Fiberbots: Robotic fibers for high-precision minimally invasive surgery.

Precise manipulation of flexible surgical tools is crucial in minimally invasive surgical procedures, necessitating a miniature and flexible robotic probe that can precisely direct the surgical instruments. In this work, we developed a polymer-based robotic fiber with a thermal actuation mechanism by local heating along the sides of a single fiber. The fiber robot was fabricated by highly scalable fiber drawing technology using common low-cost materials. This low-profile (below 2 millimeters in diameter) robotic fiber exhibits remarkable motion precision (below 50 micrometers) and repeatability. We developed control algorithms coupling the robot with endoscopic instruments, demonstrating high-resolution in situ molecular and morphological tissue mapping. We assess its practicality and safety during in vivo laparoscopic surgery on a porcine model. High-precision motion of the fiber robot delivered endoscopically facilitates the effective use of cellular-level intraoperative tissue identification and ablation technologies, potentially enabling precise removal of cancer in challenging surgical sites.

Preclinical safety and efficacy characterization of an LpxC inhibitor against Gram-negative pathogens.

The UDP-3-O-(R-3-hydroxyacyl)-N-acetylglucosamine deacetylase LpxC is an essential enzyme in the biosynthesis of lipid A, the outer membrane anchor of lipopolysaccharide and lipooligosaccharide in Gram-negative bacteria. The development of LpxC-targeting antibiotics toward clinical therapeutics has been hindered by the limited antibiotic profile of reported non-hydroxamate inhibitors and unexpected cardiovascular toxicity observed in certain hydroxamate and non-hydroxamate-based inhibitors. Here, we report the preclinical characterization of a slow, tight-binding LpxC inhibitor, LPC-233, with low picomolar affinity. The compound is a rapid bactericidal antibiotic, unaffected by established resistance mechanisms to commercial antibiotics, and displays outstanding activity against a wide range of Gram-negative clinical isolates in vitro. It is orally bioavailable and efficiently eliminates infections caused by susceptible and multidrug-resistant Gram-negative bacterial pathogens in murine soft tissue, sepsis, and urinary tract infection models. It displays exceptional in vitro and in vivo safety profiles, with no detectable adverse cardiovascular toxicity in dogs at 100 milligrams per kilogram. These results establish the feasibility of developing oral LpxC-targeting antibiotics for clinical applications.

An artificial optoelectronic synapse based on MoOxfilm.

Artificial optoelectronic synapses have the advantages of large bandwidth, low power consumption and low crosstalk, and are considered to be the basic building blocks of neuromorphic computing. In this paper, a two-terminal optoelectronic synaptic device with ITO-MoOx-Pt structure is prepared by magnetron sputtering. The performance of resistive switching (RS) and the photo plastic properties of the device are analyzed and demonstrated. Electrical characterization tests show that the device has a resistive HRS/LRS ratio of about 90, stable endurance, and retention characteristics of more than 104s (85 °C). The physical mechanism of the device is elucidated by a conducting filament composed of oxygen vacancies. Furthermore, the function of various synaptic neural morphologies is successfully mimicked using UV light as the stimulation source. Including short-term/long-term memory, paired-pulse facilitation, the transition from short-term to long-term memory, and 'learning-experience' behavior. Integrated optical sensing and electronic data storage devices have great potential for future artificial intelligence, which will facilitate the rapid development of retina-like visual sensors and low-power neuromorphic systems.

Structural basis of NPR1 in activating plant immunity.

NPR1 is a master regulator of the defence transcriptome induced by the plant immune signal salicylic acid1-4. Despite the important role of NPR1 in plant immunity5-7, understanding of its regulatory mechanisms has been hindered by a lack of structural information. Here we report cryo-electron microscopy and crystal structures of Arabidopsis NPR1 and its complex with the transcription factor TGA3. Cryo-electron microscopy analysis reveals that NPR1 is a bird-shaped homodimer comprising a central Broad-complex, Tramtrack and Bric-à-brac (BTB) domain, a BTB and carboxyterminal Kelch helix bundle, four ankyrin repeats and a disordered salicylic-acid-binding domain. Crystal structure analysis reveals a unique zinc-finger motif in BTB for interacting with ankyrin repeats and mediating NPR1 oligomerization. We found that, after stimulation, salicylic-acid-induced folding and docking of the salicylic-acid-binding domain onto ankyrin repeats is required for the transcriptional cofactor activity of NPR1, providing a structural explanation for a direct role of salicylic acid in regulating NPR1-dependent gene expression. Moreover, our structure of the TGA32-NPR12-TGA32 complex, DNA-binding assay and genetic data show that dimeric NPR1 activates transcription by bridging two fatty-acid-bound TGA3 dimers to form an enhanceosome. The stepwise assembly of the NPR1-TGA complex suggests possible hetero-oligomeric complex formation with other transcription factors, revealing how NPR1 reprograms the defence transcriptome.

