N2 Cleavage on d4/d4 Molybdenum Centers and Its Further Conversion into Iminophosphorane under Mild Conditions.

The synthesis of N-containing organophosphine compounds using N2 as the nitrogen source under mild conditions has attracted much attention. Herein, the conversion of N2 into iminophosphorane was reported. By visible light irradiation, N2 was split on a MoII complex bearing a PNCNP ligand, directly forming the MoV nitride. After the N-P bond formation on the terminal nitride, the N atom from N2 was ultimately transferred into iminophosphorane. Key intermediates were characterized.

Conversion of Dinitrogen into Nitrile: Cross-Metathesis of N2 -Derived Molybdenum Nitride with Alkynes.

The direct synthesis of nitrile from N2 under mild conditions is of great importance and has attracted much interest. Herein, we report a direct conversion of N2 into nitrile via a nitrile-alkyne cross-metathesis (NACM) process involving a N2 -derived Mo nitride. Treatment of the Mo nitride with alkyne in the presence of KOTf afforded an alkyne-coordinated nitride, which was then transformed into MoV carbyne and the corresponding nitrile upon 1 e- oxidation. Both aryl- and alkyl-substituted alkynes underwent this process smoothly. Experiments and DFT calculations have proved that the oxidation state of the Mo center plays a crucial role. This method does not rely on the nucleophilicity of the N2 -derived metal nitride, offering a novel strategy for N2 fixation chemistry.

Nitrogen-doped graphene quantum dots coated with gold nanoparticles for electrochemiluminescent glucose detection using enzymatically generated hydrogen peroxide as a quencher.

Nitrogen-doped graphene quantum dots (N-GQDs) were prepared from dicyandiamide and then used as both an electrochemiluminescence (ECL) emitter and a reductant to produce gold nanoparticles (Au-N-GQDs) on their surface without using any reagent. In order to avoid resonance energy transfer, the Au-N-GQDs were stabilized with chitosan. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV-vis spectroscopy (UV-vis) and ECL methods were used to characterize the nanocomposite. The materials was placed on a glassy carbon electrode (GCE), and the ECL signals are found to be strongly quenched by hydrogen peroxide that is enzymatically produced by oxidation of glucose. With the applied typical potential of -1.7 V, the ECL of the Au-N-GQDs modified GCE decreases linearly in the 10 nM to 5.0 µM glucose concentration range, and the lower detection limit is 3.3 nM. The influence of H2O2 to the signal has been discussed and a possible mechanism has been presented. Graphical abstract Schematic presentation of the reduction of gold nanoparticles with nitrogen-droped graphene quantum dots (N-GQDs) to form Au-N-GQDs. They were used to detect glucose by electrochemiluminescence through a signal off strategy.

Production of itaconic acid from acetate by engineering acid-tolerant Escherichia coli W.

Utilization of abundant and cheap carbon sources can effectively reduce the production cost and enhance the economic feasibility. Acetate is a promising carbon source to achieve cost-effective microbial processes. In this study, we engineered an Escherichia coli strain to produce itaconic acid from acetate. As acetate is known to inhibit cell growth, we initially screened for a strain with a high tolerance to 10 g/L of acetate in the medium, and the W strain was selected as the host. Subsequently, the WC strain was obtained by overexpression of cad (encoding cis-aconitate decarboxylase) using a synthetic promoter and 5' UTR. However, the WC strain produced only 0.13 g/L itaconic acid because of low acetate uptake. To improve the production, the acetate assimilating pathway and glyoxylate shunt pathway were amplified by overexpression of pathway genes as well as its deregulation. The resulting strain, WCIAG4 produced 3.57 g/L itaconic acid (16.1% of theoretical maximum yield) after 88 hr of fermentation with rapid acetate assimilation. These efforts support that acetate can be a potential feedstock for biochemical production with engineered E. coli.

Voltammetric chiral discrimination of tryptophan using a multilayer nanocomposite with implemented amino-modified ß-cyclodextrin as recognition element.

