Filamentous GLS1 promotes ROS-induced apoptosis upon glutamine deprivation via insufficient asparagine synthesis.

GLS1 orchestrates glutaminolysis and promotes cell proliferation when glutamine is abundant by regenerating TCA cycle intermediates and supporting redox homeostasis. CB-839, an inhibitor of GLS1, is currently under clinical investigation for a variety of cancer types. Here, we show that GLS1 facilitates apoptosis when glutamine is deprived. Mechanistically, the absence of exogenous glutamine sufficiently reduces glutamate levels to convert dimeric GLS1 to a self-assembled, extremely low-Km filamentous polymer. GLS1 filaments possess an enhanced catalytic activity, which further depletes intracellular glutamine. Functionally, filamentous GLS1-dependent glutamine scarcity leads to inadequate synthesis of asparagine and mitogenome-encoded proteins, resulting in ROS-induced apoptosis that can be rescued by asparagine supplementation. Physiologically, we observed GLS1 filaments in solid tumors and validated the tumor-suppressive role of constitutively active, filamentous GLS1 mutants K320A and S482C in xenograft models. Our results change our understanding of GLS1 in cancer metabolism and suggest the therapeutic potential of promoting GLS1 filament formation.

Low-Toxicity ZnSe/ZnS Quantum Dots as Potent Photoreductants and Triplet Sensitizers for Organic Transformations.

Colloidal quantum dots (QDs) can photocatalyze diverse organic reactions. However, reported QD-photocatalysts often contain highly-toxic elements Cd or Pb, and have not surpassed prototypical transition-metal complexes in terms of their photoredox power or excited-state energy. Here we report low-toxicity ZnSe/ZnS core/shell QDs as potent visible photocatalysts to drive challenging organic transformations. To overcome the limitation of short excited-state lifetime of the QDs, we functionalize their surfaces with benzophenone ligands which can rapidly extract electrons from photoexcited QDs and sustain long-lived charge-separated states. The benzophenone anions function as potent electron relay to drive dehalogenation of aryl chlorides and additive-free polymerization of acrylates. Alternatively, the QDs are functionalized with biphenyl ligands to store energy in long-lived, energetic triplets, enabling [2+2] homo-cycloaddition of styrene and cycloaddition of carbonyls with alkenes.

Energy-Transfer Photocatalysis Using Lead Halide Perovskite Nanocrystals: Sensitizing Molecular Isomerization and Cycloaddition.

A relatively new addition to the application portfolio of lead halide perovskites is to photosensitize molecular triplets for a variety of photochemical applications. Here we report visible-light-driven isomerization and cycloaddition of organic molecules sensitized by spectrally-tunable perovskite nanocrystals. We first demonstrate with stilbene as the substrate molecule that photoisomerization can proceed efficiently and rapidly by either directly grafting carboxylated stilbene onto nanocrystal surfaces or using triplet-acceptor ligands as the energy relay. The relay approach is more generally applicable as it does not require anchoring-group functionalization of substrate molecules, allowing us to facilely extend it to isomerization of a series of substituted stilbene molecules and ring-closing isomerization of diarylethene, as well as intermolecular [2+2] cycloaddition of acenaphthylene. This study opens an avenue of energy-transfer photocatalysis using perovskite nanocrystals.

Function of Aedes aegypti galectin-6 in modulation of Cry11Aa toxicity.

Galectins are a family of ß-galactoside binding proteins, and insect galectins play a role in immune responses and may also affect Cry toxin activity. In this study, we aimed to further understand the function and molecular mechanism of Aedes aegypti galectin-6 in modulation of Cry11Aa toxicity. A. aegypti galectin-6 was cloned, and the recombinant galectin-6 was expressed and purified. Bioassays indicated that galectin-6 could reduce the toxicity of Cry11Aa, protecting A. aegypti larvae. To determine interactions among galectin-6, Cry11Aa and putative toxin receptors, Octet Red System, western blotting, far-western blotting and ELISA assays were performed. Octet Red System showed that galectin-6 bound to BBMVs of A. aegypti larvae with lower affinity than that of Cry11Aa. Western blotting and far-western blotting analyses demonstrated that galectin-6 bound to A. aegypti ALP1 and APN2 as well as to BBMVs, consistent with the results of ELISA and protein docking simulations. However, galectin-6 did not bind to Cadherin in far-western blotting or ELISA assay, though the protein docking simulations suggested their binding potential. These findings support the conclusion that galectin-6 may block Cry11Aa from binding to ALP1 and APN2 due to structural similarity, which might decrease the mosquitocidal toxicity of Cry11Aa.

