Quantum‐confined graphene‐like electronic states are directly observed in graphene oxide and photothermally reduced graphene oxide via transient spectroscopy. An unexpected novel hybrid state arising ...from amorphous carbon‐like peripheral structure with high sp3/sp2 carbon ratio in close vicinity of confined graphene‐like states is found commonly existent in various carbon nanomaterials, including graphene oxide, graphene quantum dots, and carbon dots.
Sesquiterpene synthases (STPSs) catalyze carbocation‐driven cyclization reactions that can generate structurally diverse hydrocarbons. The deprotonation‐reprotonation process is widely used in STPSs ...to promote structural diversity, largely attributable to the distinct regio/stereoselective reprotonations. However, the molecular basis for reprotonation regioselectivity remains largely understudied. Herein, we analyzed two highly paralogous STPSs, Artabotrys hexapetalus (−)‐cyperene synthase (AhCS) and ishwarane synthase (AhIS), which catalyze reactions that are distinct from the regioselective protonation of germacrene A (GA), resulting in distinct skeletons of 5/5/6 tricyclic (−)‐cyperene and 6/6/5/3 tetracyclic ishwarane, respectively. Isotopic labeling experiments demonstrated that these protonations occur at C3 and C6 of GA in AhCS and AhIS, respectively. The cryo‐electron microscopy‐derived AhCS complex structure provided the structural basis for identifying different key active site residues that may govern their functional disparity. The structure‐guided mutagenesis of these residues resulted in successful functional interconversion between AhCS and AhIS, thus targeting the three active site residues L311‐S419‐C458/M311‐V419‐A458 that may act as a C3/C6 reprotonation switch for GA. These findings facilitate the rational design or directed evolution of STPSs with structurally diverse skeletons.
Three critical active site residues L311‐S419‐C458/M311‐V419‐A458 were identified as the switch of the regioselective C3/C6 reprotonation of germacrene A in sesquiterpene synthase catalysis through the characterization and engineering of two highly paralogous sesquiterpene synthases, AhCS and AhIS, using a combination of isotopic labeling experiments, cryo‐electron microscopy, and structure‐guided mutagenesis.
Metastasis, the cardinal feature of malignant tumors, is an important clinical variable in patient prognosis. To understand the basis for metastasis, we systematically selected for highly invasive ...cells from breast cancer cell lines, MCF7 and MDA-MB-453, with moderate to low invasive ability using Boyden chamber invasion assay. The four-cycle selected invasive lines, named MCF7-I4 and MDA-MB-453-I4, respectively, displayed epithelial-mesenchymal transition (EMT) and dramatically enhanced invasive ability. EMT changes were corroborated with decreased level of E-cadherin and increased vimentin, fibronectin, and beta(1) integrin. Twist, a basic helix-loop-helix transcription factor, and AKT2, a known proto-oncogene, were found to be elevated in the invasive cells compared with the parental. Ectopic expression and knockdown of Twist by short interference RNA resulted in significant increase and reduction, respectively, of AKT2 protein and mRNA expression. Twist bound to E-box elements on AKT2 promoter and enhanced its transcriptional activity. Moreover, silencing AKT2 decreased Twist-promoted migration, invasion, and paclitaxel resistance. Reintroducing AKT2 largely rescued the phenotype resulted from knockdown of Twist in I4 cells, suggesting that AKT2 is a downstream target and functional mediator of Twist. Finally, we observed a 68.8% correlation of elevated Twist and AKT2 expression in late-stage breast cancers as oppose to 13% in early-stage breast cancers. Our study identifies Twist as a positive transcriptional regulator of AKT2 expression, and Twist-AKT2 signaling is involved in promoting invasive ability and survival of breast cancer cells.
Seneca virus A (SVA) is an emerging novel picornavirus that has recently been identified as the causative agent of many cases of porcine vesicular diseases in multiple countries. In addition to ...cleavage of viral polyprotein, the viral 3C protease (3Cpro) plays an important role in the regulation of several physiological processes involved in cellular antiviral responses by cleaving critical cellular proteins. Through a combination of crystallography, untargeted lipidomics, and immunoblotting, we identified the association of SVA 3Cpro with an endogenous phospholipid molecule, which binds to a unique region neighboring the proteolytic site of SVA 3Cpro. Our lipid-binding assays showed that SVA 3Cpro displayed preferred binding to cardiolipin (CL), followed by phosphoinositol-4-phosphate (PI4P) and sulfatide. Importantly, we found that the proteolytic activity of SVA 3Cpro was activated in the presence of the phospholipid, and the enzymatic activity is inhibited when the phospholipid-binding capacity decreased. Interestingly, in the wild-type SVA 3Cpro-substrate peptide structure, the cleavage residue cannot form a covalent binding to the catalytic cysteine residue to form the acyl-enzyme intermediate observed in several picornaviral 3Cpro structures. We observed a decrease in infectivity titers of SVA mutants harboring mutations that impaired the lipid-binding ability of 3Cpro, indicating a positive regulation of SVA infection capacity mediated by phospholipids. Our findings reveal a mutual regulation between the proteolytic activity and phospholipid-binding capacity in SVA 3Cpro, suggesting that endogenous phospholipid may function as an allosteric activator that regulate the enzyme's proteolytic activity during infection.
