Development of a stable genetic transformation system in Erigeron breviscapus: a case study with EbYUC2 in relation to leaf number and flowering time.

MAIN CONCLUSION: A stable genetic transformation system for Erigeron breviscapus was developed. We cloned the EbYUC2 gene and genetically transformed it into Arabidopsis thaliana and E. breviscapus. The leaf number, YUC2 gene expression, and the endogenous auxin content in transgenic plants were significantly increased. Erigeron breviscapus is a prescription drug for the clinical treatment of cardiovascular and cerebrovascular diseases. The rosette leaves have the highest content of the major active compound scutellarin and are an important component in the yield of E. breviscapus. However, little is known about the genes related to the leaf number and flowering time of E. breviscapus. In our previous study, we identified three candidate genes related to the leaf number and flowering of E. breviscapus by combining resequencing data and genome-wide association study (GWAS). However, their specific functions remain to be characterized. In this study, we cloned and transformed the previously identified full-length EbYUC2 gene into Arabidopsis thaliana, developed the first stable genetic transformation system for E. breviscapus, and obtained the transgenic plants overexpressing EbYUC2. Compared with wild-type plants, the transgenic plants showed a significant increase in the number of leaves, which was correlated with the increased expression of EbYUC2. Consistently, the endogenous auxin content, particularly indole-3-acetic acid, in transgenic plants was also significantly increased. These results suggest that EbYUC2 may control the leaf number by regulating auxin biosynthesis, thereby laying a foundation for revealing the molecular mechanism governing the leaf number and flowering time of E. breviscapus.

Isoreticular Contraction of Metal-Organic Frameworks Induced by Cleavage of Covalent Bonds.

Isoreticular chemistry, in which the organic or inorganic moieties of reticular materials can be replaced without destroying their underlying nets, is a key concept for synthesizing new porous molecular materials and for tuning or functionalization of their pores. Here, we report that the rational cleavage of covalent bonds in a metal-organic framework (MOF) can trigger their isoreticular contraction, without the need for any additional organic linkers. We began by synthesizing two novel MOFs based on the MIL-142 family, (In)BCN-20B and (Sc)BCN-20C, which include cleavable as well as noncleavable organic linkers. Next, we selectively and quantitatively broke their cleavable linkers, demonstrating that various dynamic chemical and structural processes occur within these structures to drive the formation of isoreticular contracted MOFs. Thus, the contraction involves breaking of a covalent bond, subsequent breaking of a coordination bond, and finally, formation of a new coordination bond supported by structural behavior. Remarkably, given that the single-crystal character of the parent MOF is retained throughout the entire transformation, we were able to monitor the contraction by single-crystal X-ray diffraction.

Effect of perylene assembly shapes on photoelectrochemical properties and ultrasensitive biosensing behaviors toward dopamine.

In this study, a photoelectrochemical (PEC) sensor based on perylene diimide derivatives (PDIs) was developed for the ultrasensitive quantification of dopamine (DA). PDIs were able to form self-assembled semiconductor nanostructures by strong π-π stacking, suitable for photoactive substances. Moreover, the shape of the PDI significantly affected the PEC properties of these nanostructures. The results showed that amino PDI with two-dimensional (2D) wrinkled layered nanostructures exhibited superior PEC properties relative to one-dimensional (1D) nanorods and fiber-based nanostructures (methyl and carboxyl PDIs). Based on these results, a mechanism for PEC sensor action was then proposed. The presence of 2D amino-PDI resulted in accelerated charge separation and transport. Furthermore, dopamine acted as effective electron donor to cause an increase in photocurrent. The as-obtained sensor was then used to detect small molecules like DA. A blue light optimized sensor at an applied potential of 0.7 V showed a detection limit of 1.67 nM with a wide linear range of 5 nM to 10 µM. On the other hand, the sensor presented acceptable reliability in determining DA in real samples. A recovery rate between 97.99 and 101.0% was obtained. Overall, controlling the morphology of semiconductors can influence PEC performance, which is a useful finding for the future development of PEC sensors.

