Because of the importance of novel macrocycles in supramolecular science, interest in the preparation of these substances has grown considerably. However, the discovery of a new class of macrocycles ...presents challenges because of the need for routes to further functionalization of these molecules and good host–guest complexation. Furthermore, useful macrocylic hosts must be easily synthesized in large quantities. With these issues in mind, the recently discovered pillararenes attracted our attention. These macrocycles contain hydroquinone units linked by methylene bridges at para positions. Although the composition of pillararenes is similar to that of calixarenes, they have different structural characteristics. One conformationally stable member of this family is pillar5arene, which consists of five hydroquinone units. The symmetrical pillar architecture and electron-donating cavities of these macrocycles are particularly intriguing and afford them with some special and interesting physical, chemical, and host–guest properties. Due to these features and their easy accessibility, pillararenes, especially pillar5arenes, have been actively studied and rapidly developed within the last 4 years. In this Account, we provide a comprehensive overview of pillararene chemistry, summarizing our results along with related studies from other researchers. We describe strategies for the synthesis, isomerization, and functionalization of pillararenes. We also discuss their macrocyclic cavity sizes, their host–guest properties, and their self-assembly into supramolecular polymers. The hydroxyl groups of the pillararenes can be modified at all positions or selectively on one or two positions. Through a variety of functionalizations, researchers have developed many pillararene derivatives that exhibit very interesting host–guest properties both in organic solvents and in aqueous media. Guest molecules include electron acceptors such as viologen derivatives and (bis)imidazolium cations and alkyl chain derivatives such as n-hexane, alkanediamines, n-octyltrimethyl ammonium, and neutral bis(imidazole) derivatives. These host–guest studies have led to the fabrication of (pseudo)rotaxanes or poly(pseudo)rotaxanes, supramolecular dimers or polymers, artificial transmembrane proton channels, fluorescent sensors, and other functional materials.
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The first water-soluble pillar6arene was synthesized. Its water solubility can be reversibly controlled by changing the pH. This solubility control was used in reversible transformations between ...nanotubes and vesicles and dispersion of multiwalled carbon nanotubes in water.
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The complexation between a water-soluble pillar6arene (WP6) and paraquat (G1) in water was investigated. They could form a stable 1:1 2pseudorotaxane with an extremely high association constant of ...(1.02 ± 0.10) × 108 M–1 mainly driven by electrostatic interactions, hydrophobic interactions, and π–π stacking interactions. This molecular recognition has not only high binding strength but also pH-responsiveness. The threading and dethreading processes of this 2pseudorotaxane could be reversibly controlled by changing the solution pH. This novel recognition motif was further used to control the aggregation of a complex between WP6 and an amphiphilic paraquat derivative (G2) in water. The reversible transformations between micelles based on G2 and vesicles based on WP6⊃G2 were realized by adjusting the solution pH due to the pH-responsiveness of WP6. The controlled release of water-soluble dye molecules from the vesicles could be achieved by the collapse of the vesicles into the micelles upon changing the solution pH to acidity. Additionally, the high binding affinity between WP6 and paraquat could be utilized to efficiently reduce the toxicity of paraquat. After the formation of a stable host–guest complex between WP6 and paraquat, less opportunity was available for paraquat to interact with the reducing agents in the cell, which made the generation of its radical cation more difficult, resulting in the efficient reduction of paraquat toxicity.
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4.
Food versus fuel: What do prices tell us? Zhang, Zibin; Lohr, Luanne; Escalante, Cesar ...
Energy policy,
2010, 2010-01-00, 20100101, Volume:
38, Issue:
1
Journal Article
Peer reviewed
Sorting out the impacts of biofuels on global agricultural commodity prices is impossible without turning to data and distinguishing between the short-run versus the long-run impacts. Using ...time-series prices on fuels and agricultural commodities, the aim is to investigate the long-run cointegration of these prices simultaneously with their multivariate short-run interactions. Results indicate no direct long-run price relations between fuel and agricultural commodity prices, and limited if any direct short-run relationships. In terms of short-run price movements, sugar prices are influencing all the other agricultural commodity prices except rice. With sugar the number one world input for ethanol, results indicate increased ethanol production is potentially influencing short-run agricultural commodity prices. Overall, results support the effect of agricultural commodity prices as market signals which restore commodity markets to their equilibria after a demand or supply event (shock).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Although platinum-based anticancer drugs prevail in cancer treatment, their clinical applications are limited by the severe side effects as well as their ineffectiveness against drug resistant ...cancers. A precise combination of photodynamic therapy (PDT) and chemotherapy can synergistically improve the therapeutic outcome and thereby may overcome drug resistance through a multipronged assault. Herein, we employ the well-defined cavity of a discrete organoplatinum(II) metallacage (M) to encapsulate octaethylporphine (OEP), a photosensitizer, forming a dual-functionalized system M⊃OEP that is wrapped into the hydrophobic core of the nanoparticles (MNPs) self-assembled from an amphiphilic diblock copolymer. Using a copper-free click reaction, a targeting ligand is conjugated on the surface of the MNPs, aiming to specifically deliver a chemotherapeutic drug and a photosensitizer to cancer cells. Benefiting from the enhanced permeability and retention effect and active targeting capability, high tumor accumulation of MNPs is achieved, leading to an improved therapeutic outcome and reduced side effects. In vivo studies demonstrate that the combination of chemotherapy and PDT exhibits a superior antitumor performance against a drug-resistant tumor model attributed to their synergistic anticancer efficacy.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
A muscle-like metallo-supramolecular polymer based on a solvent-driven c 2daisy chain has been prepared from an amino-modified pillar5arene. The integration of terpyridine moieties on both ends of ...the c 2daisy chain and the stiff architecture of pillar5arene units facilitated the efficient formation of the metallo-supramolecular polymer. UV/vis absorption spectroscopy, dynamic light scattering, transmission electron microscopy and scanning electron microscopy were used to characterize the self-assembly behavior of the resulting polymer chains. From proton NMR studies, we confirmed that the pillar5arene-based c 2daisy chain could change its length continuously in response to changes in the polarity of the solvent. Consequently, the metallo-supramolecular polymer could change its length continuously according to the solvent polarity based on the individual contraction or extension of each daisy chain repeating unit. The current system can serve as a platform to mimic the muscle movement.