As a class of ideal fluorescent nanomaterials, self-assembled copper nanoclusters (CuNCs) have attracted increasing interest. Unfortunately, most of these CuNCs only possessed bright luminescence in ...acidic solution, which limited their practical applications in a physiological environment. Retaining the strong fluorescence of these CuNCs in neutral or alkaline solution is still a challenging task. In this strategy, self-assembled CuNCs were prepared by using 4-methylthiophenol as the protecting ligand. The self-assembled CuNCs display stable and bright luminescence with excitation/emission maxima at 330/605 nm even in neutral and alkaline environments. Interestingly, with the addition of glutathione (GSH), the fluorescence intensity of CuNCs is enhanced strongly through the GSH-controlled aggregation-induced emission enhancement of self-assembled CuNCs. The turn-on fluorescence strategy can determine the GSH concentration in the range from 1 to 100 μM with a limit of detection of 300 nM. In addition, the method is employed for the determination of GSH levels in cells. Therefore, the turn-on fluorescence strategy is reliable, sensitive and suitable for the determination of cellular GSH levels.
Cell replacement therapy is emerging as a promising treatment platform for many endocrine disorders and hormone deficiency diseases. The survival of cells within delivery devices is, however, often ...limited due to low oxygen levels in common transplantation sites. Additionally, replacing implanted devices at the end of the graft lifetime is often unfeasible and, where possible, generally requires invasive surgical procedures. Here, the design and testing of a modular transcutaneous biphasic (BP) cell delivery device that provides enhanced and unlimited oxygen supply by direct contact with the atmosphere is presented. Critically, the cell delivery unit is demountable from the fixed components of the device, allowing for surgery‐free refilling of the therapeutic cells. Mass transfer studies show significantly improved performance of the BP device in comparison to subcutaneous controls. The device is also tested for islet encapsulation in an immunocompetent diabetes rodent model. Robust cell survival and diabetes correction is observed following a rat‐to‐mouse xenograft. Lastly, nonsurgical cell refilling is demonstrated in dogs. These studies show the feasibility of this novel device for cell replacement therapies.
A refillable transcutaneous cell encapsulation device is reported. Inspired by the biphasic physiology of the cornea, the device achieves elevated oxygen levels by direct contact with the atmosphere and provides environmental protection by application of a perfluorinated oil‐infused polymer nanomembrane. Diabetes correction is accomplished in mice and nonsurgical cell refilling is achieved in dogs.
With the rapid development of the autonomous driving industry, there is increasing research on related perception tasks. However, research on road surface traffic sign detection tasks is still ...limited. There are two main challenges to this task. First, when the target object's pixel ratio is small, the detection accuracy often decreases. Second, the existing publicly available road surface traffic sign datasets have limited image data. To address these issues, this paper proposes a new instance segmentation network, RTS R-CNN, for road surface traffic sign detection tasks based on Mask R-CNN. The network can accurately perceive road surface traffic signs and provide important information for the autonomous driving decision-making system. Specifically, CSPDarkNet53_ECA is proposed in the feature extraction stage to enhance the performance of deep convolutional networks by increasing inter-channel interactions. Second, to improve the network's detection accuracy for small target objects, GR-PAFPN is proposed in the feature fusion part, which uses a residual feature enhancement module (RFA) and atrous spatial pyramid pooling (ASPP) to optimize PAFPN and introduces a balanced feature pyramid module (BFP) to handle the imbalanced feature information at different resolutions. Finally, data augmentation is used to generate more data and prevent overfitting in specific scenarios. The proposed method has been tested on the open-source dataset Ceymo, achieving a Macro
-score of 87.56%, which is 2.3% higher than the baseline method, while the inference speed reaches 23.5 FPS.
We enhanced the solid-state luminescence of lanthanoid metal ions within HOFs structured by Schiff base ligands via Zn(II) ion coordination. In addition, LnZn-HOFs can efficiently release Ln(III) ...ions in aqueous solution to achieve a highly sensitive response to very low concentrations of the heavy metal ion Cu(II). The ion-releasing properties of LnZn-HOFs can effectively inhibit the rapid proliferation of classical Gram-positive bacteria, such as Bacillus subtilis and Staphylococcus aureus.
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•Zn(II) coordination enhances the solid-state luminescence of LnHOFs.•Luminescence of LnHOFs is enhanced by metal ion coordination for the first time.•The LOD of TbZn-HOF for sensing Cu(II) ions is 1.91 nM.•LnHOFs efficiently kill bacteria through ions release.
Enhancing the antenna effect to increase energy transfer to lanthanoid ions for generating bright luminescence is an effective strategy to construct lanthanoid luminophores with excellent performance. However, the antenna effect often depends on the structure, connection, and configuration of immobilized ligands. We found for the first time that the introduction of the Zn(II) ion coordination can greatly enhance the solid-state fluorescence and phosphorescence emission of lanthanoid hydrogen-bonded organic frameworks (Ln-HOFs). Notably, relative to that of Tb-HOF, the solid-state fluorescence intensity, quantum yield, and lifetime of TbZn-HOFs had increased by 17.09, 38.81, and 12.96 times, respectively. The chelating coordination of the Zn(II) ions effectively hindered the vibration of organic ligands to weaken nonradiative transitions and stabilized and reduced the triplet excited state of the ligands through the spin–orbit coupling effect, which led to the increased efficiency of energy transfer with Tb(III) ions. In aqueous solution, LnZn-HOFs released Ln(III) ions effectively and captured low concentrations of the heavy metal ion Cu(II), and the efficient ligand-to-Cu(II) ion energy transfer quenched ligand luminescence. Notably, the limit of detection (LOD) was calculated to be 1.91 nM, which was considerably lower than the maximum level of Cu(II) ions in drinking water (20 μM) specified by the United States Environmental Protection Agency and was better than the LOD of other previously reported probes. Furthermore, LnZn-HOFs can effectively inhibit the proliferation of classical Gram-positive bacteria, such as Bacillus subtilis and Staphylococcus aureus, via ion release and thus showed a high sterilization effect. This work is the first to find that HOFs can exert efficient bacteriostatic and sterilization effects through ion release.
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