Zinc Cluster Research Articles

Probing the atomic interaction between zinc clusters and defective carbon in promoting the wide temperature applications of lithium-sulfur battery

Suppressing the dissolution and accelerating conversion kinetics of intermediate polysulfides are central to the practical usage of lithium−sulfur (Li–S) battery in a wide temperature range. Herein, an atomic engineering strategy is innovatively proposed to constructing a sulfur host consisting of chemical-anchoring zinc atomic cluster within double layer N-doped carbon matrix (ZnACCM@CL) for addressing concerns. The as-prepared ZnACCM@CL@S can deliver capacity as high as 1451 mAh g−1 at 0.2 C with electrolyte/sulfur ratio (E/S ratio) of 5.5 μL mg−1 and maintain 749 mAh g−1 after 1200 cycles (fading rate of 0.021% per cycle) at 5 C. Remarkably, the reversible capacity holds 627 mAh g−1 at 0.2 C at the −25 ℃. By a further combination analysis of electron holography (EH) and geometry phase analysis (GPA), the outstanding performance is revealed to be mainly traced to synergistic effect of the polarity N-doped multi-layer carbon matrix and internal periodical charge field induced by atomic strain, greatly enhancing the capability towards on the immobilization and conversion of intermediate polysulfides. More importantly, such an interplay also renders the strongly coupled cathode achieve a high area specific capacity of 8.71 mAh cm−2 even the area sulfur loading obtain to 7.34 mg cm−2. This atomic-level engineering strategy might shed light on the novel insights on the design of high performance for sulfur hosts.

Multiple active voltage stabilizations for multi-reflection time-of-flight mass spectrometry

The performance of a multi-reflection time-of-flight (MR-ToF) mass spectrometer is evaluated under the use of four voltage feedback loops to actively regulate its mirror potentials. Different electronic hardware is characterized to find the most useful configuration for parallel regulation of all of the MR-ToF analyzer's reflecting potentials. The gain in mass resolving power for low-abundance ion species is demonstrated by measuring pairs of molecular isobars of zinc clusters and analyzed in the context of expected flight-time fluctuations. For higher-abundance species, the resolving powers reached in short- and long-term measurements are probed with bismuth-cluster ions, resulting in values up to 500 000 and 200 000, respectively, in the absence of offline corrections. Additionally, feedback-loop regulation is found to be advantageous for changes of experiment cycles in which voltages are switched for, e.g., ion ejection.

The zinc cluster transcription factor Czf1 regulates cell wall architecture and integrity in Candida albicans.

The fungal cell wall is essential for the maintenance of cellular integrity and mediates interactions of the cells with the environment. It is a highly flexible organelle whose composition and organization is modulated in response to changing growth conditions. In the pathogenic yeast Candida albicans, a network of signaling pathways regulates the structure of the cell wall, and mutants with defects in these pathways are hypersensitive to cell wall stress. By harnessing a library of genetically activated forms of all C.albicans zinc cluster transcription factors, we found that a hyperactive Czf1 rescued the hypersensitivity to cell wall stress of different protein kinase deletion mutants. The hyperactive Czf1 induced the expression of many genes with cell wall-related functions and caused visible changes in the cell wall structure. C.albicans czf1Δ mutants were hypersensitive to the antifungal drug caspofungin, which inhibits cell wall biosynthesis. The changes in cell wall architecture caused by hyperactivity or absence of Czf1 resulted in an increased recognition of C.albicans by human neutrophils. Our results show that Czf1, which is known as a regulator of filamentous growth and white-opaque switching, controls the expression of cell wall genes and modulates the architecture of the cell wall.

Intercalation pseudocapacitance in ZnS@C sheets composites for enhanced electrochemical energy storage

Transitional metal chalcogenides have been considered as promising high-performance electrode materials for lithium ion energy storage devices. Herein, the detailed study of ZnS@C sheets composites on lithium ion intercalation pseudocapacitance performance was presented, which exhibited remarkable electrochemical performance with excellent rate capability and long cycle life. ZnS@C sheets composites were synthesized based on a facile strategy through calcine of hexanuclear zinc clusters. These composites served as promising anodic materials hold favourable reversible capacity of 692.2 mAh g−1 at 0.05 A g−1 and 529 mAh g−1 at 1.0 A g−1 for lithium storage device, which exhibited promising in alkali-ion energy storage. Furthermore, the capacity retention is maintained at 98% after 100 cycles, showing a desirable operational stability. Depending on the intercalation pseudocapacitance mechanism, it provides more insights into the development of anodic electrode materials for alkali-ion storage battery with high reversible rate capability and long cycling durability.

