Vertical depletion of ophiolitic mantle reflects melt focusing and interaction in sub-spreading-center asthenosphere.

Decompressional melting of asthenosphere under spreading centers has been accepted to produce oceanic lithospheric mantle with vertical compositional variations, but these gradients are much smaller than those observed from ophiolites, which clearly require additional causes. Here we conduct high-density sampling and whole-rock and mineral analyses of peridotites across a Tibetan ophiolitic mantle section (~2 km thick), which shows a primary upward depletion (~12% difference) and local more-depleted anomalies. Thermodynamic modeling demonstrates that these features cannot be produced by decompressional melting or proportional compression of residual mantle, but can be explained by melt-peridotite reaction with lateral melt/rock ratio variations in an upwelling asthenospheric column, producing stronger depletion in the melt-focusing center and local zones. This column splits symmetrically and flows to become the horizontal uppermost lithospheric mantle, characterized by upward depletion and local anomalies. This model provides insights into melt extraction and uppermost-mantle origin beneath spreading centers with high melt fluxes.

Nonprecious bimetallic Fe, Mo-embedded N-enriched porous biochar for efficient oxidation of aqueous organic contaminants.

Bimetallic Fe- and Mo-embedded N-enriched porous biochar (Fe-Mo@N-BC) is developed and serves as a cost-effective and highly efficient catalyst for mineralization of non-biodegradation organic contaminants. Fe-Mo@N-BC was prepared by pyrolysis of complex Fe/Mo -containing precursors. Transmission electron microscopy and elemental mapping suggested that Fe and Mo are uniformly dispersed in nitrogen-doped biochar with hierarchical mesopores. In comparison to Fe@N-BC and Mo@N-BC, Fe-Mo@N-BC exhibited a superior activity for activating peroxymonosulfate (PMS). The stable activity was ascribed to N-doping and synergistic effect of Fe and Mo species, where both Fe-Nx and Mo-Nx can simultaneously serve as the active sites and N-BC can act as a carrier and an activator as well as an electron mediator. Electron paramagnetic resonance and quenching experiments indicated that HO•, O2•- and 1O2 were responsible for organic degradation. The effects of PMS dosage, initial Orange II concentration, temperature, solution pH, coexisting anions and humic acids on organic degradation were also investigated. With the assistance of an external magnet, Fe-Mo@N-BC can be easily separated after reaction and remains stable in the reusability tests. This work demonstrates a feasible strategy towards the fabrication of Fe, Mo-embedded N-enriched porous biochar catalysts for the detoxification of organic contaminants.

Falcarindiol Isolated from Notopterygium incisum Inhibits the Quorum Sensing of Pseudomonas aeruginosa.

Quorum sensing (QS) is employed by the opportunistic pathogen Pseudomonas aeruginosa to regulate physiological behaviors and virulence. QS inhibitors (QSIs) are potential anti-virulence agents for the therapy of P. aeruginosa infection. During the screening for QSIs from Chinese herbal medicines, falcarindiol (the major constituent of Notopterygium incisum) exhibited QS inhibitory activity. The subinhibitory concentration of falcarindiol exerted significant inhibitory effects on the formation of biofilm and the production of virulence factors such as elastase, pyocyanin, and rhamnolipid. The mRNA expression of QS-related genes (lasB, phzH, rhlA, lasI, rhlI, pqsA, and rhlR) was downregulated by falcarindiol while that of lasR was not affected by falcarindiol. The transcriptional activation of the lasI promoter was inhibited by falcarindiol in the P. aeruginosa QSIS-lasI selector. Further experiments confirmed that falcarindiol inhibited the las system using the reporter strain Escherichia coli MG4/pKDT17. Electrophoretic mobility shift assay (EMSA) showed that falcarindiol inhibited the binding of the transcription factor LasR and the lasI promoter region. Molecular docking showed that falcarindiol interacted with the Tyr47 residue, leading to LasR instability. The decrease of LasR-mediated transcriptional activation was responsible for the reduction of downstream gene expression, which further inhibited virulence production. The inhibition mechanism of falcarindiol to LasR provides a theoretical basis for its medicinal application.

Nonprecious bimetallic (Mo, Fe)-N/C nanostructures loaded on PVDF membrane for toxic CrVI reduction from water.

Nonprecious bimetallic molybdenum and iron embedded into N-doped carbon (MoFe-NC) hybrids were designed and fabricated by pyrolysis of mixed precursors and then immobilized on poly (vinylidene fluoride) (PVDF) films via a phase inversion process to obtain novel catalytic membranes (MoFe-NC@PVDF) for toxic CrVI reduction. The catalytic membranes are highly active for aqueous CrVI reduction using formic acid (FA) as a sacrificial electron donor under mild conditions. The results demonstrated that the parameters of synthesis process can efficiently adjust the morphology and textural properties of the as-synthesized MoFe-NC@PVDF membrane, and thus have a significant impact on the catalytic behavior. CrVI reduction rates significantly increased with increasing FA concentrations (0.234-0.936 M) and reaction temperature (5-35℃), but declined with the increase of CrVI concentrations (5-40 mg/L) and pH values of solution (1.87-4.62). Mo-Nx, Fe-Nx, and C-Nx are the active sites, boosting the dissociation of FA molecules into active H* species for effective catalytic reduction of CrVI. The catalytic PVDF membrane exhibited distinct porous structure and numerous interaction sites, which not only stabilized metallic nanoparticles, but also promoted mass transfer across the membrane. This cost-effective catalytic membrane provides a new approach toward the treatment of CrVI-containing water.

Eugenol inhibits quorum sensing at sub-inhibitory concentrations.

UNLABELLED: In bacteria, quorum sensing (QS) is a process of chemical communication involving the production, release, and subsequent detection of signaling molecules. QS regulates the production of key virulence factors in pathogens. During the screening of herbal extracts, clove extract was found to inhibit QS-controlled gene expression in Pseudomonas aeruginosa QSIS-lasI and Chromobacterium violaceum CV026 biosensors. Using a bioautographic TLC assay, preparative TLC, and HPLC analysis, eugenol, the major constituent of clove extract, exhibited QS inhibitory activity. Eugenol at sub-inhibitory concentrations inhibited the production of virulence factors, including violacein, elastase, pyocyanin, and biofilm formation. Using two Escherichia coli biosensors, MG4/pKDT17 and pEAL08-2, we confirmed that eugenol inhibited the las and pqs QS systems. Our data identified eugenol as a novel QS inhibitor. PURPOSE OF THE WORK: The purpose of this study was to track the quorum sensing inhibitor (QSI) in herbal extracts by effective screening systems and evaluate its biological activity. The QSIs from herbal extracts are potential agents for the treatment of bacterial infections.