Manganese-Catalyzed Hydrogenative Desulfurization of Thioamides.

Earth-abundant transition metal catalysis has emerged as an important alternative to noble transition metal catalysis in hydrogenation reactions. However, there has been no Earth-abundant transition metal catalyzed hydrogenation of thioamides reported so far, presumably due to the poisoning of catalysts by sulfur-containing molecules. Herein, we described the first manganese-catalyzed hydrogenative desulfurization of thioamides to amines or imines. The key to success is the use of MnBr(CO)5 instead of commonly-employed pincer-manganese catalysts, together with simple NEt3 and CuBr. This protocol features excellent selectivity on sole cleavage of the C=S bond of thioamides, in contrast to the only known Ru-catalyzed hydrogenation of thioamides, and unprecedented chemo-selectivity tolerating vulnerable functional groups such as nitrile, ketone, aldehyde, ester, sulfone, nitro, olefin, alkyne and heterocycle, which are usually susceptible to common hydride-type reductive protocols.

Retrosynthetic Analysis Applied to Clip-off Chemistry: Synthesis of Four Rh(II)-Based Complexes as Proof-of-Concept.

Clip-off Chemistry is a synthetic strategy that our group previously developed to obtain new molecules and materials through selective cleavage of bonds. Herein, we report recent work to expand Clip-off Chemistry by introducing into it a retrosynthetic analysis step that, based on virtual extension of the products through cleavable bonds, enables one to define the required precursor materials. As proof-of-concept, we have validated our new approach by synthesising and characterising four aldehyde-functionalised Rh(II)-based complexes: a homoleptic cluster; a cis-disubstituted paddlewheel cluster; a macrocycle; and a crown.

Metal-Organic Framework UiO-66-Mediated Dual-Signal Ratiometric Electrochemical Sensor for microRNA Detection with DNA Walker Amplification.

Electrochemical nanotags with strong signal input are necessary for a ratiometric electrochemical sensor to overcome the drawbacks of inaccurate detection results. In this paper, the metal-organic framework (MOF) UiO-66 was utilized as an electrochemical signal tag. A stable and strong current response at +0.9 V can be detected in neutral conditions. MicroRNA (miRNA) was employed as the model analyte. Herein, an enzyme-free DNA-walker-based ultrasensitive ratiometric electrochemical biosensor in combination with Zr MOF (UiO-66) signal tags to detect miRNA was demonstrated. In the presence of miRNA, the autonomous walker movement can be initiated by miRNA, leading to the release of biotin-modified fragments. Thus, streptavidin-labeled UiO-66 nanomaterials were not bound to the electrode, generating a low signal response of UiO-66 at +0.9 V. However, the current signal of electrolyte solution as reference at +0.2 V was increased due to the enhancement of electrode conductivity. This ratiometic sensor demonstrated high sensitivity, selectivity, and reproducibility. It can eliminate the disturbance of environmental factors and basic electrode characteristics, providing more accurate signals. A limit of detection (LOD) of 0.17 fM was achieved. Moreover, the method was also used to detect miRNA-21 spiked in real serum samples.

A DNA tetrahedral nanomaterial-based dual-signal ratiometric electrochemical aptasensor for the detection of ochratoxin A in corn kernel samples.

Ochratoxin A (OTA) is a highly toxic food contaminant and is harmful to human beings. Herein, a ratiometric electrochemical aptasensor based on a DNA tetrahedral nanomaterial (NTH) was developed in combination with the signal tag of a zirconium metal-organic framework (UiO-66) for the detection of OTA. In the sensor, UiO-66 and a [Fe(CN)6]3-/4- electrolyte solution were used as the signal probe and the internal reference probe, respectively. In the presence of OTA, the OTA aptamer was released from the electrode due to the specific binding of OTA. Thus, signal probe P1 labeled-UiO-66 was captured on the electrode surface by hybridization with DNA NTH. Since signal probe P1 labeled-UiO-66 was close to the electrode, it leads to an increased signal current of UiO-66 at +0.9 V. As the conductivity of the modified electrode decreased, the current signal of [Fe(CN)6]3-/4- at +0.2 V also decreased. The proposed ratiometric electrochemical aptasensor could effectively eliminate external environmental influences and could avoid electrochemical background signals. The aptasensor demonstrated high specificity for OTA, and achieved a good linear range of 1 pg mL-1-100 ng mL-1 with a detection limit of 330 fg mL-1. The developed electrochemical aptamer biosensor effectively detected OTA in corn kernel samples, verifying its practical application for the determination of OTA in actual samples.

