Molybdenum: biological activity and metabolism

Effect of Palmitoylethanolamide Compared to a Placebo on the Gut Microbiome and Biochemistry in an Overweight Adult Population: A Randomised, Placebo Controlled, Double-Blind Study

This study investigates the effects of palmitoylethanolamide (PEA) on the gut microbiome of overweight adults. Fifty-eight participants (twenty males, thirty-eight females) aged 18-65 years with a BMI range of 30-40 kg/m2 were recruited. Participants were randomised to receive PEA (n = 36) or a placebo (n = 22) for 12 weeks. Microbiota composition, richness, diversity, and metabolic functions, faecal short chain fatty acids and calprotectin, pathology markers, and health-related questionnaires were analysed throughout the 12 weeks of supplementation. PEA supplementation significantly reduced triglyceride levels and IL-2 concentrations. No significant differences were found in the overall microbiota composition between the groups, and microbiota richness and diversity remained consistent for both groups. Functional analysis demonstrated no differences in functional richness and diversity, but specific pathways were modified. PEA supplementation resulted in a decrease in the abundance of pathways related to aromatic compound degradation, NAD interconversion, and L-glutamate degradation, while pathways associated with molybdopterin biosynthesis and O-antigen building blocks exhibited increased abundance. Increased production of O-antigen results in smooth LPS associated with reduced pathogenic stealth and persistence. PEA supplementation may influence specific microbial species, metabolic pathways, and reduce serum triglyceride and IL-2 concentration, shedding light on the intricate relationship between PEA, the microbiome, and host health.

In Vitro: The Extraordinary Enhancement in Rutin Accumulation and Antioxidant Activity in Philodendron "Imperial Red" Plantlets Using Ti-Mo-Ni-O Nanotubes as a Novel Elicitor

Rutin, a flavonoid phytochemical compound, plays a vital role in human health. It is used in treating capillary fragility and has anti-Alzheimer, anti-inflammatory, and antioxidant effects. In this study, Ti-Mo-Ni-O nanotubes (NTs) were used, for the first time, in an unprecedented plant biotechnology application, wherein in vitro Philodendron shoots (Philodendron erubescens) known as "Imperial Red" were targeted for rutin accumulation. The antioxidant responses and the accumulation of rutin were evaluated in treated Philodendron erubescens (P. erubescens) shoots using 5.0 mg/L of Ti-Mo-Ni-O NTs. The total phenolic content and total flavonoid content were estimated, and an ABTS+ assay, FRAP assay, and iron metal chelation assay were performed. The application of Ti-Mo-Ni-O NTs enhanced the rutin content considerably from 0.02 mg/g to 2.96 mg/g for dry-weight shootlet extracts. Therefore, the use of Ti-Mo-Ni-O NTs is proposed to be a superior alternative to elevate the rutin content. The aim of the current study is to target P. erubescens shoots grown in vitro for the accumulation of rutin compounds using Ti-Mo-Ni-O NT powder, to determine the quantitative and qualitative accumulation of rutin via HPLC-DAD analysis, and to estimate the antioxidant activity of P. erubescens shoot extract. This study presents a novel methodology for utilizing nano-biotechnology in the synthesis of plant secondary metabolites.

Design and Development of Transient Sensing Devices for Healthcare Applications

With the ever-growing requirements in the healthcare sector aimed at personalized diagnostics and treatment, continuous and real-time monitoring of relevant parameters is gaining significant traction. In many applications, health status monitoring may be carried out by dedicated wearable or implantable sensing devices only within a defined period and followed by sensor removal without additional risks for the patient. At the same time, disposal of the increasing number of conventional portable electronic devices with short life cycles raises serious environmental concerns due to the dangerous accumulation of electronic and chemical waste. An attractive solution to address these complex and contradictory demands is offered by biodegradable sensing devices. Such devices may be able to perform required tests within a programmed period and then disappear by safe resorption in the body or harmless degradation in the environment. This work critically assesses the design and development concepts related to biodegradable and bioresorbable sensors for healthcare applications. Different aspects are comprehensively addressed, from fundamental material properties and sensing principles to application-tailored designs, fabrication techniques, and device implementations. The emerging approaches spanning the last 5 years are emphasized and a broad insight into the most important challenges and future perspectives of biodegradable sensors in healthcare are provided.

