Bicyclic hydrocarbons, and bicyclo1.1.1pentanes (BCPs) in particular, are playing an emerging role as saturated bioisosteres in pharmaceutical, agrochemical and materials chemistry. Taking advantage ...of strain-release strategies, prior synthetic studies have featured the synthesis of bridgehead-substituted (C1, C3) BCPs from 1.1.1propellane. Here, we describe an approach to access multisubstituted BCPs via intramolecular cyclization. In addition to C1,C3-disubstituted BCPs, this method also enables the construction of underexplored multisubstituted (C1, C2 and C3) BCPs from readily accessible cyclobutanones. The broad generality of this method has also been examined through the synthesis of a variety of other caged bicyclic molecules, ranging from 2.1.1 to 3.2.1 scaffolds. The modularity afforded by the pendant bridgehead boron pinacol esters generated during the cyclization reaction has been demonstrated through several downstream functionalizations, highlighting the ability of this approach to enable the programmed and divergent synthesis of multisubstituted bicyclic hydrocarbons.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
In the past few years, the preparation of novel small-molecule fluorescent probes for specific detection and imaging of chemical species inside lysosomes has attracted considerable attention because ...of their wide applications in chemistry, biology, and medical science. This feature article summarizes the recent advances in the design and preparation of small-molecule fluorescent probes for specific detection of chemical species inside lysosomes. In addition, their properties and applications for the detection and imaging of pH, H
2
O
2
, HOCl, O
2
&z.rad;
−
, lipid peroxidation, H
2
S, HSO
3
−
, thiols, NO, ONOO
−
, HNO, Zn
2+
, Cu
2+
, enzymes,
etc.
in lysosomes are discussed as well.
This feature article comprehensively summarizes the development of small-molecule fluorescent probes for specific detection and imaging of chemical species inside lysosomes.
Here, we report the direct visualization of the assembly/disassembly processes of photoresponsive DNA origami nanostructures which can be placed on a lipid bilayer surface. The observation relies on ...controlled interactions between the bilayer components and cholesterol moieties introduced to the hexagonal origami structures, one of whose outer edges carries Azo-ODNs. The bilayer-placed hexagonal dimer was disassembled into monomer units by UV irradiation, and reversibly assembled again during visible light irradiation. These dynamic processes were directly monitored with high-speed atomic force microscopy. The successful application of our approach should facilitate studies of interactive and functional behaviors of various DNA nanostructures.
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Thermoset shape memory polyimides (TPIs) are widely used in the fields of high-temperature smart devices. However, the recent molding of polyimides limits most of potentials in the form of ...two-dimensional film. In this work, we synthesized a novel shape memory polyimide (SMPI) ink that could be used for both Digital Light Process and extrusion molding 3D printing. Through UV-induced free radical polymerization, 3D custom polyimides ink can be cured rapidly. Remarkably, the 3D printed PI exhibits excellent shape memory performance, with Rf of 99.8%, Rr of 98.3%, therefore the 4D printing PI was successfully prepared. The 3D printed airplane, ultrasonic motor and pagoda can actively recover the film folding, expanding combined compressing, and vertical distorting to their permanent shape, which presents the outstanding 4D printing properties. Moreover, SMPI can be used in extrusion molding to print films, the residual stress induced the self-folding and then a vector model was applied to characterize transformation of extruded plates. In order to develop the application diversity of extruded 4D polyimide, self-folding box and stimuli-response gripper are designed, the gripper is able to pull up steel ball 15 times heavier than itself. Thus, SMPI will be benefit to expand the applied scope of SMPI.
