10 research outputs found

    Construction of Isocytosine Scaffolds via DNA-Compatible Biginelli-like Reaction

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    Herein we report a DNA-compatible Biginelli reaction to construct isocytosine scaffolds. This reaction utilizes a one-pot reaction of DNA-conjugated guanidines with aldehydes and methyl cyanoacetates to give isocytosine derivatives, and the method is well compatible with different types of substrates. This is the first report on the synthesis of an isocytosine backbone in the field of DNA-compatible organic synthesis. The successful development of this reaction can widen the chemical space of DELs

    DNA-Conjugated Cyclopropane Derivatives Constructed from Sulfonium Ylides with <i>α,β</i>-Unsaturated Ketones

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    Here, we report a DNA-compatible reaction for the generation of cyclopropane derivatives using thiolides with α,β-unsaturated ketones in the absence of transition metal and N2 protection, which is convenient for DNA encoded library (DEL) construction. This approach allows the rapid and efficient production of a series of DEL libraries of potentially biologically active cyclopropanes and spirocyclopropyl oxindole derivatives

    g‑C<sub>3</sub>N<sub>4</sub>@α-Fe<sub>2</sub>O<sub>3</sub>/C Photocatalysts: Synergistically Intensified Charge Generation and Charge Transfer for NADH Regeneration

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    Graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) is an emergent metal-free photocatalyst because of its band position, natural abundance, and facile preparation. Synergetic intensification of charge generation and charge transfer of g-C<sub>3</sub>N<sub>4</sub> to increase solar-to-chemical efficiency remains a hot yet challenging issue. Herein, a nanoshell with two moieties of α-Fe<sub>2</sub>O<sub>3</sub> and carbon (C) is in situ formed on the surface of a g-C<sub>3</sub>N<sub>4</sub> core through calcination of Fe<sup>3+</sup>/polyphenol-coated melamine, thus acquiring g-C<sub>3</sub>N<sub>4</sub>@α-Fe<sub>2</sub>O<sub>3</sub>/C core@shell photocatalysts. The α-Fe<sub>2</sub>O<sub>3</sub> moiety acts as an additional photosensitizer, offering more photogenerated electrons, whereas the C moiety bridges a “highway” to facilitate the electron transfer either from α-Fe<sub>2</sub>O<sub>3</sub> moiety to g-C<sub>3</sub>N<sub>4</sub> or from g-C<sub>3</sub>N<sub>4</sub> to C moiety. By tuning the proportion of these two moieties in the nanoshell, a photocurrent density of 3.26 times higher than pristine g-C<sub>3</sub>N<sub>4</sub> is obtained. When utilized for photocatalytic regeneration of reduced nicotinamide adenine dinucleotide (NADH, a dominant cofactor in biohydrogenation reaction), g-C<sub>3</sub>N<sub>4</sub>@α-Fe<sub>2</sub>O<sub>3</sub>/C exhibits an equilibrium NADH yield of 76.3% with an initial reaction rate (<i>r</i>) of 7.7 mmol h<sup>–1</sup> g<sup>–1</sup>, among the highest <i>r</i> for photocatalytic NADH regeneration ever reported. Manipulating the coupling between charge generation and charge transfer may offer a facile, generic strategy to improve the catalytic efficiency of a broad range of photocatalysts other than g-C<sub>3</sub>N<sub>4</sub>

    Shielding of Enzyme by a Stable and Protective Organosilica Layer on Monolithic Scaffolds for Continuous Bioconversion

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    In this study, a kind of robust monolithic biocatalyst was constructed through shielding enzymes on the surface of cordierite honeycomb (cordierite-H) ceramics with an organosilica layer. In brief, penicillin G acylase, as a typical enzyme, was immobilized on the cordierite-H surface modified with polydopamine. Then, an organosilica layer was formed through the sol–gel process with (3-aminopropyl)­tetraethoxysilane and tetraethyl orthosilicate. The buffering effect of the organosilica and polydopamine layer as well as the cage effect of the organosilica layer could effectively protect the enzyme from denaturation and detachment, thus significantly improving its structural and operational stability. A fixed-bed reactor containing the above monolithic biocatalysts was then constructed. The enzyme could retain up to 89.7% of its initial activity after a 195 min reaction at 313 K and 73.1% of its initial activity after 15 reaction cycles. Furthermore, continuous bioconversion of penicillin G potassium was also achieved, with a final product yield of 41.8% after five cycles of reaction

