Showing papers on "Porphyrin published in 1969"

Porphyrins XIV. Theory for the luminescent state in VO, Co, Cu complexes

Abstract: The normal triplet state of closed shell metal porphyrins becomes a “tripdoublet” and a quartet in systems with one unpaired d electron. Exchange integrals between metal d and porphyrin π-electrons give intensity to the tripdoublet and set the tripdoublet-quartet energy gap. These integrals are evaluated theoretically giving tripdoublet radiative lifetimes between 26 and 1450 μsec and tripdoublet-quartet energy gaps in the range 156 to 639 cm−1 for the metals and porphyrin skeletons considered. Spinorbit coupling similarly gives intensity to the quartet and causes a zero field splitting dependent on a parameter Z which has value 0.7, 3.5, 20.4, 21.6 cm−1 for Zn (triplet), Cu, Co and VO complexes. Theory predicts that the intensity ratio of 0−1 to 0−0 bands will be very low for the tripdoublet but stronger for the quartet. Existing experimental evidence shows that luminescence comes from both the tripdoublet and the quartet states, their relative importance varying with metal, porphyrin skeleton, and temperature.

Mössbauer Studies of Bonding in Iron Porphyrin–Ligand Systems

Abstract: Mossbauer and electron paramagnetic resonance (EPR) spectra of several iron porphyrins have been obtained. The Mossbauer data for a series of high‐spin pentacoordinated iron (III) compounds establish that both the electric field gradient and the zero‐field splitting of the ionic Sz2 states follow the order fluoro

Nuclear magnetic resonance study of the association of porphyrins in chloroform solution. Mesoporphyrin IX dimethyl ester and its nickel chelate

Abstract: The proton nmr spectra of chloroform solutions of mesoporphyrin IX dimethyl ester and its nickel chelate exhibit an appreciable concentration dependence, all peaks shifting downfield upon dilution. This dilution shift is greater for the nickel chelate. The spectra of both porphyrins exhibit additional fine structure at higher concentrations. These results are interpreted in terms of porphyrin association with equilibrium between monomer and dimer forms. In the dimer two porphyrin molecules are stacked one above the other with the planes of the molecules parallel and separated by 10.0 A in the mesoporphyrin and 7.9 A in the chelate. In the nickel chelate, association is enhanced by the slight affinity of the nickel for further coordination. The fine structure can be accounted for by a lateral displacement of one molecule in the dimer relative to the other. This displacement is caused by steric interference of the longer side chains. No attempt was made to calculate the magnitude of the displacement for either porphyrin.

Molecular complexes of porphyrins

Abstract: Intermolecular complexes between several metal porphyrins and series of both conventional acceptors and donors have been studied in organic solvents. The stability constants and absorption spectra of the complexes have been measured. It is suggested that one of the factors contributing to stability is the matching of the sizes of the porphyrin and the donor or acceptor, but that this is not always dominant.

Electronic structure of iron in porphyrin complexes

Abstract: In the present paper I should l i e to discuss the electronic structure of the iron atom in heme, which is the well-known prosthetic group of hemoproteins. Since heme is a molecule consisting of a porphyrin and an Fe atom, the problem of the electronic structure of the Fe atom in heme is a part of the problem of the electronic structure of hemes. Many experimental results, however, particularly those of magnetic measuremWs, can be explained and discussed from the atomic viewpoint, in which the Fe atom or ion is considered to be subjected to electrostatic and other influences due to surrounding atoms such as the pyrrole and imidazole nitrogens. We can use ligand field theory, which has proved very effective in theoretical interpretations of energy levels and other electronic properties of coordination compounds of metallic ions. The heme found in Hb and Mb has the structure shown in FIGURE 1 ;the porphyrin of this heme is called protoporphyrin, and has two vinyl groups and two propionic acid groups, as well as methyl groups, attached to peripheral carbon atoms. Pi electrons of vinyl groups are conjugated with those of the main porphyrin ring. If we disregard these “tails,” the porphyrin and the heme possess tetragonal symmetry. The porphyrin is essentially planar, but there are evidences from x-ray analysis of hemes and myoglobin tha: the Fe atom is sometimes located above the porphyrin plane by as much as 1/2 A. The geometry of hemin chloride, separated from protein, has been measured in detail by Konig’ by the x-ray diffraction method, and the result is shown in FIGURE 2. This shows that the Fe atom is actually out of the porphyrin plane, and the symmetry of the molecule viewed from the Fe atom is approximately C In the following, a Cartesian coordinate system is introduced, with its origin at Fe nucleus, z axis perpendicular to the porphyrin plane, and x, y axes parallel to lines connecting pyrrole nitrogens, which are located diagonally opposite. These four pyrrole nitrogen atoms constitute the four ligands of the Fe atom under consideration. In the case of the native hemes in which we are interested, the Fe atom is further coordinated by another nitrogen atom of the imidazole of histidine. This nitrogen atom is the fifth ligand, and is situated approximately on the negative z axis. The plane of the imidazole ring is roughly perpendicular to the porphyrin plane, and the tetragonal symmetry is reduced, if we take the imidazole into account. Furthermore, at the sixth coordination point on the positive z axis, different kinds of small molecules and atomic ions can be coordinated, at least in myoglobin and hemoglobin. The reversible attachment of oxygen molecule at the sixth position is important in the physiological function of these molecules. Now, hemes can include the reduced and oxydized forms. The Fe atom exists in ferrous states in the reduced form and in ferric states in the oxidized form. The following abreviations are used for hemoglobins and myoglobins: Hb(FeZ+)X, for the hemoglobin whose hemes are in reduced form, Hb(FeS+)X for the oxidized form, and similar designations for myoglobins. Here X denotes the ligand which

