A central paradigm within virology is that each viral particle largely behaves as an independent infectious unit. Here, we demonstrate that clusters of enteroviral particles are packaged within ...phosphatidylserine (PS) lipid-enriched vesicles that are non-lytically released from cells and provide greater infection efficiency than free single viral particles. We show that vesicular PS lipids are co-factors to the relevant enterovirus receptors in mediating subsequent infectivity and transmission, in particular to primary human macrophages. We demonstrate that clustered packaging of viral particles within vesicles enables multiple viral RNA genomes to be collectively transferred into single cells. This study reveals a novel mode of viral transmission, where enteroviral genomes are transmitted from cell-to-cell en bloc in membrane-bound PS vesicles instead of as single independent genomes. This has implications for facilitating genetic cooperativity among viral quasispecies as well as enhancing viral replication.
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•Clusters of viruses are packaged and released non-lytically in PS lipid vesicles•PS lipids are co-factors in mediating subsequent infectivity and transmission•PS vesicles provide greater infection efficiency for viruses•PS vesicles enable viral genome clusters to be transmitted en bloc cell-to-cell
Clusters of enteroviruses are packaged in phosphatidylserine (PS)-enriched vesicles, thereby enhancing the infection efficiency of the viruses and enabling collective transmission of multiple viral genomes from cell-to-cell.
Controlling the size and surface functionalization of nanoparticles (NPs) can lead to improved properties and applicability. Herein, we demonstrate the efficiency of the metal‐carbene template ...approach (MCTA) to synthesize highly robust and soluble three‐dimensional polyimidazolium cages (PICs) of different sizes, each bearing numerous imidazolium groups, and use these as templates to synthesize and stabilize catalytically active, cavity‐hosted, dispersed poly‐N‐heterocyclic carbene (NHC)‐anchored gold NPs. Owing to the stabilization of the NHC ligands and the effective confinement of the cage cavities, the as‐prepared poly‐NHC‐shell‐encapsulated AuNPs displayed promising stability towards heat, pH, and chemical regents. Most notably, all the Au@PCCs (PCC=polycarbene cage) exhibited excellent catalytic activities in various chemical reactions, together with high stability and durability.
Take your PIC: Polyimidazolium cages (PICs) are used as templates to synthesize and stabilize catalytically active, cavity‐hosted, dispersed poly‐N‐heterocyclic carbene (NHC)‐anchored gold nanoparticles NPs. The resulting Au NPs display impressive thermal and chemical stability and high catalytic activities.
A procedure for the synthesis of three‐dimensional hexakisimidazolium cage compounds has been developed. The reaction of the trigonal trisimidazolium salts H3L(PF6)3, decorated with three N‐olefinic ...pendants, and silver oxide yielded trinuclear trisilver(I) hexacarbene molecular cylinders of the type Ag3L23+ with the olefinic pendants from the two different tricarbene ligands arranged in three pairs. Subsequent UV irradiation gave three cyclobutane links between the two tris‐NHC ligands in three 2+2 cycloaddition reactions, thereby generating a three‐dimensional hexakis‐NHC ligand. Removal of the metal ions resulted in the formation of three‐dimensional hexakisimidazolium cages with a large internal cavity.
All good things come in threes: An efficient template synthesis has been developed for the preparation of three‐dimensional hexakisimidazolium cage compounds starting from trigonal trisimidazolium salts decorated with three N‐olefinic pendants and silver ions as metal templates.
Thanks to the potential of aggregation‐induced emission (AIE) phenomena, improved stabilities, and the good selectivity and sensitivity of the chemical responses exhibited by the products, ...coordination‐driven self‐assembly with tetraphenylethylene (TPE) units has recently received much attention and has been widely investigated for application in chemical sensors, cell imaging agents, light‐harvesting systems, and others. Several reviews have emerged on the topics of AIE chemistry and aggregation‐induced emission luminogen (AIEgen)‐based supramolecular assembles, however, there is still a distinct lack of full overviews of emission enhancement from the viewpoint of metal‐coordination effects. Thus, this minireview offers recent advances that have been made in the design and application of TPE‐based metallacycles, metallacages, metal‐organic frameworks (MOFs) and coordination polymers (CPs).
The motions of the tetraphenylethylene (TPE) units are restricted by coordination bonds through coordination‐driven self‐assembly, thereby their non‐radiative decay is reduced to induce fluorescence emission. This minireview offers a summary of recent advances that have been made in the design and synthesis of TPE‐based metallacycles, metallacages, metal–organic frameworks (MOFs) and coordination polymers (CPs). Their potential applications as materials for chemical sensors, cell imaging agents and light‐harvesting materials, among others, are outlined.