Comprehensive transcriptomic and proteomic analyses identify intracellular targets for myriocin to induce Fusarium oxysporum f. sp. niveum cell death

BackgroundMyriocin is a natural product with antifungal activity and is derived from Bacillus amyloliquefaciens LZN01. Our previous work demonstrated that myriocin can inhibit the growth of Fusarium oxysporum f. sp. niveum (Fon) by inducing membrane damage. In this study, the antifungal actions of myriocin against Fon were investigated with a focus on the effects of myriocin on intracellular molecules.ResultsAnalysis of DNA binding and fluorescence spectra demonstrated that myriocin can interact with dsDNA from Fon cells. The intracellular-targeted mechanism of action was also supported by transcriptomic and proteomic analyses; a total of 2238 common differentially expressed genes (DEGs) were identified. The DEGs were further verified by RT-qPCR. Most of the DEGs were assigned metabolism and genetic information processing functions and were enriched in ribosome biogenesis in eukaryotes pathway. The expression of some genes and proteins in ribosome biogenesis in eukaryotes pathway was affected by myriocin, primarily the genes controlled by the C6 zinc cluster transcription factor family and the NFYA transcription factor. Myriocin influenced the posttranscriptional processing of gene products by triggering the main RI (retained intron) events of novel alternative splicing; myriocin targeted key genes (FOXG_09470) or proteins (RIOK2) in ribosome biogenesis in eukaryotes pathway, resulting in disordered translation.ConclusionsIn conclusion, myriocin was determined to exhibit activity against Fon by targeting intracellular molecules. The results of our study may help to elucidate the antifungal actions of myriocin against Fon.

Coordinated Halide and Pseudo Halide‐Dependent Structures and Photoluminescence of Defective Double Cubane Zinc(II) Clusters

AbstractTetranuclear zinc(II) complexes [Zn4(L)4(μ3‐OCH3)2(X)2] (L=2‐((benzyloxy)carbonyl)‐6‐methoxyphenolate; X=Cl− (1), Br− (2), I− (3), N3− (4), or NCS− (5)), have “defective” double‐cubane cores [Zn4O6], which are bridged by two μ3‐methoxo and four μ2‐phenolato oxygen atoms in each discrete complex. In halide complexes 1, 2 and 3, two zinc(II) ions are in slightly distorted octahedral coordinations and the other two in geometries close to the severely distorted trigonal bipyramid, respectively, while all four zinc(II) in pseudo halide complexes 4 and 5 show slightly distorted octahedral geometries. The complexes exhibit blue fluorescence (λmax=415–428 nm) with high photoluminescence quantum yields (PLQYS, Φem) in the range of 0.22‐0.53 at room temperature in the solid state. Complex 5 has the highest Φem among the alkoxo‐bridged multinuclear zinc(II) clusters ever reported.

Porous assembly of an antifungal protein mediated by zinc and sulfonato-calix[8]arene

Controlled protein assembly holds great potential in the fabrication of biohybrid materials. However, the structural diversity and complexity of proteins present an obstacle to controlled assembly. Supramolecular chemistry is a possible solution as it offers tools to mediate self-assembly with molecular precision. This paper deals with the calixarene- and zinc-mediated assembly and crystallization of the histidine-rich Penicillium chrysogenum antifungal protein B (PAFB). We report crystal structures of pure PAFB, PAFB in complex with Zn2+, and the ternary complex of PAFB, Zn2+ and sulfonato-calix[8]arene (sclx8). A comparison of the three crystal structures revealed the structural plasticity of PAFB. While the flexible and highly anionic sclx8 resulted in large molecular weight aggregates of PAFB in solution, diffraction-quality crystals of PAFB-sclx8 were not obtained. We report crystals of PAFB-Zn2+-sclx8 in which a trinuclear zinc cluster occurred adjacent to a calixarene binding site. Interestingly, the combination of sclx8 complexation and zinc coordination resulted in a porous framework with channels of circa 2 nm diameter. Detailed analysis of the crystal structure highlighted novel molecular recognition features. This research enriches the set of supramolecular interactions available to promote protein assembly.

