Development of an Organic Dye-Conjugated β-Diketonate-Europium Complex Luminescence Probe for Discrimination and Detection of Intracellular Biothiols

Small molecular biothiols, cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in organisms, and their concentration levels are indicative of some human diseases. Herein we report an organic dye-conjugated β-diketonate-Eu³⁺ complex, [Eu(NBD-keto)₃(DPBT)] (NBD-keto: 7-nitro-2,1,3-benzoxadiazole (NBD)-conjugated to 1,1,1,2,2-pentafluoro-5-phenyl-3,5-pentanedionate through a “O” ether bond; DPBT: 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine), which acts as a unique luminescent probe for detecting and discriminating biothiols. [Eu(NBD-keto)₃(DPBT)] itself is not luminescent due to intramolecular interactions between NBD and β-diketonate-Eu³⁺ moieties. Upon reaction with biothiols, the β-diketonate-Eu³⁺ complex [Eu(keto)₃(DPBT)] is generated, which emits long-lived red emission at 610 nm. Meanwhile, three biothiol-substituted NBD derivatives that exhibit different luminescence behaviors, green emissive (short-lived) NBD-NR (R=Cys or Hcy) at 540 nm and non-luminescent NBD-SR (R=GSH), are also generated. These luminescence response behaviors allow time-gated and steady-state luminescence modes to be combined for detecting total biothiols and discriminating GSH and Cys/Hcy. Using this probe, the quantitative detection and discrimination of GSH and Cys/Hcy in lysis solutions of HeLa cells were realized, which revealed the potential of the probe for biomedical applications.     

Stereodivergent synthesis of enantioenriched azepino[3,4,5-cd]-indoles via cooperative Cu/Ir-catalyzed asymmetric allylic alkylation and intramolecular Friedel–Crafts reaction

The development of enantioselective annulation reactions using readily available substrates for the construction of structurally and stereochemically diverse heterocycles is a compelling topic in diversity-oriented synthesis. Herein, we report efficient catalytic asymmetric formal 1,3-dipolar (3 + 4) cycloadditions of azomethine ylides with 4-indolyl allylic carbonates for the construction of azepino[3,4,5-cd]-indoles fused with a challenging seven-membered N-heterocycle, a frequently occurring tricyclic indole scaffold in bioactive compounds and pharmaceuticals. Through cooperative Cu/Ir-catalyzed asymmetric allylic alkylation followed by intramolecular Friedel–Crafts reaction, an array of azepino[3,4,5-cd]-indoles were obtained in good yields with excellent diastereo-/enantioselective control. More importantly, the full stereodivergence of this transformation was established via synergistic catalysis followed by acid-promoted epimerization, and up to eight stereoisomers of the cycloadducts bearing three stereogenic centers could be predictably achieved from the same set of starting materials for the first time. Quantum mechanical computations established a plausible mechanism for the synergistic Cu/Ir catalysis to stereodivergently introduce two vicinal stereocenters whose stereochemical information is remotely delivered across the fused azepine ring to control the third chiral center. Epimerization of the last center involves protonation-enabled reversal of the thermodynamically controlled relative configuration.

A stereodivergent synthesis of azepino[3,4,5-cd]-indoles bearing three stereogenic centers was established via synergistic dual-metal catalysis followed by acid-promoted epimerization, and up to all eight stereoisomers could be predictably achieved.     

The Inhibition of Gastric Cancer Cells’ Progression by 23,24-Dihydrocucurbitacin E through Disruption of the Ras/Raf/ERK/MMP9 Signaling Pathway

Gastric cancer is considered to be one of the most common causes of cancer death worldwide due to its high recurrence and metastasis rates. The molecule 23,24-Dihydrocucurbitacin E (DHCE) is a cucurbitacin-derived tetracyclic triterpenoid compound that has anti-tumor activity, but the exact mechanism remains to be elucidated. This research aimed to explore the effects of DHCE on human gastric cancer cells and the possible mechanisms. The results showed that DHCE suppressed proliferation, migration, and invasion of gastric cancer cells, as well as induced apoptosis and G2/M phase arrest. Mechanistically, the potential targets and pathways of DHCE were predicted using database screening and verified using a molecular docking study, fluorescence staining, and Western blot. The results indicated that DHCE obviously inhibited the kinase activity of ERK2 via targeting its ATP-binding domain, destroyed F-actin microfilament, and reduced the expression levels of Ras, p-c-Raf, ERK, p-ERK, and MMP9 proteins. Collectively, our study demonstrated that DHCE suppressed gastric cancer cells’ proliferation, migration, and invasion through targeting ERK2 and disrupting the Ras/Raf/ERK/MMP9 signaling pathway. These properties make DHCE a promising candidate drug for the further design and development of novel and effective Ras/Raf/ERK/MMP9 pathway inhibitors for treating gastric cancer.     