Francisella FlmX broadly affects lipopolysaccharide modification and virulence.

The outer membrane protects Gram-negative bacteria from the host environment. Lipopolysaccharide (LPS), a major outer membrane constituent, has distinct components (lipid A, core, O-antigen) generated by specialized pathways. In this study, we describe the surprising convergence of these pathways through FlmX, an uncharacterized protein in the intracellular pathogen Francisella. FlmX is in the flippase family, which includes proteins that traffic lipid-linked envelope components across membranes. flmX deficiency causes defects in lipid A modification, core remodeling, and O-antigen addition. We find that an F. tularensis mutant lacking flmX is >1,000,000-fold attenuated. Furthermore, FlmX is required to resist the innate antimicrobial LL-37 and the antibiotic polymyxin. Given FlmX's central role in LPS modification and its conservation in intracellular pathogens Brucella, Coxiella, and Legionella, FlmX may represent a novel drug target whose inhibition could cripple bacterial virulence and sensitize bacteria to innate antimicrobials and antibiotics.

Flexible Ta/TiOx/TaOx/Ru memristive synaptic devices on polyimide substrates.

It is very urgent to build memristive synapses and even wearable devices to simulate the basic functions of biological synapses. The linear conductance modulation is the basis of analog memristor for neuromorphic computing. By optimizing the interface engineering wherein Ta/TiOx/TaOx/Ru was fabricated, all the memristor devices with different TiOxthickness showed electroforming-free property. The short-term and long-term plasticity in both potentiation and depression behaviors can be mimicked when TiOxwas fixed at 25 nm. The presented memristive synapses simulated the stable paired-pulse facilitation and spike-timing dependent plasticity performance. The potentiation and depression in linearity and symmetry improved with the TiOxthickness increasing, which provides the feasibility for the application of artificial neural network. In addition, the device deposited on polyimide (PI) still exhibits the synaptic performance until the bending radii reaches 6 mm. By carefully tuning the interface engineering, this study can provide general revelation for continuous improvement of the memristive performance in neuromorphic applications.

Research on the Prediction of A-Share "High Stock Dividend" Phenomenon-A Feature Adaptive Improved Multi-Layers Ensemble Model.

Since the "high stock dividend" of A-share companies in China often leads to the short-term stock price increase, this phenomenon's prediction has been widely concerned by academia and industry. In this study, a new multi-layer stacking ensemble algorithm is proposed. Unlike the classic stacking ensemble algorithm that focused on the differentiation of base models, this paper used the equal weight comprehensive feature evaluation method to select features before predicting the base model and used a genetic algorithm to match the optimal feature subset for each base model. After the base model's output prediction, the LightGBM (LGB) model was added to the algorithm as a secondary information extraction layer. Finally, the algorithm inputs the extracted information into the Logistic Regression (LR) model to complete the prediction of the "high stock dividend" phenomenon. Using the A-share market data from 2010 to 2019 for simulation and evaluation, the proposed model improves the AUC (Area Under Curve) and F1 score by 0.173 and 0.303, respectively, compared to the baseline model. The prediction results shed light on event-driven investment strategies.

MESH1 is a cytosolic NADPH phosphatase that regulates ferroptosis.