A Data Fusion Modeling Framework for Retrieval of Land Surface Temperature from Landsat-8 and Modis Data.

Land surface temperature (LST) is a critical state variable of land surface energy equilibrium and a key indicator of environmental change such as climate change, urban heat island, and freezing-thawing hazard. The high spatial and temporal resolution datasets are urgently needed for a variety of environmental change studies, especially in remote areas with few LST observation stations. MODIS and Landsat satellites have complementary characteristics in terms of spatial and temporal resolution for LST retrieval. To make full use of their respective advantages, this paper developed a pixel-based multi-spatial resolution adaptive fusion modeling framework (called pMSRAFM). As an instance of this framework, the data fusion model for joint retrieval of LST from Landsat-8 and MODIS data was implemented to generate the synthetic LST with Landsat-like spatial resolution and MODIS temporal information. The performance of pMSRAFM was tested and validated in the Heihe River Basin located in China. The results of six experiments showed that the fused LST was high similarity to the direct Landsat-derived LST with structural similarity index (SSIM) of 0.83 and the index of agreement (d) of 0.84. The range of SSIM was 0.65-0.88, the root mean square error (RMSE) yielded a range of 1.6-3.4 °C, and the averaged bias was 0.6 °C. Furthermore, the temporal information of MODIS LST was retained and optimized in the synthetic LST. The RMSE ranged from 0.7 °C to 1.5 °C with an average value of 1.1 °C. When compared with in situ LST observations, the mean absolute error and bias were reduced after fusion with the mean absolute bias of 1.3 °C. The validation results that fused LST possesses the spatial pattern of Landsat-derived LSTs and inherits most of the temporal properties of MODIS LSTs at the same time, so it can provide more accurate and credible information. Consequently, pMSRAFM can be served as a promising and practical fusion framework to prepare a high-quality LST spatiotemporal dataset for various applications in environment studies.

Mutational Analysis of Lassa Virus Glycoprotein Highlights Regions Required for Alpha-Dystroglycan Utilization.

Lassa virus (LASV) is an enveloped RNA virus endemic to West Africa and responsible for severe cases of hemorrhagic fever. Virus entry is mediated by the glycoprotein complex consisting of a stable-signal peptide, a receptor-binding subunit, GP1, and a viral-host membrane fusion subunit, GP2. Several cellular receptors can interact with the GP1 subunit and mediate viral entry, including alpha-dystroglycan (αDG) and lysosome-associated membrane protein 1 (LAMP1). In order to define the regions within GP1 that interact with the cellular receptors, we implemented insertional mutagenesis, carbohydrate shielding, and alanine scanning mutagenesis. Eighty GP constructs were engineered and evaluated for GP1-GP2 processing, surface expression, and the ability to mediate cell-to-cell fusion after low-pH exposure. To examine virus-to-cell entry, 49 constructs were incorporated onto vesicular stomatitis virus (VSV) pseudoparticles and transduction efficiencies were monitored in HAP1 and HAP1-ΔDAG1 cells that differentially produce the αDG cell surface receptor. Seven constructs retained efficient transduction in HAP1-ΔDAG1 cells yet poorly transduced HAP1 cells, suggesting that they are involved in αDG utilization. Residues H141, N146, F147, and Y150 cluster at the predicted central core of the trimeric interface and are important for GP-αDG interaction. Additionally, H92A-H93A, 150HA, 172HA, and 230HA displayed reduced transduction in both HAP1 and HAP1-ΔDAG1 cells, despite efficient cell-to-cell fusion activity. These mutations may interfere with interactions with the endosomal receptor LAMP1 or interfere at another stage in entry that is common to both cell lines. Insight gained from these data can aid in the development of more-effective entry inhibitors by blocking receptor interactions.IMPORTANCE Countries in which Lassa virus is endemic, such as Nigeria, Sierra Leone, Guinea, and Liberia, usually experience a seasonal outbreak of the virus from December to March. Currently, there is neither a preventative vaccine nor a therapeutic available to effectively treat severe Lassa fever. One way to thwart virus infection is to inhibit interaction with cellular receptors. It is known that the GP1 subunit of the Lassa glycoprotein complex plays a critical role in receptor recognition. Our results highlight a region within the Lassa virus GP1 protein that interacts with the cellular receptor alpha-dystroglycan. This information may be used for future development of new Lassa virus antivirals.

