VIII VI IV Aenigmatite, Na4 (Fe2 +,Ti,Fe 3 +) 1 2 (SiFe 3 +) 12 0 40 , is a common constituent of sodium-rich alkaline igneous rocks and is classified as an open-branched single-chain silicate, whose structure is closely related to that of sapphirine. The first Mossbauer spectra of three valid aenigmatite specimens were recorded and the detailed crystal chemistry were obtained. In the Mossbauer...

BACKGROUND In soils and sediments, manganese oxides and oxygen usually participate in the oxidation of ferrous ions. There is limited information concerning the interaction process and mechanisms of ferrous ions and manganese oxides. The influence of air (oxygen) on reaction process and kinetics has been seldom studied. Because redox reactions usually occur in open systems, the participation of...

The complete binuclear complex in [Fe2(C7H4NO4)4(OH)2]·2H2O, is generated by the application twofold symmetry. The Fe(III) atom is coordinated by the O atoms of two bridging hydroxyl groups and by two N and two O atoms from two pyridine-2,5-di-carboxyl-ato ligands, forming a distorted octa-hedral geometry. The Fe⋯Fe separation within the dinuclear complex is 3.0657 (4) Å. In the crystal, O-H⋯O ...

Prolyl 4-hydroxylase (EC 1.14.11.2) is an essential enzyme in the post-translational modification of collagen. Inhibitors of this enzyme are of potential interest for the treatment of diseases involving excessive deposition of collagen. We have found that anthraquinones with at least two hydroxy groups ortho to each other are potent inhibitors of this enzyme. Kinetic studies revealed that 2,7,8...

Flavonoids are a class of natural phenolic compounds that show antioxidant properties. Besides the known mechanisms of action of flavonoids (binding/inactivation of free radicals and other reactive oxygen species) that determine this effect, an important factor is their ability to bind transition metal ions. In this paper, we used a HPLC method with a prechromatographic reaction of a sample wit...

In an attempt to identify components of a ferric citrate uptake system in Pseudomonas aeruginosa, a mutant library of a siderophore-deficient strain (IA614) was constructed and screened for defects in citrate-promoted growth in an Fe-restricted medium. A mutant disrupted in gene PA3901, encoding a homologue of the outer-membrane ferric citrate receptor, FecA, of Escherichia coli (FecA(E.c.)), w...

An investigation was carried out aiming at assessing the potential of vis-NIR reflectance spectroscopy, through comparison with the conventional X-ray powder diffraction (XRPD) technique, for the characterization of synthetic gleys, obtained in laboratory starting from Fe0 and Fe2+ under different conditions of initial pH (5.5, 7.0 and 8.5). XRPD analysis showed that in any case goethite formed...

The hexadentate, and ditopic ligand 2,5-bis([2,2']bipyridin-6-yl)pyrazine yields a chiral, tetrameric, square-shaped, self-assembled species upon complexation with Fe2+ ions. The racemate of this complex was resolved with antimonyl tatrate as the chiral auxiliary. The purity of the enantiomer was determined by NMR spectroscopy, by using a chiral, diamagnetic shift reagent, and by circular dichr...

The addition of calcium chloride to rat liver homogenates resulted in activation of phosphoenolpyruvate carboxykinase by as much as 50%. The enhanced activity was inhibited by quinolinic acid; it was not additive with activation by FeCl2, and stimulation was prevented by 1,10-phenanthroline. Activation by calcium was lost when the particulate fractions of liver were removed, but an activating s...