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Molecules (Basel, Switzerland) Sep 2022This article gives an overview of the research activity of the LAC2 team at LCC developed at Castres in the field of sustainable chemistry with an emphasis on the... (Review)
Review
This article gives an overview of the research activity of the LAC2 team at LCC developed at Castres in the field of sustainable chemistry with an emphasis on the collaboration with a research team from the University of Zagreb, Faculty of Science, Croatia. The work is situated within the context of sustainable chemistry for the development of catalytic processes. Those processes imply molecular complexes containing oxido-molybdenum, -vanadium, -tungsten or simple polyoxometalates (POMs) as catalysts for organic solvent-free epoxidation. The studies considered first the influence of the nature of complexes (and related ligands) on the reactivity (assessing mechanisms through DFT calculations) with model substrates. From those model processes, the work has been enlarged to the valorization of biomass resources. A part concerns the activity on vanadium chemistry and the final part concerns the use of POMs as catalysts, from molecular to grafted catalysts, (ep)oxidizing substrates from fossil and biomass resources.
Topics: Catalysis; Molybdenum; Oxidation-Reduction; Tungsten; Vanadium
PubMed: 36144747
DOI: 10.3390/molecules27186011 -
Molecules (Basel, Switzerland) Nov 2023The pyranopterin dithiolene ligand is remarkable in terms of its geometric and electronic structure and is uniquely found in mononuclear molybdenum and tungsten enzymes.... (Review)
Review
The pyranopterin dithiolene ligand is remarkable in terms of its geometric and electronic structure and is uniquely found in mononuclear molybdenum and tungsten enzymes. The pyranopterin dithiolene is found coordinated to the metal ion, deeply buried within the protein, and non-covalently attached to the protein via an extensive hydrogen bonding network that is enzyme-specific. However, the function of pyranopterin dithiolene in enzymatic catalysis has been difficult to determine. This focused account aims to provide an overview of what has been learned from the study of pyranopterin dithiolene model complexes of molybdenum and how these results relate to the enzyme systems. This work begins with a summary of what is known about the pyranopterin dithiolene ligand in the enzymes. We then introduce the development of inorganic small molecule complexes that model aspects of a coordinated pyranopterin dithiolene and discuss the results of detailed physical studies of the models by electronic absorption, resonance Raman, X-ray absorption and NMR spectroscopies, cyclic voltammetry, X-ray crystallography, and chemical reactivity.
Topics: Models, Molecular; Molybdenum; Ligands; Metalloproteins; Catalysis; Coenzymes
PubMed: 38005178
DOI: 10.3390/molecules28227456 -
Biometals : An International Journal on... Feb 2022Molybdenum (Mo) is an essential trace element for bacteria that is utilized in myriad metalloenzymes that directly couple to the biogeochemical cycling of nitrogen,...
Molybdenum (Mo) is an essential trace element for bacteria that is utilized in myriad metalloenzymes that directly couple to the biogeochemical cycling of nitrogen, sulfur, and carbon. In particular, Mo is found in the most common nitrogenase enzyme, and the scarcity and low bioavailability of Mo in soil may be a critical factor that contributes to the limitation of nitrogen fixation in forests and agroenvironments. To overcome this scarcity, microbes produce exudates that specifically chelate scarce metals, promoting their solubilization and uptake. Here, we have determined the structure and stability constants of Mo bound by protochelin, a siderophore produced by bacteria under Mo-depleted conditions. Spectrophotometric titration spectra indicated a coordination shift from a catecholate to salicylate binding mode for Mo-protochelin (Mo-Proto) complexes at pH < 5. pKa values obtained from analysis of titrations were 4.8 ± 0.3 for MoOHProto and 3.3 ± 0.1 for MoOHProto. The occurrence of negatively charged Mo-Proto complexes at pH 6 was also confirmed by mass spectrometry. K-edge Extended X-ray absorption fine structure spectroscopy confirmed the change in Mo coordination at low pH, and structural fitting provides insights into the physical architecture of complexes at neutral and acidic pH. These findings suggest that Mo can be chelated by protochelin across a wide environmental pH range, with a coordination shift occurring at pH < 5. This chelation and associated coordination shift may impact biological availability and mineral surface retention of Mo under acidic conditions.
Topics: Coordination Complexes; Molybdenum; Salicylates; Siderophores; Trace Elements
PubMed: 34837588
DOI: 10.1007/s10534-021-00352-7 -
Molecules (Basel, Switzerland) Jul 2022A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of... (Review)
Review
A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of mononuclear molybdenum enzymes. Contributions to our understanding of the structure and function of each of the major families of these enzymes is considered, providing a perspective on how spectroscopy has impacted the field.