Single-Crystal-to-Single-Crystal Transformation of Two Copper(II) Metal-Organic Frameworks Modulated by Auxiliary Ligands.

The single-crystal-to-single-crystal (SCSC) transformations of metal-organic frameworks (MOFs) are fascinating because we can directly observe the change of the crystal structure during the transformation process. It also greatly helps to understand the delicate interaction between the guest molecules and the skeleton framework and therefore fosters a deep understanding of gas storage and separation within the frameworks. Herein, we report two novel MOFs, [Cu8(BCB)4(µ3-OH)2(µ3-O)(H2O)8(Py)5]·16DMF·52H2O (1) and [Cu3(BCB)2(Py)6]·DMF·11H2O (2) (Py = pyridine; DMF = N,N'-dimethylformamide), which were constructed through the self-assembly of Cu2+ and 4,4',4″-benzenetricarbonyltribenzoic acid (H3BCB) by a solvothermal reaction. Although the structure and coordination patterns of compound 1 are pretty different from those of 2, the two Cu-MOFs were prepared from identical ligands and similar reaction conditions. Interestingly, compound 1 will change to 2 wholly and gradually after the addition of a certain amount of Py with a small amount of dilute hydrochloric acid. This conversion represents a scarce example of SCSC transformation involving transition-metal-based MOFs. Moreover, with its microporous nature, compound 2 shows large carbon dioxide (CO2) uptake capability and good selectivity for CO2/N2 separation. Furthermore, both compounds 1 and 2 could be used as excellent heterogeneous catalysts toward the cyanosilylation reaction under solvent-free conditions.

Amino-functionalized perylenediimide derivative with dual fluorescence emission for the detection of ascorbic acid in vivo and in vitro.

The rapid, sensitive, and selective detection of ascorbic acid (AA) is of significance in medical assays and diagnostics. In this work, a new aminoperylenediimide (APDI) derived ratiometric fluorescent probe based on the specific redox reaction of cobalt oxyhydroxide (CoOOH) and AA was constructed. APDI exhibited dual fluorescence emission peaks at 549 and 596 nm with an excitation wavelength of 494 nm. In the presence of CoOOH, the dual fluorescence could be quenched. The dominant fluorescence quenching mechanism was caused by the inner filter effect. Using the red emission as a reference, the fluorescence intensity ratio (F549 /F596 ) was linearly correlated with the concentration of AA over a range of 0.05 to 1 µM. The limit of detection for AA was found to be 17 nM. Importantly, the probe was successfully used to detect AA in living cells. Therefore, this high sensitivity and selectivity strategy could directly survey the AA levels in real samples.

Glucometer-based electrochemical biosensor for determination of microRNA (let-7a) using magnetic-assisted extraction and supersandwich signal amplification.

A sensitive and portable biosensor is proposed for simple detection of microRNAs based on a supersandwich hybridization signal amplification strategy and a glucometer transducer. The presence of a target microRNA triggers the cascading hybridization chain reaction to create long supersandwich assemblies containing multiple biotin-labelled DNA probes. Then, large amounts of biotin-modified invertase signal molecules can attach to the supersandwich assemblies to generate an amplified signal for the glucometer readout. With such supersandwich format, a single target microRNA can introduce many biotin-invertase signal molecules, resulting in a one-to-multiple amplification effect. Thus, the accurate quantification of microRNAs can be achieved in a simple detection fashion without the requirement of expensive or precise instrumentation. The linear range of the biosensor for microRNA was from 0.05 to 100 nM with a detection limit of 48 pM. The proposed biosensor can discriminate the target microRNA from its family members with high selectivity and can be successfully applied to the detection of target microRNA spiked in serum samples with a good recovery (96.0-108.0%). Therefore, the proposed biosensor is expected to provide more information for early and accurate cancer diagnosis.

