A sensitive inhibition chemiluminescence method for the determination of trace tannic acid using the reaction of luminol-hydrogen peroxide catalysed by tetrasulphonated manganese phthalocyanine.

A novel CL method for the determination of tannic acid (TA) was established based on TA inhibition of the chemiluminescence (CL) emission of the luminol-hydrogen peroxide CL system catalysed by tetrasulphonated manganese phthalocyanine (MnTSPc) under alkaline conditions. The peak height is proportional to the natural logarithm of concentration of TA in the range 1.0 x 10(-7)-3.0 x 10(-10) mol/L with a detection limit of 5.6 x 10(-11) mol/L and the relative standard deviation was 2.5% for the determination of 1.0 x 10(-8) mol/L TA (n = 11). The proposed method has been successfully applied to the determination of TA in Chinese gall and industrial wastewater.     

Oxygen isotope analysis of bacterial and fungal manganese oxidation

The ability of micro‐organisms to oxidize manganese (Mn) from Mn(II) to Mn(III/IV) oxides transcends boundaries of biological clade or domain. Many bacteria and fungi oxidize Mn(II) to Mn(III/IV) oxides directly through enzymatic activity or indirectly through the production of reactive oxygen species. Here, we determine the oxygen isotope fractionation factors associated with Mn(II) oxidation via various biotic (bacteria and fungi) and abiotic Mn(II) reaction pathways. As oxygen in Mn(III/IV) oxides may be derived from precursor water and molecular oxygen, we use a twofold approach to determine the isotope fractionation with respect to each oxygen source. Using both ¹⁸O‐labeled water and closed‐system Rayleigh distillation approaches, we constrain the kinetic isotope fractionation factors associated with O atom incorporation during Mn(II) oxidation to ?17.3‰ to ?25.9‰ for O₂ and ?1.9‰ to +1.8‰ for water. Results demonstrate that stable oxygen isotopes of Mn(III/IV) oxides have potential to distinguish between two main classes of biotic Mn(II) oxidation: direct enzymatic oxidation in which O₂ is the oxidant and indirect enzymatic oxidation in which superoxide is the oxidant. The fraction of Mn(III/IV) oxide‐associated oxygen derived from water varies significantly (38%–62%) among these bio‐oxides with only weak relationship to Mn oxidation state, suggesting Mn(III) disproportionation may account for differences in the fraction of mineral‐bound oxygen from water and O₂. Additionally, direct incorporation of molecular O₂ suggests that Mn(III/IV) oxides contain a yet untapped proxy of of environmental O₂, a parameter reflecting the integrated influence of global respiration, photorespiration, and several other biogeochemical reactions of global significance.     

Simultaneous hyperaccumulation of cadmium and manganese in Celosia argentea Linn.

To indentify Mn/Cd co-hyperaccumulatoion in Celosia argentea Linn., 2 pot experiments were conducted using Cd/Mn-amended and real contaminated soils, respectively. The interaction between Cd and Mn with regard to their accumulation in the plants was also assessed. The results indicated that C. argentea can simultaneously hyperaccumulate Cd and Mn. The maximum Cd and Mn concentrations in leaves were 276 and 29,000 mg/kg, respectively. Mn application significantly enhanced the biomass production and Cd accumulation in shoots (p < 0.05). However, Cd addition did not reduce Mn accumulation in the plants. The interactions between Cd and Mn in C. argentea differ from what was previously found in hydroponic experiments. This species grew healthy in soils taken from a Cd/Mn-contaminated site, indicating a high tolerance to Cd and Mn. The transfer and bioaccumulation factors of Cd and Mn were greater than 1, which showed that C. argentea had potential for Cd and Mn phytoextraction. Besides its potential practical benefits, C. argentea is an important resource to study the mechanisms of Cd/Mn hyperaccumulation and tolerance in plants.     

