Manganese Pyrophosphate Research Articles

Nanocrystalline serrabrancaite (MnPO 4·H 2O) prepared by a simple precipitation route at low temperature

MnPO 4·H 2O was precipitated from manganese nitrate tetrahydrates and phosphoric acid in the presence of water–ethanol system at low temperature. The precipitates were characterized by TG/DTG/DTA, XRD, scanning electron microscope (SEM), FTIR and UV–vis–near IR techniques. The presence of ethanol in the spontaneous precipitation process of serrabrancaite leads to highly crystalline powder. Thermal treatment at 600 °C yields a crystalline manganese pyrophosphate (Mn 2P 2O 7). The particle sizes obtained from X-ray line broadening are 66 ± 28 and 54 ± 18 nm for the MnPO 4·H 2O and Mn 2P 2O 7, respectively. FTIR spectrum of MnPO 4·H 2O is assigned base on the PO 4 3− ion and water molecules in the structure. The diffuse reflectance spectrum revealed that MnPO 4·H 2O presents a strong Jahn-Teller effect, which is in agreement with the crystal structure.

Reversible Inhibition of Escherichia coli Inorganic Pyrophosphatase by Fluoride: Trapped Catalytic Intermediates in Cryo-crystallographic Studies

Here, we describe high-resolution X-ray structures of Escherichia coli inorganic pyrophosphatase (E-PPase) complexed with the substrate, magnesium, or manganese pyrophosphate. The structures correspond to steps in the catalytic synthesis of enzyme-bound pyrophosphate (PPi) in the presence of fluoride as an inhibitor of hydrolysis. The catalytic reaction intermediates were trapped applying a new method that we developed for initiating hydrolytic activity in the E-PPase crystal. X-ray structures were obtained for three consecutive states of the enzyme in the course of hydrolysis. Comparative analysis of these structures showed that the Mn2+-supported hydrolysis of the phosphoanhydride bond is followed by a fast release of the leaving phosphate from the P1 site. The electrophilic phosphate P2 is trapped in the “down” conformation. Its movement into the “up” position most likely represents the rate-limiting step of Mn2+-supported hydrolysis. We further determined the crystal structure of the Arg43Gln mutant variant of E-PPase complexed with one phosphate and four Mn ions.

Crystal structure, vibrational spectra, and thermal decomposition and nitrogen adsorption behaviour of a new tetramanganese(II) dipyrophosphate decahydrate, Mn4(P2O7)2·10H2O

A new manganese(II) pyrophosphate, Mn4(P2O7)2·10H2O, has been synthesized and characterized by single-crystal X-ray diffraction [orthorhombic space group Pnma, with unit cell parameters of a=9.3288(3) A, b=25.9532(9) A, c=8.4783(3) A; Z=4]. All the pyrophosphate anions show non-linear P–O–P bonds with an average angle of 128.60°. The framework of this new pyrophosphate is made up of packed layers of MnO6 octahedra connected by double-tetrahedra P2O7 groups and a layer of Mn(H2O)6 units. The [P2O7]4− anions adopt a bent, near-staggered conformation. The absence of coincidences for the majority of the IR and Raman bands is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted in part on the basis of factor group effects. The structural changes occurring during heating have been investigated by TG-ATD. When Mn4(P2O7)2 .10H2O is gradually heated, it decomposes into an intermediate hydrated salt at 96°C and then to anhydrous Mn2P2O7 at 325°C. This thermal behaviour is different from that of Zn4(P2O7)2·10H2O. The crystal structure of the new managenese(II) pyrophosphate is compared with the known structures of Zn4(P2O7)2·10H2O, Mn2P2O7·2H2O and anhydrous Mn2P2O7. The adsorption and desorption isotherms of Mn4(P2O7)2·10H2O, Zn4(P2O7)2·10H2O and MnKHP2O7·2H2O have been investigated by BET measurements and the results show that the capacity for N2 sorption of the Mn(II) salt is two times lower than is that of the Zn(II) isotype and two or three times higher than is that of MnKHP2O7·2H2O.

