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Ferrous Form (ferrous + form)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Physicochemical parameters and magnetic speciation of Iron in Nakivubo Channel and Lake Victoria waters

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2009
Naziriwo Betty Bbosa
Abstract Magnetic speciation technique was used for the determination of iron species in Nakivubo Channel and Lake Victoria waters. The method consisted of a column of supported Dowex 1-X18, 20,50 US mesh (Cl) surrounded by movable permanent magnets. Dowex was supported by a porous material to permit adequate passage of the eluent through the column. In the presence of an external magnetic field, enhanced capacity for adsorption of iron III was observed. The enhanced capacity is primarily due to the magnetic field produced and ion exchange sorption mechanism. The results show that, most of the Iron in Nakivubo Channel waters is in reduced ferrous form while, in the Lake Victoria waters, it exists in the oxidized ferric form. Physicochemical parameters for the field samples are discussed in this study. Turbidity levels in catchments with substantial vegetation were significantly lower than those without. pH values up to 13 was observed for some of the point source. The physicochemical parameters along Nakivubo Channel waters were relatively higher than the Lake Victoria waters indicating slow increasing pollution load along the Nakivubo Channel. [source]

Structure and heme binding properties of Escherichia coli O157:H7 ChuX

PROTEIN SCIENCE, Issue 4 2009
Michael D. L. Suits
Abstract For many pathogenic microorganisms, iron acquisition from host heme sources stimulates growth, multiplication, ultimately enabling successful survival and colonization. In gram-negative Escherichia coli O157:H7, Shigella dysenteriae and Yersinia enterocolitica the genes encoded within the heme utilization operon enable the effective uptake and utilization of heme as an iron source. While the complement of proteins responsible for heme internalization has been determined in these organisms, the fate of heme once it has reached the cytoplasm has only recently begun to be resolved. Here we report the first crystal structure of ChuX, a member of the conserved heme utilization operon from pathogenic E. coli O157:H7 determined at 2.05 Å resolution. ChuX forms a dimer which remarkably given low sequence homology, displays a very similar fold to the monomer structure of ChuS and HemS, two other heme utilization proteins. Absorption spectral analysis of heme reconstituted ChuX demonstrates that ChuX binds heme in a 1:1 manner implying that each ChuX homodimer has the potential to coordinate two heme molecules in contrast to ChuS and HemS where only one heme molecule is bound. Resonance Raman spectroscopy indicates that the heme of ferric ChuX is composed of a mixture of coordination states: 5-coordinate and high-spin, 6-coordinate and low-spin, and 6-coordinate and high-spin. In contrast, the reduced ferrous form displays mainly a 5-coordinate and high-spin state with a minor contribution from a 6-coordinate and low-spin state. The ,Fe-CO and ,C-O frequencies of ChuX-bound CO fall on the correlation line expected for histidine-coordinated hemoproteins indicating that the fifth axial ligand of the ferrous heme is the imidazole ring of a histidine residue. Based on sequence and structural comparisons, we designed a number of site-directed mutations in ChuX to probe the heme binding sites and dimer interface. Spectral analysis of ChuX and mutants suggests involvement of H65 and H98 in heme coordination as mutations of both residues were required to abolish the formation of the hexacoordination state of heme-bound ChuX. [source]

Purification, crystallization and X-ray crystallographic analysis of Archaeoglobus fulgidus neelaredoxin

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010
Tiago M. Bandeiras
Neelaredoxins are a type of superoxide reductase (SOR), which are blue 14,kDa metalloproteins with a catalytic nonhaem iron centre coordinated by four histidines and one cysteine in the ferrous form. Anaerobic organisms such as Archaeoglobus fulgidus, a hyperthermophilic sulfate-reducing archaeon, have developed defence mechanisms against toxic oxygen species in which superoxide reductases play a key role. SOR is responsible for scavenging toxic superoxide anion radicals (O2·,), catalysing the one-electron reduction of superoxide to hydrogen peroxide. Crystals of recombinant A. fulgidus neelaredoxin in the oxidized form (13.7,kDa, 125 residues) were obtained using polyethylene glycol and ammonium sulfate. These crystals diffracted to 1.9,Å resolution and belonged to the tetragonal space group P41212, with unit-cell parameters a = b = 75.72, c = 185.44,Å. Cell-content analysis indicated the presence of a tetramer in the asymmetric unit, with a Matthews coefficient (VM) of 2.36,Å3,Da,1 and an estimated solvent content of 48%. The three-dimensional structure was determined by the MAD method and is currently under refinement. [source]

Low-Temperature EPR and Mössbauer Spectroscopy of Two Cytochromes with His,Met Axial Coordination Exhibiting HALS Signals,

CHEMPHYSCHEM, Issue 6 2006
Giorgio Zoppellaro Dr.
Abstract C-type cytochromes with histidine,methionine (His,Met) iron coordination play important roles in electron-transfer reactions and in enzymes. Low-temperature electron paramagnetic resonance (EPR) spectra of low-spin ferric cytochromes c can be divided into two groups, depending on the spread of g values: the normal rhombic ones with small g anisotropy and gmax below 3.2, and those featuring large g anisotropy with gmax between 3.3 and 3.8, also denoted as highly axial low spin (HALS) species. Herein we present the detailed magnetic properties of cytochrome c553 from Bacillus pasteurii (gmax 3.36) and cytochrome c552 from Nitrosomonas europaea (gmax 3.34) over the pH range 6.2 to 8.2. Besides being structurally very similar, cytochrome c553 shows the presence of a minor rhombic species at pH 6.2 (6,%), whereas cytochrome c552 has about 25,% rhombic species over pH 7.5. The detailed Mössbauer analysis of cytochrome c552 confirms the presence of these two low-spin ferric species (HALS and rhombic) together with an 8,% ferrous form with parameters comparable to the horse cytochrome c. Both EPR and Mössbauer data of axial cytochromes c with His,Met iron coordination are consistent with an electronic (dxy)2 (dxz)2 (dyz)1 ground state, which is typical for Type I model hemes. [source]