X‐ray fluorescence analysis of iron and manganese distribution in primary dopaminergic neurons

Transition metals have been suggested to play a pivotal role in the pathogenesis of Parkinson's disease. X‐ray microscopy combined with a cryogenic setup is a powerful method for elemental imaging in low concentrations and high resolution in intact cells, eliminating the need for fixation and sectioning of the specimen. Here, we performed an elemental distribution analysis in cultured primary midbrain neurons with a step size in the order of 300 nm and ~ 0.1 ppm sensitivity under cryo conditions by using X‐ray fluorescence microscopy. We report the elemental mappings on the subcellular level in primary mouse dopaminergic (DAergic) and non‐DAergic neurons after treatment with transition metals. Application of Fe²⁺ resulted in largely extracellular accumulation of iron without preference for the neuronal transmitter subtype. A quantification of different Fe oxidation states was performed using X‐ray absorption near edge structure analysis. After treatment with Mn²⁺, a cytoplasmic/paranuclear localization of Mn was observed preferentially in DAergic neurons, while no prominent signal was detectable after Mn³⁺ treatment. Immunocytochemical analysis correlated the preferential Mn uptake to increased expression of voltage‐gated calcium channels in DAergic neurons. We discuss the implications of this differential elemental distribution for the selective vulnerability of DAergic neurons and Parkinson's disease pathogenesis.     

Mn(II)-oxidizing Bacteria are Abundant and Environmentally Relevant Members of Ferromanganese Deposits in Caves of the Upper Tennessee River Basin

The upper Tennessee River Basin contains the highest density of our nation's caves; yet, little is known regarding speleogenesis or Fe and Mn biomineralization in these predominantly epigenic systems. Mn:Fe ratios of Mn and Fe oxide-rich biofilms, coatings, and mineral crusts that were abundant in several different caves ranged from ca. 0.1 to 1.0 as measured using ICP-OES. At sites where the Mn:Fe ratio approached 1.0 this represented an order of magnitude increase above the bulk bedrock ratio, suggesting that biomineralization processes play an important role in the formation of these cave ferromanganese deposits. Estimates of total bacterial SSU rRNA genes in ferromanganese biofilms, coatings, and crusts measured approximately 7×10⁷–9×10⁹ cells/g wet weight sample. A SSU-rRNA based molecular survey of biofilm material revealed that 21% of the 34 recovered dominant (non-singleton) OTUs were closely related to known metal-oxidizing bacteria or clones isolated from oxidized metal deposits. Several different isolates that promote the oxidation of Mn(II) compounds were obtained in this study, some from high dilutions (10^–8–10^–10) of deposit material. In contrast to studies of caves in other regions, SSU rRNA sequences of Mn-oxidizing bacterial isolates in this study most closely matched those of Pseudomonas, Leptothrix, Flavobacterium, and Janthinobacterium. Combined data from geochemical analyses, molecular surveys, and culture-based experiments suggest that a unique consortia of Mn(II)-oxidizing bacteria are abundant and promoting biomineralization processes within the caves of the upper Tennessee River Basin.     

A preliminary study of anaerobic thiosulfate‐oxidizing bacteria as denitrifiers in the Arabian Sea

Bacteria which oxidize thiosulfate and reduce nitrate (TONRB) and bacteria which oxidize thiosulfate and denitrify (TODB) sampled at 5‐, 100‐, 200‐ and 300‐m depths were enumerated in agar shake cultures by colony counting and by applying MPN technique, respectively. Lithotrophic denitrification was generally high at the surface but did not vary much with the distance from shore as indicated by the number of TODB. The number of TONRB shows that nitrate‐reduction was much higher at near‐shore stations. The low TODBITONRB ratios at intermediate depths and at 100 m show in particular that the relative abundance of these organisms could be one of the possible reasons for higher nitrite concentrations sometimes reported at these depths. Thiosulfate‐oxidizing and simultaneous nitrate‐reducing abilities of the isolates indicated that the strains isolated from near shore and surface waters were more active nitrate reducers than their counterparts in offshore or deeper waters. The growth yield values of these organisms ranged from 1.1 to 17.9 mg protein mmol^‐1 thiosulfate and from 11.7 to 36.3 mg protein mmol^‐1 sulfide and suggest that they could contribute to chemosynthetic production.     

