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1
Zhang, Chao, Shuai Wang, Zhan-fang Cao e Hong Zhong. "Recovery of manganese from manganese oxide ores in the EDTA solution". Metallurgical Research & Technology 115, n. 3 (2018): 306. http://dx.doi.org/10.1051/metal/2018004.
Testo completoAbstract (sommario):
A new process has been experimentally and theoretically established for the recovery of manganese from manganese oxide ores, mainly including the reductive leaching of manganese by ethylenediaminetetraacetic acid (EDTA), EDTA recovery, and manganese electrolysis. The experimental conditions for this process were investigated. Moderate leaching environment by EDTA with the pH in the range of 5–6 is of benefit to leach manganese from some manganese oxide ores with high-content impurities, such as iron and aluminum. Most of EDTA can be recovered by acidification. A small amount of the residual EDTA in the electrolyte can prevent the generation of anode mud. In addition, trimanganese tetroxide (Mn3O4) can be obtained by the roasting of the EDTA–Mn crystallized product.
2
Park, Yaewon, Shuang Liu, Terrence Gardner, Drake Johnson, Aaron Keeler, Nathalia Ortiz, Ghada Rabah e Ericka Ford. "Biohybrid nanofibers containing manganese oxide–forming fungi for heavy metal removal from water". Journal of Engineered Fibers and Fabrics 15 (gennaio 2020): 155892501989895. http://dx.doi.org/10.1177/1558925019898954.
Testo completoAbstract (sommario):
Manganese-oxidizing fungi support bioremediation through the conversion of manganese ions into manganese oxide deposits that in turn adsorb manganese and other heavy metal ions from the environment. Manganese-oxidizing fungi were immobilized onto nanofiber surfaces to assist remediation of heavy metal–contaminated water. Two fungal isolates, Coniothyrium sp. and Coprinellus sp., from a Superfund site (Lot 86, Farm Unit #1) water treatment system were incubated in the presence of nanofibers. Fungal hyphae had strong association with nanofiber surfaces. Upon fungal attachment to manganese chloride–seeded nanofibers, Coniothyrium sp. catalyzed the conformal deposition of manganese oxide along hyphae and nanofibers, but Coprinellus sp. catalyzed manganese oxide only along its hyphae. Fungi–nanofiber hybrids removed various heavy metals from the water. Heavy metal ions were adsorbed into manganese oxide crystalline structure, possibly by ion exchange with manganese within the manganese oxide. Hybrid materials of fungal hyphae and manganese oxides confined to nanofiber-adsorbed heavy metal ions from water.
3
Malinenko, V. P., L. A. Aleshina, A. L. Pergament e G. V. Germak. "Switching Effects and Metal−Insulator Transition in Manganese Oxide". Journal on Selected Topics in Nano Electronics and Computing 1, n. 1 (dicembre 2013): 44–50. http://dx.doi.org/10.15393/j8.art.2013.3005.
Testo completo
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Lewandowski, Z., R. Avci, M. Geiser, X. Shi, K. Braughton e N. Yurt. "Biofouling and corrosion of stainless steels in natural waters". Water Supply 2, n. 4 (1 settembre 2002): 65–72. http://dx.doi.org/10.2166/ws.2002.0122.
Testo completoAbstract (sommario):
The noble shift in corrosion potential to values between +300 and +400 mVSCE and the accompanying increase in cathodic current density and polarization slope at mild cathodic potentials that develop during microbial colonization of passive metals, are collectively known as ennoblement. This phenomenon is of concern as the noble shift in the corrosion potential may lead to pitting corrosion. We have demonstrated, by growing pure cultures of manganese oxidizing bacteria (MOB) Leptothrix discophora SP-6 under well defined conditions, that microbial deposition of manganese oxides causes ennoblement of 316L stainless steel (SS). Exposing 316L corrosion coupons in lakes and streams supported this conclusion; the rate and extent of ennoblement were positively correlated with the rates of deposition and the amounts of biomineralized manganese oxides deposited on the surfaces of the SS corrosion coupons. X-ray photoelectron spectroscopy (XPS) analyses of the deposits from the ennobled coupons revealed a mixture of manganese oxides, as expected. Many natural waters can support growth of MOB. When manganese-oxidizing biofilms accumulate on surfaces of passive metals there is a potential for manganese redox cycling on the metal surface. This process is initiated by depositing minute amounts of manganese oxides on the metal surface. These microbially deposited manganese oxides are then reduced by the electrons derived from anodic dissolution of the metal; the metal is corroding and the manganese oxides are reduced to divalent manganese ions. However, since the manganese ions are liberated within the manganese-oxidizing biofilm, the manganese ions are immediately reoxidized, and the cycle continues.
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Zhu, Xiang-Ying, Yu-Chun Zhai e Guo-Hua Zhang. "Nitriding of manganese pellet". Metallurgical Research & Technology 114, n. 5 (2017): 518. http://dx.doi.org/10.1051/metal/2017063.
Testo completo
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Sommerfeld, Marcus, David Friedmann, Thomas Kuhn e Bernd Friedrich. "“Zero-Waste”: A Sustainable Approach on Pyrometallurgical Processing of Manganese Nodule Slags". Minerals 8, n. 12 (23 novembre 2018): 544. http://dx.doi.org/10.3390/min8120544.
Testo completoAbstract (sommario):
A continuously growing demand for valuable non-ferrous metals and therefore an increase in their prices at the metal exchanges makes it necessary and profitable to investigate alternative metal resources. Polymetallic deep-sea nodules contain cobalt, copper, manganese, molybdenum and nickel, and are highly abundant on the sea floor. Developing a metallurgical process to recover the metal content from manganese nodules can close the predicted supply gap of critical metals like cobalt. This paper investigated a potential extraction process for valuable metals from manganese nodules supplied by the German Federal Institute for Geosciences and Natural Resources. The samples originated from the German license area of the Clarion-Clipperton Zone in the Pacific Ocean. Due to a low concentration of valuable metals in nodules, a pyrometallurgical enrichment step was carried out to separate cobalt, copper, molybdenum and nickel in a metallic phase. The manganese was discarded in the slag and recovered in a second smelting step as ferromanganese. To aid the experiments, FactSageTM was used for thermodynamic modeling of the smelting steps. To increase metal yields and to alter the composition of the metal alloys, different fluxes were investigated. The final slag after two reduction steps were heavy-metal free and a utilization as a mineral product was desired to ensure a zero-waste process.
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Wu, Fangfang, Zhu Xiao, Bin Zeng, Long Chen, Hui Liu, Min Liang, Peng Yu e Baobin Mi. "Experimental and reduction leaching kinetics simulation of iron-rich manganese oxide ore using tobacco stem concrete as reducing agent". Metallurgical Research & Technology 116, n. 4 (2019): 422. http://dx.doi.org/10.1051/metal/2019017.
Testo completoAbstract (sommario):
Reduction leaching behaviors of Fe and Mn from an iron-rich manganese oxide ore using waste tobacco stem concrete as reducing agent were investigated in this paper with a view to determining the feasibility of tobacco stem concrete used in reduction leaching of Mn from iron-rich manganese oxide ore. Results indicated that the leaching processes of Fe and Mn were both dominated by internal diffusion, but the effects of leaching parameters on leaching ratios of Fe and Mn were different based on established leaching kinetic equations. The leaching ratio of Mn reached up to 96.18% while that of Fe kept a lower concentration (17.66%) under optimal leaching conditions, which achieved high selectivity recovery of Mn from iron-rich manganese oxide ore. In addition, the leached solution can be used as electrolytic stock solution in the production of electrolytic manganese. Characterization of the obtained electrolytic manganese product indicated that the quality of electrolytic manganese fully met the standards of YB/T 051-2003, which disclosing a novel recycling approach of utilizing the resource coming from the tobacco industry.
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Heindl, Jason E., Michael E. Hibbing, Jing Xu, Ramya Natarajan, Aaron M. Buechlein e Clay Fuqua. "Discrete Responses to Limitation for Iron and Manganese in Agrobacterium tumefaciens: Influence on Attachment and Biofilm Formation". Journal of Bacteriology 198, n. 5 (28 dicembre 2015): 816–29. http://dx.doi.org/10.1128/jb.00668-15.
