27 research outputs found

    Depolymerization of ODPA/ODA Polyimide in a Fused Silica Capillary Reactor and Batch Autoclave Reactor from 320 to 350 °C in Hot Compressed Water

    No full text
    Depolymerization of polyimide synthesized from 4,4′-oxidiphthalic anhydride and 4,4′-diaminodiphenyl ether monomers (ODPA/ODA PI) in hot compressed water was carried out in a fused silica capillary reactor (FSCR) and batch autoclave reactor system. The phase behavior of ODPA/ODA PI in water during the heating, reaction, and cooling stages of the process in FSCR was observed with an image recording system from under the microscope. The effects of temperature (320–350 °C) and reaction time (30–90 min) on the depolymerization yield and products yields in batch autoclave reactor were investigated at a fixed H<sub>2</sub>O/PI ratio, and optimal conditions were established. Additionally, an understanding of the reaction pathway of ODPA/ODA PI depolymerization in hot compressed water was developed

    Reversible Luminescent Nanoswitches Based on Aggregation-Induced Emission Enhancement of Silver Nanoclusters for Luminescence Turn-on Assay of Inorganic Pyrophosphatase Activity

    No full text
    Unique aggregation-induced emission (AIE) property has been found and widely applied in chemo/biosensors for thiolated gold nanoclusters and copper nanoclusters; however, little is known about this property of thiolate-protected silver nanoclusters. In this work, specific aggregation-induced emission enhancement (AIEE) of glutathione-capped silver nanoclusters (AgNCs) was verified via its solid-state luminescence and enhanced emission in poor solvent, three stimuli responsive nanoswitches were constructed based on its AIEE property, and a reliable and sensitive PPase assay was developed via ion-triggered luminescence switch. Glutathione-capped AgNCs from a facile one-pot synthesis were found to possess bright red luminescence and aggregation-induced emission enhancement property. This AIEE feature enables AgNCs in sensitive response to pH and temperature in a reversible way, allowing the two nanoswitches to precisely monitor the change of environmental pH and temperature. Complexation reactions among AgNCs, aluminum cation and PPi were also designed for an ion-triggered luminescence nanoswitch, which allows selective response to aluminum cation or PPi in luminescence. This ion-driven luminescence switch is further utilized to design a novel detection strategy for PPase activity through competitive coordination reactions. Our method illustrates a novel detection strategy mediated by complexation reaction between Al<sup>3+</sup> and AgNCs avoiding the involvement of copper cations in the detection, and this developed assay performed well in detection of PPase level in fresh rat serum. This work confirms unique aggregation-induced emission enhancement property of glutathione-capped AgNCs, constructs multiple luminescence switches based on its multistimuli responsive behaviors, and demonstrates an example of Al<sup>3+</sup>-mediated detection strategy for PPase assay

    P(NMe<sub>2</sub>)<sub>3</sub>‑Mediated Regioselective N‑Alkylation of 2‑Pyridones via Direct Deoxygenation of α‑Keto Esters

    No full text
    A practical and regioselective direct N-alkylation of 2-pyridones is enabled by use of α-keto esters in the P(NMe2)3-mediated deoxygenation process. The reaction proceeds under mild conditions to produce N-alkylated 2-pyridones with high selectivity and generality, and the protocol is shown to be applicable for the scale-up synthesis, which makes it promising for practical applications

    Ammonium Acetate-Promoted One-Pot Tandem Aldol Condensation/Aza-Addition Reactions: Synthesis of 2,3,6,7-Tetrahydro‑1<i>H</i>‑pyrrolo[3,2‑<i>c</i>]pyridin-4(5<i>H</i>)‑ones

    No full text
    An efficient tandem intermolecular one-pot aldol condensation/aza-addition reaction of 2-methyl-3-carbamoylpyrroles and aldehydes was developed for the synthesis of 2,3,6,7-tetrahydro-1<i>H</i>-pyrrolo­[3,2-<i>c</i>]­pyridin-4­(5<i>H</i>)-ones. The reaction proceeded using only 3.0 equiv of ammonium acetate promoter in green solvent poly­(ethylene glycol)-400 at 100 °C to afford a series of pyrrolo­[3,2-<i>c</i>]­pyridinone derivatives in good to excellent yields