A new class of supramolecular metallacycles capable of undergoing photochemical reactions and in situ release of cyclobutanes in solution is described. The molecular metallacycles were generated ...through coordination‐driven self‐assembly of dinuclear metal‐carbene complexes as organometallic clips with olefin‐functionalized bridging ligands. Photolysis of these molecular metallacycles in situ led to structural interconversion and release of the formed cyclobutane products with quantitative conversion. Further modifications of the obtained cyclobutanes provided a series of new species containing the cyclobutane skeleton.
Catch and release: Photolysis of the pictured molecular metallacycles in situ leads to quantitative cycloaddition and release of the stereoselectively formed cyclobutane products. The pendant groups on the products include pyridyl, imidazole, benzimidazoles, and carboxylic derivatives.
Conspectus Over the last two decades, researchers have focused on the design and synthesis of supramolecular coordination complexes, which contain discrete functional structures with particular ...shapes and sizes, and are similar to classic metal–organic frameworks. Chemists can regulate many of these systems by judiciously choosing the metal centers and their adjoining ligands. These resulting complexes have unusual properties and therefore many applications, including molecular recognition, supramolecular catalysis, and some applications as nanomaterials. In addition, researchers have extensively developed synthetic methodologies for the construction of discrete self-assemblies. One of the most important challenges for scientists in this area is to be able to synthesize target structures that can be controlled in both length and width. For this reason, it is important that we understand the factors leading to special shapes and sizes of such architectures, especially how starting building blocks and functional ligands affect the final conformations and cavity sizes of the resulting assemblies. Towards this goal, we have developed a wide range of different organometallic architectures by rationally designing metal-containing precursors and organic ligands. In this Account, we present our recent work, focusing on half-sandwich iridium- and rhodium-based organometallic assemblies that we obtained through rational design. We discuss their synthesis, structures, and applications for the encapsulation of guests and enzyme-mimicking catalysis. We first describe a series of self-assembled organometallic metallarectangles and metallacages, which we constructed from preorganized dinuclear half-sandwich molecular clips and suitable pyridyl ligands. We extended this strategy to tune the size of the obtained rectangles, creating large cavities by introduction of larger molecular clips. The cavity was found to exhibit selective and reversible CH2Cl2 adsorption properties while retaining single crystallinity. By using suitable molecular clips, we found we could use a number of metallacycles as organometallic templates to direct photochemical 2 + 2 cycloaddition reactions, even in the solid state. Due to their chemical stability and potential applications in catalytic reactions, researchers are giving significant attention to complexes with cyclometalated backbones. We also highlight our efforts to develop efficient approaches to utilize cyclometalated building blocks for the formation of organometallic assemblies. By incorporation of imine ligands or benzoic acids, bipyridine linking subunits, and half-sandwich iridium or rhodium fragments, we built up a series of cationic and neutral metallacycles through cyclometalation-driven self-assembly. In addition, we have developed an efficient route to carborane-based metallacycles, involving the exploitation of metal-induced B–H activation. The method can provide prism-like metallacages, which are efficient hosts for the recognition of planar aromatic guests. This effort provides an incentive to generate new building blocks for the construction of organometallic assemblies. Taken together, our results may lead to a promising future for the design of complicated enzyme-mimetic-catalyzed systems.
Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters ...that are surface‐active for liquid‐phase catalysis without any pre‐treatment. Now, an N‐heterocyclic carbene‐stabilized Au25 nanocluster with high thermal and air stabilities is presented as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as Au25(iPr2‐bimy)10Br72+ (iPr2‐bimy=1,3‐diisopropylbenzimidazolin‐2‐ylidene) (1), was synthesized by direct reduction of AuSMe2Cl and iPr2‐bimyAuBr with NaBH4 in one pot. X‐ray crystallization analysis revealed that the cluster comprises two centered Au13 icosahedra sharing a vertex. Cluster 1 is highly stable and can survive in solution at 80 °C for 12 h, which is superior to Au25 nanoclusters passivated with phosphines or thiols. DFT computations reveal the origins of both electronic and thermal stability of 1 and point to the probable catalytic sites. This work provides new insights into the bonding capability of N‐heterocyclic carbene to Au in a cluster, and offers an opportunity to probe the catalytic mechanism at the atomic level.
An atomically precise N‐heterocyclic carbene‐stabilized Au25 nanocluster is successfully synthesized in a one‐pot reaction. It exhibits much higher thermal stability in the solution form compared to Au25 protected by thiol or phosphine ligands. The cluster displays excellent catalytic activity in the cycloisomerization of alkynyl amine as a homogeneous catalyst.