Testo completoAbstract (sommario):
ABSTRACTTransition metals such as iron and manganese are crucial trace nutrients for the growth of most bacteria, functioning as catalytic cofactors for many essential enzymes. Dedicated uptake and regulatory systems have evolved to ensure their acquisition for growth, while preventing toxicity. Transcriptomic analysis of the iron- and manganese-responsive regulons ofAgrobacterium tumefaciensrevealed that there are discrete regulatory networks that respond to changes in iron and manganese levels. Complementing earlier studies, the iron-responsive gene network is quite large and includes many aspects of iron-dependent metabolism and the iron-sparing response. In contrast, the manganese-responsive network is restricted to a limited number of genes, many of which can be linked to transport and utilization of the transition metal. Several of the target genes predicted to drive manganese uptake are required for growth under manganese-limited conditions, and anA. tumefaciensmutant with a manganese transport deficiency is attenuated for plant virulence. Iron and manganese limitation independently inhibit biofilm formation byA. tumefaciens, and several candidate genes that could impact biofilm formation were identified in each regulon. The biofilm-inhibitory effects of iron and manganese do not rely on recognized metal-responsive transcriptional regulators, suggesting alternate mechanisms influencing biofilm formation. However, under low-manganese conditions thedcpAoperon is upregulated, encoding a system that controls levels of the cyclic di-GMP second messenger. Mutation of this regulatory pathway dampens the effect of manganese limitation.IMPORTANCEResponses to changes in transition metal levels, such as those of manganese and iron, are important for normal metabolism and growth in bacteria. Our study used global gene expression profiling to understand the response of the plant pathogenAgrobacterium tumefaciensto changes of transition metal availability. Among the properties that are affected by both iron and manganese levels are those required for normal surface attachment and biofilm formation, but the requirement for each of these transition metals is mechanistically independent from the other.
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Abd Elmomen, Sanaa S. "Manganese Distribution between Slag and Metal in the Egyptian Blast Furnace". Key Engineering Materials 786 (ottobre 2018): 65–74. http://dx.doi.org/10.4028/www.scientific.net/kem.786.65.
Testo completoAbstract (sommario):
Daily average slag and the corresponding hot metal samples were collected from blast furnace No.3 (1033m3useful volume) of the Egyptian Iron and Steel Company (EISCO) charged with 100% self- fluxing sinter over a period of two months (from July to August 2015). The analyses of slag and metal were used to investigate the effects of temperature and basicity, defined as CaO/SiO2,on manganate capacity and manganese distribution between slag and metal.
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Lu, Jianming, David Dreisinger e Thomas Glück. "Electrolytic manganese metal production from manganese carbonate precipitate". Hydrometallurgy 161 (maggio 2016): 45–53. http://dx.doi.org/10.1016/j.hydromet.2016.01.010.
Testo completo
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Heilig, Elizabeth, Ramon Molina, Thomas Donaghey, Joseph D. Brain e Marianne Wessling-Resnick. "Pharmacokinetics of pulmonary manganese absorption: evidence for increased susceptibility to manganese loading in iron-deficient rats". American Journal of Physiology-Lung Cellular and Molecular Physiology 288, n. 5 (maggio 2005): L887—L893. http://dx.doi.org/10.1152/ajplung.00382.2004.
Testo completoAbstract (sommario):
High levels of airborne manganese can be neurotoxic, yet little is known about absorption of this metal via the lungs. Intestinal manganese uptake is upregulated by iron deficiency and is thought to be mediated by divalent metal transporter 1 (DMT1), an iron-regulated factor known to play a role in dietary iron absorption. To better characterize metal absorption from the lungs to the blood and test whether iron deficiency may modify this process, the pharmacokinetics of pulmonary manganese and iron absorption by control and iron-deficient rats were compared. Levels of DMT1 expression in the lungs were determined to explore potential changes induced by iron deficiency that might alter metal absorption. The pharmacokinetic curves for intratracheally instilled54Mn and59Fe were significantly different, suggesting that pulmonary uptake of the two metals involves different mechanisms. Intratracheally instilled iron-deficient rats had significantly higher blood54Mn levels, whereas blood59Fe levels were significantly reduced compared with controls. The same trend was observed when radioisotopes were delivered by intravenous injection, indicating that iron-deficient rats have altered blood clearance of manganese. In situ analysis revealed the presence of DMT1 transcripts in airway epithelium; however, mRNA levels did not change in iron deficiency. Although lung DMT1 levels and metal absorption did not appear to be influenced by iron deficiency, the differences in blood clearance of instilled manganese identified by this study support the idea that iron status can influence the potential toxicity of this metal.
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Tarutis, W. J., e R. F. Unz. "Iron and manganese release in coal mine drainage wetland microcosms". Water Science and Technology 32, n. 3 (1 agosto 1995): 187–92. http://dx.doi.org/10.2166/wst.1995.0140.
Testo completoAbstract (sommario):
The primary mechanisms responsible for the removal and retention of iron, manganese, and sulfate in constructed wetlands receiving acidic mine drainage (AMD) include the formation of metal oxides and sulfides within the sediments. This study was initiated to determine the kinetics of metal ion liberation, under reducing conditions, from synthetic and naturally occurring iron and manganese oxides typically found in AMD precipitates. Rates of metal ion liberation were determined during time series incubations of an organic substrate (spent mushroom compost) to which five metal oxides of varying crystallinity (amorphous and crystalline oxides of iron and manganese; natural AMD oxide) were added. All experiments were carried out in silicone-sealed polycarbonate centrifuge tubes incubated at 22°C for a period of 3, 7, 10, 14, 21 or 28 days. Tubes were sacrificed after each incubation period and were analyzed for redox potential, pH, sulfide, and metals. All tubes exhibited reducing potentials within 3 days coupled with rapidly increasing concentrations of iron and manganese. Liberation of iron and manganese decreased with increasing mineral crystallinity (amorphous > natural AMD ≫ crystalline). The results suggest that metal ion liberation from oxide minerals may be an important source of iron and manganese within constructed wetlands receiving AMD.
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Kehl-Fie, Thomas E., Yaofang Zhang, Jessica L. Moore, Allison J. Farrand, M. Indriati Hood, Subodh Rathi, Walter J. Chazin, Richard M. Caprioli e Eric P. Skaar. "MntABC and MntH Contribute to Systemic Staphylococcus aureus Infection by Competing with Calprotectin for Nutrient Manganese". Infection and Immunity 81, n. 9 (1 luglio 2013): 3395–405. http://dx.doi.org/10.1128/iai.00420-13.
Testo completoAbstract (sommario):
ABSTRACTDuring infection, vertebrates limit access to manganese and zinc, starving invading pathogens, such asStaphylococcus aureus, of these essential metals in a process termed “nutritional immunity.” The manganese and zinc binding protein calprotectin is a key component of the nutrient-withholding response, and mice lacking this protein do not sequester manganese fromS. aureusliver abscesses. One potential mechanism utilized byS. aureusto minimize host-imposed manganese and zinc starvation is the expression of the metal transporters MntABC and MntH. We performed transcriptional analyses of bothmntAandmntH, which revealed increased expression of both systems in response to calprotectin treatment. MntABC and MntH compete with calprotectin for manganese, which enablesS. aureusgrowth and retention of manganese-dependent superoxide dismutase activity. Loss of MntABC and MntH results in reduced staphylococcal burdens in the livers of wild-type but not calprotectin-deficient mice, suggesting that these systems promote manganese acquisition during infection. During the course of these studies, we observed that metal content and the importance of calprotectin varies between murine organs, and infection leads to profound changes in the anatomical distribution of manganese and zinc. In total, these studies provide insight into the mechanisms utilized by bacteria to evade host-imposed nutrient metal starvation and the critical importance of restricting manganese availability during infection.
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Janulczyk, Robert, Susanna Ricci e Lars Björck. "MtsABC Is Important for Manganese and Iron Transport, Oxidative Stress Resistance, and Virulence of Streptococcus pyogenes". Infection and Immunity 71, n. 5 (maggio 2003): 2656–64. http://dx.doi.org/10.1128/iai.71.5.2656-2664.2003.
Testo completoAbstract (sommario):
ABSTRACT MtsABC is a Streptococcus pyogenes ABC transporter which was previously shown to be involved in iron and zinc accumulation. In this study, we showed that an mtsABC mutant has impaired growth, particularly in a metal-depleted medium and an aerobic environment. In metal-depleted medium, growth was restored by the addition of 10 μM MnCl2, whereas other metals had modest or no effect. A characterization of metal radioisotope accumulation showed that manganese competes with iron accumulation in a dose-dependent manner. Conversely, iron competes with manganese accumulation but to a lesser extent. The mutant showed a pronounced reduction (>90%) of 54Mn accumulation, showing that MtsABC is also involved in Mn transport. Using paraquat and hydrogen peroxide to induce oxidative stress, we show that the mutant has an increased susceptibility to reactive oxygen species. Moreover, activity of the manganese-cofactored superoxide dismutase in the mutant is reduced, probably as a consequence of reduced intracellular availability of manganese. The enzyme functionality was restored by manganese supplementation during growth. The mutant was also attenuated in virulence, as shown in animal experiments. These results emphasize the role of MtsABC and trace metals, especially manganese, for S. pyogenes growth, susceptibility to oxidative stress, and virulence.
