the cationic porphyrins. Both kaolinite and montmorillonite displayed a similar saturation of sites by the porphyrins in their anionic forms at pH 9. The major differences in the adsorption isotherms are attributed to differences in the exchange capacities of the clays. Adsorption of the porphyrins at pH 9 was inhibited largely by phosphate treatment of the clays; this effect is interpreted as blockage of the anion exchange sites by irreversibly-bound phosphate. the range of values often quoted for equilibrium pHs of aqueous suspensions of the two clays (Grim, 1968).
TL;DR: Measurement of porphyrin precursors has clinical significance beyond the detection or confirmation of lead poisoning and other disorders that are unrelated to lead poisoning or the porphyrias are discussed.
Abstract: Measurement of porphyrins and porphyrin precursors has clinical significance beyond the detection or confirmation of lead poisoning. The porphyric diseases of man are characterized by the presence of a specific clinical syndrome and demonstration of abnormal porphyrin excretion or accumulation in the tissues. In addition, porphyrins accumulate in other disorders that are unrelated to lead poisoning or the porphyrias. These causes of erythrocyte porphyrin accumulation, porphyrinuria, and the porphyrias are discussed.
TL;DR: It is concluded that r-1 also makes the synthesis of δ-aminolevulinic acid insensitive to the inhibition by protochlorophyllide, and a new control feedback loop in the porphyrin biosynthetic pathway is proposed.
Abstract: A Mendelian mutant r-1 in chlamydomonas reinhardtii has been shown to make the synthesis of δ-aminolevulinic acid (ALA) insensitive to inhibition by protoporphyrin. We have now combined the r-1 mutant with the protochlorophyllideaccumulating mutant y-1. From the phenotype of the double mutant y-1 r-1 and the phenocopy produced by feeding ALA to y-1, we conclude that r-1 also makes the synthesis of ALA insensitive to the inhibition by protochlorophyllide. To explain the fact that both ALA-fed y-1 and y-1 r-1 accumulate large amounts of protoporphyrin and smaller amounts of protochlorophyllide, we propose a new control feedback loop in the porphyrin biosynthetic pathway from protochlorophyllide to the step which converts protoporphyrin to magnesium protoporphyrin.
TL;DR: In this article, Copolymers from styrene and 1-vinylimidazoles (4a-f) form low spin adducts with iron(II) porphyrins and iron(III) pmorphyrins, when the content of imidazolyl groups in the polymer is ten mole percent or more.
Abstract: Copolymers from styrene and 1-vinylimidazoles (4a–f), form low spin adducts with iron(II) porphyrins and iron(III) porphyrins, when the content of imidazolyl groups in the polymer is ten mole percent or more With polymers having a content of imidazolyl groups of less then one mole percent, only high spin adducts are observed With terpolymers, in which the porphyrin is covalently bound to the copolymer the same phenomenon is observed Only the high spin Fe(II) porphyrin adducts in the solid state adsorb molecular oxygen like cobalt(II) porphyrins under the same conditions Adsorptions and desorptions of oxygen are much slower in the cases of iron(II) porphyrins than with the cobalt(II) porphyrins Electronic and ESR spectra as well as susceptibility measurements were used to characterize the reported spin states
TL;DR: A mechanism of ferric-ferrous electron transfer involving transfer via the pi ring system is proposed because the most basic porphyrin yielded the most difficult reduction, both kinetically and thermo-dynamically, while the least basic prophyrin yield the most facile kinetic and thermodynamic reduction.
TL;DR: In this paper, the first isolation of stable acylrhodium(III) complexes from the reaction of rhodium (I) complexes with aldehydes is reported.
Abstract: Out-of-plane bisdicarbonylrhodium complexes of etioporphyrin I and a monoazaporphyrin undergo oxidative addition reactions with a variety of substrates RX [R = aryl, acyl, arylcarbonyl, alkoxycarbonyl, ethoxycarbonylmethyl, R′COCH2, or I; X = H or Br (usually) or I or CH2COMe (in certain cases)]. One rhodium atom is detached from the macrocycle. The remaining R–RhIII species is captured by the central porphyrin cavity, retaining R, but with loss of X, to give R–RhIII-etioporphyrin I or -monoazaporphyrin. Several new types of oxidative addition reaction have been observed, including insertion of rhodium into the Cα–H bond of a methyl ketone. The first isolation of stable acylrhodium(III) complexes from the reaction of rhodium(I) complexes with aldehydes is reported, and an improved method for preparing rhodium(III) porphyrins is described.
TL;DR: The crystal structure of bromo(tetraphenylporphyrin)iron(rn), BrFe{C20N4Hs(CSH5)4}, has been determined at 295 K by X-ray diffraction and refined by least squares to a residual of 0.052 as discussed by the authors.
Abstract: The crystal structure of bromo(tetraphenylporphyrin)iron(rn), BrFe{C20N4Hs(CSH5)4}, has been determined at 295 K by X-ray diffraction and refined by least squares to a residual of 0.052 (2689 'observed' reflections). Crystals are monoclinic, PZ1/c, a 10.191(2), b 16.121(5), c 23.223(4) A, a ll5.34(1)", Z 4. The iron atom lies out of the N4 plane of the porphyrin ligand by 0.49 A,
TL;DR: The N.M.R. spectra of ferrous four-coordinated octaethyl porphyrin, deuteroporphyrin IX dimethylester, meso-tetraphenyl porphin and mesotetra(ααα-o-pivalamidophenyl)porphin (the so-called ‘picket fence’ porphrin) were analyzed in this article.
Abstract: The N.M.R. spectra of ferrous four-coordinated octaethylporphyrin, deuteroporphyrin IX dimethylester, meso-tetraphenylporphin and mesotetra(αααα-o-pivalamidophenyl)porphin (the so-called ‘picket fence’ porphyrin) show that these paramagnetic complexes are in the same spin state in non-polar solvents. The isotropic paramagnetic shifts have been analysed using fluorine substituted tetraphenylporphins as probes for the estimation of the pseudocontact contribution to the observed shifts. The anisotropy of the pseudocontact interaction and the distribution pattern of the contact hyperfine interaction suggest that the spin state of these complexes corresponds to S=1. The electronic relaxation time for this configuration is very short, (T 1=5 × 10-13s), enabling the observation of high resolution spectra for these axially non-coordinated ferrous prophyrins.