Stereogenic-at-Cobalt(III) Complex Catalyzed Halocyclization of Alkynes: Enantioselective Access to Axially Chiral ortho-Halo-C2-indoles.

Here, we report an anionic stereogenic-at-cobalt(III) complex catalysis strategy for the enantioselective halocyclization of ortho-alkynylanilines using N-halosuccinimide (NXS) as the halogen source. This protocol provides a distinct atroposelective approach to access the axially chiral ortho-halo-C2-indole skeletons in excellent yields with good to high enantioselectivities (up to 99% yield, 99:1 er).

Electrodeposition of chitosan/graphene oxide conduit to enhance peripheral nerve regeneration.

Currently available commercial nerve guidance conduits have been applied in the repair of peripheral nerve defects. However, a conduit exhibiting good biocompatibility remains to be developed. In this work, a series of chitosan/graphene oxide (GO) films with concentrations of GO varying from 0-1 wt% (collectively referred to as CHGF-n) were prepared by an electrodeposition technique. The effects of CHGF-n on proliferation and adhesion abilities of Schwann cells were evaluated. The results showed that Schwann cells exhibited elongated spindle shapes and upregulated expression of nerve regeneration-related factors such as Krox20 (a key myelination factor), Zeb2 (essential for Schwann cell differentiation, myelination, and nerve repair), and transforming growth factor ß (a cytokine with regenerative functions). In addition, a nerve guidance conduit with a GO content of 0.25% (CHGFC-0.25) was implanted to repair a 10-mm sciatic nerve defect in rats. The results indicated improvements in sciatic functional index, electrophysiology, and sciatic nerve and gastrocnemius muscle histology compared with the CHGFC-0 group, and similar outcomes to the autograft group. In conclusion, we provide a candidate method for the repair of peripheral nerve defects using free-standing chitosan/GO nerve conduits produced by electrodeposition.

Anti-infammatory scalemic chromanoids and chromenoids from Rhododendron dauricum.

Four pairs of undescribed chromane and chromene meroterpenoid scalemic mixtures (1a/1b-4a/4b), together with three pairs of known chromane meroterpenoid ones (5a/5b-7a/7b) were isolated from the twigs and leaves of Rhododendron dauricum L. Among them, 1a/1b-3a/3b and 5a/5b-7a/7b were the chromane ones derived from an intramolecular [2 + 2] cyclic addition of their respective chromene precursors, forming a 6/6/6/4 and 6/6/5/4 ring fused scaffold. The absolute configurations of the chiral center at C-15 of 2a/2b were determined by Snatzke's method, and comparing the experimental and calculated electronic circular dichroism (ECD) data. The inhibitory effects of the isolated compounds were tested against lipopolysaccharide (LPS)-induced nitric oxide production in RAW264.7 macrophage cells to evaluate their anti-inflammatory activity. Compounds 4a, 4b and 6a displayed inhibitory effects on nitric oxide (NO) production, and compound 4b exhibited the obvious anti-inflammatory activity, with an IC50 value of 6.91 ± 0.97 µM, by downregulating nuclear factor kappa B (NF-κB) and reducing the expression of inducible nitric oxide synthase (iNOS) in LPS-induced RAW264.7 cells. These results intimated that 4b could be used as a leading compound to develop anti-inflammatory drugs and is worthy of further investigated.

CRISPR-Cas12a-based efficient electrochemiluminescence biosensor for ATP detection.

CRISPR-Cas12a system exhibits tremendous potential in accurate recognition and quantitation of nucleic acids and non-nucleic-acid targets thanks to the discovery of its cleavage capability toward single-stranded DNA (ssDNA). In this study, we developed an efficient electrochemiluminescence (ECL) sensing platform based on CRISPR-Cas12a for the analysis of adenosine triphosphate (ATP). In the presence of the target, the successful release of the DNA activator is specially recognized by Cas12a-crRNA duplex and activates the cleavage of ferrocene (Fc) labeled-ssDNA (Fc-ssDNA) modified on the cathode of bipolar electrode (BPE), resulting in a decrease of ECL intensity of [Ru(bpy)3]2+/TPrA in the anodic cell of BPE. By means of the unique combination of Cas12a with ECL technique based on BPE, it can convert the recognition of target ATP into a detectable ECL signal. The detection limit of ATP was determined to be 0.48 nM under the optimal conditions. This work will expand the application of CRISPR-Cas detection system and propose a potential method for the analysis of non-nucleic-acid targets.

Postmortem nucleotide degradation in turbot mince during chill and partial freezing storage.

Nucleotide degradation in fish is an important biochemical change after death, which is closely related to freshness and sensory quality. However, except ATP-relative nucleotides, it remains unclear about changes in other nucleotide metabolites during postmortem stage. In this study, a strategy for the simultaneous quantification of 28 nucleobases, nucleosides, and nucleotides using hydrophilic interaction chromatography coupled with tandem mass spectrometry (HILIC-MS/MS) with positive/negative ion switching was developed. This method showed good linearity, precision, repeatability, and recovery. Furthermore, it was successfully applied to monitor the postmortem nucleotide degradation of turbot mince during chill (4 °C) and partial freezing (-3 °C) storage for 168 h. It was noted that the patterns of the changes in nucleotide metabolites differed considerably depending on the storage temperature. Meanwhile, the different pathway and speed of nucleotide catabolism in turbot mince was summarized based on the quantification data.