Structural analysis of molybdate binding protein ModA from Klebsiella pneumoniae

Klebsiella pneumoniae, a facultative anaerobe, relies on acquiring molybdenum to sustain growth in anaerobic conditions, a crucial factor for the pathogen to establish infections within host environments. Molybdenum plays a critical role in pathogenesis as it forms an essential component of cofactors for molybdoenzymes. K. pneumoniae utilizes the ABC (ATP-Binding-Cassette) transporter encoded by the modABC operon for uptake of the group VI elements molybdenum and tungsten. In this study, we determined the X-ray crystal structures of both the molybdenum-free and molybdenum-bound substrate-binding protein (SBP) ModA from Klebsiella pneumoniae to 2.00 Å and 1.77 Å resolution respectively. ModA crystallizes in the space group P222 with a single monomer in one asymmetric unit. The purified protein remained soluble and specifically bound molybdate and tungstate with Kd values of 6.3 nM and 5.2 nM, respectively. Tungstate competes with molybdate by binding to ModA, resulting in enhanced antimicrobial activity. These data provide a starting point for structural and functional analyses of molybdate transport in K. pneumoniae.

Preliminary ionome of the parotoid gland secretion from Rhinella jimi toad

The cururu toad (Rhinella jimi) is an anuran belonging to the fauna of the Brazilian northeast region, which releases a secretion with toxins from your parotoid glands. Although it has some information about secondary metabolites and proteins, the elemental composition of the released secretion is unknown. Therefore, this is the first report on the ionome of the secretion of the parotoid glands from R. jimi, investigating the influences of abiotic factors such as biome, seasonality, and gender. ICP-MS was used for measurements combined with principal component analysis (PCA). A screening of the secretion sample detected 68 elements which the total concentration of 18 elements was determined. PCA revealed that biome and seasonality factors have a greater influence on the ionomic profile of parotoid secretion. The presence of toxic metals in the secretion samples indicates that the R. jimi toad can be considered a potential bioindicator. These findings may contribute to understanding the metabolism, lifestyle, and interaction of the R. jimi toad with environmental factors as well as open new perspectives to investigate the relationships of the ionome with other biomolecules, for example, metalloproteins and their physiological functions.

Soybean rhizosphere microorganisms alleviate Mo nanomaterials induced stress by improving soil microbial community structure

With the wide application of nanomaterials (NMs) in agriculture, it is particularly important to assess the impact of these NMs on soil microorganisms. In this study, different varieties of soybean rhizosphere microorganisms (RM) were employed to simulate the alleviate effect of molybdenum nanoparticles (Mo NPs) induced stress in presence of soybean plants. Mo NPs caused serious toxic effects on soybean growth and nitrogen fixation at a concentration of 100 mg kg^-1: plant height and biomass were reduced by 56.4% and 82.8%, respectively, and the ability to fix nitrogen was almostly lost. However, after adding different varieties of soybean RM (RM-Williams 82, RM-Youchun 1204, and RM-Zhongdou 41), the stress caused by high concentrations of Mo NPs on soybean plants was significantly reduced. The plant height, root length, biomass, and nitrogen fixation ability were improved by 70.8%, 80.7%, 145.8%, and 349.8%, respectively, following the addition of soybean RM-Williams 82. High-throughput sequencing revealed that Mo NPs treatment affected the microbial community structure. Among them, Flavisolibacter and Caulobacter genera abundance increased significantly, which might be the key factor in relieving Mo NPs-induced stress on soybean growth. These findings suggest a novel mode of RM as a promising strategy to prevent deleterious effects of stress with NPs on plants in the future.

An Overview to Technical Solutions for Molybdenum Removal: Perspective from the Analysis of the Scientific Literature on Molybdenum and Drinking Water (1990–2019)

A bibliometric analysis using the Scopus database was performed to investigate the research documents published from 1990 to 2019 in scientific sources related to molybdenum in drinking water and determine the quantitative characteristics of the research in this period. The results from the analysis revealed that the number of publications was maintained at a regular production of around 5 papers per year until 2009, followed by a fast linear increase in the production in the period from 2010 to 2016 (29 papers in 2016), but the scientific production regarding this topic was reduced in 2017 and 2018 to recover the production obtained in 2016 once again in 2019. The total contribution of the three most productive countries (USA, China and India, respectively) accounted for around 50% of the total number of publications. Environmental Science was the most common subject (51.4% contribution), followed by Chemistry (26.7% contribution). The research efforts targeted toward the search for technical solutions for molybdenum removal from water are not as important as the ones focused on the identification of molybdenum-polluted water bodies and the analysis of the health effects of the intake of molybdenum. Nevertheless, examples of technological treatments to remove molybdenum from the aqueous solution include the use of adsorption and ion exchange; coagulation, flocculation and precipitation followed by filtration; membrane technologies and biological treatments.