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•A new shape memory polyimide ink for DLP 3D printing and extrusion molding has been developed.•The SMPI have high mechanical strength, excellent shape memory property (Rf of 99.8%, Rr of 98.3%) and low contraction.•Printed or extruded 4D products can actively recover to their permanent shape in a few minutes.•The SMPI-based self-folding box and stimuli-response gripper have been designed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight of rice, employs the transcription activator-like effectors (TALEs) to induce the expression of the OsSWEET family of ...putative sugar transporter genes, which function in conferring disease susceptibility (S) in rice plants. To engineer broad-spectrum bacterial blight resistance, we used CRISPR/Cas9-mediated gene editing to disrupt the TALE-binding elements (EBEs) of two S genes, OsSWEET11 and OsSWEET14, in rice cv. Kitaake, which harbors the recessive resistance allele of Xa25/OsSWEET13. The engineered rice line MS14K exhibited broad-spectrum resistance to most Xoo strains with a few exceptions, suggesting that the compatible strains may contain new TALEs. We identified two PthXo2-like TALEs, Tal5LN18 and Tal7PXO61, as major virulence factors in the compatible Xoo strains LN18 and PXO61, respectively, and found that Xoo encodes at least five types of PthXo2-like effectors. Given that PthXo2/PthXo2.1 target OsSWEET13 for transcriptional activation, the genomes of 3000 rice varieties were analyzed for EBE variationsin the OsSWEET13 promoter, and 10 Xa25-like haplotypes were identified. We found that Tal5LN18 and Tal7PXO61 bind slightly different EBE sequences in the OsSWEET13 promoter to activate its expression. CRISPR/Cas9 technology was then used to generate InDels in the EBE of the OsSWEET13 promoter in MS14K to creat a new germplasm with three edited OsSWEET EBEs and broad-spectrum resistance against all Xoo strains tested. Collectively, our findings illustrate how to disarm TALE-S co-evolved loci to generate broad-spectrum resistance through the loss of effector-triggered susceptibility in plants.
With the discovery of PthXo2-like TALEs in Xoo and 10 EBEPthXo2 alleles of OsSWEET13 in different rice varieties, broad-spectrum bacterial blight resistance was generated by simultaneously disrupting variable TALE-binding elements of three susceptibility genes (OsSWEET11, OsSWEET13, and OsSWEET14) in rice. These novel findings provide a new breeding strategy for plant disease resistance through the loss of effector-triggered susceptibility.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Herein we report a highly selective photoredox C(sp3)−H alkylation/arylation of ethers through the combination of a photo‐organocatalyst (benzaldehyde) and a transition‐metal catalyst (nickel). This ...method provides a simple and general strategy for the C(sp3)−H alkylation/arylation of ethers. A selective late‐stage modification of (−)‐ambroxide has also been conducted to demonstrate the applicability of the method.
A combined approach: A simple and general strategy involving the combination of a photo‐organocatalyst (benzaldehyde) and a transition‐metal catalyst (nickel) has been developed for the highly selective photoredox C(sp3)−H alkylation/arylation of ethers. A selective late‐stage modification of (−)‐ambroxide has also been conducted to demonstrate the applicability of the method.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
While gold‐mediated synergistic catalytic processes involving transmetalations with other metals are well understood, AuI/AuIII cycles in these reactions are rarely reported. Herein a gold‐catalyzed ...direct alkynylation of cyclopropenes is enabled by two operating catalytic cycles, an oxidative catalytic cycle involving an alkynyl AuIII complex formed by oxidative addition and one involving a silver‐mediated C−H activation.
Gold meets silver for a bimetallic process enabling a direct functionalization of cyclopropenes. While silver activates the C−H bond, oxidative addition and reductive elimination happen at a gold Phen complex. The key steps of the reaction were confirmed by kinetic studies and by the isolation and stoichiometric transformation of a gold(III) alkyne complex.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Gold(I) complexes are considered active species toward oxidative addition; current understanding indicates a different mechanism in contrast to other late transition metals, but a rational ...understanding of the reactivity profile is lacking. Herein, we propose that the accessibility of the gold(I) center to tri- or tetra-coordination is critical in the oxidative process involving a tri- or tetra-coordinate gold(I) with the oxidizing reagent as one of the ligands as an intermediate. A computational study of the geometry of (Phen)R3PAu(I)NTf2 complexes shows that the accessibility of such tricoordinate species shows a good correlation with the “trans influence” of phosphine ligands: the weak σ-donating phosphine ligands promote tricoordination of gold(I) complexes. The oxidative addition to the asymmetric tricoordinate (Phen)R3PAu(I)NTf2 complexes with alkynyl hypervalent iodine reagents was built. The kinetic profile of the oxidative addition exhibits a good relationship to the Hammett substituent parameter (ρ = 3.75, R 2 = 0.934), in which the gold(I) complexes bearing less σ-donating phosphine ligands increase the rate of oxidative addition. The positive ρ indicates a high sensitivity of the oxidative addition to the trans influence. The reactivity profile of oxidative addition to a linear bis(pyridine)gold(I) complex further supports that the oxidative addition to gold(I) complexes is promoted by ligands with small trans influence.
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On the basis of tricabocyanine, two near-infrared fluorescent sensors CYP-1 and CYP-2 have been designed and synthesized. Both of them can selectively and sensitively recognize Cd2+ from other metal ...ions, especially the CYP-2, which can distinguish Cd2+ in neutral buffer solution.
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