    Robust and Recyclable Two-Dimensional Nanobiocatalysts for Biphasic Reactions in Pickering Emulsions

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    In this study, a facile, yet effective surface-engineering method was reported to confer graphene oxide (GO) nanosheets with amphiphilic feature and numerous binding sites toward enzymes for biphasic reactions in Pickering emulsions. Briefly, the surface of GO nanosheet is first modified and simultaneously reduced by polydopamine to endow with catechol groups. A portion of catechol groups is utilized to anchor zeolitic imidazolate framework 8 (ZIF-8) nanoparticles onto the polydopamine-modified graphene oxide (P-rGO) nanosheets through Zn<sup>2+</sup>–catechol coordination. The remaining uncoordinated catechol groups in P-rGO nanosheets are utilized to immobilize lipase onto the P-rGO nanosheets through chemical conjugation. The resulting two-dimensional P-rGO/ZIF-8/Lipase nanobiocatalysts with an enzyme loading percent values of 34.05–48.75% could be spontaneously assembled at the oil/water interface, which were then utilized to catalyze the hydrolysis of water-insoluble <i>p</i>-nitrophenyl palmitate (<i>p</i>-NPP) into water-soluble <i>p</i>-nitrophenol (<i>p</i>-NP). The Pickering emulsions, which were robustly stabilized by P-rGO/ZIF-8/Lipase, facilitated the diffusion of <i>p</i>-NP from the oil/water interface to aqueous phase, acquiring an enzymatic activity recovery of ∼60%. Moreover, P-rGO/ZIF-8/Lipase exhibited remarkably enhanced stabilities against multiple reuses and various harsh conditions compared with free lipase, GO/Lipase, and P-rGO/Lipase, showing great potential in practical applications

    Comparison among BrdU labeling, Flow Cytometry and SiLAD to check cell cycle stage.

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    <p>Black line a means only to determine the cell cycle phase roughly. Curve line b means detecting the specific time point exactly. BrdU L is stands for the BrdU labeling and FCM is Flow Cytometry.</p

    Evaluation the synchronized efficiency of serum starved A549 cells.

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    <p>(A) FACS analysis of A549 cells synchronization by serum starvation for 48 hr. (B) Western blot analysis of expression of CyclinD1 at the indicate time lengths after serum re-stimulation. (C) FACS to detect the cell cycle progress after serum re-stimulation.</p

    SiLAD profiles are served to characterize the specific state of the cell cycle progress.

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    <p>Curve 1 was from the CBB spot in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002991#pone-0002991-g003" target="_blank">Figure 3D</a>. Curve 2 was from the spot in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002991#pone-0002991-g003" target="_blank">Figure 3G</a> PH-I image labeled with downward arrow. Curve 3 was from the same image with Curve 2, but was the spot labeled with upward arrow. The right panels A and B were the defined bar codes for the two time points labeled with spotted line A and B in the left panel. The curve was made by the software Origin6.</p

    Dynamic metabolized changes of the proteins.

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    <p>(A, D, G and I) Zoom in view of the spots dynamic changes at different time points. Panel A, D, and G show three differential changed proteins in A549 model. The differential protein shown in panel I was from rat liver hepatectomy model. PH-I stands for the images were got from Phosphor-imaging, while CBB means the CBB staining. (B and E) Shown the dynamic expression changes of the spots labeled in panel A and D, respectively. The x axis is time (t), and the y axis is the protein synthesizing speed (v<sub>expressed</sub>), and the area of each rectangle means the total amount of protein synthesized during each 15 minutes interval (s<sub>expressed</sub>). The midpoint of each rectangle's top edge was used to interpolate these five points with piecewise cubic Hermite polynomial, as shown in the diagram as the green line. (C and F) Shown the dynamic total amount changes of the spots labeled in A and D. The x axis also is time (t), and the y axis is the total protein metabolized speed (v<sub>existed</sub>), consequently the area of each rectangle means the total amount of protein (s<sub>existed</sub>) variation during each time interval. This green line indicates the function of the variation speed of the total amount of existed protein (s<sub>existed</sub>) with respect to time (t), during these six hours. (H) Presence %Volumes changes of the protein labeled in chart G. Ph-R denotes phosphorylation rate, <i>i.e.</i> the percentage of phosphorylated proteins accounted for the total sum in each time point. The value of PH-R represents mean±s.e.m. for 3 independent experiments. Error bars represent mean±s.e.m., n = 3. Chart B, C, E and F were made by the software MatLab, and chart H was made by SPSS13.</p
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