Biodegradable Molybdenum (Mo) and Tungsten (W) Devices: One Step Closer towards Fully-Transient Biomedical Implants

Close monitoring of vital physiological parameters is often key in following the evolution of certain medical conditions (e.g., diabetes, infections, post-operative status or post-traumatic injury). The allocation of trained medical staff and specialized equipment is, therefore, necessary and often translates into a clinical and economic burden on modern healthcare systems. As a growing field, transient electronics may establish fully bioresorbable medical devices capable of remote real-time monitoring of therapeutically relevant parameters. These devices could alert remote medical personnel in case of any anomaly and fully disintegrate in the body without a trace. Unfortunately, the need for a multitude of biodegradable electronic components (power supplies, wires, circuitry) in addition to the electrochemical biosensing interface has halted the arrival of fully bioresorbable electronically active medical devices. In recent years molybdenum (Mo) and tungsten (W) have drawn increasing attention as promising candidates for the fabrication of both energy-powered active (e.g., transistors and integrated circuits) and passive (e.g., resistors and capacitors) biodegradable electronic components. In this review, we discuss the latest Mo and W-based dissolvable devices for potential biomedical applications and how these soluble metals could pave the way towards next-generation fully transient implantable electronic systems.

Bioactive glasses incorporating less-common ions to improve biological and physical properties

Bioactive glasses (BGs) have been a focus of research for over five decades for several biomedical applications. Although their use in bone substitution and bone tissue regeneration has gained important attention, recent developments have also seen the expansion of BG applications to the field of soft tissue engineering. Hard and soft tissue repair therapies can benefit from the biological activity of metallic ions released from BGs. These metallic ions are incorporated in the BG network not only for their biological therapeutic effects but also in many cases for influencing the structure and processability of the glass and to impart extra functional properties. The "classical" elements in silicate BG compositions are silicon (Si), phosphorous (P), calcium (Ca), sodium (Na), and potassium (K). In addition, other well-recognized biologically active ions have been incorporated in BGs to provide osteogenic, angiogenic, anti-inflammatory, and antibacterial effects such as zinc (Zn), magnesium (Mg), silver (Ag), strontium (Sr), gallium (Ga), fluorine (F), iron (Fe), cobalt (Co), boron (B), lithium (Li), titanium (Ti), and copper (Cu). More recently, rare earth and other elements considered less common or, some of them, even "exotic" for biomedical applications, have found room as doping elements in BGs to enhance their biological and physical properties. For example, barium (Ba), bismuth (Bi), chlorine (Cl), chromium (Cr), dysprosium (Dy), europium (Eu), gadolinium (Gd), ytterbium (Yb), thulium (Tm), germanium (Ge), gold (Au), holmium (Ho), iodine (I), lanthanum (La), manganese (Mn), molybdenum (Mo), nickel (Ni), niobium (Nb), nitrogen (N), palladium (Pd), rubidium (Rb), samarium (Sm), selenium (Se), tantalum (Ta), tellurium (Te), terbium (Tb), erbium (Er), tin (Sn), tungsten (W), vanadium (V), yttrium (Y) as well as zirconium (Zr) have been included in BGs. These ions have been found to be particularly interesting for enhancing the biological performance of doped BGs in novel compositions for tissue repair (both hard and soft tissue) and for providing, in some cases, extra functionalities to the BG, for example fluorescence, luminescence, radiation shielding, anti-inflammatory, and antibacterial properties. This review summarizes the influence of incorporating such less-common elements in BGs with focus on tissue engineering applications, usually exploiting the bioactivity of the BG in combination with other functional properties imparted by the presence of the added elements.

Kinetic characteristics of mobile Mo associated with Mn, Fe and S redox geochemistry in estuarine sediments

Estuarine sediments are crucial repositories and incubators of molybdenum (Mo) during its transport from rivers to the ocean. Here, Mo mobility and related processes in estuarine sediments were explored using high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques. Better correlations were observed between dissolved Mn and Mo than between dissolved Fe and Mo, implying that Mn geochemistry plays a key role in dissolved Mo mobility via molybdate adsorption onto abundant Mn oxides and its substantial release upon intense Mn reduction. As a result, oxic intertidal sediments functioned as Mo sinks, and anoxic subtidal sediments functioned as Mo sources. The opposite vertical distributions between DGT-Labile S and DGT-Labile Mo indicated that the availability of labile Mo can be blocked by aqueous sulfide. However, the corresponding high concentrations of DGT-Labile S and dissolved Mo at subtidal sites demonstrated that the abundant dissolved Mo remobilized via Mn reduction was not effectively solidified by sulfide. Simulation with the DIFS model further verified that redox conditions and induced physicochemical processes are crucial factors controlling Mo mobility, with relatively low dissolved Mo concentrations but an adequate and steady resupply capacity of the bioavailable molybdate in intertidal sediments.