MiR-199b-5p promotes malignant progression of osteosarcoma by regulating HER2.

PURPOSE: MicroRNAs (miRs) are endogenous, noncoding small RNAs that play a key role in regulating biological and pathological processes. The oncogenic properties of miR-199b-5p have been demonstrated in previous studies but the effect of miR-199b-5p on osteosarcoma (OS) has not yet been clarified. This study aimed to investigate the effect of miR-199b-5p on OS and the relationship between this miR and the pathological parameters and prognosis of OS. METHODS: MiR-199b-5p expression in 57 pairs of OS tissues, corresponding adjacent normal tissues and OS cells was measured by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR).The relationship between miR-199b-5p and the pathological features and prognosis of OS patients was examined. We constructed small interfering (si) RNA to knock down miR-199b-5p expression in OS cell lines MG63 and U2OS. Cell Counting Kit-8 (CCK-8), cell cloning assay and Transwell cell migration and invasion assay were applied for investigating the biological function of miR-199b-5p, respectively. Finally, western blot was used for exploring its underlying mechanism. RESULTS: MiR-199b-5p expression in OS was significantly higher than that of normal tissues. Compared to patients w\sith low expression of miR-199b-5p, patients with high expression level tended to be with younger age, higher incidence of distant metastases and lower overall survival. Compared with interference sequence negative control (si-NC) group, the abilities of proliferation, invasion and metastasis of cells transfected with si-miR-199b-5p were significantly decreased. Western blot analysis indicated that expressions of key proteins related to epithelial to mesenchymal transition (EMT) signaling pathway, including N-cadherin, Vimentin, ß-catenin and matrix metalloproteinase-9 (MMP9), were significantly decreased after transfection with si-miR-199b-5p. Furthermore, we found that miR-199b-5p promoted the progression of OS mainly through regulating HER2. CONCLUSIONS: Upregulated miR-199b-5p is significantly related with stage, distant metastasis and poor prognosis of OS. This MiR may promote progression of OS through regulating HER2.

Biochemical characterization of an α1,2-colitosyltransferase from Escherichia coli O55:H7.

Colitose, also known as 3,6-dideoxy-L-galactose or 3-deoxy-L-fucose, is one of only five naturally occurring 3,6-dideoxyhexoses. Colitose was found in lipopolysaccharide of a number of infectious bacteria, including Escherichia coli O55 & O111 and Vibrio cholera O22 & O139. To date, no colitosyltransferase (ColT) has been characterized, probably due to the inaccessibility of the sugar donor, GDP-colitose. In this study, starting with chemically prepared colitose, 94.6 mg of GDP-colitose was prepared via a facile and efficient one-pot two-enzyme system involving an L-fucokinase/GDP-L-Fuc pyrophosphorylase and an inorganic pyrophosphatase (EcPpA). WbgN, a putative ColT from E. coliO55:H5 was then cloned, overexpressed, purified and biochemically characterized by using GDP-colitose as a sugar donor. Activity assay and structural identification of the synthetic product clearly demonstrated that wbgN encodes an α1,2-ColT. Biophysical study showed that WbgN does not require metal ion, and is highly active at pH 7.5-9.0. In addition, acceptor specificity study indicated that WbgN exclusively recognizes lacto-N-biose (Galß1,3-GlcNAc). Most interestingly, it was found that WbgN exhibits similar activity toward GDP-l-Fuc (kcat/Km= 9.2 min(-1)mM(-1)) as that toward GDP-colitose (kcat/Km= 12 min(-1)mM(-1)). Finally, taking advantage of this, type 1 H-antigen was successfully synthesized in preparative scale.

Chemical synthesis of the outer core oligosaccharide of Escherichia coli R3 and immunological evaluation.

