Assessment of Metal Availability in Soils from a Pb-Zn Mine Site of South-Central Spain

Heavy metal pollution of the soils around an abandoned Pb-Zn mine site located in the Alcudia Valley (South Central Spain) have been characterized by analysis of extractable and total metal concentrations in 60 samples of arable, pasture, and mine lands. The samples showed a broad range of size-particle distribution, cation exchange capacity, and pH values as well as high levels of total metal concentrations (up to 98510 mg kg^?1 of Pb, up to 20912 mg kg^?1 of Zn, and up to 61 mg kg^?1 of Cd). In order to assess the potential availability of metals the metal partitioning in two different soil size fractions (<2 mm and <63 μm) was determined using EDTA and CaCl₂ as sequestering reagents. The average contents of Pb, Zn, and Cd in the <63 μm particle size fraction for both extractions were higher than those of the <2 mm fraction due to the high metal adsorption capacity of the fine soil particles. Concentrations of heavy metals extracted by CaCl₂ were up to three orders of magnitude lower than those extracted by EDTA, because CaCl₂ only extracts the easily mobile fraction. Metal concentrations extracted by both procedures in the two granulometric fractions increased with total metal concentrations, thus increasing the potential environmental risk associated to heavy metal pollution.     

Metal Projectile Points From the Deapolis Site,North Dakota

Abstract

Almost nothing is known about what kinds of metal arrowheads were European trade items and which were made bythe various native groups. A large collection of such arrowheads was made at the 19th century Deapolis Mandan Village. Analysis of these specimens has not clarified the problem of European versus native manufacture although manufacturing techniques can clearly be seen on a few. However, a number of hypothetical taxonomic groups are postulated.     

Metal Binding at the Deinococcus radiodurans Dps-1 N-Terminal Metal Site Controls Dodecameric Assembly and DNA Binding

The prokaryotic DNA protection during starvation (Dps) proteins typically protect macromolecules against damaging agents via physical association with DNA and by oxidizing and sequestering iron. However, Deinococcus radiodurans Dps-1, which binds DNA with high affinity, fails to protect DNA against hydroxyl radicals due to iron leakage from the core, raising the question of how (?)OH-mediated damage to Dps-1-bound DNA is avoided. As shown here, Mn(II) inhibits ferroxidase activity, suggesting that ferroxidation may be prevented in vivo as D. radiodurans accumulates a high ratio of Mn:Fe. Dps-1 has an N-terminal extension with a unique metal-binding site, an extension that has been proposed to be important for DNA binding and dodecameric assembly. Electrophoretic mobility shift assays show that Mn(II) restores DNA binding to bipyridyl-treated Dps-1, whereas Fe(II) fails to do so in the presence of H(2)O(2), thus preventing DNA binding under conditions of ongoing ferroxidase activity. We also show that disruption of the N-terminal metal site leads to a significant reduction in DNA binding and to compromised oligomeric assembly, with the mutant protein assembling into a hexamer in the presence of divalent metal. We propose that securing the N-terminal loop by metal binding is required to initiate dodecameric assembly by contacting the neighboring dimer and that the absence of such optimal contacts results in formation of a hexameric assembly intermediate in which three dimers associate about one of the 3-fold axes. Once dodecameric Dps-1 is assembled, metal binding no longer affects oligomeric state; instead, differential metal binding controls DNA interaction under conditions of oxidative stress.     

Ferritin as a label for high-gradient magnetic separation.

In three model systems, particles the size of cells or smaller have been surface labeled with ferritin to make them slightly paramagnetic, by virtue of the iron in the ferritin. In each case it was possible to show that labeled particles could be magnetically removed from a flowing suspension by the high-gradient magnetic separation (HGMS) technique. The first system of particles consisted of small (1 micron) carboxylate-modified latex spheres to which ferritin was covalently bound to create stable paramagnetic particles analogous to a ferritin-labeled subcellular membrane preparation. In the second system polyacrylamide beads that more closely approximated whole cells in size (5-50 microns) were labeled with immunoferritin. The third system was a biomembrane preparation: erythrocyte ghosts labeled with a ferritin-lectin conjugate. A field of 7 T (tesla) (70 kG) was used in each case, along with buffer flow rates through the HGMS column in the range 0.1-1.0 ml/min.     