Fungal-Metal Interactions: A Review of Toxicity and Homeostasis

Metal nanoparticles used as antifungals have increased the occurrence of fungal-metal interactions. However, there is a lack of knowledge about how these interactions cause genomic and physiological changes, which can produce fungal superbugs. Despite interest in these interactions, there is limited understanding of resistance mechanisms in most fungi studied until now. We highlight the current knowledge of fungal homeostasis of zinc, copper, iron, manganese, and silver to comprehensively examine associated mechanisms of resistance. Such mechanisms have been widely studied in Saccharomyces cerevisiae, but limited reports exist in filamentous fungi, though they are frequently the subject of nanoparticle biosynthesis and targets of antifungal metals. In most cases, microarray analyses uncovered resistance mechanisms as a response to metal exposure. In yeast, metal resistance is mainly due to the down-regulation of metal ion importers, utilization of metallothionein and metallothionein-like structures, and ion sequestration to the vacuole. In contrast, metal resistance in filamentous fungi heavily relies upon cellular ion export. However, there are instances of resistance that utilized vacuole sequestration, ion metallothionein, and chelator binding, deleting a metal ion importer, and ion storage in hyphal cell walls. In general, resistance to zinc, copper, iron, and manganese is extensively reported in yeast and partially known in filamentous fungi; and silver resistance lacks comprehensive understanding in both.

Inhibition of autophagy aggravates molybdenum-induced mitochondrial dysfunction by aggravating oxidative stress in duck renal tubular epithelial cells

Excessive molybdenum (Mo) has adverse effects on animals. To elucidate the effects of autophagy on Mo-induced nephrotoxicity, the duck renal tubular epithelial cells were cultured in medium in absence and presence of (NH₄)₆Mo₇O₂₄.4H₂O (0, 480, 720, 960 μM Mo), 3-Methyladenine (3-MA) (2.5 μM), and the combination of Mo and 3-MA for 12 h. After 12 h exposure, the MDC staining, morphologic observation, LC3 puncta, cell viability, autophagy-related genes mRNA and proteins levels, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) level, antioxidant indices, mitochondrial membrane potential (MMP), mitochondrial mass, mitochondrial respiratory control ratio (RCR) and oxidative phosphorylation rate (OPR) were determined. The results showed that excessive Mo exposure significantly elevated the number of autophagosome and LC3 puncta, upregulated Beclin-1, Atg5, LC3A and LC3B mRNA levels, and LC3II/LC3I and Beclin-1 protein levels, decreased mTOR, p62 and Dynein mRNA levels and p62 protein level. Besides, co-treatment with Mo and 3-MA dramatically increased LDH release, ROS level, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents as well as cell dam age, reduced cell viability, the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), MMP, mitochondrial mass, mitochondrial RCR and OPR compared to treatment with Mo alone. Taken together, these results suggest that excessive Mo exposure can induce autophagy in duck renal tubular epithelial cells, inhibition of autophagy aggravates Mo-induced mitochondrial dysfunction by regulating oxidative stress.

Cu(III)-bis-thiolato complex forms an unusual mono-thiolato Cu(III)-peroxido adduct

The stable complex [bis(toluene-3,4-dithiolato)copper(iii)][NEt3H] has been synthesised and characterised as a square-planar Cu(iii) complex by X-ray photoelectron spectroscopy, cyclic voltammetry and DFT calculations. Intriguingly, when fragmented in FTICR-MS, an unusual [(toluene-3,4-dithiolate)Cu(iii)(peroxide)]- complex is formed by reaction with oxygen. Natural 1,2-dithiolenes known to bind molybdenum might stabilise Cu(iii) in vivo.

Molybdenum and Cadmium co-induced the levels of autophagy-related genes via adenosine 5'-monophosphate-activated protein kinase/mammalian target of rapamycin signaling pathway in Shaoxing Duck (Anas platyrhyncha) kidney

To investigate Molybdenum (Mo) and Cadmium (Cd) co-induced the levels of autophagy-related genes via AMPK/mTOR signaling pathway in Shaoxing Duck (Anas platyrhyncha) kidney, 60 healthy 11-day-old ducks were randomly divided into 6 groups, which were treated with Mo or/and Cd at different doses on the basal diet for 120 d. Kidney samples were collected on day 120 to determine the mRNA expression levels of adenosine 5′-monophosphate (AMP)-activated protein kinase α1 (AMPKα1), mammalian target of rapamycin (mTOR), Beclin-1, autophagy-related gene-5 (Atg5), microtubule-associated protein light chain A (LC3A), microtubule-associated protein light chain B (LC3B), sequestosome-1, and Dynein by real-time quantitative polymerase chain reaction. Meanwhile, ultrastructural changes of the kidney were observed. The results indicated that the mTOR and P62 mRNA expression levels were significantly downregulated, but the Atg5 and Beclin-1 mRNA levels were remarkably upregulated in all treated groups compared to control group, and their changes were greater in joint groups. Additionally, compared to control group, the Dynein mRNA expression level was apparently downregulated in co-treated groups, the LC3B, LC3A, and AMPKα1 expression levels were dramatically upregulated in single treated groups and they were not obviously different in co-treated groups. Ultrastructural changes showed that Mo and Cd could markedly increase the number of autophagosomes. Taken together, it suggested that dietary Mo and Cd might induce autophagy via AMPK/mTOR signaling pathway in duck kidney, and it showed a possible synergistic relationship between the 2 elements.

