BioAssay record AID 374059 submitted by ChEMBL: Inhibition of beta-hematin formation assessed as inhibition of flavoprotein polymerization at 5 to 100 mM after 48 hrs.
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The preparation from ferriprotoporphyrin IX (FP) in aqueous acid medium of the related pigments beta- and B-hematin [see G. Blauer and M. Akkawi, Biochem. Mol. Biol. Int. 35, 231 (1995)] is presented under different conditions. Both pigments are characterized by infrared spectra which differ in the range of 1600-1700 cm-1 in their strong bands with absorption peaks measured at 1648 +/- 2 cm-1 for B-hematin and at 1663 +/- 1 cm-1 for beta-hematin. The pH dependence of B-hematin formation at 37 degrees C and at different concentrations of acetic acid and FP exhibits a maximum yield near pH 4. The formation of beta-hematin at 70 degrees C shows high yield in 6 M acetic acid or in the presence of 0.028 M trichloroacetate at pH 4.6. The dependence of the yield of the pigments on the time and temperature of incubation, concentration of FP, and the presence of different electrolytes was investigated. Both B- and beta-hematin are either insoluble or very slightly soluble in different solvents at room
Our observations on the ability of Plasmodium parasites to develop without detectable Hz formation that are resistant to CQ indicate a novel mechanism of resistance against drugs that target Hb proteolysis. Interestingly, previous studies on CQ-resistant P. berghei lines revealed that parasites are more restricted to development in reticulocytes and produced less Hz (Platel et al., 1999). It has been proposed that CQ-resistance of parasites with reduced Hz is due to detoxification of hemin by elevated levels of glutathione in parasites inside reticulocytes, thus precluding heme-polymerization and preventing CQ activity (Platel et al., 1999; Fidock and DeSilva, 2012). However, our observations may provide a more direct explanation for CQ-resistance and reduced Hz production in these parasites, namely that these parasites, like the Δpm4Δbp2, digest less Hb in reticulocytes.. Our observations may have particular relevance for the human malaria parasite, Plasmodium vivax, which is also ...
Comparison of deuterium uptake between apo- and holo-PhuS was monitored after dilution into D2O. Samples were removed at various time points, and the exchange was quenched. Regions of the protein that undergo extensive exchange at the earliest time points reflect regions that are exposed to solvent and intrinsically unstructured or regions undergoing rapid equilibrium favoring the unstructured form. In contrast, exchange times on the scale of minutes to hours are more indicative of the flexibility of the secondary and tertiary structures of the protein. The peptide fragments provided 99% coverage for both the WT and H212R PhuS apo and holo forms (Fig. S1). Global examination at all time points for deuterium exchange in apo- vs. holo-PhuS shows significant protection on heme binding, indicative of an overall decrease in the flexibility and dynamics of the protein (gray bars in Fig. 1A). The PhuS heme binding site is between the proximal C-terminal helices (α6/α7/α8), the distal N-terminal ...
Haemozoin is a disposal product formed from the digestion of blood by some blood-feeding parasites. These hematophagous organisms such as Malaria parasites (Plasmodium spp.), Rhodnius and Schistosoma digest haemoglobin and release high quantities of free heme, which is the non-protein component of hemoglobin. A heme is a prosthetic group that consists of an iron atom contained in the center of a heterocyclic porphyrin ring. Free heme is toxic to cells, so the parasites convert it into an insoluble crystalline form called hemozoin. In malaria parasites, hemozoin is often called malaria pigment. Since the formation of hemozoin is essential to the survival of these parasites, it is an attractive target for developing drugs and is much-studied in Plasmodium as a way to find drugs to treat malaria (malarias Achilles heel). Several currently used antimalarial drugs, such as chloroquine and mefloquine, are thought to kill malaria parasites by inhibiting haemozoin biocrystallization. Black-brown ...
Malaria pigment hemozoin is generally considered to be a non-toxic, high-molecular-weight, parasitic storage form of undigested,toxic, host-hemoglobin-heme.Crude pigment, as present in infected erythrocytes and shed after schizont rupture, may be considered the natural diet ingested by macrophages in malaria-infected hosts. After ingestion by macrophages hemozoin persists in the lysosomes without being degraded. The heme-degrading enzyme, the heme-oxygenase, is not induced. Hemozoin is a powerfull source of radicals that generates lipoperoxides and derived, toxic hydroxyaldehydes such as 4-hydroxynonenal. High concentrations of 4-hydroxynonenal, which have been detected in hemozoin-fed macrophages, inhibit protein kinase C. Complexes between hydroxynonenal and protein kinase C have been detected in immunoprecipitated protein kinase C from hemozoin-fed macrophages. Hydroxynonenal-mediated inhibition of protein kinase C (and of other as yet unidentified enzymes and processes) may explain ...