Lipopolysaccharides (LPS), major virulence determinants in Gram-negative bacteria, are responsible for many pathophysiological responses and can elicit strong immune responses. In order to better understand the role of LPS in host-pathogen interactions and elucidate the immunogenic properties of LPS outer core oligosaccharides, an all α-linked Escherichia coli R3 outer core pentasaccharide was first synthesized with a propyl amino linker at the reducing end. This oligosaccharide was also covalently conjugated to a carrier protein (CRM197) via the reducing end propyl amino linker. Immunological analysis demonstrated that this glycoconjugate can elicit specific anti-pentasaccharide antibodies with in vitro bactericidal activity. These findings will contribute to the further exploration of this pentasaccharide antigen as a vaccine candidate.

O-antigen polymerase adopts a distributive mechanism for lipopolysaccharide biosynthesis.

Bacterial lipopolysaccharide (LPS) is an essential cell envelope component for gram-negative bacteria. As the most variable region of LPS, O antigens serve as important virulence determinants for many bacteria and represent a promising carbohydrate source for glycoconjugate vaccines. In the Wzy-dependent O-antigen biosynthetic pathway, the integral membrane protein Wzy was shown to be the sole enzyme responsible for polymerization of O-repeat unit. Its catalytic mechanism, however, remains elusive. Herein, Wzy was successfully overexpressed in Escherichia coli with an N-terminal His10-tag. Blue native polyacrylamide gel electrophoresis (BN-PAGE) revealed that the Wzy protein exists in its native confirmation as a dimer. Subsequently, we chemo-enzymatically synthesized the substrates of Wzy, the lipid-PP-linked repeat units. Together with an optimized O-antigen visualization method, we monitored the production of reaction intermediates at varying times. We present here our result as the first biochemical evidence that Wzy functions in a distributive manner.

Assessment of lumbar disc herniation-impaired gait by using IMU data fusion method.

The inertial motion unit (IMU) is an effective tool for monitoring and assessing gait impairment in patients with lumbar disc herniation(LDH). However, the current clinical assessment methods for LDH gait focus on patients' subjective scoring indicators and lack the assessment of kinematic ability; at the same time, individual differences in the motor function degradation of the healthy and affected lower limbs of LDH patients are also ignored. To solve this problem, we propose an LDH gait feature model based on multi-source adaptive Kalman data fusion of acceleration and angular velocity. The gait phase is segmented by using an adaptive Kalman data fusion algorithm to estimate the attitude angle, and obtaining gait events through a zero-velocity update technique and a peak detection algorithm. Two IMUs were used to analyze the gait characteristics of lumbar disc patients and healthy gait people, including 12 gait characteristics such as gait spatiotemporal parameters, kinematic parameters, gait variability and stability. Statistical methods were used to analyze the characteristic model and verify the biological differences between the healthy affected side of LDH and healthy subjects. Finally, feature engineering and machine learning technology were used to identify the gait pattern of inertial movement units in patients with lumbar intervertebral disc disease, and achieved a classification accuracy of 95.50%, providing an effective gait feature set and method for clinical evaluation of LDH.

Two-Color Amplified Spontaneous Emission from Auger-Suppressed Quantum Dots in Liquids.

Colloidal quantum-dot (QD) lasing is normally achieved in close-packed solid-state films, as a high QD volume fraction is required for stimulated emission to outcompete fast Auger decay of optical-gain-active multiexciton states. Here a new type of liquid optical-gain medium is demonstrated, in which compact compositionally-graded QDs (ccg-QDs) that feature strong suppression of Auger decay are liquefied using a small amount of solvent. Transient absorption measurements of ccg-QD liquid suspensions reveal broad-band optical gain spanning a wide spectral range from 560 (green) to 675 nm (red). The gain magnitude is sufficient to realize a two-color amplified spontaneous emission (ASE) at 637 and 594 nm due to the band-edge (1S) and the excited-state (1P) transition, respectively. Importantly, the ASE regime is achieved using quasicontinuous excitation with nanosecond pulses. Furthermore, the ASE is highly stable under prolonged excitation, which stands in contrast to traditional dyes that exhibit strong degradation under identical excitation conditions. These observations point toward a considerable potential of high-density ccg-QD suspensions as liquid, dye-like optical gain media that feature readily achievable spectral tunability and stable operation under intense photoexcitation.

Defining function of lipopolysaccharide O-antigen ligase WaaL using chemoenzymatically synthesized substrates.