Sensitive detection of molybdenum through its catalysis and quenching of gold nanocluster fluorescence

Molybdenum (Mo) is an essential nutrient for the proper functioning of some enzymes in living organisms as human beings. Conventional methods for its detection require complicated instrumentations as atomic absorption or mass spectrometers. In this work, a sensitive kinetic fluorescence was developed as an alternative. Gold nanoclusters (AuNCs) with red fluorescence emission were synthesized, and this fluorescence was effectively quenched by iodine through an etching process. It was found that the presence of Mo significantly speeded up a reaction for the generation of iodine, and thus enhanced the quenching. This effect was then adopted for the development of a sensitive fluorescent measurement toward Mo. The method was capable of detecting Mo down to 0.2 nM and was successfully applied for the analyses of mung bean and tea leaf samples.

Development of New Canned Chub Mackerel Products Incorporating Edible Seaweeds-Influence on the Minerals and Trace Elements Composition

This study aimed to develop new canned chub mackerel products incorporating edible seaweeds (Ascophyllum nodosum, Fucus spiralis, Saccorhiza polyschides, Chondrus crispus, Porphyra sp. and Ulva sp.) harvested in the Portuguese North-Central coast, with simultaneous sensory improvement and minerals enrichment. Two processes were compared, namely the addition of seaweeds in i) the canning step and ii) in the brining step (as the replacement for salt). The concentrations of four macrominerals (Na, K, Ca and Mg), chloride, and twelve trace elements (Co, Cu, Fe, I, Li, Mn, Mo, Rb, Se, Sr, V and Zn) were determined by high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Results showed that canned chub mackerel incorporating C. crispus and F. spiralis was found to be the preferred sensory option, also exhibiting contents enriched with Cl, Co, Cu, Fe, I, Li, Mg, Mn, Mo, Na, Rb, Se, and Sr. This effect was more pronounced when both seaweed species were added to replace the salt added in the brining step.

Synthesis, characterization and anticandidal activity of dioxomolybdenum(VI) complexes of the type [MoO2{ON=C(CH3)Ar}2] and [MoO2{OC(R)CHC(R’)=NC6H5}2]

Interaction of [MoO₂(acac)₂] with internally functionalized oximes like HON=C(CH₃)Ar (Ar = C₄H₃S, C₄H₃O or C₅H₄N) and Schiff's Bases derived from β – diketones like HOC(R)CHC(R′)=NC₆H₅ (R = R’ = CH₃ or C₆H₅; R = CH₃ and R’ = C₆H₅) led to the formation of yellow dioxomolybdenum(VI) complexes of the type [MoO₂{ON=C(CH₃)Ar}₂] and [MoO₂{OC(R)CHC(R′)=NC₆H₅}₂]. Oximes were synthesized by green methodology. The newly synthesized complexes were characterized on basis of elemental analysis and various spectral findings.

Anticandidal activity of [MoO₂{ON=C(CH₃)C₆H₄N}₂] clearly reveals that the complex is biologically active against fungal diseases.

Experimental and simulation results of the adsorption of Mo and V onto ferrihydrite

This study aims to highlight discrepancies between experimental and simulation linked to the mechanisms of Mo and V adsorption onto ferrihydrite (FHY) nanoparticles. We have measured adsorption capacities and uptake efficiencies and then fitted and compared these with outputs from various geochemical and adsorption models that were run as a function of pH, surface area (SA) and ferrihydrite particles size distributions. Our results revealed that the experimental data for the Mo system could be fitted very well, but this was not the case for the V system, when a model default value for the SA of FHY of 600 m² g⁻¹ was used. The discrepancy in the results for the V system can be explained by the lack of specific V species and/or associated constants in databases and variation in software versions, which change the outputted chemical species. Our comparative results also confirm that any experimental variables used as modelling inputs need to be checked carefully prior to any modelling exercises.

