Herein, we report the synthesis of functionalized dihydro‐benzobfluorenones through a manganese‐mediated cascade radical cyclization of β‐alkynyl propenones 1,6‐enynes with arylboronic acids. In the ...present strategy, the in‐situ generated aryl radical undergoes chemo‐selective addition followed by 5‐exo‐trig cyclization. The reaction is emphasized by high atom‐ and step‐economy with the construction of three new C−C bonds to access the dihydrobenzobfluorenones in 68–81% yield under mild reaction conditions. The synthetic efficacy of the developed method is evidenced by the construction of new C−C and C−N bonds.
Manganese is one of the most abundant elements on Earth. The oxidation of manganese has long been theorized
-yet has not been demonstrated
-to fuel the growth of chemolithoautotrophic microorganisms. ...Here we refine an enrichment culture that exhibits exponential growth dependent on Mn(II) oxidation to a co-culture of two microbial species. Oxidation required viable bacteria at permissive temperatures, which resulted in the generation of small nodules of manganese oxide with which the cells associated. The majority member of the culture-which we designate 'Candidatus Manganitrophus noduliformans'-is affiliated to the phylum Nitrospirae (also known as Nitrospirota), but is distantly related to known species of Nitrospira and Leptospirillum. We isolated the minority member, a betaproteobacterium that does not oxidize Mn(II) alone, and designate it Ramlibacter lithotrophicus. Stable-isotope probing revealed
CO
fixation into cellular biomass that was dependent upon Mn(II) oxidation. Transcriptomic analysis revealed candidate pathways for coupling extracellular manganese oxidation to aerobic energy conservation and autotrophic CO
fixation. These findings expand the known diversity of inorganic metabolisms that support life, and complete a biogeochemical energy cycle for manganese
that may interface with other major global elemental cycles.
Manganese homeostasis in the nervous system Chen, Pan; Chakraborty, Sudipta; Mukhopadhyay, Somshuvra ...
Journal of neurochemistry,
August 2015, Letnik:
134, Številka:
4
Journal Article
Recenzirano
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Manganese (Mn) is an essential heavy metal that is naturally found in the environment. Daily intake through dietary sources provides the necessary amount required for several key physiological ...processes, including antioxidant defense, energy metabolism, immune function and others. However, overexposure from environmental sources can result in a condition known as manganism that features symptomatology similar to Parkinson's disease (PD). This disorder presents with debilitating motor and cognitive deficits that arise from a neurodegenerative process. In order to maintain a balance between its essentiality and neurotoxicity, several mechanisms exist to properly buffer cellular Mn levels. These include transporters involved in Mn uptake, and newly discovered Mn efflux mechanisms. This review will focus on current studies related to mechanisms underlying Mn import and export, primarily the Mn transporters, and their function and roles in Mn‐induced neurotoxicity.
Though and essential metal, overexposure to manganese may result in neurodegenerative disease analogous to Parkinson's disease. Manganese homeostasis is tightly regulated by transporters, including transmembrane importers (divalent metal transporter 1, transferrin and its receptor, zinc transporters ZIP8 and Zip14, dopamine transporter, calcium channels, choline transporters and citrate transporters) and exporters (ferroportin and SLC30A10), as well as the intracellular trafficking proteins (SPCA1 and ATP12A2). A manganese‐specific sensor, GPP130, has been identified, which affords means for monitoring intracellular levels of this metal.
Though and essential metal, overexposure to manganese may result in neurodegenerative disease analogous to Parkinson's disease. Manganese homeostasis is tightly regulated by transporters, including transmembrane importers (divalent metal transporter 1, transferrin and its receptor, zinc transporters ZIP8 and Zip14, dopamine transporter, calcium channels, choline transporters and citrate transporters) and exporters (ferroportin and SLC30A10), as well as the intracellular trafficking proteins (SPCA1 and ATP12A2). A manganese‐specific sensor, GPP130, has been identified, which affords means for monitoring intracellular levels of this metal.
Hexavalent chromium contamination is a global environmental issue and usually reoccurs in alkaline reduced chromite ore processing residues (rCOPR). The oxidation of Cr(III) solids in rCOPR is one ...possible cause but as yet little studied. Herein, we investigated the oxidation of Cr(OH)3, a typical species of Cr(III) in rCOPR, at alkaline pH (9–11) with δ-MnO2 under oxic/anoxic conditions. Results revealed three pathways for Cr(III) oxidation under oxic conditions: (1) oxidation by oxygen, (2) oxidation by δ-MnO2, and (3) catalytic oxidation by Mn(II). Oxidations in the latter two were efficient, and oxidation via Pathway 3 was continuous and increased dramatically with increasing pH. XANES data indicated feitknechtite (β-MnOOH) and hausmannite (Mn3O4) were the reduction products and catalytic substances. Additionally, a kinetic model was established to describe the relative contributions of each pathway at a specific time. The simulation outcomes showed that Cr(VI) was mainly formed via Pathway 2 (>51%) over a short time frame (10 days), whereas in a longer-term (365 days), Pathway 3 predominated the oxidation (>78%) with an increasing proportion over time. These results suggest Cr(III) solids can be oxidized under alkaline oxic conditions even with a small amount of manganese oxides, providing new perspectives on Cr(VI) reoccurrence in rCOPR and emphasizing the environmental risks of Cr(III) solids in alkaline environments.