Knockdown of ErbB3 suppresses HRG-β1-induced EMT in SK-BR-3 cells. The cells were transfected with control (Ctrl) or ErbB3 siRNAs and treated with 25 ng/ml of
Abstract: A recombinant bacterial expression system that generates 13C-labeled heme or 15N-labeled heme in functional cytochrome P450 enzymes and other heme-containing systems is reported here using a mutant strain of Escherichia coli (HU227) in which the HemA gene is inactive. By synthesizing several isotopomers of aminolevulinic acid with 13C or 15N at different locations, isotopes have been incorporated with high abundance into the heme cofactor of five different cytochrome P450 isoforms, along with one peroxidase. Confirmed both 13C- and 15N-incorporation; spectral and catalytic assays show the labeled enzymes produced in this system are functional.. Isotopic labeling of the heme cofactor in cytochrome p450 and other heme proteins. ...
TY - JOUR. T1 - Role of binding site loops in controlling nitric oxide release. T2 - Structure and kinetics of mutant forms of nitrophorin 4. AU - Maes, Estelle M.. AU - Weichsel, Andrzej. AU - Andersen, John F.. AU - Shepley, Donald. AU - Montfort, William R.. PY - 2004/6/1. Y1 - 2004/6/1. N2 - Nitrophorins are ferric heme proteins that transport nitric oxide (NO) from blood-sucking insects to victims. NO binding is tighter at lower pH values, as found in the insect salivary gland, and weaker at the pH of the victims tissue, facilitating NO release and subsequent vasodilation. Previous structural analyses of nitrophorin 4 (NP4) from Rhodnius prolixus revealed a substantial NO-induced conformational change involving the A-B and G-H loops, which rearrange to desolvate the distal pocket and pack nonpolar residues against the heme-ligated NO. Previous kinetic analyses revealed a slow, biphasic, and pH-dependent NO release, which was proposed to be associated with loop movements. In this study, we ...
The heme chaperone CcmE is a novel protein that binds heme covalently via a histidine residue as part of its essential function in the process of cytochrome c biogenesis in many bacteria as well as plant mitochondria. In the continued absence of a structure of the holoform of CcmE, identification of the heme ligands is an important step in understanding the molecular function of this protein and the role of covalent heme binding to CcmE during the maturation of c-type cytochromes. In this work, we present spectroscopic data that provide insight into the ligation of the heme iron in the soluble domain of CcmE from Escherichia coli. Resonance Raman spectra demonstrated that one of the heme axial ligands is a histidine residue and that the other is likely to be Tyr134. In addition, the properties of the heme resonances of the holo-protein as compared with those of a form of CcmE with non-covalently bound heme provide evidence for the modification of one of the heme vinyl side chains by the protein, most
Corynebacteria contain a heme uptake system encoded in hmuTUV genes, in which HmuT protein acts as a heme binding protein to transport heme to the cognate transporter HmuUV. The crystal structure of HmuT from Corynebacterium glutamicum (CgHmuT) reveals that heme is accommodated in the central cleft with His141 and Tyr240 as the axial ligands and that Tyr240 forms a hydrogen bond with Arg242. In this work, the crystal structures of H141A, Y240A, and R242A mutants were determined to understand the role of these residues for the heme binding of CgHmuT. Overall and heme environmental structures of these mutants were similar to those of the wild type, suggesting that there is little conformational change in the heme-binding cleft during heme transport reaction with binding and the dissociation of heme. A loss of one axial ligand or the hydrogen bonding interaction with Tyr240 resulted in an increase in the redox potential of the heme for CgHmuT to be reduced by dithionite, though the wild type was not
Predicted to have heme binding activity. Predicted to be involved in negative regulation of mitochondrial membrane potential; positive regulation of mitochondrial membrane permeability; and positive regulation of necrotic cell death. Localizes to the cytoplasm. Orthologous to human HEBP2 (heme binding protein 2 ...
