ATP‐dependent DNA binding,unwinding, and resection by the Mre11/Rad50 complex

ATP‐dependent DNA end recognition and nucleolytic processing are central functions of the Mre11/Rad50 (MR) complex in DNA double‐strand break repair. However, it is still unclear how ATP binding and hydrolysis primes the MR function and regulates repair pathway choice in cells. Here, Methanococcus jannaschii MR‐ATPγS‐DNA structure reveals that the partly deformed DNA runs symmetrically across central groove between two ATPγS‐bound Rad50 nucleotide‐binding domains. Duplex DNA cannot access the Mre11 active site in the ATP‐free full‐length MR complex. ATP hydrolysis drives rotation of the nucleotide‐binding domain and induces the DNA melting so that the substrate DNA can access Mre11. Our findings suggest that the ATP hydrolysis‐driven conformational changes in both DNA and the MR complex coordinate the melting and endonuclease activity.     

利用超高效液相色谱和离子色谱法测定注射用磷酸川芎嗪的含量

目的:建立超高效液相色谱法(UPLC)和离子色谱法(IC)测定磷酸川芎嗪中川芎嗪和磷酸的含量,为质量评价提供依据。方法:UPLC测定川芎嗪的色谱柱为Waters Acquity BEH C18 (2.1 mm×50 mm,1.7μm);检测波长:300 nm检测川芎嗪,274 nm检测有关物质邻苯二甲酸二甲酯;流动相为0.1%甲酸水溶液(A)-0.1%甲酸乙腈(B),梯度洗脱(0.0～0.8 min,10%B→90%B;0.8～0.81 min,90%B→10%B;0.81～1.00 min,10%B),流速:0.7 m L/min。IC测定磷酸的离子交换色谱柱为Dionex IonPac AS11-HC-4μm (4×250 mm),流动相为30 mmol/L KOH溶液等度洗脱15 min,流速1.0 m L/min,柱温35℃;电导检测器;抑制器电流为50 m A。结果:川芎嗪和磷酸在10～100 g/m L内具有良好的线性关系,相关系数均为1.0,UPLC法测定川芎嗪的回收率为102.0%。IC测定磷酸的回收率为99.8%。7个公司生产的注射剂中川芎嗪的含量均在药典规定的范围90%～110%内。但是其中3个公司生产的注射剂磷酸超出药典规定范围90%～110%。结论:与常规HPLC/UPLC测定磷酸川芎嗪含量方法比较,本文所用方法测定结果更加准确、全面、且重复性好,能够真实反应注射用磷酸川芎嗪的实际含量,对于注射用磷酸川芎嗪的安全性和有效性评估提供了一定的依据。     

Informing native plant sourcing for ecological restoration: cold‐hardiness dynamics,flowering phenology,and survival of Eriogonum umbellatum

Despite advances in restoration of degraded lands around the world, native plants are still underutilized. Selection of appropriate plant materials is a critical factor in determining plant establishment and persistence. To better inform decision‐making, we examined cold‐hardiness dynamics, flowering phenology, and survival among five geographically distinct sulfur‐flower buckwheat (Polygonaceae: Eriogonum umbellatum Torr.) populations in a common garden. LT₅₀ (a measure of freezing injury) was determined every 6 weeks across a complete year; one population was also evaluated at the source. Cold‐hardiness dynamics were similar across populations, with annual fluctuations in mean LT₅₀ exceeding 40°C. Rate of deacclimation (i.e. loss of cold tolerance) in spring varied across populations and was not related to the elevation from which a population came. Plants were less cold hardy in October 2014 compared to October 2013, likely reflecting a response to colder local conditions in 2013. Although the range of LT₅₀ was similar for a single comparison of common garden versus wild‐grown plants, wild‐grown plants acclimated and deacclimated earlier than common garden‐grown plants. Plants derived from a low‐elevation population showed delayed flowering phenology, while high‐elevation populations showed earlier flowering phenology, with one high‐elevation population having the lowest survival rate in the common garden. These results suggest that while considerable plasticity in seasonal cold‐hardiness dynamics occur, population variability in deacclimation and flowering phenology have implications for selection and movement of sulfur‐flower buckwheat for ecological restoration.     