Clip-off Chemistry: Synthesis by Programmed Disassembly of Reticular Materials.

Bond breaking is an essential process in chemical transformations and the ability of researchers to strategically dictate which bonds in a given system will be broken translates to greater synthetic control. Here, we report extending the concept of selective bond breaking to reticular materials in a new synthetic approach that we call Clip-off Chemistry. We show that bond-breaking in these structures can be controlled at the molecular level; is periodic, quantitative, and selective; is effective in reactions performed in either solid or liquid phases; and can occur in a single-crystal-to-single-crystal fashion involving the entire bulk precursor sample. We validate Clip-off Chemistry by synthesizing two topologically distinct 3D metal-organic frameworks (MOFs) from two reported 3D MOFs, and a metal-organic macrocycle from metal-organic polyhedra (MOP). Clip-off Chemistry opens the door to the programmed disassembly of reticular materials and thus to the design and synthesis of new molecules and materials.

CT-based radiomics combined with signs: a valuable tool to help radiologist discriminate COVID-19 and influenza pneumonia.

BACKGROUND: In this COVID-19 pandemic, the differential diagnosis of viral pneumonia is still challenging. We aimed to assess the classification performance of computed tomography (CT)-based CT signs and radiomics features for discriminating COVID-19 and influenza pneumonia. METHODS: A total of 154 patients with confirmed viral pneumonia (COVID-19: 89 cases, influenza pneumonia: 65 cases) were collected retrospectively in this study. Pneumonia signs and radiomics features were extracted from the initial unenhanced chest CT images to build independent and combined models. The predictive performance of the radiomics model, CT sign model, the combined model was constructed based on the whole dataset and internally invalidated by using 1000-times bootstrap. Diagnostic performance of the models was assessed via receiver operating characteristic (ROC) analysis. RESULTS: The combined models consisted of 4 significant CT signs and 7 selected features and demonstrated better discrimination performance between COVID-19 and influenza pneumonia than the single radiomics model. For the radiomics model, the area under the ROC curve (AUC) was 0.888 (sensitivity, 86.5%; specificity, 78.4%; accuracy, 83.1%), and the AUC was 0.906 (sensitivity, 86.5%; specificity, 81.5%; accuracy, 84.4%) in the CT signs model. After combining CT signs and radiomics features, AUC of the combined model was 0.959 (sensitivity, 89.9%; specificity, 90.7%; accuracy, 90.3%). CONCLUSIONS: CT-based radiomics combined with signs might be a potential method for distinguishing COVID-19 and influenza pneumonia with satisfactory performance.

Enzyme-Powered Porous Micromotors Built from a Hierarchical Micro- and Mesoporous UiO-Type Metal-Organic Framework.

Here, we report the design, synthesis, and functional testing of enzyme-powered porous micromotors built from a metal-organic framework (MOF). We began by subjecting a presynthesized microporous UiO-type MOF to ozonolysis, to confer it with mesopores sufficiently large to adsorb and host the enzyme catalase (size: 6-10 nm). We then encapsulated catalase inside the mesopores, observing that they are hosted in those mesopores located at the subsurface of the MOF crystals. In the presence of H2O2 fuel, MOF motors (or MOFtors) exhibit jet-like propulsion enabled by enzymatic generation of oxygen bubbles. Moreover, thanks to their hierarchical pore system, the MOFtors retain sufficient free space for adsorption of additional targeted species, which we validated by testing a MOFtor for removal of rhodamine B during self-propulsion.

Amperometric immunosensor based on covalent organic frameworks and Pt/Ru/C nanoparticles for the quantification of C-reactive protein.