Genome-wide characterization of the Zn(II)2Cys6 zinc cluster-encoding gene family in Pleurotus ostreatus and expression analyses of this family during developmental stages and under heat stress.

Pleurotus ostreatus is one of the most widely cultivated mushrooms in China. The regulatory mechanisms of fruiting body formation and the response to heat stress in P. ostreatus are main research focuses. The Zn(II)2Cys6 family is one of the largest families of transcriptional factors and plays important roles in multiple biological processes in fungi. In this study, we identified 66 zinc cluster proteins in P. ostreatus (PoZCPs) through a genome-wide search. The PoZCPs were classified into 15 types according to their zinc cluster domain. Physical and chemical property analyses showed a huge diversity among the PoZCPs. Phylogenetic analysis of PoZCPs classified these proteins into six groups and conserved motif combinations and similar gene structures were observed in each group. The expression profiles of these PoZCP genes during different developmental stages and under heat stress were further investigated by RNA-sequencing (RNA-seq), revealing diverse expression patterns. A total of 13 PoZCPs that may participate in development or the heat stress response were selected for validation of their expression levels through real-time quantitative PCR (RT-qPCR) analysis, and some developmental stage-specific and heat stress-responsive candidates were identified. The findings contribute to our understanding of the roles and regulatory mechanisms of ZCPs in P. ostreatus.

In Situ Pyrolysis Tracking and Real‐Time Phase Evolution: From a Binary Zinc Cluster to Supercapacitive Porous Carbon

The in situ tracking of the pyrolysis of a binary molecular cluster [Zn7 (μ3 -CH3 O)6 (L)6 ][ZnLCl2 ]2 is presented with one brucite disk and two mononuclear fragments (L=mmimp: 2-methoxy-6-((methylimino)-methyl)phenolate) to porous carbon using TG-MS from 30 to 900 °C. Following up the spilled gas product during the decomposed reaction of zinc cluster along the temperature rising, and in conjunction with XRD, SEM, BET and other materials characterization, where three key steps were observed: 1) cleavage of the bulky external ligand; 2) reduction of ZnO and 3) volatilization of Zn. The real-time-dependent phase-sequential evolution of the remaining products and the processing of pore forming template transformation are proposed simultaneously. The porous carbon structure featuring a uniform nano-sized pore distribution synthesized at 900 °C with the highest surface area of 1644 m2 g-1 and pore volume of 0.926 cm3 g-1 exhibits the best known capacitance of 662 F g-1 at 0.5 A g-1 .

In Situ Pyrolysis Tracking and Real‐Time Phase Evolution: From a Binary Zinc Cluster to Supercapacitive Porous Carbon

AbstractThe in situ tracking of the pyrolysis of a binary molecular cluster [Zn7(μ3‐CH3O)6(L)6][ZnLCl2]2 is presented with one brucite disk and two mononuclear fragments (L=mmimp: 2‐methoxy‐6‐((methylimino)‐methyl)phenolate) to porous carbon using TG‐MS from 30 to 900 °C. Following up the spilled gas product during the decomposed reaction of zinc cluster along the temperature rising, and in conjunction with XRD, SEM, BET and other materials characterization, where three key steps were observed: 1) cleavage of the bulky external ligand; 2) reduction of ZnO and 3) volatilization of Zn. The real‐time‐dependent phase‐sequential evolution of the remaining products and the processing of pore forming template transformation are proposed simultaneously. The porous carbon structure featuring a uniform nano‐sized pore distribution synthesized at 900 °C with the highest surface area of 1644 m2 g−1 and pore volume of 0.926 cm3 g−1 exhibits the best known capacitance of 662 F g−1 at 0.5 A g−1.

A Zinc Cluster Transcription Factor Contributes to the Intrinsic Fluconazole Resistance of Candida auris.