Direct Oxidation of Benzene to Phenol on Manganese Pyrophosphate with Hydrogen Peroxide

A solid catalyst manganese pyrophosphate based on non-sieves to oxidize benzene to phenol with oxidant hydrogen peroxide has shown good conversion with good selectivity in CH3CN at 65°C investigating water contact angle data of three manganese salts, it is found manganese pyrophosphate has certain repulsive water character. It is further to be confirmed by benzene and phenol adsorption experiments onto catalyst surface by GC. With benzene/H2O2 ratio of 1, the benzene conversion of 13.8% with phenol selectivity of 85.0% was achieved. It is noteworthy that no any products are obtained using manganese pyrophosphate as catalyst in the oxidation of phenol in CH3CN solvent.

Behavioral effects of manganese injected in the rat substantia nigra are potentiated by dicumarol, a DT-diaphorase inhibitor

The purpose of this study was to evaluate the contribution of DT-diaphorase inhibition to in vivo neurodegenerative effects of dopamine (DA) oxidation to the corresponding o-quinones. The neurotoxicity to nigrostriatal DA neurons was induced by injection of manganese pyrophosphate (Mn 3+) complex as a prooxidizing agent alone or together with the DT-diaphorase inhibitor dicumarol into the right rat substantia nigra. The behavioral effects were compared with those induced after selective lesions of dopaminergic neurons with 6-hydroxydopamine (6-OHDA). Intranigral injection of Mn 3+ and Mn 3+ plus dicumarol produced significant impairment in motor behavior compared with control animals. However, the effect seen in the Mn 3+ plus dicumarol injected group was significantly more severe than that observed in the Mn 3+ alone injected group. In motor activity and rearing behavior, the simultaneous injection of Mn 3+ plus dicumarol produced a 6-OHDA-like impairment. Similar effects were observed in the acquisition of a conditioned avoidance response (CAR). Dicumarol significantly impaired avoidance conditioning although without affecting the motor behavior. The behavioral effects were correlated to the extent of striatal tyrosine hydroxylase (TH)-positive fiber loss. Rats receiving unilateral intranigral Mn 3+ and Mn 3+ plus dicumarol injections exhibited a significant reduction in nigrostriatal TH-positive fiber density in medial forebrain bundle compared with the contralateral noninjected side. In conclusion, this study provides evidence that the neurotoxicity of Mn 3+ in vivo is potentiated by DT-diaphorase inhibition, suggesting that this enzyme could play a neuroprotective role in the nigrostriatal DA systems.

1H and 13C NMR characterization of hemiamidal isoniazid-NAD(H) adducts as possible inhibitors of InhA reductase of Mycobacterium tuberculosis.

Isoniazid (INH) is easily oxidized with manganese(III) pyrophosphate, a chemical model of the KatG protein involved in activation of INH inside the bacteria Mycobacterium tuberculosis. Performed in the presence of NAD(+), this oxidation generates a family of isomeric INH-NAD(H) adducts, which have been shown to be effective inhibitors of InhA, an enzyme essential in mycolic acid biosynthesis. In this work, we fully characterized by (1)H and (13)C NMR spectroscopy four main species of INH-NAD(H) adducts that coexist in solution. Two of them are open diastereoisomers consisting of the covalent attachment of the isonicotinoyl radical at position four of the nicotinamide coenzyme. The other two result from a cyclization involving the amide group from the nicotinamide and the carbonyl group from the isonicotinoyl radical to give diastereoisomeric hemiamidals. Although an INH-NAD(H) adduct with a 4S configuration has been characterized within the active site of InhA from Xray crystallography and this bound adduct interpreted as an open form (Rozwarski et al., Science 1998, 279, 98-102), it is legitimate to raise the question about the effective active form(s), open or cyclic, of INH-NAD(H) adduct(s). Is there a single active form or are several forms able to inhibit the InhA activity with different levels of inhibitory potency?

Thermal behavior of Mn- and P-containing anodic-spark coatings on titanium

Differential thermogravimetric, and x-ray photoelectron spectral, as well as diffraction, analyses were applied to investigate anodic coatings formed under electric-breakdown conditions in electrolytes containing polyphosphate manganese complexes. It is shown that annealing at temperatures of up to 1000°C does not affect the concentration of elements in coatings, but is conducive to crystallizing Na0.23TiO2-bronze, manganese pyrophosphate Mn2P2O7 , sodium, as well as manganese, titanophosphates NaTi2(PO4)3 and Mn(II)Mn(III)Ti(PO4)3 , respectively.