Interleukin-13 interferes with CFTR and AQP5 expression and localization during human airway epithelial cell differentiation

Interleukin-13 (IL-13) is a central regulator of Th2-dominated respiratory disorders such as asthma. Lesions of the airway epithelial barrier frequently observed in chronic respiratory inflammatory diseases are repaired through proliferation, migration and differentiation of epithelial cells. Our work is focused on the effects of IL-13 in human cellular models of airway epithelial cell regeneration. We have previously shown that IL-13 altered epithelial cell polarity during mucociliary differentiation of human nasal epithelial cells. In particular, the cytokine inhibited ezrin expression and interfered with its apical localization during epithelial cell differentiation in vitro. Here we show that CFTR expression is enhanced in the presence of the cytokine, that two additional CFTR protein isoforms are expressed in IL-13-treated cells and that part of the protein is retained within the endoplasmic reticulum. We further show that aquaporin 5 expression, a water channel localized within the apical membrane of epithelial cells, is completely abolished in the presence of the cytokine. These results show that IL-13 interferes with ion and water channel expression and localization during epithelial regeneration and may thereby influence mucus composition and hydration.     

Solution structure of agelenin, an insecticidal peptide isolated from the spider Agelena opulenta, and its structural similarities to insect-specific calcium channel inhibitors

Agelenin, isolated from the Agelenidae spider Agelena opulenta, is a peptide composed of 35 amino acids. We determined the three-dimensional structure of agelenin using two-dimensional NMR spectroscopy. The structure is composed of a short antiparallel beta-sheet and four beta-turns, which are stabilized by three disulfide bonds. Agelenin has characteristic residues, Phe9, Ser28 and Arg33, which are arranged similarly to the pharmacophore of the insect channel inhibitor, omega-atracotoxin-Hv1a. These observations suggest that agelenin and omega-atracotoxin-Hv1a bind to insect calcium channels in a similar manner. We also suggest that another mode of action may operate in the channel inhibition by omega-agatoxin-IVA and omega-atracotoxin-Hv2a.     

Taenia crassiceps organic acids detected in cysticerci

Taenia crassiceps cysticerci is used as an experimental model to cysticercosis studies; however there are subcutaneous cases of cysticercosis caused by these cysticerci. It remains unclear in the literature the energetic and fatty acid metabolism in cestodes. Its metabolic study may provide knowledge of pathways that may serve as potential anti-helminthic drugs sites of action. In this work we studied the citric acid cycle organic acids and the fatty acid oxidation in cysticerci removed from mice with 21 and 42 days of infection in two different evolutive stages: growing and final. The organic acids were extracted using perchloric acid and analyzed by HPLC methodology. We found significant statistically differences in oxalate, malate, lactate, and beta-hydroxybutirate concentrations between cysticerci. These results indicate the aerobic metabolism in vivo in spite of the low oxygen concentration of its habitat, and also indicate the presence of fatty acid oxidation as an alternative energetic source.     

Recent advancement in the discovery and development of COX-2 inhibitors: Insight into biological activities and SAR studies (2008–2019)

Cyclooxygenase-2 is a very important physiological enzyme playing key roles in various biological functions especially in the mechanism of pain and inflammation, among other roles, making it a molecule of high interest to the pharmaceutical community as a target. COX 2 enzyme is induced only during inflammatory processes or cancer and reflects no role in the guarding stomach lining. Thus, selective COX-2 inhibition can significantly reduce the adverse effects including GI tract damage and hepatotoxic effects of traditional NSAIDs like aspirin, ibuprofen, etc. Recent developments on COX-2 inhibitors is primarily focused on improving the selectivity index of the drug towards COX-2 along with enhancing the potency of the drug by modifying the scaffolds of Coxibs currently in the market like Celecoxib, Indomethacin, Oxaprozin, etc. We have reported the progress on new COX-2 inhibitors in the last decade (2008–2019) focussing on five heterocyclic rings- Pyrazole, Indole, Oxazole, Pyridine and Pyrrole. The addition of various moieties to these core rings and their structure-activity relationship along with their molecular modelling data have been explored in the article. This review aims to aid medicinal chemists in the design and discovery of better COX-2 inhibitors constructed on these five heterocyclic pharmacophores.