Enhancing the catalytic performance of Co-N-C derived from ZIF-67 by mesoporous silica encapsulation for chemoselective hydrogenation of furfural.

Developing Cr-free and non-noble metal catalysts with high activity, selectivity and durability for chemoselective hydrogenation of furfural to furfuryl alcohol is highly desirable yet challenging. In this study, we design a hollow mesoporous Co-N-C@mSiO2 nanostructure derived from ZIF-67 via the encapsulation-pyrolysis strategy. The Co-N-C@mSiO2 catalyst exhibits excellent catalytic performance in the furfural hydrogenation towards furfuryl alcohol with good stability, and is much better than the Co-N-C catalyst originating from plain ZIF-67 and other reported transition metal catalysts. Characterization methods and control experiments show that Co-Nx species rather than Co metal should be catalytically active sites for the above reaction. The enhanced performance is associated with abundant Co-Nx active sites, good mass transport, and the SiO2 shell protection. This work provides a novel and facile strategy for preparing highly efficient non-precious metal catalysts to replace Cr-based and noble metal catalysts for furfural hydrogenation.

Synthesis and in vitro anticancer evaluation of novel flavonoid-based amide derivatives as regulators of the PI3K/AKT signal pathway for TNBC treatment.

Aberrant activation of the PI3K/AKT pathway is considered in many malignant tumors and plays a crucial role in mediating malignancy progression, metastasis, and chemoresistance. Consequently, development of PI3K/AKT pathway targeted drugs is currently an attractive research field for tumor treatment. In this study, twenty-six flavonoid-based amide derivatives were synthesized and evaluated for their antiproliferation effects against seven cancer cell lines, including MDA-MB-231, MCF-7, HCC1937, A549, HepG2, GTL-16 and HeLa. Among them, compound 7t possessed the best specific cytotoxicity against triple negative breast cancer MDA-MB-231 cells with an IC50 value of 1.76 ± 0.91 µM and also presented inhibitory ability on clonal-formation, migration and invasion of MDA-MB-231 cells. Further cell-based mechanistic studies demonstrated that compound 7t caused cell cycle arrest of MDA-MB-231 cells at the G0/G1 phase and induced apoptosis. Meanwhile, the western blot assay revealed that compound 7t could down-regulate the expression of p-PI3K, p-AKT, and Bcl-2 and up-regulate the production of PTEN, Bax, and caspase-3. Molecular docking also showed a possible binding mode of 7t with PI3Kα. Together, compound 7t was eligible as a potential TNBC therapeutic candidate for further development.

Transcription factor OsNAC055 regulates GA-mediated lignin biosynthesis in rice straw.

Crop straws represent enormous biomass resource that mainly contain secondary cell walls (SCWs) consisting of cellulose, hemicelluloses and lignin. Nevertheless, the regulatory mechanism of SCW biosynthesis still needs to be well understood. In this study, we identified a rice NAC (NAM, ATAF1/2, CUC2) transcription factor OsNAC055 that regulates GA-mediated lignin biosynthesis. As a nucleus-localized transcription factor, OsNAC055 exhibits the transcriptional activation activity. Overexpression of OsNAC055 increases the lignin content in rice straw. Transcriptomic analyses showed that the expression of multiple lignin biosynthetic genes was increased in OsNAC055-overexpressing plants. Further ChIP-qPCR analysis and transient transactivation assays indicated that OsNAC055 directly activates rice lignin biosynthetic genes CINNAMOYL-CoA REDUCTASE 10 (OsCCR10) and CINNAMYL ALCOHOL DEHYDROGENASE 2 (OsCAD2) by binding to their promoters. On the other hand, phytohormone measurement showed that OsNAC055 overexpression significantly increased exogenous GA3 levels in rice plants by regulating GA biosynthetic gene OsGA20ox2. Moreover, yeast two-hybrid and bimolecular fluorescence complement (BiFC) assays indicated that OsNAC055 interacts with SLENDER RICE1 (SLR1), the repressor in GA signaling. More importantly, exogenous GA treatment markedly enhanced the transcription of OsCCR10 and OsCAD2, suggesting the role of GA in lignin biosynthesis. Together, our results provide the evidence that OsNAC055 functions as an essential transcription factor to regulate the GA-mediated lignin biosynthesis, which provides a strategy for manipulating lignin production.

OsNAC016 regulates plant architecture and drought tolerance by interacting with the kinases GSK2 and SAPK8.