The WaaL-mediated ligation of O-antigen onto the core region of the lipid A-core block is an important step in the lipopolysaccharide (LPS) biosynthetic pathway. Although the LPS biosynthesis has been largely characterized, only a limited amount of in vitro biochemical evidence has been established for the ligation reaction. Such limitations have primarily resulted from the barriers in purifying WaaL homologues and obtaining chemically defined substrates. Accordingly, we describe herein a chemical biology approach that enabled the reconstitution of this ligation reaction. The O-antigen repeating unit (O-unit) of Escherichia coli O86 was first enzymatically assembled via sequential enzymatic glycosylation of a chemically synthesized GalNAc-pyrophosphate-undecaprenyl precursor. Subsequent expression of WaaL through use of a chaperone co-expression system then enabled the demonstration of the in vitro ligation between the synthesized donor (O-unit-pyrophosphate-undecaprenyl) and the isolated lipid A-core acceptor. The previously reported ATP and divalent metal cation dependence were not observed using this system. Further analyses of other donor substrates revealed that WaaL possesses a highly relaxed specificity toward both the lipid moiety and the glycan moiety of the donor. Lastly, three conserved amino acid residues identified by sequence alignment were found essential for the WaaL activity. Taken together, the present work represents an in vitro systematic investigation of the WaaL function using a chemical biology approach, providing a system that could facilitate the elucidation of the mechanism of WaaL-catalyzed ligation reaction.

Synthesis of a Comprehensive Polyprenol Library for Evaluation of Bacterial Enzyme Lipid Substrate Specificity.

Polyprenols, a type of universal glycan lipid carrier, play important roles for glycan bio-assembly in wide variety of living systems. Chemical synthesis of natural polyisoprenols such as undecaprenol and dolichols, but especially their homologs, could serves as a powerful molecular tool to dissect and define the functions of enzymes involved in glycan biosynthesis. In this paper, we report an efficient and reliable method to construct this type of hydrophoic molecule through a base-mediated iterative coupling approach using a key bifunctional (Z, Z)-diisoprenyl building block. The ligation with N-acetyl-D-glactosamine (GalNAc) with a set of the synthesized lipid analogs forming polyprenol pyrophosphate linked GalNAc (GalNAc-PP-lipid) conjugates is also demonstrated.

Effect of multiple washing operations on the removal of potentially toxic metals from an alkaline farmland soil and the strategy for agricultural reuse.

Few studies have carried out soil washing experiments using pot experiments to simulate in situ soil washing operations, particularly for alkaline soils. This study explored the effects of multiple washing operations using pot experiments on the removal efficiencies of potentially toxic metals (PTM) from alkaline farmland soil and the reuse strategy of washed soil for safe agricultural production. The results showed that the removal efficiencies of Cd, Pb, Cu, and Zn after seven washings with a mixed chelator (EDTA, GLDA, and citric acid) were 41.1%, 47.1%, 14.7%, and 26.5%, respectively, which was close to the results of the EDTA treatment. For the alkaline soil studied, the second washing with the mixed chelators most effectively removed PTM owing to the activation of them after the first washing operation. The mixed chelator more effectively increased the proportion of stable fraction of PTM and maintained soil nutrients (e.g., nitrogen content) than EDTA, indicating little disturbance of alkaline soil quality after washing with the mixed chelator. After the amendment of the washed soil, there was no visible difference in the biomass weight of crops from the soils washed with different agents, indicating that the inhibitory effect of both washing agents on plant growth was effectively alleviated. The Cd and Pb contents in Z. mays were below the threshold of Hygienical Standard for Feeds of China (GB 13078-2017) (1 and 30 mg·kg-1). Moreover, after three cropping operations, the available concentrations of PTM in the soil washed with the mixed chelator were lower than those in the soil washed with EDTA, indicating the value and potential of agricultural reuse of alkaline farmland soil washed with the mixed chelator.

Constructing spin crossover-fluorescence bifunctional iron(II) complexes based on tetraphenyl ethylene-decorated AIEgens.

