103 research outputs found

    Study on Acidizing Effect of Cationic β‑Cyclodextrin Inclusion Complex with Sandstone for Enhancing Oil Recovery

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    A novel supramolecular inclusion complex was prepared with cationic β-cyclodextrin and organic phosphoric acid. The inclusion action was investigated by UV–vis spectroscopy, and the cationic β-cyclodextrin inclusion complex was structurally evidenced by <sup>1</sup>H and <sup>31</sup>P NMR and FT-IR. With linear expansion tests, it was found that the novel inclusion complex possessed excellent clay stability. FT-IR, single-factor, and response surface method analyses showed that the inclusion complex acid system could not only retard acid–rock reaction but also intelligently regulate the acid–rock reaction rate to ensure a sufficient amount of acid to react with high-temperature oil-bearing sandstone reservoir in the progress of acid stimulation. On the basis of the core flood tests, an interaction mechanism was suggested that the inclusion complex acid system may open up for a new possibility to exhibit greater acidizing performance in high clay content, high-temperature, and low-permeability oil reservoirs, which contributes to improving core permeability and enhancing oil recovery

    Distinct amino acid motifs carrying multiple positive charges regulate membrane targeting of dysferlin and MG53

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    <div><p>Dysferlin (Dysf) and mitsugumin53 (MG53) are two key proteins involved in membrane repair of muscle cells which are efficiently recruited to the sarcolemma upon lesioning. Plasma membrane localization and recruitment of a Dysf fragment to membrane lesions in zebrafish myofibers relies on the presence of a short, polybasic amino acid motif, WRRFK. Here we show that the positive charges carried by this motif are responsible for this function. In mouse MG53, we have identified a similar motif with multiple basic residues, WKKMFR. A single amino acid replacement, K279A, leads to severe aggregation of MG53 in inclusion bodies in HeLa cells. This result is due to the loss of positive charge, as shown by studying the effects of other neutral amino acids at position 279. Consequently, our data suggest that positively charged amino acid stretches play an essential role in the localization and function of Dysf and MG53.</p></div

    The cellular distribution of smDysf depends on the positive charge of the WRRFK motif.

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    <p>The cytoplasmic fraction is significantly increased upon reducing the net charge but not by polypeptide truncation on the C-terminal side of smDysf. For this plot, the cytoplasmic fluorescence of 9–15 myofibers was measured and averaged for each mutant. All data are referenced to the wildtype set to 100% and plotted as mean ± SD. The original data are provides as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0202052#pone.0202052.s001" target="_blank">S1 Dataset</a>. Zebrafish embryos expressing these ten variants were injected, treated and imaged under identical conditions. The mutant sequences are grouped according to the net charge (1+– 3+) of the different motifs under physiological conditions. Significance was tested against the wildtype control smDysf (WRRFK-TM-C) by Student’s t-test (** <i>p</i> < 0.01, *** <i>p</i> < 0.001).</p

    Cellular localization of turboGFP:MG53 mutants K279S, K279Y and K279R in HeLa cells and C2C12 myoblasts.

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    <p>Representative images of (A) HeLa cells and(B) C2C12 myoblasts show that the charge-maintaining modification K279R rescues membrane targeting of MG53. Fluorescence was excited with a 488-nm laser. Scale bars, 10 ÎĽm.</p

    Digital Gene-Expression Profiling Analysis of the Cholesterol-Lowering Effects of Alfalfa Saponin Extract on Laying Hens

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    <div><p>Background</p><p>To prevent cardiovascular disease, people are advised to limit their intake of dietary cholesterol to less than 300 mg/day. Egg consumption has been seriously reduced because of the high levels of cholesterol. The purpose of the present study was to evaluate the cholesterol-lowering effects of alfalfa saponin extract (ASE) in yolk and the molecular mechanisms underlying these effects using digital gene-expression profiling analysis. Liver and ovary tissues were isolated from laying hens fed with ASE for RNA sequencing.</p><p>Results</p><p>The cholesterol content of the yolks of eggs from hens fed 120 mg/kg ASE declined considerably on day 60. Other groups (60, 240, 480 mg/kg ASE group) also showed decreases, but they were not significant. Digital gene expression generated over nine million reads per sample, producing expression data for least 12,384 genes. Among these genes, 110 genes showed greater than normal expression in the liver and 107 genes showed greater than normal expression in the ovary. Cholesterol 7 alpha-hydroxylase (<i>Cyp7a1</i>) and apolipoprotein H (<i>Apoh</i>), which act in the synthesis of bile acid and cholesterol efflux, showed more expression in the livers of hens given dietary ASE supplementation. In the ovary, levels of very low density lipoprotein receptor (<i>Vldlr</i>), apolipoprotein B (<i>Apob</i>), apovitellenin 1 (<i>ApovldlII</i>) and vitellogenin (<i>VtgI</i>, <i>VtgII</i> and <i>VtgIII</i>) in ovary decreased with dietary ASE supplementation.</p><p>Conclusion</p><p>Transcriptome analysis revealed that the molecular mechanisms underlying the cholesterol-lowering effects of ASE were partially mediated by enhancement of cholesterol efflux in the liver and this reduced of cholesterol deposition in the ovary.</p></div

    Accumulation of smDysf at the lesion site depends on the positive charge of the WRRFK motif <i>in vivo</i>.

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    <p>(A) Domain structure of Dysf. The boxed fragment is smDysf, which was used to test accumulation at the lesion patch. (B) Representative images showing accumulation of smDysf and different mutants. Basic AAs are highlighted in red; arrows indicate the site of lesion. Z-line (z) and sarcolemmal (sc) regions are noted. (C-D) Corresponding kinetics of accumulation of zebrafish (C) or human (D) smDysf at the damage site, again with the basic AAs highlighted in red. The fluorescence intensity at the lesion was normalized to the one of the undamaged state. Intensity courses are averages over 9–15 damaged cells. Scale bars, 4 μm.</p

    Mutation K279A leads to mislocalization of MG53.

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    <p>(A) Domain structure of the fusion protein turboGFP:MG53. (B) Cellular localization of (top to bottom) turboGFP:MG53 and mutants K278A, R282A, K278A/R282A, K279A, K278A/K279A in HeLa cells. Three representative images are shown for each variant, all imaged with excitation at 488 nm. Scale bars, 10 ÎĽm.</p

    Colocalization analysis by dual-color confocal imaging.

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    <p>Two-channel imaging of turboGFP:MG53 (green fluorescence excited with 488-nm light, first column) with (second column) early endosomes, excited with 561-nm light (A), late endosomes, excited with 561-nm light (B), lysosomes, excited with 405-nm light (C), and inclusion bodies, excited with 561-nm light (D). Overlay images are shown in the third column. Scale bars, 10 ÎĽm.</p

    Confocal images of C2C12 myoblasts expressing turboGFP:MG53 and mutants K278A, R282A, K279A.

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    <p>Fluorescence was excited with a 488-nm laser. As in HeLa cells, K279A shows substantial vesicular localization in myoblasts. Scale bars, 10 ÎĽm.</p
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