An electrochemical chiral multilayer nanocomposite was prepared by modifying a glassy carbon electrode (GCE) via opposite-charge adsorption of amino-modified ß-cyclodextrin (NH2-ß-CD), gold-platinum core-shell microspheres (Au@Pts), polyethyleneimine (PEI), and multi-walled carbon nanotubes (MWCNTs). The modified GCE was applied to the enantioselective voltammetric determination of tryprophan (Trp). The Au@Pts enable an effective immobilization of the chiral selector (NH2-ß-CD) and enhance the electrochemical performance. Scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, FTIR and electrochemical methods were used to characterize the nanocomposite. Trp enantiomers were then determined by differential pulse voltammetry (DPV) (with a peak potential of +0.7 V vs. Ag/AgCl). The recognition efficiency was expressed by an increase in peak height by about 32% for DPV determinations of L-Trp compared to D-Trp in case of a 5 mM Trp solution of pH 7.0. Response was linear in the 10 µM to 5.0 mM concentration range, and the limits of detection were 4.3 µM and 5.6 µM with electrochemical sensitivity of 43.5 µA·µM-1·cm-2 and 34.6 µA·µM-1·cm-2 for L-Trp and D-Trp, respectively (at S/N = 3). Graphical Abstract Schematic of an electrochemical chiral multilayer nanocomposite composed of multi-walled carbon nanotubes (MWCNTs), polyethyleneimine (PEI), gold-platinum core-shell microspheres (Au@Pt) and amino-modified ß-cyclodextrin (NH2-ß-CD). It was prepared by modifying a glassy carbon electrode (GCE) for enantioselective voltammetric determination of tryptophan (Trp) enantiomers.

Abnormal intrinsic functional hubs and connectivity in patients with post-stroke depression.

OBJECTIVE: The present study aimed to investigate the specific alterations of brain networks in patients with post-stroke depression (PSD), and further assist in elucidating the brain mechanisms underlying the PSD which would provide supporting evidence for early diagnosis and interventions for the disease. METHODS: Resting-state functional magnetic resonace imaging data were acquired from 82 nondepressed stroke patients (Stroke), 39 PSD patients, and 74 healthy controls (HC). Voxel-wise degree centrality (DC) conjoined with seed-based functional connectivity (FC) analyses were performed to investigate the PSD-related connectivity alterations. The relationship between these alterations and depression severity was further examined in PSD patients. RESULTS: Relative to both Stroke and HC groups, (1) PSD showed increased centrality in regions within the default mode network (DMN), including contralesional angular gyrus (ANG), posterior cingulate cortex (PCC), and hippocampus (HIP). DC values in contralesional ANG positively correlated with the Patient Health Questionnaire-9 (PHQ-9) scores in PSD group. (2) PSD exhibited increased connectivity between these three seeds showing altered DC and regions within the DMN: bilateral medial prefrontal cortex and middle temporal gyrus and ipsilesional superior parietal gyrus, and regions outside the DMN: bilateral calcarine, ipsilesional inferior occipital gyrus and contralesional lingual gyrus, while decreased connectivity between contralesional ANG and contralesional supramarginal gyrus. Moreover, these FC alterations could predict PHQ-9 scores in PSD group. INTERPRETATION: These findings highlight that PSD was related with increased functional connectivity strength in some areas within the DMN, which might be attribute to the specific alterations of connectivity between within DMN and outside DMN regions in PSD.

Blocking cGAS-STING pathway promotes post-stroke functional recovery in an extended treatment window via facilitating remyelination.

BACKGROUND: Ischemic stroke is a major cause of worldwide death and disability, with recombinant tissue plasminogen activator being the sole effective treatment, albeit with a limited treatment window. The cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) pathway is emerging as the major DNA-sensing pathway to invoke immune responses in neuroinflammatory disorders. METHODS: By performing a series of neurobehavioral assessments, electrophysiological analysis, high-throughput sequencing, and cell-based assays based on the transient middle cerebral artery occlusion (tMCAO) mouse stroke model, we examined the effects and underlying mechanisms of genetic and pharmacological inhibition of the cGAS-STING pathway on long-term post-stroke neurological functional outcomes. FINDINGS: Blocking the cGAS-STING pathway, even 3 days after tMCAO, significantly promoted functional recovery in terms of white matter structural and functional integrity as well as sensorimotor and cognitive functions. Mechanistically, the neuroprotective effects via inhibiting the cGAS-STING pathway were contributed not only by inflammation repression at the early stage of tMCAO but also by modifying the cell state of phagocytes to facilitate remyelination at the sub-acute phase. The activation of the cGAS-STING pathway significantly impeded post-stroke remyelination through restraining myelin debris uptake and degradation and hindering oligodendrocyte differentiation and maturation. CONCLUSIONS: Manipulating the cGAS-STING pathway has an extended treatment window in promoting long-term post-stroke functional recovery via facilitating remyelination in a mouse stroke model. Our results highlight the roles of the cGAS-STING pathway in aggregating stroke pathology and propose a new way for improving functional recovery after ischemic stroke. FUNDING: This work was primarily funded by the National Key R&D Program of China.