Optimization of Naringenin Nanoparticles to Improve the Antitussive Effects on Post-Infectious Cough

Naringenin (NRG) is a natural compound with several biological activities; however, its bioavailability is limited owing to poor aqueous solubility. In this study, NRG nanoparticles (NPs) were prepared using the wet media milling method. To obtain NRG NPs with a small particle size and high drug-loading content, the preparation conditions, including stirring time, temperature, stirring speed, and milling media amount, were optimized. The NRG (30 mg) and D-α-tocopherol polyethylene glycol succinate (10 mg) were wet-milled in deionized water (2 mL) with 10 g of zirconia beads via stirring at 50 °C for 2 h at a stirring speed of 300 rpm. As a result, the NRG NPs, with sheet-like morphology and a diameter of approximately 182.2 nm, were successfully prepared. The NRG NPs were stable in the gastrointestinal system and were released effectively after entering the blood circulation. In vivo experiments indicated that the NRG NPs have good antitussive effects. The cough inhibition rate after the administration of the NRG NPs was 66.7%, cough frequency was three times lower, and the potential period was 1.8 times longer than that in the blank model group. In addition, the enzyme biomarkers and histological analysis results revealed that the NRG NPs can effectively regulate the inflammatory and oxidative stress response. In conclusion, the NRG NPs exhibited good oral bioavailability and promoted antitussive and anti-inflammatory effects.     

Stepwise Diagnostic Product Ions Filtering Strategy for Rapid Discovery of Diterpenoids in Scutellaria barbata Based on UHPLC-Q-Exactive-Orbitrap-MS

Diterpenoids are considered the major bioactive components in Scutellaria barbata to treat cancer and inflammation, but few comprehensive profiling studies of diterpenoids have been reported. Herein, a stepwise diagnostic product ions (DPIs) filtering strategy for efficient and targeted profiling of diterpenoids in Scutellaria barbata was developed using UHPLC-Q-Exactive-Orbitrap-MS. After UHPLC-HRMS/MS analysis of six diterpenoid reference standards, fragmentation behaviors of these references were studied to provide DPIs. Then, stepwise DPIs filtering aimed to reduce the potential interferences of matrix ions and achieve more chromatographic peaks was conducted to rapidly screen the diterpenoids. The results demonstrated that stepwise DPIs were capable of simplifying the workload in data post-processing and the effective acquisition of low abundance compounds. Subsequently, DPIs and MS/MS fragment patterns were adopted to identify the targeted diterpenoids. As a result, 381 diterpenoids were unambiguously or tentatively identified, while 141 of them with completely new molecular weights were potential new diterpenoids for Scutellaria barbata. These results demonstrate that the developed stepwise DPIs filtering method could be employed as an efficient, reliable, and valuable strategy to screen and identify the diterpenoid profile in Scutellaria barbata. This might accelerate and simplify target constituent profiling from traditional Chinese medicine (TCM) extracts.     

Synthesis and characterization of ABA-type block copolymer of poly(trimethylene carbonate) with poly(ethylene glycol): Bioerodible copolymer

ABA-type block copolymers of poly(trimethylene carbonate) with poly(ethylene glycol) (M_n 6820), PTMC-b-PEG-b-PTMC, were synthesized by the ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) in the presence of poly-(ethylene glycol) with stannous octoate catalyst, and the copolymers with various compositions were obtained. The PTMC-b-PEG-b-PTMC copolymers were characterized with Fourier transform infrared and nuclear magnetic resonance spectroscopies. The intrinsic viscosities of resulting copolymers increased with the increase of 1,3-dioxan-2-one content in feed while the molar ratio of monomer over catalyst kept constant. It has been observed that the glass transition temperature (T_g) of the PTMC segments in copolymers, recorded from differential scanning calorimetry, was dependent on the composition of copolymers. The melting temperature (T_m) of PEG blocks in copolymer was lower than that of PEG polymer, and then disappeared as the length of PTMC blocks increased. The results of dynamic contact angle measurement clearly revealed that the hydrophilicity of resulting copolymers increased greatly with the increase of PEG content in copolymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 695–702, 1998     