Critical to the bacterial stringent response is the rapid relocation of resources from proliferation toward stress survival through the respective accumulation and degradation of (p)ppGpp by RelA and SpoT homologues. While mammalian genomes encode MESH1, a homologue of the bacterial (p)ppGpp hydrolase SpoT, neither (p)ppGpp nor its synthetase has been identified in mammalian cells. Here, we show that human MESH1 is an efficient cytosolic NADPH phosphatase that facilitates ferroptosis. Visualization of the MESH1-NADPH crystal structure revealed a bona fide affinity for the NADPH substrate. Ferroptosis-inducing erastin or cystine deprivation elevates MESH1, whose overexpression depletes NADPH and sensitizes cells to ferroptosis, whereas MESH1 depletion promotes ferroptosis survival by sustaining the levels of NADPH and GSH and by reducing lipid peroxidation. The ferroptotic protection by MESH1 depletion is ablated by suppression of the cytosolic NAD(H) kinase, NADK, but not its mitochondrial counterpart NADK2. Collectively, these data shed light on the importance of cytosolic NADPH levels and their regulation under ferroptosis-inducing conditions in mammalian cells.

Structural basis of the UDP-diacylglucosamine pyrophosphohydrolase LpxH inhibition by sulfonyl piperazine antibiotics.

The UDP-2,3-diacylglucosamine pyrophosphate hydrolase LpxH is an essential lipid A biosynthetic enzyme that is conserved in the majority of gram-negative bacteria. It has emerged as an attractive novel antibiotic target due to the recent discovery of an LpxH-targeting sulfonyl piperazine compound (referred to as AZ1) by AstraZeneca. However, the molecular details of AZ1 inhibition have remained unresolved, stymieing further development of this class of antibiotics. Here we report the crystal structure of Klebsiella pneumoniae LpxH in complex with AZ1. We show that AZ1 fits snugly into the L-shaped acyl chain-binding chamber of LpxH with its indoline ring situating adjacent to the active site, its sulfonyl group adopting a sharp kink, and its N-CF3-phenyl substituted piperazine group reaching out to the far side of the LpxH acyl chain-binding chamber. Intriguingly, despite the observation of a single AZ1 conformation in the crystal structure, our solution NMR investigation has revealed the presence of a second ligand conformation invisible in the crystalline state. Together, these distinct ligand conformations delineate a cryptic inhibitor envelope that expands the observed footprint of AZ1 in the LpxH-bound crystal structure and enables the design of AZ1 analogs with enhanced potency in enzymatic assays. These designed compounds display striking improvement in antibiotic activity over AZ1 against wild-type K. pneumoniae, and coadministration with outer membrane permeability enhancers profoundly sensitizes Escherichia coli to designed LpxH inhibitors. Remarkably, none of the sulfonyl piperazine compounds occupies the active site of LpxH, foretelling a straightforward path for rapid optimization of this class of antibiotics.

Metabolic engineering of Escherichia coli to produce a monophosphoryl lipid A adjuvant.

Monophosphoryl lipid A (MPLA) species, including MPL (a trade name of GlaxoSmithKline) and GLA (a trade name of Immune Design, a subsidiary of Merck), are widely used as an adjuvant in vaccines, allergy drugs, and immunotherapy to boost the immune response. Even though MPLA is a derivative of lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, bacterial strains producing MPLA have not been found in nature nor engineered. In fact, MPLA generation involves expensive and laborious procedures based on synthetic routes or chemical transformation of precursors isolated from Gram-negative bacteria. Here, we report the engineering of an Escherichia coli strain for in situ production and accumulation of MPLA. Furthermore, we establish a succinct method for purifying MPLA from the engineered E. coli strain. We show that the purified MPLA (named EcML) stimulates the mouse immune system to generate antigen-specific IgG antibodies similarly to commercially available MPLA, but with a dramatically reduced manufacturing time and cost. Our system, employing the first engineered E. coli strain that directly produces the adjuvant EcML, could transform the current standard of industrial MPLA production.

The Lipid A 1-Phosphatase, LpxE, Functionally Connects Multiple Layers of Bacterial Envelope Biogenesis.