草菇锰过氧化物酶编码基因生物信息学分析及其转录水平和酶活性的测定

在草菇全基因组中发现了4个担子菌锰过氧化物酶MnP基因同源物(vv-mnp1、vv-mnp2、vv-mnp3和vv-mnp4)的基础上,对这4个MnP进行了生物信息学分析,并对其基因表达和酶活性进行测定。结果表明vv-mnp1与vv-mnp2基因结构相同,vv-mnp3与vv-mnp4基因结构相似。在4个草菇MnP基因启动子区域存在AP-2、cAMP、MRE、XRE和HSE等调控元件,预示着草菇中MnP基因的转录可能会受到氮源、碳源、重金属离子、芳香族化合物以及热击的影响。草菇MnP具有信号肽,不存在跨膜区域,表明其是分泌蛋白。草菇MnP中形成4个二硫键的8个半胱氨酸、潜在的锰离子和钙离子结合位点,在担子菌MnP中高度保守。系统进化树分析显示草菇MnP1和MnP2与香菇MnP1亲缘关系最近,而MnP3和MnP4与灰盖鬼伞过氧化物酶有较近的亲缘关系。RT-PCR检测到vv-mnp1、vv-mnp3与vv-mnp4能在含锰离子的培养基中表达,但运用锰离子氧化法没有检测到MnP活性,推测草菇中的MnP不具有将Mn2+氧化成Mn3+的能力。     

The influence of environmental factors on the rate and extent of stainless steel ennoblement mediated by manganese‐oxidizing biofilms

The increase in the open circuit potential of passive metals in natural waters due to biofilm formation at the metal surface, termed ennoblement, has been reported for nearly 30 years. Although its occurrence is undoubtedly associated with microbial colonization, the underlying mechanism of ennoblement remains controversial. Recent work produced in the authors’ laboratory has provided convincing experimental evidence that ennoblement can be caused by deposition of biomineralized manganese produced by manganese‐oxidizing biofilms. The purpose of this study was to determine the effects of environmental factors on the rate and extent of ennoblement of 316L stainless steel exposed to natural waters. This was accomplished by exposing corrosion coupons to four freshwater systems over a 4‐yearperiod. The rate and extent of ennoblement observed in these locations was correlated with dissolved manganese concentrations, the mass of accumulated manganese oxides, organic carbon concentration, dissolved oxygen concentration, flow, conditions, temperature, and pH in these environments.     

Facile Synthesis of 3D MnO2–Graphene and Carbon Nanotube–Graphene Composite Networks for High‐Performance,Flexible, All‐Solid‐State Asymmetric Supercapacitors

The integration of graphene nanosheets on the macroscopic level using a self‐assembly method has been recognized as one of the most effective strategies to realize the practical applications of graphene materials. Here, a facile and scalable method is developed to synthesis two types of graphene‐based networks, manganese dioxide (MnO₂)–graphene foam and carbon nanotube (CNT)–graphene foam, by solution casting and subsequent electrochemical methods. Their practical applications in flexible all‐solid‐state asymmetric supercapacitors are explored. The proposed method facilitates the structural integration of graphene foam and the electroactive material and offers several advantages including simplicity, efficiency, low‐temperature, and low‐cost. The as‐prepared MnO₂–graphene and CNT–graphene electrodes exhibit high specific capacitances and rate capability. By using polymer gel electrolytes, a flexible all‐solid‐state asymmetric supercapacitor was synthesized with MnO₂–graphene foam as the positive electrode and CNT‐graphene as the negative electrode. The asymmetric supercapacitors can be cycled reversibly in a high‐voltage region of 0 to 1.8 V and exhibit high energy density, remarkable rate capability, reasonable cycling performance, and excellent flexibility.