Thermodynamics of pyridine and 1-alkyl-pyridinium complexes of protohaemin in aqueous solution.

Abstract: 1 In alkaline aqueous solution (pH > 10) protohaemin forms a green coloured pyridine complex containing two ligands per haemin dimer. The thermodynamics of this reaction is characterized by a considerable entropy change due to hydrophobic interactions between both partners. 2 Similar haemin complexes are formed by N-alkyl-pyridinium halides. The absorption spectra are nearly identical to those of the corresponding pyridine complexes although there is no possibility of interaction with the positively charged haemin iron. Pyridinium cations develop a higher affinity towards haemin than the neutral pyridines. This behaviour is attributed to electrostatic attractions between the propionylic groups of porphyrin and the positively charged pyridinium salts. 3 The introduction of methyl groups intensifies the haemin complex stability both of the pyridines and the pyridinium salts. In order of increasing methylation of the ligands the reaction entropy increases. 4 Following the substitution of pyridine in position 4 by a cyano group or following the transition from N-alkyl-pyridinium halides to N-alkyl-quinolinium halides the affinity towards haemin increases and the thermodynamics show a decrease of the reaction enthalpy whilst the entropy of the system changes only little. For this behaviour π-donor-acceptor interactions should be responsible. 5 The results demonstrate the contribution of several types of chemical bond in the reaction of protohaemin with ligands. Apart from the well investigated coordinative linkage to the iron atom, π-donor-acceptor and hydrophobic interactions between ligands and the porphyrin system as well as ionic bonds between the propionylic groups of the porphyrin and positively charged ligands contribute to their haemin complex formation. 6 The significance of the results is discussed with regard to the haemin-protein interaction in haemoproteins.

Trace porphyrin complexes - Fluorescence detection by demetallation with methanesulfonic acid.

Abstract: A method is described for the detection and spectral examination of traces of porphyrin complexes by controlled demetallation and spectrofluorometry. By carrying out the demetallation with methanesulfonic acid in the optical cell, difficulties connected with handling losses and introduction of contamination are minimized. The method is sensitive to quantities as low as 0.05 ng.

Effect of Oxygen on Heme and Porphyrin Accumulation from δ-Aminolevulinic Acid by Suspensions of Anaerobically Grown Staphylococcus epidermidis

Abstract: The effect of various conditions on the accumulation of porphyrins and heme by resting suspensions of anaerobically grown cells of Staphylococcus epidermidis was examined Anaerobically grown cells contain 10 to 15% of the amount of protoheme found in cells grown aerobically Resting suspensions of anaerobically grown cells, when incubated aerobically in buffer with delta-aminolevulinic acid and glucose for 60 min, exhibited a fourfold increase in protoheme content At high levels of delta-aminolevulinic acid, there was also a significant accumulation of porphyrins with the solubility and chromatographic properties of coproporphyrin and uroporphyrin Protoporphyrin was not accumulated When oxygen was excluded from the incubation mixture, accumulation of protoheme was prevented, but accumulation of coproporphyrin and total porphyrin was enhanced Nitrate served as an electon acceptor as indicated by its reduction to nitrite; however, nitrate did not substitute for oxygen in causing the accumulation of protoheme These results suggested that oxygen is required for one of the late steps of heme synthesis in S epidermidis, possibly for the conversion of coproporphyrinogen to protoporphyrin The inability of nitrate to substitute for oxygen suggests a role for molecular oxygen as a substrate rather than as an electron acceptor for heme synthesis