99,210 (2 years) for "Acute kidney injury from antiviral drugs for herpes infections: A population-based study of older adults". $139,828 (2 years) for "Electrolyte Disorders from Common Medications: Risk and Mitigation". $119,920 (2 years) for "Preoperative Medications and Acute Kidney Injury: A VISION sub-study". $59,951 (1 year) for "Filtering Medline for Renal Information: Renal Sub-Filters". Lakshman Gunaratnam received $100,000 (I year) for "Exploiting KIM-1 signalling to ameliorate acute kidney injury through clearance of apoptotic cells". Daniel Hardy received $364,704 (3 years) for the project, "Molecular mechanisms underlying the in utero origins of hypercholesterolemia". Robert Hegele received $599,814 (5 years) for the project, "Genetic architecture of cardiometabolic risk in families and communities". David Heinrichs received $702,770 (5 years) for the project, "Role of iron and heme binding proteins in pathogenesis of Staphlococcus aureus". David Holdsworth received $752,848 (5 ...
1D06: Sensory mechanism of oxygen sensor FixL from Rhizobium meliloti: crystallographic, mutagenesis and resonance Raman spectroscopic studies
We studied effects of NO-donor iron nitrosyl complex with N-ethylthiourea ligand (ETM) on normal or tumor-derived cell lines. ETM was mildly toxic to most cell lines studied except the human glioma cell line A172 that proved to be highly sensitive to the complex and underwent cell death after ETM exposure. The high susceptibility of A172 cells to ETM was attributed to its NO-donor properties since no toxicity was detected for the N-ethylthiourea ligand.
In this study, some differences between heme polymerase activity in rings and trophozoites of P. falciparum have been detected. Although equal numbers (2.7 × 107) of infected erythrocytes were used, mean hemozoin synthesis in ring hemolysate was only 50% of that in trophozoites. The initial quantity of hemozoin in the lysates was also lower in the rings than in the trophozoites, but Slater and Cerami (1992) have shown that hemozoin by itself does not have heme polymerase activity. They showed that heme polymerase activity increased linearly with protein concentration in parasite lysate. Obviously, hemoglobin-free P. falciparumparasites are expected to contain less protein at the ring than at the trophozoite stage, and this may account for the differences in hemozoin synthesis observed in the present study. However, Dorn et al. (1995) have shown that protein-free hemozoin can promote formation of additional hemozoin. In the present study, there was more preexisting hemozoin in the trophozoite ...
The long-term objective of this project is to understand the structure-function relationship in oxygen-linked respiratory hemoproteins such as myoglobin and hem...
During the erythrocytic stage, the malaria parasite digests host cell haemoglobin into amino acids. Toxic haeme is released and is incorporated into an insoluble non-toxic crystal called haemozoin. Haemozoin is released ...
Very little is known about heme transport in eukaryotes and a heme-specific transport uptake systems have not been identified in yeast. Heme is synthesized in m...
Steinbach, P.J.; Ansari, A.; Berendzen, J.; Braunstein, D.; Chu, K.; Cowen, B.R.; Ehrenstein, D.; Frauenfelder, H.; Johnson, J.B.; Lamb, D.C.; Luck, S.; Mourant, J.R.; Nienhaus, G.U.; Ormos, P.; Philipp, R.; Xie, A.; Young, R.D ...
1LH1: X-Ray Structural Investigation of Leghemoglobin. Vi. Structure of Acetate-Ferrileghemoglobin at a Resolution of 2.0 Angstroms (Russian)
TY - JOUR. T1 - The crystal structure of nitrophorin 2. A trifunctional antihemostatic protein from the saliva of Rhodnius prolixus. AU - Andersen, John F.. AU - Montfort, William R.. PY - 2000/9/29. Y1 - 2000/9/29. N2 - Nitrophorin 2 (NP2) (also known as prolixin-S) is a salivary protein that transports nitric oxide, binds histamine, and acts as an anticoagulant during blood feeding by the insect Rhodnius prolixus. The 2.0-Å crystal structure of NP2 reveals an eight-stranded antiparallel β-barrel containing a ferric heme coordinated through His57, similar to the structures of NP1 and NP4. All four Rhodnius nitrophorins transport NO and sequester histamine through heme binding, but only NP2 acts as an anticoagulant. Here, we demonstrate that recombinant NP2, but not recombinant NP1 or NP4, is a potent anticoagulant; recombinant NP3 also displays minor activity. Comparison of the nitrophorin structures suggests that a surface region near the C terminus and the loops between β strands B-C and ...