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Lei, Sihua, Fei Lu, Shuai Wang, Hong Zhong, Zhanfang Cao e Xiaoping Huang. "Study on corrosion resistance behavior and formation mechanism of Ce conversion coating on manganese". Metallurgical Research & Technology 118, n. 3 (2021): 319. http://dx.doi.org/10.1051/metal/2021041.
Testo completoAbstract (sommario):
Ce conversion coatings have received extensive attention from researchers due to their excellent corrosion resistance and environmental friendliness. Here, Ce conversion coatings on manganese were prepared by treating in the cerium nitrate conversion solution. The influence of treating parameters was studied and optimized. The surface morphology, element composition and chemical state of Ce conversion coatings were studied by means of SEM, EDS, XRD and XPS. Electrochemical methods of polarization curve and electrochemical impedance were used to study the corrosion resistance of conversion coatings. The results showed that the Ce conversion coating contained mainly Mn, O and Ce, and its forms were manganese oxide and cerium oxide. Electrochemical tests showed that Ce conversion coating can not only effectively improve the corrosion resistance of manganese substrate, but also has good acid and alkali resistance. Discussion on the formation mechanism of cerium conversion coating shows that the conversion treatment is beneficial to inhibit the further oxidation of manganese to the higher valence state.
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Winslow, James W. W., Kirsten H. Limesand e Ningning Zhao. "The Functions of ZIP8, ZIP14, and ZnT10 in the Regulation of Systemic Manganese Homeostasis". International Journal of Molecular Sciences 21, n. 9 (7 maggio 2020): 3304. http://dx.doi.org/10.3390/ijms21093304.
Testo completoAbstract (sommario):
As an essential nutrient, manganese is required for the regulation of numerous cellular processes, including cell growth, neuronal health, immune cell function, and antioxidant defense. However, excess manganese in the body is toxic and produces symptoms of neurological and behavioral defects, clinically known as manganism. Therefore, manganese balance needs to be tightly controlled. In the past eight years, mutations of genes encoding metal transporters ZIP8 (SLC39A8), ZIP14 (SLC39A14), and ZnT10 (SLC30A10) have been identified to cause dysregulated manganese homeostasis in humans, highlighting the critical roles of these genes in manganese metabolism. This review focuses on the most recent advances in the understanding of physiological functions of these three identified manganese transporters and summarizes the molecular mechanisms underlying how the loss of functions in these genes leads to impaired manganese homeostasis and human diseases.
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Jensen, Laran T., Mark C. Carroll, Matthew D. Hall, Christopher J. Harvey, Sara E. Beese e Valeria C. Culotta. "Down-Regulation of a Manganese Transporter in the Face of Metal Toxicity". Molecular Biology of the Cell 20, n. 12 (15 giugno 2009): 2810–19. http://dx.doi.org/10.1091/mbc.e08-10-1084.
Testo completoAbstract (sommario):
The yeast Smf1p Nramp manganese transporter is posttranslationally regulated by environmental manganese. Smf1p is stabilized at the cell surface with manganese starvation, but is largely degraded in the vacuole with physiological manganese through a mechanism involving the Rsp5p adaptor complex Bsd2p/Tre1p/Tre2p. We now describe an additional level of Smf1p regulation that occurs with toxicity from manganese, but not other essential metals. This regulation is largely Smf1p-specific. As with physiological manganese, toxic manganese triggers vacuolar degradation of Smf1p by trafficking through the multivesicular body. However, regulation by toxic manganese does not involve Bsd2p/Tre1p/Tre2p. Toxic manganese triggers both endocytosis of cell surface Smf1p and vacuolar targeting of intracellular Smf1p through the exocytic pathway. Notably, the kinetics of vacuolar targeting for Smf1p are relatively slow with toxic manganese and require prolonged exposures to the metal. Down-regulation of Smf1p by toxic manganese does not require transport activity of Smf1p, whereas such transport activity is needed for Smf1p regulation by manganese starvation. Furthermore, the responses to manganese starvation and manganese toxicity involve separate cellular compartments. We provide evidence that manganese starvation is sensed within the lumen of the secretory pathway, whereas manganese toxicity is sensed within an extra-Golgi/cytosolic compartment of the cell.
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Devereux, Michael, Malachy McCann, Vanessa Leon, Majella Geraghty, Vickie McKee e Jan Wikaira. "Synthesis and Biological Activity of Manganese (II) Complexes of Phthalic and Isophthalic Acid: X-Ray Crystal Structures of [Mn(ph)(Phen)2(H2O)]· 4H2O, [Mn(Phen)2(H2O)2]2(Isoph)2(Phen)· 12H2O and {[Mn(Isoph)(bipy)]4· 2.75biby}n(phH2 = Phthalic Acid; isoph = Isophthalic Acid; phen = 1,10-Phenanthroline; bipy = 2,2-Bipyridine)". Metal-Based Drugs 7, n. 5 (1 gennaio 2000): 275–88. http://dx.doi.org/10.1155/mbd.2000.275.
Testo completoAbstract (sommario):
Manganese(II) acetate reacts with phthalic acid (phH2) to give [Mn(ph)]·0.5H2O (1). Reaction of 1 with 1,10-phenanthroline produces [Mn(ph)(phen)]·2H2O (2) and [Mn(ph)(phen)2(H2O)]·4H2O (3). Reaction of isophthalic acid (isophH2) with manganese(II) acetate results in the formation of [Mn(isoph)]·2H2O (4). The addition of the N,N-donor ligands 1,10-phenanthroline or 2,2'-bipyridine to 4 leads to the formation of [Mn2 (isoph)2(phen)3)]·4H2O (5), [(Mn(phen)2(H2O)2]2(isoph)2(phen)·12H2O (6) and {[Mn(isoph)(bipy)]4·2.75 biby}n (7), respectively. Molecular structures of 3, 6 and 7 were determined crystallographically. In 3 the phthalate ligand is bound to the manganese via just one of its carboxylate groups in a monodentate mode with the remaining coordination sites filled by four phenanthroline nitrogen and one water oxygen atoms. In 6 the isophthalates are uncoordinated with the octahedral manganese center ligated by two phenanthrolines and two waters. In 7 the Isophthalate ligands act as bridges resulting in a polymeric structure. One of the carboxylate groups is chelating a single manganese with the other binding two metal centres in a bridging bidentate mode. The phthalate and isophthalate complexes, the metal free ligands and a number of simple manganes salts were each tested for their ability, to inhibit the growth of Candida albicans. Only the “metal free” 1,10-phenanthroline and its manganese complexes were found to be active.
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Luk, Edward E.-Ching, e Valeria Cizewski Culotta. "Manganese Superoxide Dismutase inSaccharomyces cerevisiaeAcquires Its Metal Co-factor through a Pathway Involving the Nramp Metal Transporter, Smf2p". Journal of Biological Chemistry 276, n. 50 (15 ottobre 2001): 47556–62. http://dx.doi.org/10.1074/jbc.m108923200.
Testo completoAbstract (sommario):
Eukaryotes express both copper/zinc (SOD1)- and manganese (SOD2)-requiring superoxide dismutase enzymes that guard against oxidative damage. Although SOD1 acquires its copper through a specific copper trafficking pathway, nothing is known regarding the intracellular manganese trafficking pathway for SOD2. We demonstrate here that inSaccharomyces cerevisiaecells delivery of manganese to SOD2 in the mitochondria requires the Nramp metal transporter, Smf2p. SOD2 activity is greatly diminished insmf2Δ mutants, even though the mature SOD2 polypeptide accumulates to normal levels in mitochondria. Treatingsmf2Δ cells with manganese supplements corrected the SOD2 defect, as did elevating intracellular manganese through mutations inPMR1.Hence, manganese appears to be inaccessible to mitochondrial SOD2 insmf2mutants. Cells lackingSMF2also exhibited defects in manganese-dependent steps in protein glycosylation and showed an overall decrease in steady-state levels of accumulated manganese. By comparison, mutations in the cell surface Nramp transporter, Smf1p, had very little impact on manganese accumulation and trafficking. Smf2p resides in intracellular vesicles and shows no evidence of plasma membrane localization, even in anend4mutant blocked for endocytosis. We propose a model in which Smf2p-containing vesicles play a central role in manganese trafficking to the mitochondria and other cellular sites as well.