An ultrasensitive and nonenzymatic electrochemical sandwich-type immunoassay using covalent organic framework (COF-LZU1) material applied as a fixed matrix was developed for the determination of C-reactive protein (CRP). COFs with large specific surface area, good conductivity and stability were employed for functionalisation of the surface. Au nanoparticles were loaded on COF-LZUl to immobilise the CRP antibody (anti-CRP) on the surface of a glassy carbon electrode. Microwave method was employed for the synthesis of the Pt/Ru/C nanoparticles to imitate the protein enzyme with high catalytic activity. The as-synthesised activated carbon-supported bimetallic Pt/Ru/C nanoparticle composite was used to label secondary CRP antibody because it exhibited excellent catalytic behaviour toward hydrogen peroxide. After incubation of CRP, Pt/Ru/C-labelled anti-CRP was combined with CRP through specific antibody-antigen recognition process. The reduction current of H202 at - 0.2 V catalysing by tag Pt/Ru/C as measured by a chronoamperometric method is proportional to the concentration of CRP. Under optimal experimental conditions, employing chronoamperometry to investigate the CRP, the obtained linear range was 0.2 to 20 ng/mL with a detection limit of 0.1 ng/mL. This immunosensor provides an attractive platform for the applicability of COF-LZU1 materials and Pt/Ru/C nanoparticles in electrochemical assays. Graphical abstract An ultrasensitive and nonenzymatic electrochemical immunoassay using covalent organic frameworks (COF-LZU1) material as the fixed matrix was developed for the detection of C-reactive protein (CRP). Microwave method was employed to synthesis the bimetallic metal composites Pt/Ru/C nanoparticles, which exhibited excellent catalytic behavior toward small molecules H2O2. COFs with large specific surface area, good conductivity and stability were employed for surface functionalization. Our proposed biosensor is highly sensitive, with the detection limit of 0.1 ng/mL.

Manganese-Catalyzed Hydroarylation of Unactivated Alkenes.

Transition-metal-catalyzed hydroarylation of unactivated alkenes with strategic use of remote coordinating functional groups has received significant attention recently to address the issues of both low reactivity and poor selectivity. The bidentate 8-aminoquinoline amide group is the most successfully adopted in unactivated alkenes for Pd and Ni catalysis. We describe the first manganese-catalyzed hydroarylation of unactivated alkenes bearing diverse simple functionalities with arylboronic acids. A series of δ- and γ-arylated amides, ketones, pyridines, and amines was accessed with excellent regioselectivity and in high yields. Hydroalkenylation of unactivated alkenes was also shown to be applicable under this manganese-catalysis regime. The method features earth-abundant manganese catalysis, easily available substrates, broad functional-group tolerance, and excellent regioselective control.

Re-Catalyzed Annulations of Weakly Coordinating N-Carbamoyl Indoles/Indolines with Alkynes via C-H/C-N Bond Cleavage.

Described herein are rhenium-catalyzed [3+2] annulations of N-carbamoyl indoles with alkynes via C-H/C-N bond cleavage, which provide rapid access to fused-ring pyrroloindolone derivatives. For the first time, the weakly coordinating O-directing group was successfully employed in rhenium-catalyzed C-H activation reactions, enabled by the unique catalytic trio of Re2 (CO)10 , Me2 Zn and ZnCl2 . Mechanistic studies revealed that aminozinc species plays an important role in the reaction. Based on the mechanistic understanding, a more powerful catalytic trio of Re2 (CO)10 , [MeZnNPh2 ]2 and Zn(OTf)2 was devised and applied successfully in the [4+2] annulations of indolines and alkynes affording pyrroloquinolinone derivatives.

The Preparation of C-Reactive Protein Immunosensor Based on Amino Graphene and Hollow Silver Platinum Nanomaterials.