The recently emerged pathogenic yeast Candida auris is a major concern for human health, because it is easily transmissible, difficult to eradicate from hospitals, and highly drug resistant. Most C. auris isolates are resistant to the widely used antifungal drug fluconazole due to mutations in the target enzyme Erg11 and high activity of efflux pumps, such as Cdr1. In the well-studied, distantly related yeast Candida albicans, overexpression of drug efflux pumps also is a major mechanism of acquired fluconazole resistance and caused by gain-of-function mutations in the zinc cluster transcription factors Mrr1 and Tac1. In this study, we investigated a possible involvement of related transcription factors in efflux pump expression and fluconazole resistance of C. auris The C. auris genome contains three genes encoding Mrr1 homologs and two genes encoding Tac1 homologs, and we generated deletion mutants lacking these genes in two fluconazole-resistant strains from clade III and clade IV. Deletion of TAC1b decreased the resistance to fluconazole and voriconazole in both strain backgrounds, demonstrating that the encoded transcription factor contributes to azole resistance in C. auris strains from different clades. CDR1 expression was not or only minimally affected in the mutants, indicating that Tac1b can confer increased azole resistance by a CDR1-independent mechanism.IMPORTANCECandida auris is a recently emerged pathogenic yeast that within a few years after its initial description has spread all over the globe. C. auris is a major concern for human health, because it can cause life-threatening systemic infections, is easily transmissible, and is difficult to eradicate from hospital environments. Furthermore, C. auris is highly drug resistant, especially against the widely used antifungal drug fluconazole. Mutations in the drug target and high activity of efflux pumps are associated with azole resistance, but it is not known how drug resistance genes are regulated in C. auris We have investigated the potential role of several candidate transcriptional regulators in the intrinsic fluconazole resistance of C. auris and identified a transcription factor that contributes to the high resistance to fluconazole and voriconazole of two C. auris strains from different genetic clades, thereby providing insight into the molecular basis of drug resistance of this medically important yeast.

Structural analysis and catalytic activity of tetranuclear metal carboxylate clusters with a [KZn3(μ3-OH)(OOCCPh3)6] or [Zn4(μ4-O)(OOCCPh3)6] central motif

Tetranuclear triphenylacetato zinc–potassium or zinc clusters of formula [KxZn4−x(μ3-OH)x(μ4-O)1−x(Ph3CCOO)6] where x = 0, 1, with interesting structural, physicochemical or catalytic properties were obtained.

Genome-wide investigation of WRKY transcription factors in sweet osmanthus and their potential regulation of aroma synthesis.

WRKY transcription factors, one of the largest transcription factor families, play important roles in regulating the synthesis of secondary metabolites. In sweet osmanthus (Osmanthus fragrans), the monoterpenes have been demonstrated as the most important volatile compounds, and the W-box, which is the cognate binding site of WRKY transcription factors, could be identified in most of the terpene-synthesis-related genes' promoters. However, the role of the WRKY family in terpene synthesis in sweet osmanthus has rarely been examined. In this study, 154 WRKY genes with conserved WRKY domain were identified and classified into three groups. The group II was further divided into five subgroups, and almost all members of IId contained a plant zinc cluster domain. Eight OfWRKYs (OfWRKY7/19/36/38/42/84/95/139) were screened from 20 OfWRKYs for their flower-specific expression patterns in different tissues. Simultaneously, the expression patterns of OfWRKYs and emission patterns of volatile compounds during the flowering process were determined and gas chromatography-mass spectrometry results showed that monoterpenes, such as linalool and ocimene, accounted for the highest proportion, contributing to the floral scent of sweet osmanthus in two cultivars. In addition, correlation analysis revealed the expression patterns of OfWRKYs (OfWRKY7/19/36/139) were each correlated with distinct monoterpenes (linalool, linalool derivatives, ocimene and ocimene derivatives). Subcellular localization analysis showed that p35S::GFP-OfWRKY7/38/95/139 were localized in the nucleus and OfWRKY139 had very strong transactivation activity. Collectively, the results indicated potential roles of OfWRKY139 and OfWRKYs with plant zinc cluster domain in regulating synthesis of aromatic compounds in sweet osmanthus, laying the foundation for use of OfWRKYs to improve the aroma of ornamental plants.