Topics: Electron Spin Resonance Spectroscopy; Molybdenum
PubMed: 35956757
DOI: 10.3390/molecules27154802 -
Biosensors Nov 2023Azithromycin (AZY) is a well-known top-prioritized antibiotic and is used by humans in strong concentrations. However, the side effects of the AZY antibiotic may cause...
Azithromycin (AZY) is a well-known top-prioritized antibiotic and is used by humans in strong concentrations. However, the side effects of the AZY antibiotic may cause some serious and significant damage to humans and the environment. Thus, there is a need to develop effective and sensitive sensors to monitor accurate concentrations of AZY. In the last decade, electrochemistry-based sensors have received enormous attention from the scientific community because of their high sensitivity, selectivity, cost-effectiveness, fast response, rapid detection response, simple fabrication, and working principle. It is important to mention that electrochemical sensors rely on the properties of electrode modifiers. Hence, the selection of electrode materials is of great significance when designing and developing efficient and robust electrochemical sensors. In this study, we fabricated an AZY sensor by utilizing a molybdenum disulfide/titanium aluminum carbide (MoS@TiAlC) composite as the electrode material. The MoS@TiAlC composite was synthesized via a simple sonication process. The synthesized MoS@TiAlC composite was characterized using a powder X-ray diffraction (XRD) method to examine the phase purity and formation of the MoS@TiAlC composite. Scanning electron microscopy (SEM) was used to study the surface morphological features of the prepared MoS@TiAlC composite, whereas energy dispersive X-ray spectroscopy (EDAX) was adopted to determine the elemental composition of the prepared MoS@TiAlC composite. The glassy carbon (GC) electrode was modified with the prepared MoS@TiAlC composite and applied as the AZY sensor. The sensing performance of the MoS@TiAlC composite-modified GC electrode was studied using linear sweep voltammetry. The sensor demonstrated excellent performance when determining AZY and showed a good detection limit of 0.009 µM with a sensitivity of 6.77 µA/µM.cm.
Topics: Humans; Molybdenum; Azithromycin; Carbon; Microscopy, Electron, Scanning; Anti-Bacterial Agents; Electrodes; Limit of Detection; Electrochemical Techniques
PubMed: 37998161
DOI: 10.3390/bios13110986 -
Journal of the American Chemical Society Aug 2022Splitting of N via six-electron reduction and further functionalization to value-added products is one of the most important and challenging chemical transformations in...
Splitting of N via six-electron reduction and further functionalization to value-added products is one of the most important and challenging chemical transformations in N fixation. However, most N splitting approaches rely on strong chemical or electrochemical reduction to generate highly reactive metal species to bind and activate N, which is often incompatible with functionalizing agents. Catalytic and sustainable N splitting to produce metal nitrides under mild conditions may create efficient and straightforward methods for N-containing organic compounds. Herein, we present that a readily available and nonredox (-Bu)NBr can promote N-splitting with a Mo(III) platform. Both experimental and theoretical mechanistic studies suggest that simple X (X = Br, Cl, etc.) anions could induce the disproportionation of Mo[N()Ar] at the early stage of the catalysis to generate a catalytically active {Mo[N()Ar]} species. The quintet Mo species prove to be more favorable for N fixation kinetically and thermodynamically, compared with the quartet Mo counterpart. Especially, computational studies reveal a distinct heterovalent {Mo-N-Mo} dimeric intermediate for the N≡N triple bond cleavage.
Topics: Catalysis; Electrons; Molybdenum
PubMed: 35882019
DOI: 10.1021/jacs.2c01507 -
Nature Communications Sep 2019The recent decline in energy, size and complexity scaling of traditional von Neumann architecture has resurrected considerable interest in brain-inspired computing....
The recent decline in energy, size and complexity scaling of traditional von Neumann architecture has resurrected considerable interest in brain-inspired computing. Artificial neural networks (ANNs) based on emerging devices, such as memristors, achieve brain-like computing but lack energy-efficiency. Furthermore, slow learning, incremental adaptation, and false convergence are unresolved challenges for ANNs. In this article we, therefore, introduce Gaussian synapses based on heterostructures of atomically thin two-dimensional (2D) layered materials, namely molybdenum disulfide and black phosphorus field effect transistors (FETs), as a class of analog and probabilistic computational primitives for hardware implementation of statistical neural networks. We also demonstrate complete tunability of amplitude, mean and standard deviation of the Gaussian synapse via threshold engineering in dual gated molybdenum disulfide and black phosphorus FETs. Finally, we show simulation results for classification of brainwaves using Gaussian synapse based probabilistic neural networks.