A novel and sensitive nonenzymatic sandwich-type electrochemical immunosensor was developed for the detection of C-reactive protein. The catalytic activity of Ag/Pt nanomaterials that possessed an intrinsic enzyme catalytic activity similar to that of horseradish peroxidase (HRP) was utilized as a label to improve the stability and sensitivity using amino graphene as an immobilization matrix. Comparing with the common methods of using HRP as labels for electrochemical detection, Ag/Pt nanoparticles might have longer lifetime than that of enzymes. As far as know, there is no other report using Ag/Pt as catalytic labels for electrocatalyzed reduction of H2O2 to fabricate the amperometric immunosensor. Under the optimized experimental conditions, the detection range of the sensor is from 0.5 ng/mL to 140 ng/mL with a linear correlation coefficient of 0.9934 and the detection limit of 0.17 ng/mL at 3σ . The sensor has good stability, reproducibility and high sensitivity. Therefore, the immunosensor is promising for applications in point-of-care diagnostics.

Metal-Organic Framework Nanomaterials as Novel Signal Probes for Electron Transfer Mediated Ultrasensitive Electrochemical Immunoassay.

A novel and simple electrochemical immunoassay for C-reactive protein was developed using metal-organic frameworks (Au-MOFs) as signal unit. In this study, we found MOFs could be used as signal probe. And this new class of signal probe differs from traditional probe. The signal of the copper ions (Cu2+) from MOFs could be directly detected without acid dissolution and preconcentration, which would greatly simplify the detection steps and reduce the detection time. Moreover, MOFs contain large amounts of Cu2+ ions, providing high electrochemical signals. Our report represents the first example of using MOFs themselves as electrochemical signal probe for biosensors. Platinum nanoparticle modified covalent organic frameworks (Pt-COFs) with high electronic conductivity was employed as the substrate, which is the first time demonstrating the use of Pt-COFs for electrochemical immunoassay. Under the optimized experimental conditions, the proposed sensing strategy provides a linear dynamic ranging from 1 to 400 ng/mL. A detection limit of 0.2 ng/mL was obtained, indicating an improved analytical performance. With these merits, this stable, simple, low-cost, sensitive and selective electrochemical immunoassay shows promise for applications in the point-of-care diagnostics of dieses and environmental monitoring.

DLISA: A DNAzyme-Based ELISA for Protein Enzyme-Free Immunoassay of Multiple Analytes.

A DNAzyme-based ELISA, termed DLISA, was developed as a novel protein enzyme-free, triply amplified platform, combining a catalytic and molecular beacon (CAMB) system with a cation exchange reaction for ultrasensitive multiplex fluorescent immunosorbent assay. Classical ELISA, which employs protein enzymes as biocatalysts to afford amplified signals, suffers from poor stability caused by the irreversible denaturation of these enzymes under harsh conditions, such as heat and acidity. Compared with proteins, nucleic acids are more stable and adaptable, and they can be easily produced using a commercial DNA synthesizer. Moreover, the catalytic and cleavage activities of DNAzyme can be achieved in solution; thus, no enzyme immobilization is needed for detection. Taken together, these attributes suggest that a DNAzyme-based ELISA detection approach will be more robust than current ELISA assays. Importantly, the proposed triply amplified DLISA immunoassay method shows ultrasensitive detection of such targets as human IgG with a detection limit of 2 fg/mL (3 × 10(-17) M), which is well within the range of many important disease biomarkers. DLISA can also be used to construct a sensing array for simultaneous multiplexed detection. With these merits, this high-throughput, stable, simple, sensitive, and low-cost multiplex fluorescence immunoassay shows promise for applications in clinical diagnosis.

A Novel Sensitive Electrochemical Sensor for Podophyllotoxin Assay Based on the Molecularly Imprinted Poly-o-Phenylenediamine Film.

An electrochemical sensor for podophyllotoxin (PPT) based on the molecular imprinting polymer (MIP) membranes was constructed. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of PPT as template, and then removing the template by immersing the modified GCE in ethanol. Experimental parameters such as the types of monomer, scan cycles, concentration of o-PD and extraction condition were optimized. Under optimal conditions, the sensor exhibits a good selectivity and high sensitivity. A good linearity was obtained in the range of 4 x 10-8 mol · L(-1) to 3.2 x 10(-5) mol · L(-1) with an estimated detection limit of 4.8 x 10(-9) mol · L(-1). The sensor was applied to the determination of PPT in podophyllum hexandrum and human serum samples with satisfactory results.