Some of the chemical and physico-chemical characteristics of the respiratory blood pigment chlorocruorin have been dealt with in previous papers (H. M. Fox, 1926, 1932). An experimental investigation is described below of the blood circulation in sabellids and serpulids. These polychæte worms have chlorocruorin in solution in their blood plasma. The work was done in part in the Marine Biological Laboratories of Banyuls, Plymouth, and Tamaris, and my sincere thanks are due to the Directors and staffs of these institutions for their welcom and help. 1. The Normal Blood Circulation. In sabellids and serpulids both the anatomy of the blood system and the mode of blood circulation are peculiar and different from those in other polychæte worms. The best description of the anatomy of the blood system is that of Meyer (1888) ...
Severe malarial anemia (SMA) is a leading cause of mortality among children in sub-Saharan Africa. Although the novel cytokine, interleukin (IL)-23, promotes anemia in chronic inflammatory diseases, the role of IL-23 in SMA remains undefined. Since IL-23 and IL-12 share the IL-12p40 subunit and IL-12Rbeta1 receptor, and are down-regulated by IL-10, relationships among these cytokines were explored in Kenyan children with varying severities of malarial anemia. Children with malarial anemia had increased circulating IL-23 and IL-10 and decreased IL-12 relative to healthy controls. Enhanced anemia severity and elevated parasitemia were associated with increased IL-10 relative to IL-23 and IL-12. Further exploration of the relationships among the cytokines using an in vitro model in which peripheral blood mononuclear cells were treated with synthetic hemozoin (sHz, malarial pigment) revealed that IL-12p35 and IL-23p19 transcripts had a sustained induction over 72 h, while IL-12p40 and IL-10 message ...
Tryptophan fluorescence quenching is a type of fluorescence spectroscopy used for binding assays. The assay relies on the ability to quench the intrinsic fluorescence of tryptophan residues within a protein that results from changes in the local environment polarity experienced by the tryptophan(s) upon the addition of a binding partner or ligand. The quenching can arise from local changes near the interaction site or from binding-induced conformational changes. In cases where the titrant absorbs at or near the excitation or emission wavelengths of tryptophan, significant quenching can occur even without an interaction. This is known as the inner filter effect. This protocol describes how to use tryptophan fluorescence quenching to investigate the binding affinity of a protein for its partner/ligand and how to check and correct for the inner filter effect. As an example, we measured the binding affinity of the haem-binding protein, HusA, from Porphyromonas gingivalis for haem, and showed how we
Hemoproteins have diverse biological functions including the transportation of diatomic gases, chemical catalysis, diatomic gas detection, and electron transfer. The heme iron serves as a source or sink of electrons during electron transfer or redox chemistry. In peroxidase reactions, the porphyrin molecule also serves as an electron source. In the transportation or detection of diatomic gases, the gas binds to the heme iron. During the detection of diatomic gases, the binding of the gas ligand to the heme iron induces conformational changes in the surrounding protein.[5] In general, diatomic gases only bind to the reduced heme, as ferrous Fe(II) while most peroxidases cycle between Fe(III) and Fe(IV) and hemeproteins involved in mitochondrial redox, oxidation-reduction, cycle between Fe(II) and Fe(III). It has been speculated that the original evolutionary function of hemoproteins was electron transfer in primitive sulfur-based photosynthesis pathways in ancestral cyanobacteria-like organisms ...
A novel class of benzoheterocyclic analogues of amodiaquine designed to avoid toxic reactive metabolite formation was synthesized and evaluated for antiplasmodial activity against K1 (multidrug resistant) and NF54 (sensitive) strains of the malaria parasite Plasmodium falciparum. Structure-activity relationship studies led to the identification of highly promising analogues, the most potent of which had IC50s in the nanomolar range against both strains. The compounds further demonstrated good in vitro microsomal metabolic stability while those subjected to in vivo pharmacokinetic studies had desirable pharmacokinetic profiles. In vivo antimalarial efficacy in Plasmodium berghei infected mice was evaluated for four compounds, all of which showed good activity following oral administration. In particular, compound 19 completely cured treated mice at a low multiple dose of 4×10mg/kg. Mechanistic and bioactivation studies suggest hemozoin formation inhibition and a low likelihood of forming ...
Hemozoin is generally considered a waste deposit that is formed for the sole purpose of detoxification of free heme that results from the digestion of hemoglobin by Plasmodium parasites. However, several observations of parasite multiplication, both in vertebrate and invertebrate hosts are suggestive of a wider, but overlooked, metabolic role for this product. The presence of clinical peripheral blood samples of P. falciparum with high parasitemia containing only hemozoin-deficient (non-pigmented) asexual forms has been repeatedly confirmed. Such samples stand in contrast with other samples that contain mostly pigmented circulating trophozoites and gametocytes, indicating that pigment accumulation is a prominent feature of gametocytogenesis. The restricted size, i.e. below detection by light microscopy, of hemozoin in asexual merozoites and ringforms of P. falciparum implies its continuous turnover, supporting a role in metabolism. The prominent interaction of hemozoin with several antimalarial ...