铁蛋白的生物工程应用

铁蛋白是一种普遍存在于生物体内的储铁蛋白,具有铁离子代谢、抗氧化胁迫及消除其他过量金属离子毒害作用的功能。随着对铁蛋白结构和生化功能认识的深入,铁蛋白作为一个含有四氧化三铁核心的特殊蛋白复合体,被广泛应用于生物医学、纳米材料、生物分子成像等各种生物工程领域。该综述针对已知的主要铁蛋白分子,论述了铁蛋白的结构及酶活性机理,基于铁蛋白的多功能分子骨架应用,以及基于铁蛋白磁性的生物分子开关等热点研究,最后对铁蛋白生物工程、生物医学领域的应用和发展进行了展望。     

Ferritin: a cytoprotective antioxidant strategem of endothelium.

Phagocyte-mediated oxidant damage to vascular endothelium is likely involved in various vasculopathies including atherosclerosis and pulmonary leak syndromes such as adult respiratory distress syndrome. We have shown that heme, a hydrophobic iron chelate, is rapidly incorporated into endothelial cells where, after as little as 1 h, it markedly aggravates cytotoxicity engendered by polymorphonuclear leukocyte oxidants or hydrogen peroxide (H2O2). In contrast, however, if cultured endothelial cells are briefly pulsed with heme and then allowed to incubate for a prolonged period (16 h), the cells become highly resistant to oxidant-mediated injury and to the accumulation of endothelial lipid peroxidation products. This protection is associated with the induction within 4 h of mRNAs for both heme oxygenase and ferritin. After 16 h heme oxygenase and ferritin have increased approximately 50-fold and 10-fold, respectively. Differential induction of these proteins determined that ferritin is probably the ultimate cytoprotectant. Ferritin inhibits oxidant-mediated cytolysis in direct relation to its intracellular concentration. Apoferritin, when added to cultured endothelial cells, is taken up in a dose-responsive manner and appears as cytoplasmic granules by immunofluorescence; in a similar dose-responsive manner, added apoferritin protects endothelial cells from oxidant-mediated cytolysis. Conversely, a site-directed mutant of ferritin (heavy chain Glu62----Lys; His65----Gly) which lacks ferroxidase activity and is deficient in iron sequestering capacity, is completely ineffectual as a cytoprotectant. We conclude that endothelium and perhaps other cell types may be protected from oxidant damage through the iron sequestrant, ferritin.     

Ferritin intestinal absorption.

Ferritin as a source of iron was consiered. A good iron absorption rate appears in normal rats with an in vivo absorption technique. The same absorption appears in iron-deficient animals. The iron stored in intestinal wall is lower in anemic rats than in normal ones, suggesting a higher draw of iron from lumen to blood.     

A Practical Examination of the Use of Geostatistics in the Remediation of a Site with a Complex Metal Contamination History

Targeted remediation strategies offer the potential to treat only those areas where contamination exceeds predefined threshold levels. We used geostatistical techniques to characterize spatial distribution of heavy metals across a contaminated site, with the aim of delineating the contaminants, which is essential for successful implementation of targeted remediation strategies. Samples collected from three depths, 0–20 cm, 20–40 cm and 40–60 cm at 50 sample locations, were analyzed for As, Sb, Hg, Pb, Cd and Cu contents. The geostatistical analysis of this data enabled the identification of a number of contamination hotspots and trends. The visual interpretation of the data was supported by the statistical analysis in the form of Spearman's rank correlation coefficient. Additionally, classical statistics, based on the central limit theorem, showed that, in terms of obtaining the true mean for each of the contaminants within acceptable limits of precision, the site has been more than adequately sampled.It has been demonstrated that kriging can offer the potential to map the spatial distribution of contaminants. However, the possibility of an undetected hotspot remains, even when probabilistic modelling and a secondary phase of validatory sampling are employed. This together with the large number of samples required may preclude the commercial use of geostatistics in the remediation of contaminated land.     

Ferritin as a source of iron for oxidative damage.

The generation of deleterious activated oxygen species capable of damaging DNA, lipids, and proteins requires a catalyst such as iron. Once released, ferritin iron is capable of catalyzing these reactions. Thus, agents that promote iron release may lead to increased oxidative damage. The superoxide anion formed enzymatically, radiolytically, via metal-catalyzed oxidations, or by redox cycling xenobiotics reductively mobilizes ferritin iron and promotes oxidative damage. In addition, a growing list of compounds capable of undergoing single electron oxidation/reduction reactions exemplified by paraquat, adriamycin, and alloxan have been reported to release iron from ferritin. Because the rapid removal of iron from ferritin requires reduction of the iron core, it is not surprising that the reduction potential of a compound is a primary factor that determines whether a compound will mobilize ferritin iron. The reduction potential does not, however, predict the rate of iron release. Therefore, ferritin-dependent oxidative damage may be involved in the pathogenesis of diseases where increased superoxide formation occurs and the toxicity of chemicals that increase superoxide production or have an adequate reduction potential to mobilize ferritin iron.     