微乳液介质-对乙酰基偶氮氯膦光度法测定微量的锆

研究了在微乳液介质中锆与对乙酰基偶氮氯膦显色反应的条件。络合物的最大吸收波长在685nm处,锆含量在0～30μg/25mL的范围内符合比尔定律,表观摩尔吸光系数为3.0×10~4L/(mol·cm),络合物的络合比为1:1。对乙酰基偶氮氯膦与锆的显色反应体系稳定性及重现性较好。直接用于实际样品的测定,结果较好。     

Sorption and desorption of radioselenium on red earth and its solid components

The effect of organic matter and iron oxides as solid components of the red earth on the retention of SeO₃ has been investigated by a batch technique and selective extraction method. The sorption and desorption isotherms of SeO₃ on the untreated red earth and the three treated soils were determined at 20°C, pH 6.8 or 7.2 and in the presence of 0.01M CaCl₂. It was found that the sorption-desorption hysteresis for untreated an treated soils is obvious and the clays play an important role in the sorption-desorption hysteresis, and that the retention of SeO₃ on red earth is attributed to the iron oxides to a great extent.     

Theoretical study of properties of H bonds and intermolecular interactions in linear cis-,trans-cyclotriazane clusters (n = 2-8)

Our calculations based upon Becke's three-parameter functional of density-functional theory (DFT) with the correlation of Lee, Yang, and Parr (B3LYP), natural bond orbital, and atoms in molecule indicate that in drastic contrast to most H-bonded systems, the anticooperative and cooperative effects coexist in the linear H-bonded cis-,trans (c,t)-cyclotriazane clusters (n = 2-8). As cluster size increases, the properties along the H-bonded chains at trans-positions take on the unexpectedly anticooperative changes which are reflected in elongation of the N...H hydrogen bonds, frequency blueshift in the N-H stretching vibrations, decay in the n(N)-->sigma*(N-H) charge transfers, and weakening of strengths of the N...H bonds. And the cooperative changes in the corresponding properties for the cis- H-bonded chains are observed to be concurrent with the anticooperativities. The rise and fall in the n(N)-->sigma*(N-H) interactions cause increment and decrement in capacities of the clusters to concentrate electrons at the bond critical points of the N...H bonds, and thereby leading to the cooperative and the anticooperative changes especially in the N...H lengths and the N-H stretching frequencies. In terms of three-body symmetry-adapted perturbation theory (three-body SAPT), the first exchange nonadditivity plays a more important role in stabilizing trimer than the nonadditive induction. However, the dominance of the first exchange nonadditivity in three-body interaction unexpectedly triggers the anticooperative effect that counteracts the concurrent cooperative effect. According to the SAPT(DFT), which is a combination of SAPT with asymptotically corrected DFT, DFT/B3LYP is able to succeed in describing the electrostatic, exchange, and induction components, but fails to yield satisfactory interaction energies due to the fact that about 40% of short-range dispersion energy is neglected by the DFT, which is different from many H-bonded described well by the DFT. A quantum cluster equilibrium model illustrates that the c,t-cyclotriazane liquid phase exhibits a weak cooperative effect.     

Expression of hepatitis C virus nonstructural 4B in transgenic mice

Hepatitis C virus (HCV) is a pathogen that is of great medical significance in chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Although the HCV proteins have been intensively investigated over the past decade, the biochemical functions of the NS4B protein are still largely unknown. To investigate NS4B as a potential causative agent of liver disease, transgenic mice expressing the NS4B protein in liver tissue were produced. The transgenic animals were phenotypically similar to their normal littermates for up to 18 months of age. Our results suggest that the HCV NS4B protein is not directly cytopathic or oncogenic in our transgenic mice model.