The ability to replace the native heme cofactor of proteins with an unnatural porphyrin of interest affords new opportunities to study heme protein chemistry and engineer heme proteins for new functions. Previous methods for porphyrin substitution rely on removal of the native heme followed by porphyrin reconstitution. However, conditions required to remove the native heme often lead to denaturation, limiting success at heme replacement. An expression-based strategy for porphyrin substitution was developed to circumvent the heme removal and reconstitution steps, whereby unnatural porphyrin incorporation occurs under biological conditions. The approach uses the RP523 strain of Escherichia coli, which has a deletion of a key gene involved in heme biosynthesis and is permeable to porphyrins. The expression-based strategy for porphyrin substitution detailed here is a robust platform to generate heme proteins containing unnatural porphyrins for diverse applications ...
The expression of recombinant protein is essential for the investigation of the functions and properties of heme-containing protein as an electron carrier. For the expression of fully active recombinant protein, conversion of the expressed apoprotein into holoprotein is the most important and difficult problem. In this study, a system was developed for the production of heme-containing protein in a pure, recombinant holoprotein form, using the bovine cytochrome b5 tryptic fragment and Escherichia coli bacterioferritin as heterologous and homologous heme-containing model proteins, respectively. This system is based on the slow synthesis of recombinant apoprotein, which can maintain the balanced consumption of amino acids between protein synthesis and heme synthesis, so that the synthesized apoprotein continues to act as a heme sink. From a 1-l culture, 15 mg of cytochrome b5 and 40 mg of bacterioferritin were purified as pure holoprotein forms. Our expression system provides a rapid and simple ...
A rapid malaria test uses ATR-FTIR spectroscopy to detect lipids and the pigment hemozoin in red blood cells at different stages of infection. Although several established tests already exist for detecting malaria infection, each one appears to have some unsatisfactory properties. For example, the polymerase chain reaction PCR is regarded as the...
File:P450cycle.svg The active site of cytochrome P450 contains a heme iron center. The iron is tethered to the P450 protein via a thiolate ligand derived from a cysteine residue. This cysteine and several flanking residues are highly conserved in known CYPs and have the formal PROSITE signature consensus pattern [FW] - [SGNH] - x - [GD] - {F} - [RKHPT] - {P} - C - [LIVMFAP] - [GAD].[4] Because of the vast variety of reactions catalyzed by CYPs, the activities and properties of the many CYPs differ in many aspects. In general, the P450 catalytic cycle proceeds as follows: 1: The substrate binds to the active site of the enzyme, in close proximity to the heme group, on the side opposite to the peptide chain. The bound substrate induces a change in the conformation of the active site, often displacing a water molecule from the distal axial coordination position of the heme iron[5], and sometimes changing the state of the heme iron from low-spin to high-spin[6]. This gives rise to a change in the ...
The small heme-containing protein cytochrome b5 can facilitate, inhibit, or have no effect on cytochrome P450 catalysis, often in a P450-dependent and substrate-dependent manner that is not well understood. Herein solution NMR was used to identify b5 residues interacting with different human drug-metabolizing P450 enzymes. NMR results revealed that P450 enzymes bound to either b5 α4-5 (CYP2A6 and CYP2E1) or this region and α2-3 (CYP2D6 and CYP3A4) and suggested variation in the affinity for b5 Mutations of key b5 residues suggest that not only are different b5 surfaces responsible for binding different P450 enzymes, but that these different complexes are relevant to the observed effects on P450 catalysis ...
Jani, D., Nagarkatti, R., Beatty, W., Angel, R., Slebodnick, C., Andersen, J., Kumar, S. and Rathore, D. (2008). "HDP-a novel heme detoxification protein from the malaria parasite". PLoS Pathog. 4: e1000053-e1000053. PMID 18437218. ...
c-Type cytochromes are widespread proteins, fundamental for respiration or photosynthesis in most cells. They contain heme covalently bound to protein in a highly conserved, highly stereospecific post-translational modification. In many bacteria, mitochondria, and archaea this heme attachment is catalyzed by the cytochrome c maturation (Ccm) proteins. Here we identify and characterize a covalent, ternary complex between the heme chaperone CcmE, heme, and cytochrome c. Formation of the complex from holo-CcmE occurs in vivo and in vitro and involves the specific heme-binding residues of both CcmE and apocytochrome c. The enhancement and attenuation of the amounts of this complex correlates completely with known consequences of mutations in genes for other Ccm proteins. We propose the complex is a trapped catalytic intermediate in the cytochrome c biogenesis process, at the point of heme transfer from CcmE to the cytochrome, the key step in the maturation pathway.