3D printing of Mo-containing scaffolds with activated anabolic responses and bi-lineage bioactivities

When osteochondral tissues suffer from focal or degenerative lesions caused by trauma or disorders, it is a tough challenge to regenerate them because of the limited self-healing capacity of articular cartilage. In this study, a series of Mo-doped bioactive glass ceramic (Mo-BGC) scaffolds were prepared and then systematically characterized. The released MoO42- ions from 7.5Mo-BGC scaffolds played a vital role in regenerating articular cartilage and subchondral bone synchronously. Methods: The Mo-BGC scaffolds were fabricated through employing both a sol-gel method and 3D printing technology. SEM, EDS, HRTEM, XRD, ICPAES and mechanical strength tests were respectively applied to analyze the physicochemical properties of Mo-BGC scaffolds. The proliferation and differentiation of rabbit chondrocytes (RCs) and human bone mesenchymal stem cells (HBMSCs) cultured with dilute solutions of 7.5Mo-BGC powder extract were investigated in vitro. The co-culture model was established to explore the possible mechanism of stimulatory effects of MoO42- ions on the RCs and HBMSCs. The efficacy of regenerating articular cartilage and subchondral bone using 7.5Mo-BGC scaffolds was evaluated in vivo. Results: The incorporation of Mo into BGC scaffolds effectively enhanced the compressive strength of scaffolds owing to the improved surface densification. The MoO42- ions released from the 7.5Mo-BGC powders remarkably promoted the proliferation and differentiation of both RCs and HBMSCs. The MoO42- ions in the co-culture system significantly stimulated the chondrogenic differentiation of RCs and meanwhile induced the chondrogenesis of HBMSCs. The chondrogenesis stimulated by MoO42- ions happened through two pathways: 1) MoO42- ions elicited anabolic responses through activating the HIF-1α signaling pathway; 2) MoO42- ions inhibited catabolic responses and protected cartilage matrix from degradation. The in vivo study showed that 7.5Mo-BGC scaffolds were able to significantly promote cartilage/bone regeneration when implanted into rabbit osteochondral defects for 8 and 12 weeks, displaying bi-lineage bioactivities. Conclusion: The 3D-printed Mo-BGC scaffolds with bi-lineage bioactivities and activated anabolic responses could offer an effective strategy for cartilage/bone interface regeneration.

Exposure to sodium molybdate results in mild oxidative stress in Drosophila melanogaster

OBJECTIVES

The study was conducted to assess the redox status of Drosophila flies upon oral intake of insulin-mimetic salt, sodium molybdate (Na2MoO4).

METHODS

Oxidative stress parameters and activities of antioxidant and associated enzymes were analyzed in two-day-old D. melanogaster insects after exposure of larvae and newly eclosed adults to three molybdate levels (0.025, 0.5, or 10 mM) in the food.

RESULTS

Molybdate increased content of low molecular mass thiols and activities of catalase, superoxide dismutase, glutathione-S-transferase, and glucose-6-phosphate dehydrogenase in males. The activities of these enzymes were not affected in females. Males exposed to molybdate demonstrated lower carbonyl protein levels than the control cohort, whereas females at the same conditions had higher carbonyl protein content and catalase activity than ones in the control cohort. The exposure to 10 mM sodium molybdate decreased the content of protein thiols in adult flies of both sexes. Sodium molybdate did not affect the activities of NADP-dependent malate dehydrogenase and thioredoxin reductase in males or NADP-dependent isocitrate dehydrogenase in either sex at any concentration.

DISCUSSION

Enhanced antioxidant capacity in upon Drosophila flies low molybdate levels in the food suggests that molybdate can be potentially useful for the treatment of certain pathologies associated with oxidative stress.

Non-Specific Root Transport of Nutrient Gives Access to an Early Nutritional Indicator: The Case of Sulfate and Molybdate

Under sulfur (S) deficiency, crosstalk between nutrients induced accumulation of other nutrients, particularly molybdenum (Mo). This disturbed balanced between S and Mo could provide a way to detect S deficiency and therefore avoid losses in yield and seed quality in cultivated species. Under hydroponic conditions, S deprivation was applied to Brassica napus to determine the precise kinetics of S and Mo uptake and whether sulfate transporters were involved in Mo uptake. Leaf contents of S and Mo were also quantified in a field-grown S deficient oilseed rape crop with different S and N fertilization applications to evaluate the [Mo]:[S] ratio, as an indicator of S nutrition. To test genericity of this indicator, the [Mo]:[S] ratio was also assessed with other cultivated species under different controlled conditions. During S deprivation, Mo uptake was strongly increased in B. napus. This accumulation was not a result of the induction of the molybdate transporters, Mot1 and Asy, but could be a direct consequence of Sultr1.1 and Sultr1.2 inductions. However, analysis of single mutants of these transporters in Arabidopsis thaliana suggested that other sulfate deficiency responsive transporters may be involved. Under field conditions, Mo content was also increased in leaves by a reduction in S fertilization. The [Mo]:[S] ratio significantly discriminated between the plots with different rates of S fertilization. Threshold values were estimated for the hierarchical clustering of commercial crops according to S status. The use of the [Mo]:[S] ratio was also reliable to detect S deficiency for other cultivated species under controlled conditions. The analysis of the leaf [Mo]:[S] ratio seems to be a practical indicator to detect early S deficiency under field conditions and thus improve S fertilization management.