Manganese oxidation state and its implications for toxicity.

Manganese (Mn) is ubiquitous in mammalian systems and is essential for proper development and function, though it can also be toxic at elevated exposures. While essential biologic functions of Mn depend on its oxidation state [e.g., Mn(II), Mn(III)], little is known about how the oxidation state of elevated Mn exposures affect cellular uptake, and function/toxicity. Here we report the dynamics of EPR measurable Mn(II) in fresh human plasma and cultured PC12 cell lysates as a function of exposure to either manganese(II) chloride or manganese(III) pyrophosphate, and the effects of exposure to Mn(II) versus Mn(III) on total cellular aconitase activity and cellular Mn uptake. The results indicate that Mn(II) or Mn(III) added in vitro to fresh human plasma or cell lysates yielded similar amounts of EPR measurable Mn(II). In contrast, Mn added as Mn(III) was significantly more effective in inhibiting total cellular aconitase activity, and intact PC12 cells accumulated significantly more Mn when exposures occurred as Mn(III). Collectively, these data reflect the dynamic nature of Mn speciation in simple biological systems, and the importance of Mn oxidation/speciation state in mediating potential cellular toxicity. This study supports concern over increased environmental exposures to Mn in different oxidation states [Mn(II), Mn(III), and Mn(IV)] that may arise from combustion products of the gasoline antiknock additive methycyclopentadienyl manganese tricarbonyl (MMT).

Mn(III) pyrophosphate as an efficient tool for studying the mode of action of isoniazid on the InhA protein of Mycobacterium tuberculosis.

The antituberculosis drug isoniazid (INH) is quickly oxidized by stoichiometric amounts of manganese(III) pyrophosphate. In the presence of nicotinamide coenzymes (NAD+, NADH, nicotinamide mononucleotide [NMN+]) and nicotinic acid adenine dinucleotide (DNAD+), INH oxidation produced the formation of INH-coenzyme adducts in addition to known biologically inactive products (isonicotinic acid, isonicotinamide, and isonicotinaldehyde). A pool of INH-NAD(H) adducts preformed in solution allowed the rapid and strong inhibition of in vitro activity of the enoyl-acyl carrier protein reductase InhA, an INH target in the biosynthetic pathway of mycolic acids: the inhibition was 90 or 60% when the adducts were formed in the presence of NAD+ or NADH, respectively. Under similar conditions, no inhibitory activity of INH-NMN(H) and INH-DNAD(H) adducts was detected. When an isolated pool of 100 nM INH-NAD(H) adducts was first incubated with InhA, the enzyme activity was inhibited by 80%; when present in excess, both NADH and decenoyl-coenzyme A are able to prevent this phenomenon. InhA inhibition by several types of INH-coenzyme adducts coexisting in solution is discussed in relation with the structure of the coenzyme, the stereochemistry of the adducts, and their existence as both open and cyclic forms. Thus, manganese(III) pyrophosphate appears to be an efficient and convenient alternative oxidant to mimic the activity of the Mycobacterium tuberculosis KatG catalase-peroxidase and will be useful for further mechanistic studies of INH activation and for structural investigations of reactive INH species in order to promote the design of new inhibitors of InhA as potential antituberculous drugs.

A Fast and Efficient Metal-Mediated Oxidation of Isoniazid and Identification of Isoniazid-NAD(H) Adducts

It is currently believed that isoniazid (INH) is oxidised inside Mycobacterium tuberculosis to generate, by covalent attachment to the nicotinamide ring of NAD(H) (beta-nicotinamide adenine dinucleotide), a strong inhibitor of InhA, an enzyme essential for mycolic acid biosynthesis. This work was carried out to characterise the InhA inhibitors (named INH-NAD(H) adducts) which are generated, in the presence of the nicotinamide coenzyme NAD+, by oxidation of INH with manganese(III) pyrophosphate, a nonenzymatic and efficient oxidant used to mimic INH activation by the catalase-peroxidase KatG inside M. tuberculosis. The oxidation process is almost complete in less than 15 minutes (in comparison to the slow activation obtained in the KatG-dependent process (2.5 hours) or in the nonenzymatic O2/Mn(II)-dependent activation (5 hours)). The alkylation of NAD+ by the postulated isonicotinoyl radical generates, in solution, a family of INH-NAD(H) adducts. Analyses with liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS) and experiments performed with 18O- and 2H-labelled substrates allowed us to propose two open and four hemiamidal cyclised dihydropyridine structures as the main forms present in solution; these result from the combination of the isonicotinoyl radical and the nicotinamide part of NAD+. A small amount of a secondary oxidation product was also detected. Structural data on the forms present in solution should help in the design of inhibitors of enzymes involved in the biosynthesis of mycolic acids to act as potential antituberculosis drugs.