A synthetic cycle for iminophosphorane synthesis involving direct intermolecular NP bond formation on N2-derived molybdenum nitride.

NP bonds were built straightforwardly between N2-derived molybdenum terminal nitride and phosphines. Subsequent PCET, oxidative decarbonylation and then reduction regenerated the N2 complex, developing a synthetic cycle transferring N2 into various iminophosphoranes. Both aryl and alkyl substituted phosphines proceeded smoothly.

Integrated proteomics and phosphoproteomics profiling reveals the cardioprotective mechanism of bioactive compounds derived from Salvia miltiorrhiza Burge.

BACKGROUND: Natural products are an important source for discovering novel drugs due to their various pharmacological activities. Salvia miltiorrhiza Burge (Danshen) has been shown to have promising therapeutic potential in the management of heart diseases, making it a candidate for cardiovascular drug discovery. Currently, there is limited quantitative analysis of the phosphorylation levels of Danshen-derived natural products on a proteome-wide, which may bias the study of their mechanisms of action. PURPOSE: This study aimed to evaluate the global signaling perturbation induced by Danshen-derived bioactive compounds and their potential relationship with myocardial ischemia/reperfusion (IR) injury therapy. STUDY DESIGN: We employed quantitative proteome and phosphoproteome analysis to identify dysregulated signaling in IR injury hearts from mice. We compared changes induced by Danshen-derived compounds based on IR-associated phospho-events, using an integrative approach that maps relative abundance of proteins and phosphorylation sites. METHODS: Isobaric chemical tandem mass tags (TMT) labeled multiplexing strategy was used to generate unbiased quantitative proteomics and phosphoproteomics data. Highly accurate and precise TMT quantitation was performed using the Orbitrap Fusion Tribrid Mass Spectrometer with synchronous precursor selection MS3 detection mode. Mass spectrometric raw files were analyzed with MaxQuant (2.0.1.0) and statistical and bioinformatics analysis was conducted with Perseus (1.6.15). RESULTS: We quantified 3661 proteins and over 11,000 phosphosites in impaired heart tissue of the IR mice model, expanding our knowledge of signaling pathways and other biological processes disrupted in IR injury. Next, 1548 and 5545 differently expressed proteins and phosphosites were identified by quantifying the proteome and phosphoproteome of H9c2 cells treated by five Danshen bioactive compounds respectively. Results revealed the vast differences in abilities of five Danshen-derived bioactive compounds to regulate phosphorylation modifications in cardiomyocytes, with dihydrotanshinone I (DHT) showing potential for protecting against IR injury by modulating the AMPK/mTOR signaling pathway. CONCLUSIONS: This study provides a new strategy for analyzing drug/natural product-regulated phosphorylation modification levels on a proteome-wide scale, leading to a better understanding of cell signaling pathways and downstream phenotypic responses.

Characteristics and Discrimination of the Commercial Chinese Four Famous Vinegars Based on Flavor Compositions.

Shanxi aged vinegar (SAV), Zhenjiang aromatic vinegar (ZAV), Sichuan bran vinegar (SBV), and Fujian monascus vinegar (FMV) are the representative Chinese traditional vinegars. However, the basic differential compositions between the four vinegars are unknown. In this study, compositions of commercial vinegar were investigated to evaluate the influence of diverse technologies on their distinct flavor. Unlike amino acids and organic acids which were mostly shared, only five volatiles were detected in all vinegars, whereas a dozen volatiles were common to each type of vinegar. The four vinegars could only be classified well with all compositions, and difference analysis suggested the most significant difference between FMV and SBV. However, SAV, ZAV, and SBV possessed similar volatile characteristics due to their common heating treatments. Further, the correlation of identification markers with vinegars stressed the contributions of the smoking process, raw materials, and Monascus inoculum to SAV, SBV, and FMV clustering, respectively. Therefore, regardless of the technology modification, this basic process supported the uniqueness of the vinegars. This study contributes to improving the standards of defining the characteristics of types of vinegar.

Time-course RNA-Seq profiling reveals isoform-level gene expression dynamics of the cGAS-STING pathway.