Mono- and Stereopictres of 5.0 Angstrom coordination sphere of Iron atom in PDB 1koi: Crystal Structure of Nitrophorin 4 From Rhodnius Prolixus Complexed With Nitric Oxide At 1.08 A Resolution
Protein secretion in Pseudomonas aeruginosa involves different mechanisms. The type II and type III secretory pathways control the extracellular release of a wide range of substrates. The type I secretion process, or ABC transporter, was believed to be exclusively involved in alkaline protease secretion. Recently, it was discovered that a P. aeruginosa heme binding protein, HasAp, is also secreted by a type I process. We present here the identification of a third putative type I-dependent protein of P. aeruginosa, AprX. The function of this protein has not yet been elucidated but very interestingly it appears to be linked to the apr cluster, and organized in one single operon together with the aprD, -E and -F genes.
article{44846ede-d441-4e41-b7e9-5579df433b3c, abstract = {Heme A is a prosthetic group of many respiratory oxidases. It is synthesized from protoheme IX (heme B) seemingly with heme O as a stable intermediate. The Bacillus subtilis ctaA and ctaB genes are required for heme A and heme O synthesis, respectively (B. Svensson, M. Lubben, and L. Hederstedt, Mol. Microbiol. 10:193-201, 1993). Tentatively, CtaA is involved in the monooxygenation and oxidation of the methyl side group on porphyrin ring D in heme A synthesis from heme B. B. subtilis ctaA and ctaB on plasmids in both B. subtilis and Escherichia coli were found to result in a novel membrane-bound heme-containing protein with the characteristics of a low-spin b type cytochrome. It fan be reduced via the respiratory chain, and in the reduced state it shows light absorption maxima at 428, 528, and 558 nm and the or-band is split. Purified cytochrome isolated from both B. subtilis and E. coli membranes contained one polypeptide identified as ...
Written by authors active in the field of Leishmania and Trypanosoma research, this volume reviews the current research in kinetoplastid parasites with an emphasis on cellular and molecular biology. Includes epigenetic regulation, cellular defence, manipulation of host macrophages, B lymphocyte response, adhesion and invasion of host tissues, immune evasion, immunotherapy, hemeproteins, phospholipids biosynthesis and DNA topoisomerases.
Dashper, S. G. et al "Characterization of a Novel Outer Membrane Hemin-Binding Protein of Porphyromonas gingivalis ." Journal of Bacteriology 182.22 (2000): 6456-6462. Web. 20 Nov. 2019. ...
Heme detoxifying enzyme that converts heme to crystalline hemozoin (beta-hematin) to protect the organism from the toxic effects of heme. During its development, P.falciparum proteolyzes vast amounts of host hemoglobin, leading to heme release.
1. Pyridine reacts with alkaline haematin to form a dipyridine dihydroxy dimeric haematin in which there is no competition between pyridine and OH− for coordination positions on the iron of haematin. 2. Imidazole competes directly with OH− to form the monomeric imidazole parahaematin in alkaline media. 3. The monomeric imidazole parahaematin aggregates readily to form a species that is precipitated on standing. 4. A structure is proposed for the haematin-pyridine compound in alkaline media.. ...
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Cytochrome b5 is a membrane-bound hemoprotein which acts as an electron carrier for several membrane-bound oxygenases [1]. There are two homologous forms of b5, one found in microsomes and one found in the outer membrane of mitochondria. Two conserved histidine residues serve as axial ligands for the heme group. The structure of a number of oxidoreductases consists of the juxtaposition of a heme-binding domain homologous to that of b5 and either a flavodehydrogenase or a molybdopterin domain. These enzymes are: ...
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We have analyzed the non-exponential kinetics, the temperature variation, and the CO isotope effects of the CO recombination reactions with myoglobin and single-chain hemoglobin.
F-150 oxygen sensor diagrams the O2 sensor has 4 wires coming off it,2 white, 1 black, 1 gray -- Im trying to find - Ford 2001 F150 Styleside SuperCrew question