Kinetic Behavior of Mn(III) Complexes of Pyrophosphate, EDTA, and Citrate

Aqueous complexes of Mn3+ ion with the ligands pyrophosphate (P2O74-), EDTA (C10H12O8N24-, ethylenediaminotetraacetate4-), or citrate (CIT3-, C6H5O73-) were prepared rapidly in solution by the general reaction: Mn(VII) + 4Mn(II)L + L→ 5Mn(III)L, where L is the ligand (in known excess). Different initial pH values of the complex solutions were obtained by prior addition of required acid, base, or buffer. Disappearance of Mn(III)L complex with time was monitored by light absorbance at appropriate wavelengths. Rates of loss for each Mn(III)L complex are found to depend on pH and the ratio [ligand]T/[Mn]T. Relative chemical time scales for Mn(III)L disappearance at neutral pH and similar ligand-to-metal ratios were manganese(III) pyrophosphate > manganese(III) citrate >> manganese(III) EDTA. The kinetic observations are interpreted as reflecting ligand hydrolysis and disproportionation in the case of pyrophosphate (a nonredox active compound), inner-sphere electron transfer from citrate to Mn3+, and both out...

Manganese(III) Oxidation of L-Lysine and L-Histidine in Pyrophosphate Solution: A Kinetic and Mechanistic Study

Kinetic studies on the oxidation of two basic amino acids (AA), L-lysine and L-histidine, by manganese(III) ions have been performed in pyrophosphate solution at 328 K and pH 1.3. Manganese(III) pyrophosphate solution was prepared by a known chemical method and the nature of the oxidizing species present in the solution was determined by spectrophotometric and redox potential measurements. The reaction follows the rate law: rate = k [Mn(III)] [AA] [H+][x/[Mn(II)]y [P2O7 4−]z] where x, y, and z are all fractional. The effects of added anions, fluoride, chloride, and perchlorate, and of varying solvent composition were studied. A solvent isotope effect in D2O medium was investigated. The dependence of the rate on temperature was studied and activation parameters were evaluated from the Arrhenius and Eyring plots. A mechanism, which is consistent with the kinetic data, has been discussed.

New manganese pyrophosphates: The syntheses, crystallographic characterizations and magnetic properties of BaMnP 2O 7 and CaMnP 2O 7

The new compound BaMnP 2O 7 was obtained in two crystallographic modifications, (monoclinic- 1) and (triclinic- 2), by heating mixtures of BaCO 3, P 2O 5 and MnO 2 to 1100°C and to 1000°C for 72 h, respectively. CaMnP 2O 7 ( 3) was obtained by heating a mixture of CaCO 3, P 2O 5 and MnO 2 to 1050°C for 48 h. Both crystallographic forms of BaMnP 2O 7 and CaMnP 2O 7 ( 3) were investigated by single-crystal X-ray diffraction analysis. The high-temperature monoclinic form of BaMnP 2O 7 could not be obtained free of the low-temperature triclinic form in the bulk form. In monoclinic- 1 the manganese ions exist in a distorted MnO 6 octahedron surrounded by five closely and one remotely positioned oxygen atoms. In triclinic- 2 and - 3 forms the manganese ions are associated in pairs by the formation of Mn 2O 10 units that share one edge of two adjacent octahedra. The magnetic properties of the triclinic- 2 and - 3 forms were also investigated. The effective magnetic moments, μ eff, are 5.7 B.M. and 5.8 B.M./Mn atom for triclinic- 2 and - 3, respectively, and are consistent with a high-spin Mn 2+ ion in an octahedral environment with five unpaired electrons. The temperature-dependent magnetic measurements of 2 and 3 have revealed a combination of short-range antiferromagnetic coupling, J, between the two Mn ions within the Mn 2O 10 units and a longer range weaker antiferromagnetic coupling, J′, between the neighbouring Mn 2O 10 units, | J′/ J| = 0.18 and 0.074 for 2 and 3, respectively.