Ideal plant architecture and drought tolerance are important determinants of yield potential in rice (Oryza sativa). Here, we found that OsNAC016, a rice NAC (NAM, ATAF, and CUC) transcription factor, functions as a regulator in the crosslink between brassinosteroid (BR)-mediated plant architecture and abscisic acid (ABA)-regulated drought responses. The loss-of-function mutant osnac016 exhibited erect leaves and shortened internodes, but OsNAC016-overexpressing plants had opposite phenotypes. Further investigation revealed that OsNAC016 regulated the expression of the BR biosynthesis gene D2 by binding to its promoter. Moreover, OsNAC016 interacted with and was phosphorylated by GSK3/SHAGGY-LIKE KINASE2 (GSK2), a negative regulator in the BR pathway. Meanwhile, the mutant osnac016 had improved drought stress tolerance, supported by a decreased water loss rate and enhanced stomatal closure in response to exogenous ABA, but OsNAC016-overexpressing plants showed attenuated drought tolerance and reduced ABA sensitivity. Further, OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE8 (SAPK8) phosphorylated OsNAC016 and reduced its stability. The ubiquitin/26S proteasome system is an important degradation pathway of OsNAC016 via the interaction with PLANT U-BOX PROTEIN43 (OsPUB43) that mediates the ubiquitination of OsNAC016. Notably, RNA-sequencing analysis revealed global roles of OsNAC016 in promoting BR-mediated gene expression and repressing ABA-dependent drought-responsive gene expression, which was confirmed by chromatin immunoprecipitation quantitative PCR analysis. Our findings establish that OsNAC016 is positively involved in BR-regulated rice architecture, negatively modulates ABA-mediated drought tolerance, and is regulated by GSK2, SAPK8, and OsPUB43 through posttranslational modification. Our data provide insights into how plants balance growth and survival by coordinately regulating the growth-promoting signaling pathway and response under abiotic stresses.

CRISPR-Cas9 Mediated Mutation in OsPUB43 Improves Grain Length and Weight in Rice by Promoting Cell Proliferation in Spikelet Hull.

Grain weight, a crucial trait that determines the grain yield in rice, is influenced by grain size. Although a series of regulators that control grain size have been identified in rice, the mechanisms underlying grain development are not yet well understood. In this study, we identified OsPUB43, a U-box E3 ubiquitin ligase, as an important negative regulator determining the gain size and grain weight in rice. Phenotypes of large grain are observed in ospub43 mutants, whereas overexpression of OsPUB43 results in short grains. Scanning electron microscopy analysis reveals that OsPUB43 modulates the grain size mainly by inhibiting cell proliferation in the spikelet hull. The OsPUB43 protein is localized in the cytoplasm and nucleus. The ospub43 mutants display high sensitivity to exogenous BR, while OsPUB43-OE lines are hyposensitive to BR. Furthermore, the transient transcriptional activity assay shows that OsBZR1 can activate the expression of OsPUB43. Collectively, our results indicate that OsPUB43 negatively controls the gain size by modulating the expression of BR-responsive genes as well as MADS-box genes that are required for lemma/palea specification, suggesting that OsPUB43 has a potential valuable application in the enlargement of grain size in rice.

An Expectation Maximization Based Adaptive Group Testing Method for Improving Efficiency and Sensitivity of Large-Scale Screening of COVID-19.

The pathogen of the ongoing coronavirus disease 2019 (COVID-19) pandemic is a newly discovered virus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Testing individuals for SARS-CoV-2 plays a critical role in containing COVID-19. For saving medical personnel and consumables, many countries are implementing group testing against SARS-CoV-2. However, existing group testing methods have the following limitations: (1) The group size is determined without theoretical analysis, and hence is usually not optimal. This adversely impacts the screening efficiency. (2) These methods neglect the fact that mixing samples together usually leads to substantial dilution of the SARS-CoV-2 virus, which seriously impacts the sensitivity of tests. In this paper, we aim to screen individuals infected with COVID-19 with as few tests as possible, under the premise that the sensitivity of tests is high enough. We propose an eXpectation Maximization based Adaptive Group Testing (XMAGT) method. The basic idea is to adaptively adjust its testing strategy between a group testing strategy and an individual testing strategy such that the expected number of samples identified by a single test is larger. During the screening process, the XMAGT method can estimate the ratio of positive samples. With this ratio, the XMAGT method can determine a group size under which the group testing strategy can achieve a maximal expected number of negative samples and the sensitivity of tests is higher than a user-specified threshold. Experimental results show that the XMAGT method outperforms existing methods in terms of both efficiency and sensitivity.

Effects of Preparation Parameters of NiAl Oxide-Supported Au Catalysts on Nitro Compounds Chemoselective Hydrogenation.