Manganese (Mn) is an important micronutrient for plant growth and development and sustains metabolic roles within different plant cell compartments. The metal is an essential cofactor for the ...oxygen-evolving complex (OEC) of the photosynthetic machinery, catalyzing the water-splitting reaction in photosystem II (PSII). Despite the importance of Mn for photosynthesis and other processes, the physiological relevance of Mn uptake and compartmentation in plants has been underrated. The subcellular Mn homeostasis to maintain compartmented Mn-dependent metabolic processes like glycosylation, ROS scavenging, and photosynthesis is mediated by a multitude of transport proteins from diverse gene families. However, Mn homeostasis may be disturbed under suboptimal or excessive Mn availability. Mn deficiency is a serious, widespread plant nutritional disorder in dry, well-aerated and calcareous soils, as well as in soils containing high amounts of organic matter, where bio-availability of Mn can decrease far below the level that is required for normal plant growth. By contrast, Mn toxicity occurs on poorly drained and acidic soils in which high amounts of Mn are rendered available. Consequently, plants have evolved mechanisms to tightly regulate Mn uptake, trafficking, and storage. This review provides a comprehensive overview, with a focus on recent advances, on the multiple functions of transporters involved in Mn homeostasis, as well as their regulatory mechanisms in the plant's response to different conditions of Mn availability.
► We examine intellectual function in 299 8–11 year olds in Bangladesh, in four groups. ► Groups are stratified by design on well-water arsenic (±10μg/L) and manganese (±500μg/L). ► With adjustment ...for other sociodemographic features, Blood Mn was associated with poorer Perceptual Reasoning and Working Memory scores. ► With adjustment for other sociodemographic features, Blood As was associated with poorer Verbal Comprehension scores. ► By design, children's exposure was relatively lower than in earlier work: at these levels, we found no evidence for a Mn x As interaction.
Recently, epidemiologic studies of developmental neurotoxicology have been challenged to increase focus on co-exposure to multiple toxicants. Earlier reports, including our own work in Bangladesh, have demonstrated independent associations between neurobehavioral function and exposure to both arsenic (As) and manganese (Mn) in school-aged children. Our earlier studies, however, were not designed to examine possible interactive effects of exposure to both As and Mn. To allow investigation of possible synergistic impact of simultaneous exposures, we recruited a new sample of 299 8–11 year old children, stratified by design on As (above and below 10μg/L) and Mn (above and below 500μg/L) concentrations of household wells. When adjusted only for each other, both As and Mn in whole blood (BAs; BMn) were significantly negatively related to most WISC-IV subscale scores. With further adjustment for socio-demographic features and ferritin, BMn remained significantly associated with reduced Perceptual Reasoning and Working Memory scores; associations for BAs, and for other subscales, were expectably negative, significantly for Verbal Comprehension. Urinary As (per gram creatinine) was significantly negatively associated with Verbal Comprehension scores, even with adjustment for BMn and other contributors. Mn by As interactions were not significant in adjusted or unadjusted models (all p's>0.25). Findings are consistent with other reports documenting adverse impact of both As and Mn exposure on child developmental outcomes, although associations appear muted at these relatively low exposure levels.
Abiotic stress has become one of the most challenging problems for agriculture as the world population keeps increasing dramatically. Crop stress management using manganese (Mn) compounds has been ...recently employed to reduce the negative effects caused by drought, harsh temperature, and salinity. In response to abiotic stress, an adequate supply of Mn has shown to remediate plant manganese deficiency, induce Mn superoxide dismutase at the transcriptional level to face reactive oxygen species production, and stimulate manganese-dependent proteins to maintain cell integrity. Lately, nanoparticles (NPs) have been explored in agriculture applications. Recent studies have implied that Mn NPs may help plants to overcome abiotic stresses at higher efficiency and lower toxicity, compared to their bulk or ionic counterparts. Although studies have shown that Mn compounds promote crop growth and alleviate abiotic stress, many questions related to Mn-plant networking, their mode of signaling, and the Mn-dependent regulation processes need to be answered.
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•Mn element is essential for proper enzymatic and photosynthetic reactions in plants.•Conventional bulk/ionic Mn compounds can alleviate abiotic stress in plant.•MnNPs have the potential to be used as nano-fertilizer and in plant stress management.•More investigations on the role of MnNPS in plants exposed to stress are needed.
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