Ferritin, a physiological iron donor for microsomal lipid peroxidation

In the process of lipid peroxidation of microsomes induced either by oxygen radicals generated by xanthine oxidase or by NADPH, ferritin is able to donate the necessary iron. The amount of ferritin necessary to catalyze the process of lipid peroxidation is in the physiological range. In contrast to the finding with phospholipid liposomes, catalase hardly stimulates the lipid peroxidation of microsomes.     

Ferritin and superoxide-dependent lipid peroxidation

Ferritin was found to promote the peroxidation of phospholipid liposomes, as evidenced by malondialdehyde formation, when incubated with xanthine oxidase, xanthine, and ADP. Activity was inhibited by superoxide dismutase but markedly stimulated by the addition of catalase. Xanthine oxidase-dependent iron release from ferritin, measured spectrophotometrically using the ferrous iron chelator 2,2'-dipyridyl, was also inhibited by superoxide dismutase, suggesting that superoxide can mediate the reductive release of iron from ferritin. Potassium superoxide in crown ether also promoted superoxide dismutase-inhibitable release of iron from ferritin. Catalase had little effect on the rate of iron release from ferritin; thus hydrogen peroxide appears to inhibit lipid peroxidation by preventing the formation of an initiating species rather than by inhibiting iron release from ferritin. EPR spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide was used to observe free radical production in this system. Addition of ferritin to the xanthine oxidase system resulted in loss of the superoxide spin trap adduct suggesting an interaction between superoxide and ferritin. The resultant spectrum was that of a hydroxyl radical spin trap adduct which was abolished by the addition of catalase. These data suggest that ferritin may function in vivo as a source of iron for promotion of superoxide-dependent lipid peroxidation. Stimulation of lipid peroxidation but inhibition of hydroxyl radical formation by catalase suggests that, in this system, initiation is not via an iron-catalyzed Haber-Weiss reaction.     

微生物铁蛋白的研究进展

铁蛋白作为一种重要的铁储存蛋白,在不同的微生物体中普遍存在.通过对典型的微生物铁蛋白分子(FTN)的结构及其功能的归纳分析发现,铁蛋白依赖其独特的结构特点,在铁的补充、转运、氧化、成核和储存中扮演着重要作用,也对生物体内的多种生物化学反应影响显著.同时借助基因工程技术对铁蛋白进行相应的分子改造,增加了其作为纳米载体的应...     

Ferritin in Parkinsonian and control brains

Heme oxygenase-1 (HO-1) is a stress protein expressed in various pathological conditions associated with oxidative stress. Brain HO-1 expression and activity in response to LPS treatment showed regional variability with the highest levels in the substantia nigra (SN) and hippocampus. HO-1 induction by LPS was redox-sensitive and associated with increased levels of NO synthase and arginase, two proteins involved in the regulation of cellular redox state. Brain HO-2 and HO-3 expression, studied by quantitative RT-PCR, did not show significant changes. Our data suggest an interaction between NO and the HO system in the brain after LPS treatment. As SN and hippocampus are involved in Parkinson's and Alzheimer's diseases, understanding interaction of these proteins in the brain will help to elucidate the mechanisms involved in neurodegeneration.     

Ferritin is a translationally regulated heat shock protein of avian reticulocytes

Heat-shock avian reticulocytes exhibit enhanced synthesis of a greater than 450-kDa protein. Biochemical, immunochemical, and visual criteria were used to identify this protein as the iron storage protein ferritin. The 21-kDa ferritin subunits synthesized during heat shock are similar in size and pI to the subunits that are constitutively synthesized. The 2-6-fold heat shock-induced increase in ferritin synthesis appears to be regulated at the translational level as it is insensitive to actinomycin D. Northern and dot-blot hybridization analyses of cytoplasmic RNAs with avian H-ferritin cDNA fragments support the contention that the heat shock stimulation of ferritin synthesis is translationally regulated. These latter studies demonstrate that the heat shock-induced synthesis of ferritin does not involve a change in the amount of total cytoplasmic ferritin mRNAs, but rather appears to entail a translocation of cytoplasmic H-ferritin mRNAs from a polyribosome-free, translationally repressed state to a polyribosome-associated, translationally active state. These results suggest that thermally stressed avian reticulocytes have a critical and functional need for the synthesis of additional ferritin and that its enhanced synthesis, unlike the new and/or enhanced synthesis of the well-established avian heat shock proteins, is regulated wholly at the translational level.