Proton magnetic resonance spectra of porphyrins. Part VI. Complex formation between nickel(II)–mesoporphyrin IX dimethyl ester and piperidine

Abstract: Complex formation between nickel(II)–mesoporphyrin IX dimethyl ester and piperidine has been studied by 1H n.m.r. resonance. The dependence of the chemical shifts of the porphyrin protons on the piperidine concentration indicates that only one ligand is added, and the alternation in the sign of the shifts of the meso- and β-CH protons suggests that delocalisation of the unpaired spin occurs mainly via a π-mechanism.In order to obtain a quantitative interpretation of the results it is necessary to correct for simultaneous formation of a chloroform–piperidine complex. A separate study on this system gave K ca. 0·2 l. mole–1 and a low-field complex shift of the chloroform proton of 2·08 p.p.m. The porphyrin shifts when combined with these results are consistent with a contact shift of the meso-protons of ca. 103 Hz and an equilibrium constant for the 1 : 1 complex of ca. 10–2 l. mole–1.

Formation of porphyrin isomers from porphobilinogen by various hemolysates of red cells from bovine and human subjects with erythropoietic (uro-) porphyria.

Abstract: Hemolysatc* of crytbrocyte» from bovine and human subject& having erythropoictic porphyria, and from normal subject*,, have been incubated with PBG*>, Cell* obtained by differential centrifugation or osmotic lysis as well as total cells were hcmolyxcd. The proportion utilised or unaccounted for after incubation was generally much greater with the porphyric than the normal Kemolysates, with the lesser than the greater density fractions, and with the bemolysate» of the osmoticalfy more fragile cells, Larger amount» of PBG in relation to cells left« protection against ambient temperature and longer incubation were associated with greater formation of type J porphyrim by normal a» well as porphyric hcmolysatc*. With more nearly optima) conditions, only or mainly type III was in evidence in the normal while the porphyric hcmolysates formed both T and II). Porphyric hemolysatcs regularly formed larger amounts of protoporphyrin 9 (HI) than the normal. After repeated bleeding of bovine porphyries, the hcmolysates formed larger amount» of porphyrin arid significantly greater proportions of type J isomer than before bleeding. This is interpreted a» an enhanced dcaminasc-isomcrasc imbalance in young cells. Under the same conditions the normal bovine hemo« Jysates formed mainly type III. These observations are considered in respect to the question whether the normobla&t» are unior bimodal in terms of the genetic abnormality, i. e,, the dcaminasc-isomerasc imbalance. The present evidence is in better accord with a unimodal distribution,

Application of gas chromatography and mass spectrometry to porphyrin microanalysis - A study of homologous porphyrin series in ancient biological residues

Abstract: Gas chromatography and mass spectrometry applied to porphyrin microanalysis, studying homologous porphyrin series in ancient sediments and oils

Manganese porphyrin complexes ii-electronic spectroscopy and structure

Abstract: In green plant photosynthesis several transition elements are needed for normal function of the chloroplast. One of these, manganese, is required for the oxygen evolution that occurs in photosystem II.1 Several investigations have suggested, on the basis of photochemical experiments, that the manganese is involved in the breakdown of a primary oxidant which is formed in the photolytic splitting of water.2 The nature of the primary oxidant and the detailed description of the action of manganese on it are still to be determined. It appears that there is one manganese atom present per 50 chlorophylls in the photosynthetic unit.3 The metal atoms are physically located in the protein portion of photosystem II.4 The manganese is difficult to remove from the chloroplast and no physical property (namely, ESR spectra) of the metal can be observed in vivo. The ligand atoms binding the metal are not known. The manganese complex does not appear to be a special chlorophyll molecule associated with chlorophyll in the lipid phase.4 The evidence, however, does not rule out a similar complex contained in the protein phase. Recent evidence4 indicates that the manganese is in a high oxidation state, +3 or +4. Calvin has suggested that the manganese atoms in the chloroplast are bound to porphyrin-like ligands.5 In fact, it has been demonstrated that porphyrin complexes can be generated in which the manganese atom is in the + 3 and +4 oxidation states.6

Heme and globin synthesis and related parameters in blood from the x-irradiated duck.

Abstract: Decreases in the rates of heme and globin synthesis, turnover of free protoporphyrin, transfer of plasma iron to erythrocytes, and incorporation of plasma iron into heme in duck blood in vitro and in the concentration of protoporphyrin and proportion of reticulocytes in blood were observed at 1 to 8 days after x-irradiation of the animal. The decreases in rates and porphyrin concentration apparently were a consequence of the decrease in reticulocytes-that is, of erythropoietic arrest. The various parameters were found unchanged at 5 and 30 minutes after irradiation of the animal and after direct irradiation of blood. The estimations of synthesis and porphyrin turnover were based on incorporation of $\text{glycine-}2\text{-}{}^{14}{\rm C}$, the other rates on incorporation of labeled iron.