Although distinct lipid phosphatases are thought to be required for processing lipid A (component of the outer leaflet of the outer membrane), glycerophospholipid (component of the inner membrane and the inner leaflet of the outer membrane), and undecaprenyl pyrophosphate (C55-PP; precursors of peptidoglycan and O antigens of lipopolysaccharide) in Gram-negative bacteria, we report that the lipid A 1-phosphatases, LpxEs, functionally connect multiple layers of cell envelope biogenesis in Gram-negative bacteria. We found that Aquifex aeolicus LpxE structurally resembles YodM in Bacillus subtilis, a phosphatase for phosphatidylglycerol phosphate (PGP) with a weak in vitro activity on C55-PP, and rescues Escherichia coli deficient in PGP and C55-PP phosphatase activities; deletion of lpxE in Francisella novicida reduces the MIC value of bacitracin, indicating a significant contribution of LpxE to the native bacterial C55-PP phosphatase activity. Suppression of plasmid-borne lpxE in F. novicida deficient in chromosomally encoded C55-PP phosphatase activities results in cell enlargement, loss of O-antigen repeats of lipopolysaccharide, and ultimately cell death. These discoveries implicate LpxE as the first example of a multifunctional regulatory enzyme that orchestrates lipid A modification, O-antigen production, and peptidoglycan biogenesis to remodel multiple layers of the Gram-negative bacterial envelope.IMPORTANCE Dephosphorylation of the lipid A 1-phosphate by LpxE in Gram-negative bacteria plays important roles in antibiotic resistance, bacterial virulence, and modulation of the host immune system. Our results demonstrate that in addition to removing the 1-phosphate from lipid A, LpxEs also dephosphorylate undecaprenyl pyrophosphate, an important metabolite for the synthesis of the essential envelope components, peptidoglycan and O-antigen. Therefore, LpxEs participate in multiple layers of biogenesis of the Gram-negative bacterial envelope and increase antibiotic resistance. This discovery marks an important step toward understanding the regulation and biogenesis of the Gram-negative bacterial envelope.

Structure-Activity Relationship of Sulfonyl Piperazine LpxH Inhibitors Analyzed by an LpxE-Coupled Malachite Green Assay.

The UDP-2,3-diacylglucosamine pyrophosphatase LpxH in the Raetz pathway of lipid A biosynthesis is an essential enzyme in the vast majority of Gram-negative pathogens and an excellent novel antibiotic target. The 32P-radioautographic thin-layer chromatography assay has been widely used for analysis of LpxH activity, but it is inconvenient for evaluation of a large number of LpxH inhibitors over an extended time period. Here, we report a coupled, nonradioactive LpxH assay that utilizes the recently discovered Aquifex aeolicus lipid A 1-phosphatase LpxE for quantitative removal of the 1-phosphate from lipid X, the product of the LpxH catalysis; the released inorganic phosphate is subsequently quantified by the colorimetric malachite green assay, allowing the monitoring of the LpxH catalysis. Using such a coupled enzymatic assay, we report the biochemical characterization of a series of sulfonyl piperazine LpxH inhibitors. Our analysis establishes a preliminary structure-activity relationship for this class of compounds and reveals a pharmacophore of two aromatic rings, two hydrophobic groups, and one hydrogen-bond acceptor. We expect that our findings will facilitate the development of more effective LpxH inhibitors as potential antibacterial agents.

Low-Operating-Voltage Resistive Memory Based on Bi1+δFe0.95Zn0.05)O3 Films.

A resistive memory device based on the Ag/Bi1+δ(Fe0.95Zn0.05)O3/SRO/Pt/TiO2/SiO2/Si(100) structure was prepared using radio frequency magnetron sputtering. The composition of the thin film element was analyzed by X-ray photoelectron spectroscopy and the thickness of the thin film was characterized by scanning electron microscope. Through the electrical test, we found that the device exhibited low operating voltage, which included VSET of about 0.1 V, VRESET of about -0.1 V, and VF of about 0.25 V. This facilitated the perfect integration of the device with the circuit design. Testing for 10,000 s at a substrate temperature of 85 °C, the device showed excellent retention. The I-V fitting curves of the resistive devices were analyzed. The low resistance state was in line with the ohmic mechanism and the high resistance state was in accordance with the Space Charge Limited Current mechanism. The resistance change of the device was attributed to the formation of Ag conductive filaments.

Intravenous lidocaine infusion for pain control after laparoscopic cholecystectomy: A meta-analysis of randomized controlled trials.