Two new copillar5arenes were prepared. They are arranged in two completely different motifs, a cyclic dimer containing two monomers with two different conformations that are mirror images of each ...other and linear supramolecular polymers in the solid state. Not only has it been shown that to form this kind of dimer is a unique feature associated with pillar5arene macrocycles but also it was demonstrated that weak van der Waals forces can be used to control the self-organization of monomers during their supramolecular polymerization process.
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Ischemic stroke is a leading cause of death among human in the world, and a critical cause for long-term disability. Accumulating studies have indicated that inflammatory response regulated by ...microglia contributes a lot to neuronal death, but the molecular mechanism still remains unclear. V-set and immunoglobulin domain-containing 4 (Vsig4), a complement receptor of the immunoglobulin superfamily (CRIg) that specifically expresses in resting tissue-resident macrophages, plays a critical role in regulating various inflammatory diseases via multiple signaling pathways. However, the effects of Vsig4 on ischemic stroke have not been investigated. In this study, we identified that Vsig4 expression was decreased after cerebral ischemic injury induced by middle cerebral artery occlusion (MCAO). Immunofluorescence staining showed that Vsig4 was co-localized with Iba1 in microglial cells from the infarct region of MCAO-operated mice. After over-expressing Vsig4 in mice, MCAO-induced infarction area and neurological deficits score were markedly attenuated. In addition, neurological dysfunction due to MCAO surgery was improved by Vsig4 over-expression. Microglial M1 polarization was detected in mice with MCAO surgery, which was markedly inhibited by Vsig4 over-expression, as evidenced by the markedly reduced expression of CD16, CD11b, inducible nitric oxide synthase (iNOS) and interleukin 6 (IL-6); however, the expression of M2-like phenotype hallmarks such as arginase 1 (Arg1), CD206, IL-10 and Ym-1 was significantly up-regulated. Mechanistically, the anti-inflammatory role of Vsig4 was mainly through the blockage of toll-like receptor 4/nuclear factor kappa B (TLR4/NF-κB) signaling via the in vivo and in vitro experiments. Also, we found that microglial TLR4 expression in the cerebral infarct area of MCAO mice was highly suppressed by Vsig4 over-expression. In vitro, the neuron-glial mixed culture by fluorescent staining showed that oxygen glucose deprivation (OGD) treatment led to significant cell death, while being attenuated by Vsig4 over-expression in primary microglial cells. Finally, we showed that Vsig4 could interact with TLR4 and repress its expression, subsequently alleviating ischemic stroke. Collectively, our findings demonstrated that microglial Vsig4 protected against post-stroke neuro-inflammation mainly through interacting with TLR4.
•Vsig4 attenuates cerebral I/R injury in mice after reperfusion.•Vsig4 inhibits M1 like phenotype but promotes M2 like phenotype after stroke.•Vsig4-associated inflammation inhibition in microglia is rely on interacting with TLR4 pathway.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Control of self-assembly is significant to the preparation of supramolecular materials and illustration of diversities in either natural or artificial systems. Supra-amphiphiles have remarkable ...advantages in the construction of nanostructures but control of shape and size of supramolecular nanostructures is still a great challenge. Here, we fabricate a series of supra-amphiphiles by utilizing the recognition motifs based on a heteroditopic porphyrin amphiphile and its zinc complex. These porphyrin amphiphiles can bind with a few guests including Cl
, coronene, C
, 4,4'-bipyridine and 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine, which are further applied to facilitate the controllable self-assembly. Addition of these guests result in the formation of various supra-amphiphiles with well-defined structures, thus induce the generation of different aggregates. A diverse of aggregation morphologies including nanospheres, nanorods, films, spheric micelles, vesicles and macrowires are constructed upon the influence of specific complexation, which highlights the present work with abundant control on the shapes and dimensions of self-assemblies.
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