Investigating spin crossover (SCO)-fluorescence bifunctional materials and establishing their structure-function relationships are attractive topics in chemistry and materials science. However, it remains challenging to preserve the fluorescence and SCO properties simultaneously in aggregated solid states. Herein, we design an (E)-2,6-bis(1H-pyrazol-1-yl)-4-(4-(1,2,2-triphenylvinyl)styryl)pyridine (tpe-bpp) ligand, which contains coordinated SCO and fluorescence units of an aggregation-induced emission luminogen (AIEgen). The coordination of the tpe-bpp ligand with different FeII salts generated three mononuclear complexes: [Fe(tpe-bpp)2](ClO4)2·5.75CH2Cl2 (1), [Fe(tpe-bpp)2](ClO4)2·CH2Cl2·3CH3OH (2) and [Fe(tpe-bpp)2](BF4)2·CH2Cl2·3CH3OH (3). Single-crystal X-ray diffraction studies showed that they shared a similar [Fe(tpe-bpp)2]2+ complex cation. Their counterions and co-crystallized solvents were different. Magnetic measurements revealed that 1, 2, and 3 exhibited a complete SCO behavior with the transition temperatures T1/2 of 375, 260, and 248 K, respectively. Fluorescence measurements confirmed the existence of the AIE property for both the tpe-bpp ligand and Fe(II) complexes. A monotonic decrease of the photoluminescence (PL) intensity upon increasing the temperature was behavior observed for all three complexes.

In vitro bacterial polysaccharide biosynthesis: defining the functions of Wzy and Wzz.

Polysaccharides constitute a major component of bacterial cell surfaces and play critical roles in bacteria-host interactions. The biosynthesis of such molecules, however, has mainly been characterized through in vivo genetic studies, thus precluding discernment of the details of this pathway. Accordingly, we present a chemical approach that enabled reconstitution of the E. coli O-polysaccharide biosynthetic pathway in vitro. Starting with chemically prepared undecaprenyl-diphospho-N-acetyl-D-galactosamine, the E. coli O86 oligosaccharide repeating unit was assembled by means of sequential enzymatic glycosylation. Successful expression of the putative polymerase Wzy using a chaperone coexpression system then allowed demonstration of polymerization in vitro using this substrate. Analysis of more substrates revealed a defined mode of recognition for Wzy toward the lipid moiety. Specific polysaccharide chain length modality was furthermore demonstrated to result from the action of Wzz. Collectively, polysaccharide biosynthesis was chemically reconstituted in vitro, providing a well defined system for further underpinning molecular details of this biosynthetic pathway.

[Application of wavelet analysis in pick-up of breath signal from oscillations in chest wall].

In order to pick up breath signal from correlated noise background of the pulse of heart and artery etc, an algorithm based on wavelet de-noising has been introduced. With wavelet db4, the raw signal was decomposed into the scale space of six layers; threshold treatment was done with the self-adaptive threshold created by Stein's Unbiased Risk Estimate; then the wavelet coefficients were reconstructed. The result showed that the noise was significantly depressed.

Orbital Mixing between Colloidal Quantum Dots and Surface-Bound Molecules.

Orbital mixing is paramount to chemistry as it plays a central role in bond formation. It is also important for technologies such as molecular doping of polymers, where the concept of fractional charge transfer is essentially orbital mixing between dopants and hosts. Likewise, it would be both fundamentally interesting and technologically relevant to investigate orbital mixing in emerging hybrid materials containing both inorganic and organic moieties. Here we report experimental observation of orbital mixing between valence band levels of strongly confined PbS quantum dots (QDs) and lowest unoccupied molecular levels of surface-bound high-electron affinity molecules (F4TCNQ), manifested as both an absorption blue-shift of PbS and the emergence of visible and infrared signatures of the fractional charge-transfer species of F4TCNQ. The degree of mixing can be controlled by varying the QD size or by varying the molecule/QD ratio for a specific QD size and can be quantitatively reproduced by a nondegenerate, two-level perturbation model.

Synthesis of rare sugars with L-fuculose-1-phosphate aldolase (FucA) from Thermus thermophilus HB8.

We report herein a one-pot four-enzyme approach for the synthesis of the rare sugars d-psicose, d-sorbose, l-tagatose, and l-fructose with aldolase FucA from a thermophilic source (Thermus thermophilus HB8). Importantly, the cheap starting material DL-GP (DL-glycerol 3-phosphate), was used to significantly reduce the synthetic cost.