The cGAS-STING pathway, orchestrating complicated transcriptome-wide immune responses, is essential for host antiviral defense but can also drive immunopathology in severe COVID-19. Here, we performed time-course RNA-Seq experiments to dissect the transcriptome expression dynamics at the gene-isoform level after cGAS-STING pathway activation. The in-depth time-course transcriptome after cGAS-STING pathway activation within 12 h enabled quantification of 48,685 gene isoforms. By employing regression models, we obtained 13,232 gene isoforms with expression patterns significantly associated with the process of cGAS-STING pathway activation, which were named activation-associated isoforms. The combination of hierarchical and k-means clustering algorithms revealed four major expression patterns of activation-associated isoforms, including two clusters with increased expression patterns enriched in cell cycle, autophagy, antiviral innate-immune functions, and COVID-19 coronavirus disease pathway, and two clusters showing decreased expression pattern that mainly involved in ncRNA metabolism, translation process, and mRNA processing. Importantly, by merging four clusters of activation-associated isoforms, we identified three types of genes that underwent isoform usage alteration during the cGAS-STING pathway activation. We further found that genes exhibiting protein-coding and non-protein-coding gene isoform usage alteration were strongly enriched for the factors involved in innate immunity and RNA splicing. Notably, overexpression of an enriched splicing factor, EFTUD2, shifted transcriptome towards the cGAS-STING pathway activated status and promoted protein-coding isoform abundance of several key regulators of the cGAS-STING pathway. Taken together, our results revealed the isoform-level gene expression dynamics of the cGAS-STING pathway and uncovered novel roles of splicing factors in regulating cGAS-STING pathway mediated immune responses.

m6A-mediated modulation coupled with transcriptional regulation shapes long noncoding RNA repertoire of the cGAS-STING signaling.

The cGAS-STING signaling plays pivotal roles not only in host antiviral defense but also in various noninfectious contexts. Compared with protein-coding genes, much less was known about long noncoding RNAs involved in this pathway. Here, we performed an integrative study to elucidate the lncRNA repertoire and the mechanisms modulating lncRNA's expression following cGAS-STING signaling activation. We uncovered a reliable set of 672 lncRNAs closely linked to cGAS-STING signaling activation (cs-lncRNA), which might be associated with type-I interferon response and infection-related phenotypes. The ChIP-seq analysis demonstrated that cs-lncRNA was strongly regulated at the transcriptional level. We further found N6-methyladenosine (m6A) regulatory machinery was indispensable for establishing cs-lncRNA repertoire via modulating m6A modification on cs-lncRNA transcripts and promoting the expression of signaling transduction key components, including IFNAR1. Loss of IFNAR1 led to the dysregulation of cs-lncRNAs resembled that of loss of an essential subunit of m6A writer METTL14. We also found m6A system affected transcriptional machinery to modulate cs-lncRNAs by targeting multiple crucial transcription factors. Inhibiting an m6A modification regulated transcription factor, EZH2, markedly enhanced the expression pattern of cs-lncRNAs. Taken together, our results uncovered the composition of the cs-lncRNAs and revealed m6A-mediated modulation coupled with transcriptional regulation significantly shaped cs-lncRNA repertoire.

A widened emission window of the peroxydisulfate-oxygen system for the detection of L-alanine.

Peroxydisulfate-oxygen (S2O82--O2) system has become one of the most used systems in electrogenerated chemiluminscence (ECL) field. Due to S2O82- can be used as Fenton Reagent, this work designed an ECL biosensor based on the S2O82--O2 system for the detection of L-alanine in a widened emission window and using hemin/G-quadruplex and platinum and palladium nanowires (Pt-Pd NWs) to in situ generate O2 to amplify the ECL intensity. The proposed ECL sensor showed an excellent analytical property for the detection of L-alanine in a linear range of 5.0 × 10-3 M to 1.0 × 10-8 M with the detection limit of 3.3 × 10-9 M (S/N = 3). This work with high selectivity, stability and reproducibility may open a new door to apply S2O82- in ECL field.

An Ascorbic Acid Oxidase-based Sensing Platform for Stereoselective Interaction with Ascorbic Acid and Isoascorbic Acid.

A simple enzyme-based nanohybrid material was fabricated via immobilizing ascorbic acid oxidase (AO) on the surface of flower-like electrodeposited gold nanoparticles (dpAu) and reduced graphene oxide (rGO) modified glassy carbon electrodes (GCEs). The composite material was used for stereoselective interaction with ascorbic acid (AA) and isoascorbic acid (IAA). Herein, AO was applied as a stereoselective selector, and the dpAu/rGO nanohybrid not only acted as a supporter for high loading of AO, but also served as the nanomaterial for signal amplification. The results showed obvious peak current differences between AA and IAA, indicating that this strategy could be employed to recognize AA and IAA. Under the optimum conditions, the sensor exhibited a good linear response to AA and IAA in a linear range of 1.0 × 10-4 - 5.0 × 10-3 M. This approach with the merits of simplicity and rapid response provided a promising perspective for identification of AA and IAA.