Metabolism of porphyrin and heme on experimental chloroma

Abstract: 緑色腫は白血病のうちでも,その細胞集団が肉眼的に緑色を呈することを特徴としている. ratの実験的緑色腫も多量のporphyrinを含有している.この大量のporphyrin蓄積の原因として, 1) porphyrinの異常合成, 2) porphyrinよりhemeの経路の障害が考えられる. 1), 2)の検討を行なうことによりporphyrin合成系の追求をし,次の結果をえた.(1)実験的緑色腫のporphyrinは,その約90%はprotoporphyrinである. (2)ALA synthetase活性値の増大がある. (3)porphyrinへ鉄を挿入させる反応は酵素反応である. (4)proto-porphyrinからheme合成能も存在する.(5)heme合成は生成されるgorphyrinに比して少ない.以上の結果からporphyrinの異常な蓄積の原因は主としてALA synthetase活性の増大とheme合成の比較的障害によるものと考えられ,これらをfeedback mecnanismおよびoperon説によつて考察を加えた.

Coordination Studies of Iron(II) Protoporphyrin IX and Iron(II) Hematoporphyrin IX with 4,4′-Dipyridyl and other Nitrogenous Bases

Abstract: The results of spectral studies of iron(II) protopor-phyrin IX and iron(II) hematoporphyrin IX with several substituted pyridines are reported. The existence in solution of an iron(II) porphyrin complex coordinated to a water molecule and to a substituted pyridine was shown by isolation of the complex from solution. The complex isolated was dimeric inono-4,4′-dipyridyl diaquo iron(II) hematoporphyrin. Addition of ethanol to the aqueous solvent inhibits coordination of iron(II) porphyrins with substituted pyridines. The protoporphyrin ring enhances coordination relative to the hematoporphyrin ring.

Porphyrin analysis in a case of a hyporegenerative anaemia.

Abstract: Porphyrins are fractionated by a pH gradient on TBP columns) according to the number of carboxyl groups(n); isomers, with the exception of CP-I/III, can be separated on the same columns, using IN hydrochloric acid as elutriant. For identification, the predominant fractions were decarboxylated to the corresponding coproporphyrin derivatives. Separation on activated silica gel plates in the 2.6-lutidine/water system before and after decarboxylation revealed the degree of decarboxylation and the isomeric type by comparison of the J?F obtained with those of pure reference substances. In order to characterize the different fractions, some additional parameters are used: 1. The centre of the dissociation interval XD of the porphyrins, the carboxyl groups of which are converted into the anionic form. These values can be obtained with small amounts of material (min. l ^) and a high accuracy (± 0.05 pH units) with the aid of the pH gradient on TBP columns. 2. The peak position of the soret band Ap of the porphyrins, before and after decarboxylation. This determination can be carried out with amounts down to 0.2 ̂ g (CHCI = l.OON). 3. The retention time or volume of the single porphyrin fractions on TBP columns under standard conditions (CHCI = IN; Ts = 20°). By the methods described, it was possible to decompose the urinary porphyrin mixture of Patient U. into at least 27 fractions, most of which ranged in a total percentage of 0.1—2%. This finding showed clearly that not only intermediate compounds of the haem synthesis are present in the mixture, but also fractions which differ from those with respect to their substituents (pseudoporphyrins). From the iron kinetic studies with Fe and the pattern of porphyrins in fig. 16 we may assume that the production of haem is also inhibited by a disordered reutilization of the iron. !:

Porphyrins and their metabolites

Abstract: This chapter discusses the application of fluorometry as investigative tool for the analysis of animal porphyrins and their metabolites. Porphyrins are among the most highly fluorescent substances in nature, and their spectral characteristics were among the first to be determined. Assays of heme, porphyrins, and their metabolites in tissues, urine, and feces provide valuable information in clinical diagnosis. Porphyrins are a major source of the autofluorescence of animal tissues. A microfluorospectrophotometer was developed that was sufficiently sensitive to detect as little as 10 –10 g of porphyrin in tissue sections. At these levels, Runge was able to obtain emission spectra from various animal tissues and identify the porphyrin by comparison with spectra of known porphyrins. Speciflc porphyrins in tissues and plasma were identified following administration of certain drugs. An interesting application of fluorescence has been in the identification of porphyrins formed under experimental conditions designed to simulate geochemical conditions. Hodgson observed porphyrin fluorescence following an electric discharge through a gaseous mixture of ammonia, methane, and water.