High-Throughput, Rapid Quantification of Phthalic Acid Esters and Alkylphenols in Fish Using a Coated Direct Inlet Probe Coupled with Atmospheric Pressure Chemical Ionization.

Intake of endocrine-disrupting chemicals (EDCs) by humans could disturb the metabolism of hormones, induce cancer, and damage the liver and other organs. Phthalate acid esters (PAEs) and alkylphenols (APs) are important EDCs and environmental contaminants. With the increasing use of plastics and nonionic surfactants worldwide, PAEs and APs have entered environmental water and accumulated in edible fish, which are finally consumed by humans. In this study, a coated direct inlet probe (CDIP) based on an atmospheric solid analysis probe, which can rapidly and simultaneously extract both PAEs and APs in fish, was developed. Twelve PAEs and APs were quantified by using a stable-isotope-labeled internal standard. Standard curves of the PAEs and APs having correlation coefficients of R2 ≥ 0.9837 were obtained. The limit of detection of the PAEs and APs was distributed from 0.01 to 40 ng g-1. The relative recovery of the method was 78-120% between low, medium, and high spiked levels. Combined with principal component analysis, PAE- and AP-contaminated Carassius auratus from different habitats could be identified. Multiple sample analysis mode allowed the extraction of up to 12 samples at once, and the total analysis time (including sample pretreatment, extraction, and analysis time) was less than 10 min per sample, which indicates that CDIP is useful for rapid quantitative analysis.

Coated direct inlet probe coupled with atmospheric-pressure chemical ionization and high-resolution mass spectrometry for fast quantitation of target analytes.

The coated direct inlet probe (CDIP) is a new laboratory-made low-cost technology developed from a direct inlet probe (DIP), which has the advantage of quick enrichment/cleanup of an analyte from liquid samples. A capillary probe is coated with hydroxy-terminated polydimethylsiloxane (OH-PDMS), divinylbenzene (DVB), and ß-cyclodextrin (ß-CD) by a sol-gel method. This probe can be directly coupled with a commercialized atmospheric-pressure chemical ionization (APCI) ion source and high-resolution mass spectrometry, which are widely applicable, reliable, and durable. The ability to perform quantitative analyses with the use of a stable-isotope-labeled internal standard (SIL-IS) was tested by using different concentrations of acenaphthylene (ACY), acenaphthene (ACP), fluorene (FLR), fluoranthene (FLT), phenanthrene (PHE), and benzo[a]pyrene (B[a]P). Calibration curves with a coefficient of determination of R2 ≥ 0.9982 for different polycyclic aromatic hydrocarbons (PAHs) were obtained. A limit of detection (LOD) of 0.008-0.04 ng mL-1 for PAHs was determined. The entire workflow is solvent-free and can be completed in less than 5 min, which demonstrates the advantages of this technique for quantitative analysis.

Unfolding/Refolding Study on Collagen from Sea Cucumber Based on 2D Fourier Transform Infrared Spectroscopy.

We aimed to explore the differences of thermal behaviors between insoluble collagen fibrils (ICFs) and pepsin-solubilized collagens (PSCs) from sea cucumber Stichopus japonicus. The unfolding/refolding sequences of secondary structures of ICFs and PSCs during the heating and cooling cycle (5 → 70 → 5 °C) were identified by Fourier transform infrared spectrometry combined with curve-fitting and 2D correlation techniques. ICFs showed a higher proportion of α-helical structures and higher thermostability than PSCs, and thus had more-stable triple helical structures. The sequences of changes affecting the secondary structures during heating were essentially the same between ICFs and PSCs. In all cases, α-helix structure was the most important conformation and it disappeared to form a ß-sheet structure. In the cooling cycle, ICFs showed a partially refolding ability, and the proportion of ß-sheet structure rose before the increasing proportion of α-helix structure. PSCs did not obviously refold during the cooling stage.

Comparison of high ligation and stripping of the great saphenous vein combined with foam sclerotherapy versus conventional surgery for the treatment of superficial venous varicosities of the lower extremity.

The aim of this study was to compare the results of high ligation and stripping of the great saphenous vein (GSV) trunk combined with foam sclerotherapy with conventional surgery for the treatment of superficial venous varicosities of the lower extremity. One hundred and thirty eight patients with primary or secondary superficial venous varicosities of the lower extremity were included. 60 underwent conventional surgery and 78 were treated with high ligation and stripping of the GSV trunk and foam sclerotherapy of GSV branches, spider veins, and reticular veins. Surgical time and amount of bleeding of single limb, recurrence of varicose vein, complications and patients satisfactory were recorded. Compared with the conventional surgery group, the GSV trunk stripping and foam sclerotherapy group had a significantly lower surgical time (P < 0.05), amount of bleeding and duration of hospital stays (P < 0.01). No statistically significant difference with respect to the wound infection, local discomfort, postoperative recurrence rates of varicosity and patients satisfaction score was observed (P > 0.05). GSV trunk stripping and foam sclerotherapy group at a 6 months of follow up had a higher recurrence rate of varicosity as compared to the conventional surgery group (P < 0.05). High ligation and GSV trunk stripping combined with foam sclerotherapy prior to conventional surgery for patients with superficial venous varicosities of the lower extremity with a shorter surgical time, fewer bleeding, duration of hospital stays and higher patients satisfactory scores.