Moessbauer spectra of some porphyrin complexes with pyridine, piperidine, and imidazole

Epstein, Lawrence; Straub, Darel K.; Maricondi, Chris

doi:10.1021/ic50055a024

Cited by 159 publications

(73 citation statements)

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“…Because these Mossbauer parameters are so similar to those found in hemin imidazole (28) or in the acid form of metmyoglobin and cytochrome C peroxidase (16), it is reasonable to assume that iron coordination in the c component is similar to that found in the compounds mentioned. The absence of this component in adult cells indicates that the concentration of this unidentified oxidized Hb in these cells is less than 2%.…”

Section: Discussionmentioning

confidence: 67%

Oxidative Stress in Newborn Erythrocytes

et al. 1991

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ABSTRACT. Phenylhydrazine (PHZ) exposure is used to study in vitro red cell aging mechanisms dependent on Hb oxidation. The effect of PHZ on normal neonatal red blood cells was studied in unseparated blood and after separation into light and heavy cells. PHZ Neonatal RBC differ from adult RBC in several of their characteristics. Most of the intracellular Hb is HbF, a highaffinity Hb adapted to intrauterine life (1). Most of the enzymatic activities in neonatal RBC are greater than those in adult RBC and may be attributed to their younger mean age (2). However, it is known that neonatal RBC have a shorter life-span (2, 3). The cause of this shortened survival time has not yet been clarified. Recently, red cell senescence in adults has been correlated with the oxidation of intracellular Hb to methemoglobin and hemichromes (4). Low et al. (4) have shown that exposure of normal cells to PHZ oxidizes the Hb to methemoglobin and hemichromes. These oxidized Hb products attach themselves to the intracellular portion of band 3 membrane protein, causing changes in surface antigenicity and increased IgG binding. Similar changes have been demonstrated in untreated cells containing pathologic Hb, such as Hb Koln, known for its high affinity to oxygen and its lack of stability (5).Our purpose was to assess the impact of oxidative stress, induced by low dose of PHZ, on neonatal erythrocytes, specifically: 1 ) to study Hb oxidation in neonatal and adult cells by two methods (measuring total oxidized Hb by spectrophotometry and identifying specific oxidation products by Mossbauer spectra) and 2) to see whether neonatal heavy cells, enriched with old cells, are more sensitive to oxidation than lighter and younger cells. MATERIALS AND METHODS Collection and preparation of blood samples. Blood sampleswere obtained from umbilical veins immediately after delivery. Newborn infants, whose mothers had experienced normal pregnancies, were all healthy and mature. Blood counts and glucose-6-phosphate dehydrogenase activity were normal. Control studies were performed using blood drawn from healthy adult volunteers according to the conditions of the Helsinki Declaration. The blood was collected into heparinized tubes; the buffy coat and plasma were removed and the cells were washed three times in PBS, pH 7.4.The cells were studied both as a whole, unsevarated vovulation and after separation on a Percoll gradient. he cellskere separated into 10% high ("old") and 10% low ("young") density cells, according to Ellory and Young (6). The cells were exposed to PHZ at final concentrations of 0.1-10 mM in PBS at hematocrit of 20%, pH 7.4, for 45 min at 37°C (7). Parallel control studies were performed by means of incubation of cells in PBS alone at 37°C or room temperature.

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Section: Discussionmentioning

confidence: 67%

Oxidative Stress in Newborn Erythrocytes

et al. 1991

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“…It was achieved by the reaction of (piperidine)2(TPP)Fe(II) [14,15] with CO in CH2C12. However, the resulting carbonyl complex is not very stable.…”

Section: Resultsmentioning

confidence: 99%

“…(Piperidine)2(TPP)Fe(II) *) was prepared according to a published procedure [14,15]. Photolysis procedure.…”

Section: Methodsmentioning

confidence: 99%

Photochemistry of Biologically Important Transition Metal Complexes. II. Carbonylpiperidinetetraphenylporphine Complexes of Iron(II) and Ruthenium(II)

