22 research outputs found

    RNase-Resistant Virus-Like Particles Containing Long Chimeric RNA Sequences Produced by Two-Plasmid Coexpression Systemâ–ż

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    RNase-resistant, noninfectious virus-like particles containing exogenous RNA sequences (armored RNA) are good candidates as RNA controls and standards in RNA virus detection. However, the length of RNA packaged in the virus-like particles with high efficiency is usually less than 500 bases. In this study, we describe a method for producing armored L-RNA. Armored L-RNA is a complex of MS2 bacteriophage coat protein and RNA produced in Escherichia coli by the induction of a two-plasmid coexpression system in which the coat protein and maturase are expressed from one plasmid and the target RNA sequence with modified MS2 stem-loop (pac site) is transcribed from another plasmid. A 3V armored L-RNA of 2,248 bases containing six gene fragments—hepatitis C virus, severe acute respiratory syndrome coronavirus (SARS-CoV1, SARS-CoV2, and SARS-CoV3), avian influenza virus matrix gene (M300), and H5N1 avian influenza virus (HA300)—was successfully expressed by the two-plasmid coexpression system and was demonstrated to have all of the characteristics of armored RNA. We evaluated the 3V armored L-RNA as a calibrator for multiple virus assays. We used the WHO International Standard for HCV RNA (NIBSC 96/790) to calibrate the chimeric armored L-RNA, which was diluted by 10-fold serial dilutions to obtain samples containing 106 to 102 copies. In conclusion, the approach we used for armored L-RNA preparation is practical and could reduce the labor and cost of quality control in multiplex RNA virus assays. Furthermore, we can assign the chimeric armored RNA with an international unit for quantitative detection

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    Metabolite Profiling of Four Major Flavonoids of Herba Epimdii in Zebrafish

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    The zebrafish model organism was applied first in a metabolic study of icariin, baohuoside I, epimedin A and epimedin C, which are flavonoids in Herba Epimedii. Metabolites of these compounds in zebrafish after exposure for 24 h were identified by HPLC-ESI-MS, whereby the separation was performed with a Zorbax C-18 column using a gradient elution of 0.05% formic acid acetonitrile-0.05% formic acid water. The quasi-molecular ions of compounds were detected in simultaneous negative and positive ionization modes. Metabolic products of icariin and epimedin C via cleavage of glucose residue instead of rhamnose residues were found, which coincided with the results using regular metabolic analysis methods. In addition, the zebrafish model was used to predict the metabolism of the trace component epimedin A, whose metabolic mechanisms haven’t been clearly elucidated with the current metabolism model. The metabolic pathway of epimedin A in zebrafish was similar to those of its homologue icariin and epimedin C. Our study demonstrated that the zebrafish model can successfully imitate the current models in elucidating metabolic pathways of model flavonoids, which has advantages of lower cost, far less amount of compound needed, easy set up and high performance. This novel model can also be applied in quickly predicting the metabolism of Chinese herb components, especially trace compounds

    Gravity flow sedimentation and tight oil exploration in lower first member of Shahejie Formation in slope area of Qikou Sag, Bohai Bay Basin

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    Based on observation of cores and thin slices and analysis of drilling, log and test data, the gravity flow deposits characteristics and formation conditions and characteristics of tight oil in lower first member of Shahejie Formation (Es1x) were systematically analyzed in Qikou Sag, Huanghua depression, Bohai Bay Basin. There mainly developed sandy debris flow, muddy debris flow and classical turbidity flow in the study area, and sandstone with boulder-clay is mostly sandy debris flow origin, muddy debris flow deposits are mudstone or silty mudstone with sandy lumps, the normal graded bedding is a reliable sign of classical turbidite. Affected by multi-source supply, slope break, different trigger mechanism and fluctuation of lake level, multi-gravity flows formed multi-level fans in mid-low slope to main sag, which can be divided into five micro-facies including submerged main channel, submerged distributary channel, lateral channel margin, mud between channels and turbidite sheet sand. Multi-level and multi-stage gravity flow sediments provide material foundations for tight oil and gas in the deep mud and sand-rich lake, where wide spread tight reservoirs and high quality source rocks contact closely vertically, forming multiple sets of sandwich-like source-reservoir-seal assemblages. Exploration shows that the submerged distributary channel and turbidite sheet sand of sandy debris flow are two main exploration facies of gravity flow in Es1x and important area of scale reserve increase in slope zones of Qikou Sag. Key words: gravity flow sedimentation, tight oil, Shahejie Formation, slope area, Qikou Sag, Bohai Bay Basi
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