The Fungal Cell Death Regulator czt-1 Is Allelic to acr-3.

Fungal infections have far-reaching implications that range from severe human disease to a panoply of disruptive agricultural and ecological effects, making it imperative to identify and understand the molecular pathways governing the response to antifungal compounds. In this context, CZT-1 (cell death-activated zinc cluster transcription factor) functions as a master regulator of cell death and drug susceptibility in Neurospora crassa. Here we provide evidence indicating that czt-1 is allelic to acr-3, a previously described locus that we now found to harbor a point mutation in its coding sequence. This nonsynonymous amino acid substitution in a low complexity region of CZT-1/ACR-3 caused a robust gain-of-function that led to reduced sensitivity to acriflavine and staurosporine, and increased expression of the drug efflux pump abc-3. Thus, accumulating evidence shows that CZT-1 is an important broad regulator of the cellular response to various antifungal compounds that appear to share common molecular targets.

Molecular and genetic basis of azole antifungal resistance in the opportunistic pathogenic fungus Candida albicans.

Candida albicans is an opportunistic yeast and the major human fungal pathogen in the USA, as well as in many other regions of the world. Infections with C. albicans can range from superficial mucosal and dermatological infections to life-threatening infections of the bloodstream and vital organs. The azole antifungals remain an important mainstay treatment of candidiasis and therefore the investigation and understanding of the evolution, frequency and mechanisms of azole resistance are vital to improving treatment strategies against this organism. Here the organism C. albicans and the genetic changes and molecular bases underlying the currently known resistance mechanisms to the azole antifungal class are reviewed, including up-regulated expression of efflux pumps, changes in the expression and amino acid composition of the azole target Erg11 and alterations to the organism's typical sterol biosynthesis pathways. Additionally, we update what is known about activating mutations in the zinc cluster transcription factor (ZCF) genes regulating many of these resistance mechanisms and review azole import as a potential contributor to azole resistance. Lastly, investigations of azole tolerance in C. albicans and its implicated clinical significance are reviewed.

Synthesis, Solid State, Solution and ESI‐MS Studies of Zinc(II) Cluster Complexes with a Branched Mixed Donor Thiolate Ligand

Synthesis of the unusual spirobicyclic pentanuclear complex [Zn((ZnL)2(µ‐OH))2](ClO4)4·CH3CN·7H2O (1) (LH = N‐(2‐pyridylmethyl)‐N‐(2‐(methylthio)ethyl)‐N‐(2‐thioethyl)‐amine is described. Compound 1 was thoroughly characterized by a combination of X‐ray crystallography, XPRD, IR, variable temperature 1H NMR and ESI‐MS. The peripheral zinc ions of 1 have distorted trigonal bipyramidal coordination geometry provided by the NN′SS′ donor set of one L and a µ2‐hydroxido bridge to another peripheral zinc ion. The central zinc atom has a distorted tetrahedral Zn(SR)4 coordination environment provided by four µ2‐thiolate bridges from L. In crystalline form, the complex ions of 1 are largely insulated from contact by an elaborate hydrogen bond network involving µ2‐hydroxido bridges, perchlorate ions and all the solvent molecules. Dissociation of 1 in CD3CN solution and recombination to form other multinuclear complexes was investigated by variable temperature 1H NMR.

Impact of the Major Candida glabrata Triazole Resistance Determinants on the Activity of the Novel Investigational Tetrazoles VT-1598 and VT-1161.