Effects of preparation parameters of NiAl oxide-supported Au nanocatalysts on their performance in the chemoselective hydrogenation of nitro compounds were investigated. The deposition-precipitation method, low Au loading, and low Ni/Al molar ratio of the support contributed to the generation of small-sized Au nanoparticles. High catalytic properties were related to the small sizes of Au particles and appropriate basicity of supports. Accordingly, the 0.43% Au/NiAlO-2-500 (the Ni/Al molar ratio of the support = 2) showed high activity and excellent selectivity for nitro hydrogenation. It also showed good versatility for other nitro compounds and good recyclability. Interestingly, for the first time, this Au catalyst switched its selectivity to vinyl hydrogenation by mere regulation of the composition of the support (the Ni/Al molar ratio of the support = 4). The observed shift in selectivity was ascribed to the different adsorption behaviors of the nitro and vinyl group on Au nanocatalysts. It provides a novel and facile strategy to construct Au nanocatalysts with high activity and switchable selectivity for hydrogenation of nitro compounds by the fine tuning of preparation parameters.

A pair of 2D chiral Ag(i) enantiomers with dual chiral elements: syntheses, structures, and photoluminescent and chiroptical properties.

In this work, two new enantiopure bis-monodentate N-donor chiral ligands, namely (-)/(+)-2-(4'-pyridyl)-4,5-pinene-pyridine (L R /L S ), have been designed and synthesized. Using L R and L S as bridging ligands to react with AgClO4, a pair of novel 2D chiral Ag(i) enantiomers formulated as [Ag2(L R )2(ClO4)2] n (R-1) and [Ag2(L S )2(ClO4)2] n (S-1) were isolated and characterized. In R-1 and S-1, each Ag(i) ion is bonded by two N atoms from two different chiral L R or L S ligands, leading to the formation of 1D right- or left-handed -L-Ag(i)-L- helical chains. Moreover, two adjacent helical chains are further doubly linked by two monodentate ClO4 - anions through weak Ag-O contacts to form 2D network structures, in which dual chiral elements, i.e., center chirality and helical chirality coexist. Interestingly, each free ligand L R /L S and R-1/S-1 enantiomers show very different ECD spectra in the solid state and in solution, which are correlated to the intermolecular interactions and molecular structures in each state, respectively. Notably, as a representative, R-1 exhibits intense room temperature photoluminescence both in the solid state and in solution with different emission features and mechanisms, while it also shows more intense emission than that of free ligand L R . In particular, R-1 and S-1 represent the first examples of 2D Ag(i) chiral coordination polymers (CCPs) supported by ClO4 - anions, possessing dual chiral elements.

Heterogeneous gold catalysts for selective hydrogenation: from nanoparticles to atomically precise nanoclusters.

Gold nanocatalysts with different sizes (nanoparticles and nanoclusters) show different catalytic performances for various selective hydrogenation reactions. The recent breakthrough in a controllable synthesis of atomically precise gold nanoclusters provides unprecedented opportunities for understanding the catalytic behavior at the atomic/molecular levels. Herein, we review the progress in catalytic hydrogenation over gold nanoparticles and atomically precise gold nanoclusters in the last five years. We also compare the results obtained from different reactions so that a better understanding of their catalytic behavior can be obtained. Finally, we provide some future perspectives on gold nanocatalysis.

Characterization of Cr(V)-induced genotoxicity using CdTe nanocrystals as fluorescent probes.

CdTe nanocrystals capped by cysteamine were synthesized to study Cr(V)-induced genotoxicity. On the surface of TiO2 thin films, the stepwise process of DNA breakage induced by Cr(V)-GSH complexes was vividly observed by using CdTe-DNA self-assembled fluorescent probes; in acetate buffer solution, an analytical method was developed to detect Cr(V)-induced genotoxicity with CdTe fluorescent probes.

[Characterization of processing batch for preparation of radix scutellariae based on dependent component analysis and infrared spectrometry].

Dependent component analysis (DCA) was applied to directly estimate source spectral profiles from IR spectra of synthetic mixtures and characterize processing batch for preparation of radix scutellariae. The results show that DCA can estimate information of dependent components (DCs) from the measured infrared spectral (IR) signal obtained during the processing batch for preparation of radix scutellariae, and the estimated information of DCs is corresponding to the IR features of the active components of scutelliare; by inspection of the change trends of the estimated DCs, the endpoint of the processing batch was determined as 55 min. The proposed approach provides a novel way for process analysis and endpoint determination of procedure for preparation of scutellariae.

Flow injection analysis of volatile phenols in environmental water samples using CdTe/ZnSe nanocrystals as a fluorescent probe.