Microwave plasma torch mass spectrometry for the direct detection of copper and molybdenum ions in aqueous liquids

Microwave plasma torch (MPT) is a simple and low power-consumption ambient ion source. And the MPT Mass spectra of many metal elements usually exhibit some novel features different from their inductively coupled plasma (ICP) mass spectra, which may be helpful for metal element analysis. Here, we presented the results about the MPT mass spectra of copper and molybdenum elements by a linear ion trap mass spectrometer (LTQ). The generated copper or molybdenum contained ions in plasma were characterized further in collision-induced dissociated (CID) experiments. These researches built a novel, direct and sensitive method for the direct analysis of trace levels of copper and molybdenum in aqueous liquids. Quantitative results showed that the limit of detection (LOD) by using MS(2) procedure was estimated to be 0.265 µg/l (ppb) for copper and 0.497 µg/l for molybdenum. The linear dynamics ranges cover at least 2 orders of magnitude and the analysis of a single aqueous sample can be completed in 5-6 min with a reasonable semi-quantitative sense. Two practical aqueous samples, milk and urine, were also analyzed qualitatively with reasonable recovery rates and RSD. These experimental data demonstrated that the MPT MS is able to turn into a promising and hopeful tool in field analysis of copper and molybdenum ions in water and some aqueous media, and can be applied in many fields, such as environmental controlling, hydrogeology, and water quality inspection. Moreover, MPT MS could also be used as the supplement of ICP-MS for the rapid and in-situ analysis of metal ions. Copyright © 2016 John Wiley & Sons, Ltd.

Structural and functional models in molybdenum and tungsten bioinorganic chemistry: description of selected model complexes, present scenario and possible future scopes

A brief description about some selected model complexes in molybdenum and tungsten bioinorganic chemistry is provided. The synthetic strategies involved and their limitations are discussed. Current status of molybdenum and tungsten bioinorganic modeling chemistry is presented briefly and synthetic problems associated therein are analyzed. Possible future directions which may expand the scope of modeling chemistry are suggested.

Incorporation of molybdenum in rubredoxin: models for mononuclear molybdenum enzymes

Molybdenum is found in the active site of enzymes usually coordinated by one or two pyranopterin molecules. Here, we mimic an enzyme with a mononuclear molybdenum-bis pyranopterin center by incorporating molybdenum in rubredoxin. In the molybdenum-substituted rubredoxin, the metal ion is coordinated by four sulfurs from conserved cysteine residues of the apo-rubredoxin and two other exogenous ligands, oxygen and thiol, forming a Mo((VI))-(S-Cys)4(O)(X) complex, where X represents -OH or -SR. The rubredoxin molybdenum center is stabilized in a Mo(VI) oxidation state, but can be reduced to Mo(IV) via Mo(V) by dithionite, being a suitable model for the spectroscopic properties of resting and reduced forms of molybdenum-bis pyranopterin-containing enzymes. Preliminary experiments indicate that the molybdenum site built in rubredoxin can promote oxo transfer reactions, as exemplified with the oxidation of arsenite to arsenate.

Redox chemistry of molybdenum in natural waters and its involvement in biological evolution

The transition element molybdenum (Mo) possesses diverse valances (+II to +VI), and is involved in forming cofactors in more than 60 enzymes in biology. Redox switching of the element in these enzymes catalyzes a series of metabolic reactions in both prokaryotes and eukaryotes, and the element therefore plays a fundamental role in the global carbon, nitrogen, and sulfur cycling. In the present oxygenated waters, oxidized Mo(VI) predominates thermodynamically, whilst reduced Mo species are mainly confined within specific niches including cytoplasm. Only recently has the reduced Mo(V) been separated from Mo(VI) in sulfidic mats and even in some reducing waters. Given the presence of reduced Mo(V) in contemporary anaerobic habitats, it seems that reduced Mo species were present in the ancient reducing ocean (probably under both ferruginous and sulfidic conditions), prompting the involvement of Mo in enzymes including nitrogenase and nitrate reductase. During the global transition to oxic conditions, reduced Mo species were constrained to specific anaerobic habitats, and efficient uptake systems of oxidized Mo(VI) became a selective advantage for current prokaryotic and eukaryotic cells. Some prokaryotes are still able to directly utilize reduced Mo if any exists in ambient environments. In total, this mini-review describes the redox chemistry and biogeochemistry of Mo over the Earth’s history.