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Sehn, A. P., e B. Meier. "Regulation of an in vivo metal-exchangeable superoxide dismutase from Propionibacterium shermanii exhibiting activity with different metal cofactors". Biochemical Journal 304, n. 3 (15 dicembre 1994): 803–8. http://dx.doi.org/10.1042/bj3040803.
Testo completoAbstract (sommario):
The anaerobic, but aerotolerant Propionibacterium freudenreichii sp. shermanii contains a single superoxide dismutase [EC 1.15.1.1.] exhibiting comparable activity with iron or manganese as metal cofactor. The formation of superoxide dismutase is not depending on the supplementation of iron or manganese to the culture medium. Even in the absence of these metals the protein is built in comparable amounts. Bacteria grown in the absence of iron and manganese synthesize a superoxide dismutase with very low activity which had incorporated copper. If the medium was also depleted of copper, cobalt was incorporated, leading to an enzymically inactive form. In the absence of cobalt an enzymically inactive superoxide dismutase was built with unknown metal contents. Upon aeration the amount of superoxide dismutase activity increased continuously up to 9 h, due to a de novo synthesis of the protein. This superoxide dismutase had incorporated iron into the active centre. The superoxide dismutase of Propionibacterium shermanii is able to form a much wider variety of complexes with trace metal ions in vivo than previously recognized, leading to the hypothesis that the original function of these proteins was the binding of cytoplasmic trace metals present in excess.
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Tong, Huiyan, Zhongyue Li, Xingshuai Hu, Weiping Xu e Zhengkun Li. "Metals in Occluded Water: A New Perspective for Pollution in Drinking Water Distribution Systems". International Journal of Environmental Research and Public Health 16, n. 16 (9 agosto 2019): 2849. http://dx.doi.org/10.3390/ijerph16162849.
Testo completoAbstract (sommario):
Occluded water is water that remains inside corrosion scales within deteriorating distribution pipes. The accumulation of iron and manganese in the occluded water is a potential risk for water quality. Thus, this study investigated the change in metal (iron, manganese, copper and chromium) concentration in occluded water, the effect of these metals on the flowing water, and the source of iron and manganese in the occluded water using a simulation device. The results showed that total iron and total manganese were enriched in the occluded water, while the concentrations of total copper and total chromium in the occluded water gradually decreased over time. The iron and manganese in the occluded water migrate to the flowing water causing pollution in the flowing water. Also, copper and chromium adsorb on the corrosion scales within the pipes. The iron and manganese in the occluded water mainly came from the corrosion of the metal pipes, and the corrosion scales had a certain obstructive effect on the outward migration of iron in the occluded water but had less hindrance to the migration of manganese. Occluded water plays a critical role in the pollution of drinking water, and additional work is needed to control metal accumulation and release.
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KIM, BONG-SEO, SU-DONG PARK, HEE-WOONG LEE, DONG-YOON LEE e WON-SUB CHUNG. "ELECTRONIC STATE CALCULATION OF MANGANESE DIOXIDE ELECTRODE WITH ADDITIVE TRANSITION METALS". International Journal of Modern Physics B 20, n. 25n27 (30 ottobre 2006): 4255–60. http://dx.doi.org/10.1142/s0217979206041185.
Testo completoAbstract (sommario):
The electronic states of manganese dioxide substituted with transition metals were theoretically calculated by DV-Xα method, cluster model was Mn 15 O 56 and Mn 14 XO 56 (X = transition metal). The energy band gap of manganese-X oxides is lower than that of manganese dioxide from theoretical calculation. Also it is identified that the electrical conductivity of manganese-tungsten oxide is better than that of manganese dioxide from experiment of anodic deposition method. It is confirmed that the theoretical calculation coincides with experimental results.
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An, Qi, Mei-Ling Han, Lu-Sen Bian, Zhi-Chao Han, Ning Han, Yun-Feng Xiao e Fang-Bo Zhang. "Enhanced laccase activity of white rot fungi induced by different metal ions under submerged fermentation". BioResources 15, n. 4 (18 settembre 2020): 8369–83. http://dx.doi.org/10.15376/biores.15.4.8369-8383.
Testo completoAbstract (sommario):
Submerged fermentation with single or mixed metal ions as inducers was used for laccase production from white rot fungi. Mixed metal ions were used for the first time as inducers for Pleurotus ostreatus and Flammulina velutipes to enhance laccase activity. The maximum laccase activity from P. ostreatus in basal media, metal ion media 1 containing copper ion, metal ion media 2 containing manganese ion, metal ion media 3 containing manganese and copper ions, metal ion media 4 containing ferrous ion, metal ion media 5 containing manganese and ferrous ions, metal ion media 6 containing ferrous and copper ions, and metal ion media 7 containing manganese, copper and ferrous ions were, respectively, approximately 21.5-fold, 4.7-fold, 14.9-fold, 16.9-fold, 4.0-fold, 11.0-fold, 12.7-fold, and 24.8-fold higher than that from F. velutipes. The combination of copper and manganese ions as inducers was superior to that of a single copper ion or manganese ion. The maximum laccase activity of P. ostreatus rose in media containing manganese and copper ions. The single copper ion as the inducer for enhancing laccase activity was more suitable for F. velutipes. These findings are helpful in selecting the appropriate single metal ion or mixed metal ions to enhance laccase activity.
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Sánchez-España e Yusta. "Coprecipitation of Co2+, Ni2+ and Zn2+ with Mn(III/IV) Oxides Formed in Metal-Rich Mine Waters". Minerals 9, n. 4 (10 aprile 2019): 226. http://dx.doi.org/10.3390/min9040226.
Testo completoAbstract (sommario):
Manganese oxides are widespread in soils and natural waters, and their capacity to adsorb different trace metals such as Co, Ni, or Zn is well known. In this study, we aimed to compare the extent of trace metal coprecipitation in different Mn oxides formed during Mn(II) oxidation in highly concentrated, metal-rich mine waters. For this purpose, mine water samples collected from the deepest part of several acidic pit lakes in Spain (pH 2.7–4.2), with very high concentration of manganese (358–892 mg/L Mn) and trace metals (e.g., 795–10,394 µg/L Ni, 678–11,081 µg/L Co, 259–624 mg/L Zn), were neutralized to pH 8.0 in the laboratory and later used for Mn(II) oxidation experiments. These waters were subsequently allowed to oxidize at room temperature and pH = 8.5–9.0 over several weeks until Mn(II) was totally oxidized and a dense layer of manganese precipitates had been formed. These solids were characterized by different techniques for investigating the mineral phases formed and the amount of coprecipitated trace metals. All Mn oxides were fine-grained and poorly crystalline. Evidence from X-Ray Diffraction (XRD) and Scanning Electron Microscopy coupled to Energy Dispersive X-Ray Spectroscopy (SEM–EDX) suggests the formation of different manganese oxides with varying oxidation state ranging from Mn(III) (e.g., manganite) and Mn(III/IV) (e.g., birnessite, todorokite) to Mn(IV) (e.g., asbolane). Whole-precipitate analyses by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), and/or Atomic Absorption Spectrometry (AAS), provided important concentrations of trace metals in birnessite (e.g., up to 1424 ppm Co, 814 ppm Ni, and 2713 ppm Zn), while Co and Ni concentrations at weight percent units were detected in asbolane by SEM-EDX. This trace metal retention capacity is lower than that observed in natural Mn oxides (e.g., birnessite) formed in the water column in a circum-neutral pit lake (pH 7.0–8.0), or in desautelsite obtained in previous neutralization experiments (pH 9.0–10.0). However, given the very high amount of Mn sorbent material formed in the solutions (2.8–4.6 g/L Mn oxide), the formation of these Mn(III/IV) oxides invariably led to the virtually total removal of Co, Ni, and Zn from the aqueous phase. We evaluate these data in the context of mine water pollution treatment and recovery of critical metals.
25
YANG, Mei, Laran T. JENSEN, Allison J. GARDNER e Valeria C. CULOTTA. "Manganese toxicity and Saccharomyces cerevisiae Mam3p, a member of the ACDP (ancient conserved domain protein) family". Biochemical Journal 386, n. 3 (8 marzo 2005): 479–87. http://dx.doi.org/10.1042/bj20041582.