Conspectus As versatile, modular, and strongly coordinating moieties in organometallic compounds, N-heterocyclic carbenes (NHCs) have led to numerous breakthroughs in transition-metal catalysis, main ...group chemistry, and organocatalysis. In contrast, the chemistry of NHC-based metallosupramolecular assemblies, in which discrete individual components are held together via metal (M)–CNHC bonds, has been underdeveloped. Integrating NHCs into supramolecular assemblies would endow them with some unforeseen functions. However, one of the most critical challenges is seeking an appropriate combination of the rigid CNHC–M–CNHC units with the resulting topologies and applications. Toward this goal, for the last decade we have focused on the development of M–NHC directed toward metallosupramolecular synthesis. This Account aims to summarize our contributions to the application of M–NHC chemistry toward supramolecular synthesis from structural design to postassembly modification (PAM) and their functional applications since integrating NHCs into supramolecular assemblies has garnered much attention among organometallic, photochemical, and supramolecular researchers. While presenting representative examples of NHC-based architectures, we try to illustrate the purposes and concepts behind the systems developed to aid the rational approach to the design and fabrication of complex assemblies and M–NHC-templated photochemical reactions. We present synthetic approaches for new architectures by the rational design of starting NHC precursors, including the poly-NHC-based mechanically interlocked metallacages and the heteroleptic architectures based on electronic complementary and self-sorting mechanisms. The structural regulation of poly-NHC-based architectures with increasing topological complexity is elaborated on by selective combinations of tetraphenylethylene (TPE) units, NHC backbones, and N-wingtip substituents in a controllable manner. Subsequently, we move to elucidating an M–NHC-templated PAM approach that leads to functional organic cages featuring polyimidazolium/triazolium groups of different shapes and sizes that are difficult to access using alternative organic approaches. These organic cages possess well-defined cavities, and their in situ-generated NHC sites are ideal platforms for stabilizing metal nanoparticles (MNPs) within their cavities for improved catalytic performance. Finally, we demonstrate how to design supramolecular M–NHC templates to synthesize cyclobutane derivatives in homogeneous solutions in a catalytic fashion. Selected examples of M–NHC template-dependent structural transformations and photoreactions are discussed. Their applications in molecular recognition, aggregation-induced emission (AIE), cell imaging, anticancer activity, radical chemistry, and stimuli-responsive materials are also described. Taken together, M–NHC-templated approaches have proven to be powerful methods for constructing diverse architectures with functional applications. The development of this methodology is still in its infancy, with tremendous growth potential and a promising future. We believe that this Account will guide researchers to design fascinating and valuable M–carbene species for diverse applications.
Half-sandwich Cp*Ir and Cp*Rh metalacycles have been successfully applied in traditional domains encompassing organic transformations and catalysis in recent years, especially the catalytic ...activation of C-H bonds. Cyclometalation has proven to be a highly attractive and versatile synthetic method for the formation of organometallic metalacycles. This review intends to describe isolated and well-defined cyclometalated iridium/rhodium complexes that contain a Cp*M-C (M = Ir, Rh) bond stabilised by the intramolecular coordination of neutral donor atoms (N, C, O or P). The formation of metalamacrocycles and cages employing cyclometalated approaches is discussed. In focusing on selected mechanistic insights garnered from iridium/rhodium-catalysed functionalisation of C-H bonds involving cyclometalated complexes, a limited number of substrates will be discussed, but a broad range of mechanistic features is highlighted.
Microglial cells are important resident innate immune components in the central nervous system that are often activated during neuroinflammation. Activated microglia can display one of two ...phenotypes, M1 or M2, which each play distinct roles in neuroinflammation. Rutin, a dietary flavonoid, exhibits protective effects against neuroinflammation. However, whether rutin is able to influence the M1/M2 polarization of microglia remains unclear. In this study, in vitro BV-2 cell models of neuroinflammation were established using 100 ng/mL lipopolysaccharide to investigate the effects of 1-hour rutin pretreatment on microglial polarization. The results revealed that rutin pretreatment reduced the expression of the proinflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 and increased the secretion of interleukin-10. Rutin pretreatment also downregulated the expression of the M1 microglial markers CD86 and inducible nitric oxide synthase and upregulated the expression of the M2 microglial markers arginase 1 and CD206. Rutin pretreatment inhibited the expression of Toll-like receptor 4 and myeloid differentiation factor 88 and blocked the phosphorylation of I kappa B kinase and nuclear factor-kappa B. These results showed that rutin pretreatment may promote the phenotypic switch of microglia M1 to M2 by inhibiting the Toll-like receptor 4/nuclear factor-kappa B signaling pathway to alleviate lipopolysaccharide-induced neuroinflammation.
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