    <i>Citrobacter amalonaticus</i> Phytase on the Cell Surface of <i>Pichia pastoris</i> Exhibits High pH Stability as a Promising Potential Feed Supplement

    No full text
    <div><p>Phytase expressed and anchored on the cell surface of <i>Pichia pastoris</i> avoids the expensive and time-consuming steps of protein purification and separation. Furthermore, yeast cells with anchored phytase can be used as a whole-cell biocatalyst. In this study, the phytase gene of <i>Citrobacter amalonaticus</i> was fused with the <i>Pichia pastoris</i> glycosylphosphatidylinositol (GPI)-anchored glycoprotein homologue <i>GCW61</i>. Phytase exposed on the cell surface exhibits a high activity of 6413.5 U/g, with an optimal temperature of 60°C. In contrast to secreted phytase, which has an optimal pH of 5.0, phytase presented on the cell surface is characterized by an optimal pH of 3.0. Moreover, our data demonstrate that phytase anchored on the cell surface exhibits higher pH stability than its secreted counterpart. Interestingly, our <i>in vitro</i> digestion experiments demonstrate that phytase attached to the cell surface is a more efficient enzyme than secreted phytase.</p></div

    <i>In vitro</i> digestibility test of cell surface and secreted phytases.

    No full text
    <p>A: Measured phosphate (Pi) released from a corn-based diet mixed with cell surface or secreted phytases. B: Simulation of the pelleting process (i.e., incubation for 3 min at 80°C or 5 min at 90°C prior to activity measurement), followed by determination of the amount of released Pi. The levels of released Pi were compared with samples without heat treatment. GS115/ZαA served as a background measurement.</p

    Fluorescence microscopy and flow cytometry analyses of yeast cells.

    No full text
    <p>Fluorescence microscopy and flow cytometry analyses of yeast cells.</p

    Phytase activity after induction with methanol and after treatment with laminarinase.

    No full text
    <p>A: Time dependence of the activity of cell surface phytase after induction with methanol. B: Cell surface phytase activity after laminarinase treatment. Column 1 represents cell wall fractions without treatment with laminarinase. Columns 2 and 4 represent cell wall fractions after laminarinase treatment, and column 3 and 5 represent supernatant fractions after laminarinase treatment. Columns 2 and 3 show phytase activities after treatment with 5 mU of laminarinase, while columns 4 and 5 represent the remaining activities after treatment with 50 mU of laminarinase. All activities were compared to the activity of the whole cell surface phytase, with GS115/ZαA as a background measurement.</p

    Effect of metal ions on cell surface and secreted phytases.

    No full text
    <p>The counter of all metals was chloride. <i><sup>b</sup></i>Without metal ion added (as 100%). <i><sup>c</sup></i>Values in the same column differ significantly from values without metal added (<i>p</i><0.05).</p><p>Effect of metal ions on cell surface and secreted phytases.</p

    Ammonium Acetate-Promoted One-Pot Tandem Aldol Condensation/Aza-Addition Reactions: Synthesis of 2,3,6,7-Tetrahydro‑1<i>H</i>‑pyrrolo[3,2‑<i>c</i>]pyridin-4(5<i>H</i>)‑ones

    No full text
    An efficient tandem intermolecular one-pot aldol condensation/aza-addition reaction of 2-methyl-3-carbamoylpyrroles and aldehydes was developed for the synthesis of 2,3,6,7-tetrahydro-1<i>H</i>-pyrrolo­[3,2-<i>c</i>]­pyridin-4­(5<i>H</i>)-ones. The reaction proceeded using only 3.0 equiv of ammonium acetate promoter in green solvent poly­(ethylene glycol)-400 at 100 °C to afford a series of pyrrolo­[3,2-<i>c</i>]­pyridinone derivatives in good to excellent yields
    corecore