Testo completoAbstract (sommario):
Manganese is an essential, but potentially toxic, trace metal in biological systems. Overexposure to manganese is known to cause neurological deficits in humans, but the pathways that lead to manganese toxicity are largely unknown. We have employed the bakers' yeast Saccharomyces cerevisiae as a model system to identify genes that contribute to manganese-related damage. In a genetic screen for yeast manganese-resistance mutants, we identified S. cerevisiae MAM3 as a gene which, when deleted, would increase cellular tolerance to toxic levels of manganese and also increased the cell's resistance towards cobalt and zinc. By sequence analysis, Mam3p shares strong similarity with the mammalian ACDP (ancient conserved domain protein) family of polypeptides. Mutations in human ACDP1 have been associated with urofacial (Ochoa) syndrome. However, the functions of eukaryotic ACDPs remain unknown. We show here that S. cerevisiae MAM3 encodes an integral membrane protein of the yeast vacuole whose expression levels directly correlate with the degree of manganese toxicity. Surprisingly, Mam3p contributes to manganese toxicity without any obvious changes in vacuolar accumulation of metals. Furthermore, through genetic epistasis studies, we demonstrate that MAM3 operates independently of the well-established manganese-trafficking pathways in yeast, involving the manganese transporters Pmr1p, Smf2p and Pho84p. This is the first report of a eukaryotic ACDP family protein involved in metal homoeostasis.
26
Permyakov, Eugene A. "Metal Binding Proteins". Encyclopedia 1, n. 1 (15 marzo 2021): 261–92. http://dx.doi.org/10.3390/encyclopedia1010024.
Testo completoAbstract (sommario):
Metal ions play several major roles in proteins: structural, regulatory, and enzymatic. The binding of some metal ions increase stability of proteins or protein domains. Some metal ions can regulate various cell processes being first, second, or third messengers. Some metal ions, especially transition metal ions, take part in catalysis in many enzymes. From ten to twelve metals are vitally important for activity of living organisms: sodium, potassium, magnesium, calcium, manganese, iron, cobalt, zinc, nickel, vanadium, molybdenum, and tungsten. This short review is devoted to structural, physical, chemical, and physiological properties of proteins, which specifically bind these metal cations.
27
Arslan, Servet, e Adem Arıkan. "Arı Ürünlerindeki Ağır metal Birikimine Karayollarından Uzaklığın Etkisi". Turkish Journal of Agriculture - Food Science and Technology 1, n. 2 (2 gennaio 2014): 90. http://dx.doi.org/10.24925/turjaf.v1i2.90-93.38.
Testo completoAbstract (sommario):
Distance from the highway to the effect of heavy metal accumulation in bee products in order to investigate in this study; four different apiaries which have four km interval have been established from Tokat-Turhal highway side towards the north. Each station of a total 9 of 36 units bee colonies were placed. Honey, pollen and propolis samples were taken from these colonies in the months of April-July in 2009. The obtained samples (copper, zinc, iron, cadmium, chromium, lead and heavy metals such as manganese) content were investigated. According to the distance from the highway in honey samples averages of zinc, iron, chromium and manganese, there was no statistical difference between averages, while averages of copper, cadmium and lead were found significant differences between the averages. In the pollen samples, averages of zinc, iron, cadmium, chromium and manganese indicated no statistical difference between the averages, while, averages of copper and lead were found to be statistically significant. İn the Propolis samples, averages of copper, zinc, iron, chromium, lead and manganese determined no statistical difference between the averages, significant differences were detected between the averages of cadmium. Cadmium accumulation in the maximum occurs at the edge of the highway, the maximum accumulation of other metals have been seen in other stations When considering, due to traffic only metal cadmium at a level that considered as important in bee products be said to constitute pollution.
28
Bow, Rusdianasari, Susila Arita, Eddy Ibrahim e Ngudiantoro Ngudiantoro. "Reduction of Metal Contents in Coal Stockpile Wastewater Using Electrocoagulation". Applied Mechanics and Materials 391 (settembre 2013): 29–33. http://dx.doi.org/10.4028/www.scientific.net/amm.391.29.
Testo completoAbstract (sommario):
Stockpile wastewater consisted of ferrous metal, manganese metal and total suspended solid (TSS). In addition, it also has high acidity (pH) which is possibly harmful to the environment. This research objectives were to reduce ferrous and manganese metal in coal stockpile wastewater using electrocoagulation technique using aluminum electrode with variation in electrics current and processing time. The most effective conditions in reducing ferrous and manganese concentrations with electric current of ± 2.5 A in 90 minutes. Effectivity in ferrous and manganese metal reduction was 98.7% and 99.6%, respectively. The final concentration of ferrous and manganese metal was 0.08 mg/L and 0.01 mg/L respectively. Optimum concentration of TSS reduction was 83.7% with the final concentration of 72 mg/L. The wastewater pH value became 7,1. Finally, the results demonstrated that the electrocoagulation process using aluminium electrode is a reliable technique for removal of pollutants from coal stockpile wastewater.
29
Benítez, Ángel, Jefferson Medina, Cristina Vásquez, Talía Loaiza, Yesenia Luzuriaga e James Calva. "Lichens and Bromeliads as Bioindicators of Heavy Metal Deposition in Ecuador". Diversity 11, n. 2 (25 febbraio 2019): 28. http://dx.doi.org/10.3390/d11020028.
Testo completoAbstract (sommario):
We evaluated heavy metal deposition in Parmotrema arnoldii and Tillandsia usneoides in response to air pollution in Loja city, Ecuador. We assessed heavy metal (cadmium, copper, manganese, lead and zinc) content in these organisms at nine study sites inside Loja city and three control sites in nearby forests. Concentrations of all studied heavy metals (i.e., cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn) and zinc (Zn)) were highest in downtown Loja. Our study confirms that passive monitoring using lichens and/or bromeliads can be an efficient tool to evaluate heavy metal deposition related to urbanization (e.g., vehicle emissions). We recommend these organisms to be used in cost-effective monitoring of air pollution in tropical countries.
30
Liu, Yu, Guangqiang Li, Qiang Wang, Ru Lu, Xijie Wang e Yufeng Tian. "Effect of slag composition on desulfurization during recycling rejected electrolytic manganese metal by electroslag remelting". Metallurgical Research & Technology 118, n. 2 (2021): 206. http://dx.doi.org/10.1051/metal/2021019.
Testo completoAbstract (sommario):
To reduce the Mn vaporization during recycling rejected electrolytic manganese metal by electroslag remelting, it is proposed to reduce the temperature of molten slag pool, but which leads to the degradation of slag desulfurization. The desulfurization by interaction between CaF2–CaO–Al2O3–Na2O slag and rejected electrolytic manganese metal scrap was studied from the view of thermodynamics in this study. The results show that sulfur distribution ratio decreases with increase of CaF2 content, and increases with the increase of Na2O content and temperature. Na2O increases sulfur distribution ratio of slag by increasing CaO activity. Na2O addition in CaF2–CaO–Al2O3–Na2O slag can enhance desulfurization ability of slag due to the larger sulfur distribution ratio and lower viscosity. Thus, sulfur content in test of slag T3 bearing 45.8 wt% CaF2-23.2 wt% CaO-22.7 wt% Al2O3-8.3 wt% Na2O is much lower than that of slag without Na2O, implying that 45.8 wt% CaF2-23.2 wt% CaO-22.7 wt% Al2O3-8.3 wt%Na2O slag is the promising slag for recycling rejected electrolytic manganese metal by ESR.
31
Latta, Drew E., Christopher A. Gorski e Michelle M. Scherer. "Influence of Fe2+-catalysed iron oxide recrystallization on metal cycling". Biochemical Society Transactions 40, n. 6 (21 novembre 2012): 1191–97. http://dx.doi.org/10.1042/bst20120161.
Testo completoAbstract (sommario):
Recent work has indicated that iron (oxyhydr-)oxides are capable of structurally incorporating and releasing metals and nutrients as a result of Fe2+-induced iron oxide recrystallization. In the present paper, we briefly review the current literature examining the mechanisms by which iron oxides recrystallize and summarize how recrystallization affects metal incorporation and release. We also provide new experimental evidence for the Fe2+-induced release of structural manganese from manganese-doped goethite. Currently, the exact mechanism(s) for Fe2+-induced recrystallization remain elusive, although they are likely to be both oxide-and metal-dependent. We conclude by discussing some future research directions for Fe2+-catalysed iron oxide recrystallization.