BACKGROUND: This meta-analysis aimed to assess the efficiency and safety of intravenous infusion of lidocaine for pain management after laparoscopic cholecystectomy (LC). METHODS: A systematic search was performed in PubMed (August 1966-2017), Medline (August 1966-2017), Embase (August 1980-2017), ScienceDirect (August 1985-2017), and the Cochrane Library. Only randomized controlled trials (RCTs) were included. Fixed/random effect model was used according to the heterogeneity tested by I2 statistic. Meta-analysis was performed using Stata.11.0 software. RESULTS: A total of 5 RCTs were retrieved involving 274 patients. The present meta-analysis indicated that there were significant differences between groups in terms of visual analog scale scores at 12hours (weighted mean difference [WMD]=-0.743, 95% CI: -1.246 to -0.240, P = .004), 24hours (WMD=-0.712, 95% CI: -1.239 to -0.184, P = .008), and 48hours (WMD=-0.600, 95% CI: -0.972 to -0.229, P = .002) after LC. Significant differences were found regarding opioid consumption at 12hours (WMD=-3.136, 95% CI: -5.591 to -0.680, P = .012), 24hours (WMD=-4.739, 95% CI: -8.291 to -1.188, P = .009), and 48hours (WMD=-3.408, 95% CI: -5.489 to -1.326, P = .001) after LC. CONCLUSION: Intravenous lidocaine infusion significantly reduced postoperative pain scores and opioid consumption after LC. In addition, there were fewer adverse effects in the lidocaine groups. Higher quality RCTs are still required for further research.

Highly Flexible Resistive Switching Memory Based on the Electronic Switching Mechanism in the Al/TiO2/Al/Polyimide Structure.

A highly flexible resistive switching (RS) memory was fabricated in the Al/TiO2/Al/polyimide structure using a simple and cost-effective method. An electronic-resistive-switching-based flexible memory with high performance that can withstand a bending strain of up to 3.6% was obtained. The RS properties showed no obvious degradation even after the bending tests that were conducted up to 10 000 times, and over 4000 writing/erasing cycles were confirmed at the maximally bent state. The superior electrical properties against the mechanical stress of the device can be ascribed to the electronic RS mechanism related to electron trapping/detrapping, which can prevent the inevitable degradation in the case of the RS related with the ionic defects.

Structure, inhibition, and regulation of essential lipid A enzymes.

The Raetz pathway of lipid A biosynthesis plays a vital role in the survival and fitness of Gram-negative bacteria. Research efforts in the past three decades have identified individual enzymes of the pathway and have provided a mechanistic understanding of the action and regulation of these enzymes at the molecular level. This article reviews the discovery, biochemical and structural characterization, and regulation of the essential lipid A enzymes, as well as continued efforts to develop novel antibiotics against Gram-negative pathogens by targeting lipid A biosynthesis. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.

Structure of the essential Haemophilus influenzae UDP-diacylglucosamine pyrophosphohydrolase LpxH in lipid A biosynthesis.

In most Gram-negative pathogens, the hydrolysis of UDP-2,3-diacylglucosamine to generate lipid X in lipid A biosynthesis is catalysed by the membrane-associated enzyme LpxH. We report the crystal structure of LpxH in complex with its product, lipid X, unveiling a unique insertion lid above the conserved architecture of calcineurin-like phosphoesterases. This structure reveals elaborate interactions surrounding lipid X and provides molecular insights into the substrate selectivity, catalysis and inhibition of LpxH.

In Vivo and in Vitro Synthesis of Phosphatidylglycerol by an Escherichia coli Cardiolipin Synthase.

Phosphatidylglycerol (PG) makes up 5-20% of the phospholipids of Escherichia coli and is essential for growth in wild-type cells. PG is synthesized from the dephosphorylation of its immediate precursor, phosphatidylglycerol phosphate (PGP) whose synthase in E. coli is PgsA. Using genetic, biochemical, and highly sensitive mass spectrometric approaches, we identified an alternative mechanism for PG synthesis in E. coli that is PgsA independent. The reaction of synthesis involves the conversion of phosphatidylethanolamine and glycerol into PG and is catalyzed by ClsB, a phospholipase D-type cardiolipin synthase. This enzymatic reaction is demonstrated herein both in vivo and in vitro as well as by using the purified ClsB protein. When the growth medium was supplemented with glycerol, the expression of E. coli ClsB significantly increased PG and cardiolipin levels, with the growth deficiency of pgsA null strain also being complemented under such conditions. Identification of this alternative mechanism for PG synthesis not only expands our knowledge of bacterial anionic phospholipid biosynthesis, but also sheds light on the biochemical functions of the cls gene redundancy in E. coli and other bacteria. Finally, the PGP-independent PG synthesis in E. coli may also have important implications for the understanding of PG biosynthesis in eukaryotes that remains incomplete.