Crystal chemistry, single crystal X-ray structure and magnetism of nickel manganese pyrophosphate

A study of the crystal chemistry of the Ni 2 − xMn xP 2O 7 systems in powder form, 0 ≤ x ≤ 2, has revealed the existence of three solid solutions. When x < 0.10, the solution is isostructural with low temperature form, α-Ni 2P 2O 7. When 0.10 ≤ x ≤ 0.40, the structure of the solid solution is similar to that of σ-Ni 2P 2O 7. When 0.60 ≤ x ≤ 2, a form similar to β-Ni 2P 2O 7 (or Mn 2P 2O 7) is seen. The single crystal structure of material corresponding to x = 0.816 has been determined in monoclinic space group Cm, a = 6.557(3), b = 8.738(5), c = 4.498(3), β = 103.24(1) °, V = 240.6(2)Å 3, Z = 2, R R w = 3.8 5.3% and shows a structural deformation of the parent lattice. The system shows antiferromagnetic interactions at low temperature.

Oxidation of Arginine by Manganese(III) in Pyrophosphate and Acetate media: A kinetic study

AbstractKinetics of manganese(III) oxidation of L‐arginine has been studied in the presence of pyrophosphate and acetate ions in acidic media at 328 K and 323 K, respectively. The nature of the oxidizing species formed in manganese(III) solutions was determined by spectrophotometric and redox potential measurements. The reaction shows a first‐order dependence on [manganese(III) pyrophosphate] in the pyrophosphate medium, pH 2–3, and a half‐order on [manganese(III) acetate] in HOAc‐acetate medium. In both media, the kinetic order is one with respect to [arginine]. The dependencies of the rate on the reduction product, manganese(II), concentration are zero‐ and inverse first‐orders in acetate and pyrophosphate media, respectively. Effects of varying dielectric constant of the medium and of added anions such as acetate, pyrophosphate, fluoride, chloride, and perchlorate have been investigated, in both media. There is evidence for the existence of free radicals as transient species. Activation parameters have been evaluated using the Arrhenius and Eyring plots. Mechanisms consistent with the observed kinetic data have been proposed and discussed. Kinetic data for the oxidations of some α‐amino acids by manganese(III) species of different forms are summarized and compared. © 1994 John Wiley &amp; Sons, Inc.

Effect of Acetic Acid on the Oxidation of Mandelic Acid by Manganese(III) Pyrophosphate

Effect of Acetic Acid on the Oxidation of Mandelic Acid by Manganese(III) Pyrophosphate

ChemInform Abstract: THE THERMAL DECOMPOSITION OF MANGANESE(III) PHOSPHATE MONOHYDRATE

AbstractMnPO4 ′H2O beginnt sich bei 200°C unter Dehydratisierung bei gleichzeitiger Reduktion des Mn(III) zu zersetzen und wandelt sich bei 500°C vollständig in Mn2P,O‐, um.

The Thermal Decomposition of Manganese(III) Phosphate Monohydrate

Abstract Manganese(III) phosphate monohydrate begins to decompose at 200 °C by the dehydration accompanying the reduction of manganese(III) and changes completely to manganese(II) pyrophosphate at 500 °C. The reaction order and activation energy for the reduction process are 1.3 and 176.8 kJ mol−1, respectively.

Kinetics of reactions of manganese(III) pyrophosphate with some hexitols

Kinetics of reactions of manganese(III) pyrophosphate with some hexitols

Kinetics of oxidation of adonitol by manganese(III) pyrophosphate

Adonitol is oxidized to ribose by Mn(III) pyrophosphate under the conditions [adonitol] ≫ [Mn(III)]. The oxidation rate is first order with respect to both oxidatn and substrate and decreases inversly with [pyrophosphate]free. Thermodynamic parameters are reported and a suitable mechanism involving free radicals is proposed.