32
Bozzi, Aaron T., Lukas B. Bane, Wilhelm A. Weihofen, Anne L. McCabe, Abhishek Singharoy, Christophe J. Chipot, Klaus Schulten e Rachelle Gaudet. "Conserved methionine dictates substrate preference in Nramp-family divalent metal transporters". Proceedings of the National Academy of Sciences 113, n. 37 (29 agosto 2016): 10310–15. http://dx.doi.org/10.1073/pnas.1607734113.
Testo completoAbstract (sommario):
Natural resistance-associated macrophage protein (Nramp) family transporters catalyze uptake of essential divalent transition metals like iron and manganese. To discriminate against abundant competitors, the Nramp metal-binding site should favor softer transition metals, which interact either covalently or ionically with coordinating molecules, over hard calcium and magnesium, which interact mainly ionically. The metal-binding site contains an unusual, but conserved, methionine, and its sulfur coordinates transition metal substrates, suggesting a vital role in their transport. Using a bacterial Nramp model system, we show that, surprisingly, this conserved methionine is dispensable for transport of the physiological manganese substrate and similar divalents iron and cobalt, with several small amino acid replacements still enabling robust uptake. Moreover, the methionine sulfur’s presence makes the toxic metal cadmium a preferred substrate. However, a methionine-to-alanine substitution enables transport of calcium and magnesium. Thus, the putative evolutionary pressure to maintain the Nramp metal-binding methionine likely exists because it—more effectively than any other amino acid—increases selectivity for low-abundance transition metal transport in the presence of high-abundance divalents like calcium and magnesium.
33
Manivannan, D., e V. M. Biju. "Determination of toxic heavy metals in sea water by FAAS after preconcentration with a novel chelating resin". Water Science and Technology 64, n. 4 (1 agosto 2011): 803–8. http://dx.doi.org/10.2166/wst.2011.501.
Testo completoAbstract (sommario):
A solid phase extraction procedure was developed for preconcentration of toxic heavy metals such as cadmium, cobalt, copper, manganese, lead and zinc in sea water samples. A microcolumn packed with 6-[(4-hydroxyphenyl)diazenyl]naphthalene-2,3-diol-formaldehyde (HPDN-F) resin acts as a sorbent to retain the analyte ions by forming metal chelates. The retained trace level metal was subsequently eluted with 1 mol/L HCl and the acid eluent was analysed by Flame Atomic Absorption Spectrophotometer (FAAS). The HPDN-F chelating resin and its metal chelates were characterized by spectral and thermal analysis. The chelating property of the HPDN-F resin towards divalent metal ions was studied as a function of pH and preconcentration flow rate. The recoveries of cadmium, cobalt, copper, manganese, lead and zinc under the optimum working conditions were above 95%. The relative standard deviations were <2%. The limits of detection were <0.1 μg/L. The method presented was applied for the determination of cadmium, cobalt, copper, manganese, lead and zinc in sea water samples.
34
Couillard, D., e M. Chartier. "Influence des caractéristiques des boues digérées en aérobiose sur la solubilisation biologique des métaux". Canadian Journal of Civil Engineering 20, n. 3 (1 giugno 1993): 509–17. http://dx.doi.org/10.1139/l93-065.
Testo completoAbstract (sommario):
A process for metal removal by thiobacilli was applied to aerobic sludge from three different sources: treated sludge not subjected to phosphate removal, sludge subjected to a FeCl3 phosphate-removal process, and sludge subjected to an alum phosphate-removal process. Solubilization varied, and a number of hypotheses were formulated and tested to explain the results: influence of digestion factors, addition of Percol, metal concentrations of the sludge, and phosphate-removal processes during sludge generation. Sludge digestion and addition of Percol proved not to affect metal solubilization resulting from application of the metal removal process. Solubilized copper concentration was plotted against copper content of the sludge studied, yielding a regression with an r2 of 0.72. For manganese, an r2 of 0.53 was obtained for the same type of regression. The more contaminated the sludge, the higher the element solubilization (%). Copper solubilization correlated with sludge phosphate content (r2 = 0.46), suggesting the phosphate-removal process affected copper solubilization. With manganese, no correlation with phosphate content was established. Under optimum reactor operating conditions, metal content was the main factor in copper and manganese solubilization in the aerobic sludges studied. Key words: heavy metals, biological solubilization, thiobacilli, Thiobacillus ferrooxidans, sewage sludge. [Journal translation]
35
Borah, K. K., B. Bhuyan e H. P. Sarma. "Heavy Metal Contamination of Groundwater in the Tea Garden Belt of Darrang District, Assam, India". E-Journal of Chemistry 6, s1 (2009): S501—S507. http://dx.doi.org/10.1155/2009/760953.
Testo completoAbstract (sommario):
A study has been carried out on heavy metal contamination of groundwater with respect to cadmium, manganese, zinc and copper in the tea garden belt of Darrang district, Assam, India. Heavy metals in groundwater are estimated by using Atomic Absorption Spectrometer, Perkin Elmer AA 200. Univariate statistics along with skewness, kurtosis and ‘t’ test have been employed to test the distribution normality for each metal. The study reveals that the groundwater of the area is highly contaminated with cadmium. A good number of samples are also found to contain manganese at an alert level. The concentrations of copper and zinc in the groundwater of the area are within the guideline values of WHO. Statistical results show that all the metals under study exhibit an asymmetric distribution in the area with a long asymmetric tail on the right of the median. Keeping in view of the high concentrations of cadmium and manganese, it is suggested to test the potability of groundwater of the area before using it for drinking.
36
Fisher, Carolyn R., Elizabeth E. Wyckoff, Eric D. Peng e Shelley M. Payne. "Identification and Characterization of a Putative Manganese Export Protein in Vibrio cholerae". Journal of Bacteriology 198, n. 20 (1 agosto 2016): 2810–17. http://dx.doi.org/10.1128/jb.00215-16.
Testo completoAbstract (sommario):
ABSTRACTManganese plays an important role in the cellular physiology and metabolism of bacterial species, including the human pathogenVibrio cholerae. The intracellular level of manganese ions is controlled through coordinated regulation of the import and export of this element. We have identified a putative manganese exporter (VC0022), namedmneA(manganeseexporterA), which is highly conserved amongVibriospp. AnmneAmutant exhibited sensitivity to manganese but not to other cations. Under high-manganese conditions, themneAmutant showed an almost 50-fold increase in intracellular manganese levels and reduced intracellular iron relative to those of its wild-type parent, suggesting that the mutant's manganese sensitivity is due to the accumulation of toxic levels of manganese and reduced iron. Expression ofmneAsuppressed the manganese-sensitive phenotype of anEscherichia colistrain carrying a mutation in the nonhomologous manganese export gene,mntP, further supporting a manganese export function forV. choleraeMneA. The level ofmneAmRNA was induced approximately 2.5-fold after addition of manganese to the medium, indicating regulation of this gene by manganese. This study offers the first insights into understanding manganese homeostasis in this important pathogen.IMPORTANCEBacterial cells control intracellular metal concentrations by coordinating acquisition in metal-limited environments with export in metal-excess environments. We identified a putative manganese export protein, MneA, inVibrio cholerae. AnmneAmutant was sensitive to manganese, and this effect was specific to manganese. ThemneAmutant accumulated high levels of intracellular manganese with a concomitant decrease in intracellular iron levels when grown in manganese-supplemented medium. Expression ofmneAintranssuppressed the manganese sensitivity of anE. coli mntPmutant. This study is the first to investigate manganese export inV. cholerae.
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Radka, Christopher D., Lawrence J. DeLucas, Landon S. Wilson, Matthew B. Lawrenz, Robert D. Perry e Stephen G. Aller. "Crystal structure ofYersinia pestisvirulence factor YfeA reveals two polyspecific metal-binding sites". Acta Crystallographica Section D Structural Biology 73, n. 7 (30 giugno 2017): 557–72. http://dx.doi.org/10.1107/s2059798317006349.