Discovery of the Elusive UDP-Diacylglucosamine Hydrolase in the Lipid A Biosynthetic Pathway in Chlamydia trachomatis.

Constitutive biosynthesis of lipid A via the Raetz pathway is essential for the viability and fitness of Gram-negative bacteria, includingChlamydia trachomatis Although nearly all of the enzymes in the lipid A biosynthetic pathway are highly conserved across Gram-negative bacteria, the cleavage of the pyrophosphate group of UDP-2,3-diacyl-GlcN (UDP-DAGn) to form lipid X is carried out by two unrelated enzymes: LpxH in beta- and gammaproteobacteria and LpxI in alphaproteobacteria. The intracellular pathogenC. trachomatislacks an ortholog for either of these two enzymes, and yet, it synthesizes lipid A and exhibits conservation of genes encoding other lipid A enzymes. Employing a complementation screen against aC. trachomatisgenomic library using a conditional-lethallpxHmutantEscherichia colistrain, we have identified an open reading frame (Ct461, renamedlpxG) encoding a previously uncharacterized enzyme that complements the UDP-DAGn hydrolase function inE. coliand catalyzes the conversion of UDP-DAGn to lipid Xin vitro LpxG shows little sequence similarity to either LpxH or LpxI, highlighting LpxG as the founding member of a third class of UDP-DAGn hydrolases. Overexpression of LpxG results in toxic accumulation of lipid X and profoundly reduces the infectivity ofC. trachomatis, validating LpxG as the long-sought-after UDP-DAGn pyrophosphatase in this prominent human pathogen. The complementation approach presented here overcomes the lack of suitable genetic tools forC. trachomatisand should be broadly applicable for the functional characterization of other essentialC. trachomatisgenes.IMPORTANCEChlamydia trachomatisis a leading cause of infectious blindness and sexually transmitted disease. Due to the lack of robust genetic tools, the functions of manyChlamydiagenes remain uncharacterized, including the essential gene encoding the UDP-DAGn pyrophosphatase activity for the biosynthesis of lipid A, the membrane anchor of lipooligosaccharide and the predominant lipid species of the outer leaflet of the bacterial outer membrane. We designed a complementation screen against theC. trachomatisgenomic library using a conditional-lethal mutant ofE. coliand identified the missing essential gene in the lipid A biosynthetic pathway, which we designatedlpxG We show that LpxG is a member of the calcineurin-like phosphatases and displays robust UDP-DAGn pyrophosphatase activityin vitro Overexpression of LpxG inC. trachomatisleads to the accumulation of the predicted lipid intermediate and reduces bacterial infectivity, validating thein vivofunction of LpxG and highlighting the importance of regulated lipid A biosynthesis inC. trachomatis.

Drug design from the cryptic inhibitor envelope.

Conformational dynamics plays an important role in enzyme catalysis, allosteric regulation of protein functions and assembly of macromolecular complexes. Despite these well-established roles, such information has yet to be exploited for drug design. Here we show by nuclear magnetic resonance spectroscopy that inhibitors of LpxC--an essential enzyme of the lipid A biosynthetic pathway in Gram-negative bacteria and a validated novel antibiotic target--access alternative, minor population states in solution in addition to the ligand conformation observed in crystal structures. These conformations collectively delineate an inhibitor envelope that is invisible to crystallography, but is dynamically accessible by small molecules in solution. Drug design exploiting such a hidden inhibitor envelope has led to the development of potent antibiotics with inhibition constants in the single-digit picomolar range. The principle of the cryptic inhibitor envelope approach may be broadly applicable to other lead optimization campaigns to yield improved therapeutics.