VT-1161 and VT-1598 are promising investigational tetrazole antifungals that have shown in vitro and in vivo activity against Candida and other fungi. Candida glabrata is a problematic opportunistic pathogen that is associated with high mortality in invasive infection, as well as both intrinsic and rapidly acquired antifungal resistance. The MICs of VT-1161 and VT-1598 were determined by CLSI methodology to evaluate their in vitro activities against clinical C. glabrata isolates and strains containing individual deletions of the zinc cluster transcription factor genes PDR1 and UPC2A as well as the efflux transporter genes CDR1, PDH1, and SNQ2 Overall, both tetrazoles demonstrated relative activities comparable to those of the tested triazole antifungals against clinical C. glabrata isolates (MIC range, 0.25 to 2 mg/liter and 0.5 to 2 μg/ml for VT-1161 and VT-1598, respectively). Deletion of the PDR1 gene in fluconazole-resistant matched clinical isolate SM3 abolished the decreased susceptibility phenotype completely for both VT-1161 and VT-1598, similarly to the triazoles. UPC2A deletion also increased susceptibility to both triazoles and tetrazoles but to a lesser extent than PDR1 deletion. Of the three major transporter genes regulated by Pdr1, CDR1 deletion resulted in the largest MIC reductions for all agents tested, while PDH1 and SNQ2 deletion individually impacted MICs very little. Overall, both VT-1161 and VT-1598 have comparable activities to those of the available triazoles, and decreased susceptibility to these tetrazoles in C. glabrata is driven by many of the same known resistance mechanisms.

Rational Design of Artificial Metalloproteins and Metalloenzymes with Metal Clusters.

Metalloproteins and metalloenzymes play important roles in biological systems by using the limited metal ions, complexes, and clusters that are associated with the protein matrix. The design of artificial metalloproteins and metalloenzymes not only reveals the structure and function relationship of natural proteins, but also enables the synthesis of artificial proteins and enzymes with improved properties and functions. Acknowledging the progress in rational design from single to multiple active sites, this review focuses on recent achievements in the design of artificial metalloproteins and metalloenzymes with metal clusters, including zinc clusters, cadmium clusters, iron–sulfur clusters, and copper–sulfur clusters, as well as noble metal clusters and others. These metal clusters were designed in both native and de novo protein scaffolds for structural roles, electron transfer, or catalysis. Some synthetic metal clusters as functional models of native enzymes are also discussed. These achievements provide valuable insights for deep understanding of the natural proteins and enzymes, and practical clues for the further design of artificial enzymes with functions comparable or even beyond those of natural counterparts.

A Lysine-Targeted Affinity Label for Serine-β-Lactamase Also Covalently Modifies New Delhi Metallo-β-lactamase-1 (NDM-1).

The divergent sequences, protein structures, and catalytic mechanisms of serine- and metallo-β-lactamases hamper the development of wide-spectrum β-lactamase inhibitors that can block both types of enzymes. The O-aryloxycarbonyl hydroxamate inactivators of Enterobacter cloacae P99 class C serine-β-lactamase are unusual covalent inhibitors in that they target both active-site Ser and Lys residues, resulting in a cross-link consisting of only two atoms. Many clinically relevant metallo-β-lactamases have an analogous active-site Lys residue used to bind β-lactam substrates, suggesting a common site to target with covalent inhibitors. Here, we demonstrate that an O-aryloxycarbonyl hydroxamate inactivator of serine-β-lactamases can also serve as a classical affinity label for New Delhi metallo-β-lactamase-1 (NDM-1). Rapid dilution assays, site-directed mutagenesis, and global kinetic fitting are used to map covalent modification at Lys211 and determine KI (140 μM) and kinact (0.045 min-1) values. Mass spectrometry of the intact protein and the use of ultraviolet photodissociation for extensive fragmentation confirm stoichiometric covalent labeling that occurs specifically at Lys211. A 2.0 Å resolution X-ray crystal structure of inactivated NDM-1 reveals that the covalent adduct is bound at the substrate-binding site but is not directly coordinated to the active-site zinc cluster. These results indicate that Lys-targeted affinity labels might be a successful strategy for developing compounds that can inactivate both serine- and metallo-β-lactamases.

Exclusive Recognition of Acetone in a Luminescent BioMOF through Multiple Hydrogen-Bonding Interactions.

An anionic microporous metal-organic framework (1), featuring a combination of mononuclear and tetranuclear zinc clusters and a mix-and-match strategy of two different types of organic ligands, has been successfully constructed via a solvothermal reaction. Its luminescence can be exclusively quenched by acetone. In situ single-crystal X-ray diffraction studies reveal the specific acetone binding sites and the existence of multiple hydrogen bonds between acetone and the framework. Together with its chemical and thermal stability, 1 has been demonstrated to be a potential luminescence probe for the rapid detection of acetone with a remarkable anti-interference and a low detection limit (1.85 ppm).