Vogler

Kunkely

1976

Ber Bunsenges Phys Chem

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Absorptionsspektren, sichtbar und ultraviolett / Emissionsspektren / Komplexverbindungen / PhotochemieCarbonylpiperidinetetraphenylporphineiron(II) and dipiperidinetetraphenylporphineiron(II) do not emit the characteristic porphyrin phosphorescence. It is suggested that the porphyrin singlets initially excited undergo an efficient radiationless transition to an excited state which lies below the lowest porphyrin triplet. It is concluded that this lower excited state initiates the release of coordinated CO which has been observed for a variety of biologically important carbonylporphyrins of iron(II). It is assumed that the reactive state is either an excited CT or, more likely, a LF state. If iron(II) is replaced by the homologous ruthenium(II) the lowest LF excited state lies apparently at higher energies than the lowest porphyrin triplet due to the larger LF splitting of the heavier ruthenium. Hence carbonylpiperidinetetraphenylporphineruthenium(II) dissolved in piperidine shows the typical porphyrin phosphorescence, but undergoes also a simultaneous photosubstitution of CO by piperidine with low efficiency. Quantum yields of CO release and relative emission intensities were determined at two irradiating wavelengths (412 and 530 nm) and at two temperatures (25 °C and 80 °C). The results led to the suggestion that the reactive LF state can be populated from the lower porphyrin triplet by thermal activation. In addition to this thermally activated photolysis a temperature independent contribution seems to be important at higher excitation energies. It is assumed that the deactivation cascade starting from higher excited singlets of the porphyrin ligand includes the population of the reactive LF state before the lowest porphyrin triplet is reached. It is also possible that it is not a LF state but a low-lying CT state which is responsible for the photoreactivity.Carbonylpiperidintetraphenylporphineisen(II) und Dipiperidintetraphenylporphineisen(II) zeigen nicht die charakteristische Porphyrinphosphoreszenz. Es wird angenommen, daß die Porphyrinsinguletts, die zunächst angeregt werden, einer raschen strahlungslosen Desaktivierung zu einem angeregten LF

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“…[61] The effect of differing trans bond distances is likely the difference that imidazoles are modest π-electron-donors compared to the modest π-accepting character of pyridine. [62,63] Clearly, one can expect that the cyanide and pyridine will compete for the same iron π density whereas the imidazole can π-donate and hence form a stronger bond.…”

Section: Discussionmentioning

confidence: 99%

New Insights on the Electronic and Molecular Structure of Cyanide-Ligated Iron(III) Porphyrinates

Noll

Schulz

et al. 2007

Inorg. Chem.

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The preparation and characterization of several new cyanoligated six-coordinate low-spin iron(III) porphyrinates are reported. The synthesis and structure of the new bis(cyanide) derivative K(222)] [Fe(TMP)(CN) 2 ] (TMP= tetramesitylporphyrinate) is described. Three mixed-ligand species of the general form [Fe(Porph)(CN)(L)], where L = 1-methylimidazole or pyridine, have also been prepared and structurally characterized. All complexes have been studied with EPR spectroscopy in frozen solution and in microcrystalline form. In some cases, especially those of the bis(cyanide) derivative above and the previously reported [Fe(TPP)(CN) 2 ] − , there are significant differences in the EPR spectra as a result of the state change. These spectral differences can be correlated with changes in the electron configuration that are the likely result of a differing environment of the coordinated cyanide ligands; core conformation and electronic structure of the porphyrin ligand are unlikely to play a role. All four new complexes and [Fe(TPP)(CN) 2 ] − have been studied by Mössbauer spectroscopy with variable temperature and applied magnetic field measurements. The sign of the quadrupole splitting value has been established as negative. These measurements have allowed us to give estimates of the energy difference between the two close-lying d π (d xz and d yz ) orbitals. These splitting values range from ∼267 cm −1 for [Fe(TPP)(CN) 2 ] − to ∼614 cm −1 for [Fe(TPP)(CN)(Py)].

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Moessbauer spectra of some porphyrin complexes with pyridine, piperidine, and imidazole

Cited by 159 publications

References 1 publication

Oxidative Stress in Newborn Erythrocytes

Oxidative Stress in Newborn Erythrocytes

Photochemistry of Biologically Important Transition Metal Complexes. II. Carbonylpiperidinetetraphenylporphine Complexes of Iron(II) and Ruthenium(II)

New Insights on the Electronic and Molecular Structure of Cyanide-Ligated Iron(III) Porphyrinates

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