Testo completoAbstract (sommario):
Gram-negative bacteria use siderophores, outer membrane receptors, inner membrane transporters and substrate-binding proteins (SBPs) to transport transition metals through the periplasm. The SBPs share a similar protein fold that has undergone significant structural evolution to communicate with a variety of differentially regulated transporters in the cell. InYersinia pestis, the causative agent of plague, YfeA (YPO2439, y1897), an SBP, is important for full virulence during mammalian infection. To better understand the role of YfeA in infection, crystal structures were determined under several environmental conditions with respect to transition-metal levels. Energy-dispersive X-ray spectroscopy and anomalous X-ray scattering data show that YfeA is polyspecific and can alter its substrate specificity. In minimal-media experiments, YfeA crystals grown after iron supplementation showed a threefold increase in iron fluorescence emission over the iron fluorescence emission from YfeA crystals grown from nutrient-rich conditions, and YfeA crystals grown after manganese supplementation during overexpression showed a fivefold increase in manganese fluorescence emission over the manganese fluorescence emission from YfeA crystals grown from nutrient-rich conditions. In all experiments, the YfeA crystals produced the strongest fluorescence emission from zinc and could not be manipulated otherwise. Additionally, this report documents the discovery of a novel surface metal-binding site that prefers to chelate zinc but can also bind manganese. Flexibility across YfeA crystal forms in three loops and a helix near the buried metal-binding site suggest that a structural rearrangement is required for metal loading and unloading.
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Karakurkchi, Ann V., Nykolay D. Sakhnenko, Maryna V. Ved’, Ihor S. Luhovskyi, Hryhoriy A. Drobakha e Maryna V. Mayba. "Features of Plasma Electrolytic Formation of Manganese- and Cobalt-Containing Composites on Aluminum Alloys". Advances in Materials Science and Engineering 2019 (7 agosto 2019): 1–13. http://dx.doi.org/10.1155/2019/6381291.
Testo completoAbstract (sommario):
This paper presents the results of studies on the electrochemical treatment characteristics of aluminum and alloys in alkaline electrolytes. It is shown that the heterogeneity of the alloys composition complicates the formation of the surface oxide layer. To homogenize the treated surface and obtain oxide coatings doped with manganese and cobalt, electrolytes based on KOH and K4P2O7 with the addition of KMnO4 and CoSO4 were used. Plasma electrolytic oxidizing (PEO) in these electrolytes in the range of current densities 5–20 A/dm2 allows to obtain mixed oxide coatings which contained both aluminum oxide matrix and doping metal oxides Al2O3·MnOx and Al2O3·CoOy. It is shown that an increase in the PEO current density and the concentration of manganate- and cobalt(II) ions in the solution leads to an increase the content of dopant metals in the coatings outer layer. The incorporation of manganese and cobalt oxides in the composition of the surface layers was confirmed by the results of X-ray structural analysis. The rational modes of aluminum alloys PEO treatment were substantiated to obtain coatings with manganese and cobalt contents up to 25–40 аt.%. Formed oxide systems have a developed surface and high adhesion to the base metal and show an increased corrosion resistance and catalytic activity. This allows us to view them as promising materials for air- and water-cleaning technologies and internal combustion engine waste gas purification systems.
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Nohrina, Olga I., Irina D. Rogihina, Ivan E. Proshunin e Denis V. Valuev. "Preparation and Usage of High Quality Manganese-Containing Materials from Ferroalloy Production Waste". Key Engineering Materials 839 (aprile 2020): 106–13. http://dx.doi.org/10.4028/www.scientific.net/kem.839.106.
Testo completoAbstract (sommario):
We propose a flow diagram for processing ferroalloy production waste, such as silicothermic slag from manganese metal, as well as wet and dry powder of cleaning gas from ferroalloy furnaces that smelt manganese alloys. We experimentally determined the parameters for intensifying the calcium chloride method of enriching ferroalloy production waste, which resulted in a manganese extraction rate of 78-86%, with high-quality manganese concentrates. We present the results of studies related to the use of high-quality concentrates to dope steel with manganese, when processing it in a bucket, and smelting manganese metal via the aluminothermic method.
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Neville, Stephanie L., Jennie Sjöhamn, Jacinta A. Watts, Hugo MacDermott-Opeskin, Stephen J. Fairweather, Katherine Ganio, Alex Carey Hulyer et al. "The structural basis of bacterial manganese import". Science Advances 7, n. 32 (agosto 2021): eabg3980. http://dx.doi.org/10.1126/sciadv.abg3980.
Testo completoAbstract (sommario):
Metal ions are essential for all forms of life. In prokaryotes, ATP-binding cassette (ABC) permeases serve as the primary import pathway for many micronutrients including the first-row transition metal manganese. However, the structural features of ionic metal transporting ABC permeases have remained undefined. Here, we present the crystal structure of the manganese transporter PsaBC from Streptococcus pneumoniae in an open-inward conformation. The type II transporter has a tightly closed transmembrane channel due to “extracellular gating” residues that prevent water permeation or ion reflux. Below these residues, the channel contains a hitherto unreported metal coordination site, which is essential for manganese translocation. Mutagenesis of the extracellular gate perturbs manganese uptake, while coordination site mutagenesis abolishes import. These structural features are highly conserved in metal-specific ABC transporters and are represented throughout the kingdoms of life. Collectively, our results define the structure of PsaBC and reveal the features required for divalent cation transport.
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Bartnikas, Thomas Benedict. "SLC30A10 Deficiency: A Novel Cause of Polycythemia and Hepcidin Deficiency". Blood 128, n. 22 (2 dicembre 2016): 78. http://dx.doi.org/10.1182/blood.v128.22.78.78.
Testo completoAbstract (sommario):
Like iron, manganese is an essential yet potentially toxic metal. While inherited forms of iron excess were discovered long ago, the first disease of inherited manganese excess was only recently reported in 2012. Mutations in a metal transport protein, SLC30A10, were described in patients with manganese excess, polycythemia, liver failure and Parkinsonism. Manganese excess in these patients is attributed to an essential role for SLC30A10 in hepatobiliary manganese excretion. Polycythemia, liver failure and Parkinsonism are attributed to manganese excess although the underlying mechanisms have yet to be established. To explore the role of SLC30A10 in metal biology and disease, we have generated Slc30a10-deficient mice. Characterization of these mice indicates that murine Slc30a10 deficiency recapitulates the human disease. Given that manganese and iron share some transport pathways, we interrogated iron homeostasis in these mutant mice. Intriguingly, mice display hepcidin deficiency and tissue iron excess. While hepcidin deficiency may explain the tissue iron excess, the cause of hepcidin deficiency is unclear. Based on expression profiling of hypoxia-regulated genes, we propose that hepcidin deficiency reflects aberrant activation of hypoxia signaling by manganese excess in the absence of true hypoxia. Overall, this data suggests novel interactions between iron and manganese with implications for our understanding of the mechanisms by which aberrant metal homeostasis leads to human disease. Disclosures No relevant conflicts of interest to declare.
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Schmidt e Husted. "The Biochemical Properties of Manganese in Plants". Plants 8, n. 10 (27 settembre 2019): 381. http://dx.doi.org/10.3390/plants8100381.
Testo completoAbstract (sommario):
Manganese (Mn) is an essential micronutrient with many functional roles in plant metabolism. Manganese acts as an activator and co-factor of hundreds of metalloenzymes in plants. Because of its ability to readily change oxidation state in biological systems, Mn plays and important role in a broad range of enzyme-catalyzed reactions, including redox reactions, phosphorylation, decarboxylation, and hydrolysis. Manganese(II) is the prevalent oxidation state of Mn in plants and exhibits fast ligand exchange kinetics, which means that Mn can often be substituted by other metal ions, such as Mg(II), which has similar ion characteristics and requirements to the ligand environment of the metal binding sites. Knowledge of the molecular mechanisms catalyzed by Mn and regulation of Mn insertion into the active site of Mn-dependent enzymes, in the presence of other metals, is gradually evolving. This review presents an overview of the chemistry and biochemistry of Mn in plants, including an updated list of known Mn-dependent enzymes, together with enzymes where Mn has been shown to exchange with other metal ions. Furthermore, the current knowledge of the structure and functional role of the three most well characterized Mn-containing metalloenzymes in plants; the oxygen evolving complex of photosystem II, Mn superoxide dismutase, and oxalate oxidase is summarized.
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Sadeghi, Leila, Farzeen Tanwir e Vahid Yousefi Babadi. "Physiological and Biochemical Effects of Echium Amoenum Extract on Mn2+-Imposed Parkinson Like Disorder in Rats". Advanced Pharmaceutical Bulletin 8, n. 4 (29 settembre 2018): 705–13. http://dx.doi.org/10.15171/apb.2018.079.