Leaching and accumulation of trace elements in sulfate reducing granular sludge under concomitant thermophilic and low pH conditions

The leaching and/or accumulation of trace elements in sulfate reducing granular sludge systems was investigated. Two thermophilic up-flow anaerobic sludge bed (UASB) reactors operated at pH 5 were fed with sucrose (4 gCOD l(reactor)(-1)d(-1)) and sulfate at different COD/SO(4)(2-) ratios. During the start-up of such acidogenic systems, an initial leaching of trace elements from the inoculum sludge occurred regardless of trace elements supplementation in the reactor influent. The granular sludge maintained the physical structure despite high Fe leaching. After start-up and nonetheless the acidic conditions, Co, Ni, Cu, Zn, Mo and Se were retained or accumulated by the sludge when added. Particularly, Ni and Co accumulated in the carbonates and exchangeable fractions ensuring potential bioavailability. Otherwise, the initial stock in the inoculum sludge sufficed to operate the process for nearly 1 year without supplementation of trace elements and no significant sludge wash-out occurred.

Comparative Genomics and Evolution of Molybdenum Utilization

The trace element molybdenum (Mo) is the catalytic component of important enzymes involved in global nitrogen, sulfur, and carbon metabolism in both prokaryotes and eukaryotes. With the exception of nitrogenase, Mo is complexed by a pterin compound thus forming the biologically active molybdenum cofactor (Moco) at the catalytic sites of molybdoenzymes. The physiological roles and biochemical functions of many molybdoenzymes have been characterized. However, our understanding of the occurrence and evolution of Mo utilization is limited. This article focuses on recent advances in comparative genomics of Mo utilization in the three domains of life. We begin with a brief introduction of Mo transport systems, the Moco biosynthesis pathway, the role of posttranslational modifications, and enzymes that utilize Mo. Then, we proceed to recent computational and comparative genomics studies of Mo utilization, including a discussion on novel Moco-binding proteins that contain the C-terminal domain of the Moco sulfurase and that are suggested to represent a new family of molybdoenzymes. As most molybdoenzymes need additional cofactors for their catalytic activity, we also discuss interactions between Mo metabolism and other trace elements and finish with an analysis of factors that may influence evolution of Mo utilization.

Algae and humans share a molybdate transporter

Almost all living organisms need to obtain molybdenum from the external medium to achieve essential processes for life. Activity of important enzymes such as sulfite oxidase, aldehyde oxidase, xanthine dehydrogenase, and nitrate reductase is strictly dependent on the presence of Mo in its active site. Cells take up Mo in the form of the oxianion molybdate, but the molecular nature of the transporters is still not well known in eukaryotes. MOT1 is the first molybdate transporter identified in plant-type eukaryotic organisms, but it is absent in animal genomes. Here we report a molybdate transporter different from the MOT1 family, encoded by the Chlamydomonas reinhardtii gene MoT2, that is also present in animals including humans. The knockdown of CrMoT2 transcription leads to the deficiency of molybdate uptake activity in Chlamydomonas. In addition, heterologous expression in Saccharomyces cerevisiae of MoT2 genes from Chlamydomonas and humans support the functionality of both proteins as molybdate transporters. Characterization of CrMOT2 and HsMOT2 activities showed an apparent Km of about 550 nM that, though higher than the Km reported for MOT1, still corresponds to high affinity systems. CrMoT2 transcription is activated when extracellular molybdate concentration is low but in contrast to MoT1 is not activated by nitrate. Analysis of protein databases revealed the presence of four motifs present in all the proteins with high similarity to MOT2, that label a previously undescribed family of proteins probably related to molybdate transport. Our results open the way toward the understanding of molybdate transport as part of molybdenum homeostasis and Moco biosynthesis in animals.

Molybdenum speciation in uranium mine tailings using X-ray absorption spectroscopy

Uranium (U) mill tailings in northern Saskatchewan, Canada, contain elevated concentrations of molybdenum (Mo). The potential for long-term (>10,000 years) mobilization of Mo from the tailings management facilities to regional groundwater systems is an environmental concern. To assist in characterizing long-term stability, X-ray absorption spectroscopy was used to define the chemical (redox and molecular) speciation of Mo in tailings samples from the Deilmann Tailings Management Facility (DTMF) at the Key Lake operations of Cameco Corporation. Comparison of Mo K near-edge X-ray absorption spectra of tailings samples and reference compounds of known oxidation states indicates Mo exists mainly as molybdate (+6 oxidation state). Principal component analysis of tailings samples spectra followed by linear combination fitting using spectra of reference compounds indicates that various proportions of NiMoO(4) and CaMoO(4) complexes, as well as molybdate adsorbed onto ferrihydrite, are the Mo species present in the U mine tailings. Tailings samples with low Fe/Mo (<708) and high Ni/Mo (>113) molar ratios are dominated by NiMoO(4), whereas those with high Fe/Mo (>708) and low Ni/Mo (<113) molar ratios are dominated by molybdate adsorbed onto ferrihydrite. This suggests that the speciation of Mo in the tailings is dependent in part on the chemistry of the original ore.