On the basis of flow injection analysis technology, a simple, accurate, and sensitive method has been developed for the determination of volatile phenols in environmental water samples by using CdTe/ZnSe nanocrystals as a fluorescent probe. The influences of coexisting metal ions and volatile phenol substitutes were also investigated. The method developed for analysis of volatile phenols displayed very good linearity in the range from 1.0 × 10(-8) to 4.0 × 10(-7) g L(-1), with a correlation coefficient greater than 0.995 and a detection limit down to 2.7 × 10(-9) g L(-1) (signal-to-noise ratio 3). The proposed method was successfully applied to determine the content of volatile phenols in environmental water samples, and the quantitative recoveries were 93.4-106.1%. A possible reaction mechanism for the quenching of fluorescence is discussed using UV-vis absorption spectra, fluorescence spectra, and time-resolved luminescence spectra of volatile phenols obtained by titrating a CdTe/ZnSe nanocrystal aqueous solution and zeta potential data.

[Extraction of spectral information of additives from activated manganese dioxide products using adaptive kernel independent component analysis].

The additives were abstracted from the manganese dioxide products with four kinds of organic solvents, ether, acetone, chloroform and toluene. The extracts were then baked and their attenuated total reflectance (ATR) FTIR spectra were measured using liquid membrane method. The number of chemical components of the additives was determined by median absolute deviation (MAD), and the spectral information of the pure component was extracted by kernel independent component analysis (KICA). The extracted spectral information of the additives is accordant to that of the practically used compounds. An adaptive kernel independent component analysis (AKICA) was proposed for directive extraction of spectral information from chemical mixtures. The results demonstrated that the AKICA method provides an alternative approach to extracting spectral information from the chemical mixtures without previously chemical or physical preseparation for direct extracting spectral information of pure components in the mixed system.

In situ synthesis of highly luminescent glutathione-capped CdTe/ZnS quantum dots with biocompatibility.

This paper focuses on the in situ synthesis of novel CdTe/ZnS core-shell quantum dots (QDs) in aqueous solution. Glutathione (GSH) was used as both capping reagent and sulfur source for in situ growth of ZnS shell on the CdTe core QDs. The maximum emission wavelengths of the prepared CdTe/ZnS QDs can be simply tuned from 569 nm to 630 nm. The PL quantum yield of CdTe/ZnS QDs synthesized is up to 84%, larger than the original CdTe QDs by around 1.7 times. The PL lifetime results reveal a triexponential decay model of exciton and trap radiation behavior. The average exciton lifetime at room temperature is 17.1 ns for CdTe (2.8 nm) and 27.4 ns for CdTe/ZnS (3.7 nm), respectively. When the solution of QDs is dialyzed for 3 h, 1.17 ppm of Cd(2+) is released from CdTe QDs and 0.35 ppm is released from CdTe/ZnS. At the dose of 120 microg/ml QDs, 9.5% of hemolysis was induced by CdTe QDs and 3.9% was induced by CdTe/ZnS QDs. These results indicate that the synthesized glutathione-capped CdTe/ZnS QDs are of less toxicity and better biocompatibility, so that are attractive for use in biological detection and related fields.

Selective synthesis of CdTe and high luminescence CdTe/CdS quantum dots: the effect of ligands.

This paper describes the selective syntheses of high luminescence CdTe and core-shell CdTe/CdS quantum dots (QDs) in aqueous solution by simple heating refluxing at 100 degrees C. CdTe QDs are prepared by using three kinds of ligands (thioglycolic acid-TGA, tiopronin-TP, and glutathione-GSH) as stabilizer, respectively. The results of refluxing for 10 min to several hours indicate that GSH-capped CdTe QDs have higher photoluminescence quantum yields (QY 54%) than TGA (QY 41%)- and TP (QY 24%)-stabilized CdTe QDs. Further, using TP-CdTe as core template and GSH as stabilizer and sulfur source, high luminescence GSH-capped CdTe/CdS core-shell QDs have been successfully synthesized in aqueous solution by simple refluxing at 100 degrees C. The GSH-CdTe/CdS QDs exhibit high fluorescence QYs about 55% over a broad spectral range of 530-588 nm, with the best QY of 83%. TP-stabilized CdTe/CdS QDs are also synthesized with TP as stabilizer and thioacetamide (TAA) as sulfur source, and with the best QY of 80%. GSH-stabilized CdTe and CdTe/CdS QDs are highly biocompatible, monodispersed, and stable under physiological conditions. The method of QDs prepared using GSH is simple and environmentally friendly, and it can be easily extended to the large-scale, aqueous-phase production of QDs.