Testo completoAbstract (sommario):
Purpose: Manganism is a cognitive disorder take places in peoples are exposed to environmental manganese pollution. Overexposure to manganese ion (Mn2+) mainly influences central nervous system and causes symptoms that increase possibility of hippocampal damages. Methods: In this study rats were administrated by two different doses of MnCl2 and behavioral and physiological consequences were evaluated. We also investigated effects of E. Amoenum on Mn2+-imposed toxicity by behavioral, biochemical, immunoblotting and histological studies on hippocampus tissue. Results: Results showed metal overexposure increases oxidative stress mainly by lipid peroxidation and reactive oxygen species overproduction. Histological studies and caspase 3 analyses by immunoblotting revealed Mn2+ induced apoptosis from mitochondrial-dependent pathway in the presence of low metal dose. This study provides evidence that oral administration of E. amoenum extract inhibited manganese neurotoxicity by oxidative stress attenuation and apoptosis reduction that lead to improved depression like behavior. Plant extract also increased catecholamine content in Mn2+ treated hippocampus. Conclusion: As molecular and pathophysiological effects of E. amoenum, it could be considered as a pre-treatment for Parkinson and Parkinson like disorders in high-risk people.
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Whittaker, James W. "Metal uptake by manganese superoxide dismutase". Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics 1804, n. 2 (febbraio 2010): 298–307. http://dx.doi.org/10.1016/j.bbapap.2009.08.014.
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Adams, Richard D., O.-Sung Kwon e Shaobin Miao. "Disulfido Metal Carbonyl Complexes Containing Manganese". Accounts of Chemical Research 38, n. 3 (marzo 2005): 183–90. http://dx.doi.org/10.1021/ar0402457.
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Glück, T. "Mechanisms of nitriding electrolytic manganese metal". Chemical Engineering Journal and the Biochemical Engineering Journal 54, n. 3 (luglio 1994): 167–73. http://dx.doi.org/10.1016/0923-0467(94)00206-1.
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Bastanov, R. I., S. S. Shakirova, O. A. Gumenyuk, A. O. Derkho e E. A. Krasnoperva. "Assessment of ecological safety of fish from anthropogenically polluted freshwater reservoir". E3S Web of Conferences 282 (2021): 03004. http://dx.doi.org/10.1051/e3sconf/202128203004.
Testo completoAbstract (sommario):
The content of heavy metals in fish of different ecological groups in the conditions of the Argazinsky reservoir (Russia) has been studied, its ecological safety when used as a product nutrition was given. The material of the study was “local” fish (bream, pike, perch, roach, whitefish) caught by fishermen. The content of heavy metals was determined by atomic absorption method. Compared to muscular tissue, bone tissue has been found to accumulate more manganese, zinc, cadmium, lead, cobalt, nickel, iron (except for roach), copper, except for perch. The value of the metal pollution index (Pi) is greater than one in bream muscles in nickel, lead and cobalt; pike — nickel. The multifactor index of metal contamination (MPI) in the muscular tissue of fish are located in the following order: bream > pike > roach, whitefish > perch. Pi >1.0 value in skeletal tissue of bream in lead, nickel, cobalt, manganese, cadmium, zinc, iron; pike — lead, nickel, cadmium, zinc, manganese; perch — lead, cadmium; roach — zinc, cobalt, lead, cadmium; whitefish — manganese, lead, cadmium. By the magnitude of MPI, the skeletal tissue is ranked in the following order: pike > bream > whitefish > roach > perch. Pike MPI=3, 85, bream MPI=3, 10. The following row is formed by the value of fish fatness: perch > roach > whitefish > bream > pike. The fatness amount in the body of pike and bream is affected by excessively accumulated metals (nickel, cobalt and lead in bream, nickel, cadmium, and lead in pike), and in perch, roach, and whitefish - essential (iron, cobalt, copper and zinc in perch, manganese, iron and copper in roach, manganese, cobalt and zinc in whitefish).
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Scott, R. E., A. Jones, K. S. Lam e G. M. Gaucher. "Manganese and antibiotic biosynthesis. I. A specific manganese requirement for patulin production in Penicillium urticae". Canadian Journal of Microbiology 32, n. 3 (1 marzo 1986): 259–67. http://dx.doi.org/10.1139/m86-051.
Testo completoAbstract (sommario):
The effect of trace metal nutrition on the functioning of the patulin biosynthetic pathway in submerged cultures of Penicillium urticae (NRRL 2159A) was examined by both chromatographic and enzymological means. Comprehensive metal ion analysis showed generally low levels of contaminating metal ions in media components. Of eight metal ions examined, only manganese strongly influenced secondary metabolite production. In control cultures or cultures deficient in calcium, iron, cobalt, copper, zinc, or molybdenum, pathway metabolites appeared in the medium at about 25 h after inoculation. The first pathway-specific metabolite, 6-methylsalicylic acid, accumulated only transiently before being converted to patulin whose concentration steadily increased. In manganese-deficient cultures, however, 6-methylsalicylic acid continued to accumulate, with only minor amounts of patulin being produced. Additionally, a marker enzyme for the pathway showed only 0–20% of control activity. Clear dose responses (patulin versus manganese) were found in different media, with no effect on growth yield. Addition of manganese to depleted cultures at 18, 26, or 36 h resulted in increasing marker enzyme activity and patulin concentrations. It is concluded that manganese exerts a specific, positive effect on patulin biosynthesis and may in some way control the section of the patulin pathway occurring after 6-methylsalicylic acid.
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Teodorovic, Ivana, Ivana Planojevic, Petar Knezevic, Sonja Radak e Irena Nemet. "Sensitivity of bacterial vs. acute Daphnia magna toxicity tests to metals". Open Life Sciences 4, n. 4 (1 dicembre 2009): 482–92. http://dx.doi.org/10.2478/s11535-009-0048-7.
Testo completoAbstract (sommario):
AbstractThe objectives of this study were to evaluate the sensitivity of two bacterial tests commonly used in metal toxicity screening — the Vibrio fischeri bioluminescence inhibition test and the Pseudomonas putida growth inhibition test — in comparison to the standard acute Daphnia magna test, and to estimate applicability of the selected methods to the toxicity testing of environmental samples. The D. magna acute test proved to be more sensitive to cadmium (Cd), zinc (Zn) and manganese (Mn) than the two bacterial assays, whereas P. putida seems to be the most sensitive species to lead (Pb). Manganese appears to be slightly toxic to D. magna and non-toxic to the two selected bacteria. This leads to the conclusion that even in regions with high background concentrations, manganese would not act as a confounding factor. Low sensitivity of V. fischeri to heavy metals questions its applicability as the first screening method in assessing various environmental samples. Therefore, it is not advisable to replace D. magna with bacterial species for metal screening tests. P. putida, V. fischeri and/or other bacterial tests should rather be applied in a complex battery of ecotoxicological tests, as their tolerance to heavy metals can unravel other potentially present toxic substances and mixtures, undetectable by metal-sensitive species.
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Whittaker, J. W. "The irony of manganese superoxide dismutase". Biochemical Society Transactions 31, n. 6 (1 dicembre 2003): 1318–21. http://dx.doi.org/10.1042/bst0311318.
Testo completoAbstract (sommario):
The manganese and iron SODs (superoxide dismutases) form a superfamily of closely related antioxidant defence metalloenzymes. MnSOD requires Mn (not Fe) for activity. However, when MnSOD is expressed in Escherichia coli grown in medium supplemented with ferrous salts, Fe substitutes for Mn in the active site, reflecting relatively indiscriminate uptake of either Mn or Fe and a surprisingly low selectivity for the identity of the bound metal ion. X-ray crystallographic studies on Fe-substituted MnSOD show that the substrate access channel is blocked by solvent (hydroxide), providing a structural explanation for the observed metal specificity of the catalytic activity. The mechanism of metal binding has been investigated in vitro using recombinant thermophilic SODs. The thermophilic Thermus thermophilus MnSOD expressed in E. coli was isolated as the metal-free apoprotein when heat treatment was eliminated from the purification procedure. While incubation of the purified MnSOD apoprotein with metal salts at ambient temperatures did not restore SOD activity, re-activation could be achieved by heating the protein with Mn salts at elevated temperatures. This in vitro thermally triggered metal uptake is non-specific for the metal ion; both Mn and Fe bind, but only Mn restores catalytic activity. Formation of the metal complex is essentially irreversible under these conditions. The metallation process is strongly temperature-dependent, suggesting that there are substantial activation barriers to metal uptake at ambient temperatures that are overcome by a transition in the apoprotein structure under physiological conditions. Two mechanisms may be proposed for SOD metallation: one involving subunit dissociation and another involving domain separation. Thermally triggered metal binding by thermophilic SODs is providing new insight into the metallation mechanism of the SOD apoprotein, which is likely to be conserved over this family of enzymes.