Topics: Disulfides; Molybdenum; Nanotechnology; Neural Networks, Computer; Normal Distribution; Transistors, Electronic
PubMed: 31519885
DOI: 10.1038/s41467-019-12035-6 -
Chemical Reviews Jun 2020Biological nitrogen fixation is catalyzed by the enzyme nitrogenase, which facilitates the cleavage of the relatively inert triple bond of N. Nitrogenase is most... (Review)
Review
Biological nitrogen fixation is catalyzed by the enzyme nitrogenase, which facilitates the cleavage of the relatively inert triple bond of N. Nitrogenase is most commonly associated with the molybdenum-iron cofactor called FeMoco or the M-cluster, and it has been the subject of extensive structural and spectroscopic characterization over the past 60 years. In the late 1980s and early 1990s, two "alternative nitrogenase" systems were discovered, isolated, and found to incorporate V or Fe in place of Mo. These systems are regulated by separate gene clusters; however, there is a high degree of structural and functional similarity between each nitrogenase. Limited studies with the V- and Fe-nitrogenases initially demonstrated that these enzymes were analogously active as the Mo-nitrogenase, but more recent investigations have found capabilities that are unique to the alternative systems. In this review, we will discuss the reactivity, biosynthetic, and mechanistic proposals for the alternative nitrogenases as well as their electronic and structural properties in comparison to the well-characterized Mo-dependent system. Studies over the past 10 years have been particularly fruitful, though key aspects about V- and Fe-nitrogenases remain unexplored.
Topics: Models, Molecular; Molybdenum; Nitrogen; Nitrogen Fixation; Nitrogenase
PubMed: 32129988
DOI: 10.1021/acs.chemrev.9b00704 -
Journal of Materials Chemistry. B Jun 2022The development of nanomaterial-based antibiotics can be the most potent alternative due to the increasing resistance against conventional antibiotics. However, one of...
The development of nanomaterial-based antibiotics can be the most potent alternative due to the increasing resistance against conventional antibiotics. However, one of the important parameters in the development of antibacterial agents is their Gram selectivity, which has been seldomly explored in the case of nano-antibiotics. The multimodal action of surface-functionalized nanomaterials can exhibit strain selectivity and enhanced antibacterial activity. Herein, we designed a Gram-selective antibacterial system based on two-dimensional molybdenum disulphide (2D-MoS) functionalized with different proportions of positively and negatively charged ligands. Two representative ESKAPE pathogenic strains, , Gram-positive methicillin-resistant (MRSA) and Gram-negative () were considered to evaluate the selective antibacterial activity. The mechanistic insight behind selectivity was established by evaluating the degree of membrane depolarization together with oxidative stress. The selective generation of intracellular reactive oxygen species (ROS) together with membrane depolarization contributed to the selective killing of the pathogenic bacteria. Gram selectivity was achieved by simply controlling the surface functionality based on the different cell wall compositions and structures of bacterial strains. The interplay between polyvalent electrostatic and non-covalent interactions was mainly responsible for damaging the cell membrane. Furthermore, to establish the antibacterial mechanism, we performed extracellular and intracellular reactive oxidative stress, membrane depolarization and permeabilization assays. In summary, we prepared simple and efficient Gram-selective 2D-MoS-based antibacterial agents, which can be extended to other nano-antibiotic systems.
Topics: Anti-Bacterial Agents; Methicillin-Resistant Staphylococcus aureus; Molybdenum; Pseudomonas aeruginosa
PubMed: 35640626
DOI: 10.1039/d2tb00361a -
Chembiochem : a European Journal of... Mar 2024The connection between 3d (Cu) and 4d (Mo) via the "Mo-S-Cu" unit is called Mo-Cu antagonism. Biology offers case studies of such interactions in metalloproteins such as... (Review)
Review
The connection between 3d (Cu) and 4d (Mo) via the "Mo-S-Cu" unit is called Mo-Cu antagonism. Biology offers case studies of such interactions in metalloproteins such as Mo/Cu-CO Dehydrogenases (Mo/Cu-CODH), and Mo/Cu Orange Protein (Mo/Cu-ORP). The CODH significantly maintains the CO level in the atmosphere below the toxic level by converting it to non-toxic CO for respiring organisms. Several models were synthesized to understand the structure-function relationship of these native enzymes. However, this interaction was first observed in ruminants, and they convert molybdate (MoO ) into tetrathiomolybdate (MoS ; TTM), reacting with cellular Cu to yield biological unavailable Mo/S/Cu cluster, then developing Cu-deficiency diseases. These findings inspire the use of TTM as a Cu-sequester drug, especially for treating Cu-dependent human diseases such as Wilson diseases (WD) and cancer. It is well known that a balanced Cu homeostasis is essential for a wide range of biological processes, but negative consequence leads to cell toxicity. Therefore, this review aims to connect the Mo-Cu antagonism in metalloproteins and anti-copper therapy.
Topics: Humans; Copper; Molybdenum; Metalloproteins
PubMed: 38205937
DOI: 10.1002/cbic.202300679