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An efficient synthesis of bisbenzopyrones by a N-heterocyclic carbene (NHC)-catalyzed intramolecular hydroacylation-Stetter reaction cascade has been developed. A series of symmetrical and unsymmetrical bisbenzopyrones were obtained with good to excellent yields. Bisbenzopyran-4-ol was synthesized efficiently. [ABSTRACT FROM AUTHOR]

An efficient N-heterocyclic carbene catalyzed glycosylation of 2-nitrogalactals with alcohols and phenol has been developed for the first time. A wide variety of 1,2-cis-2-nitroglycosides can be obtained with good to excellent yields and high to excellent α-selectivities. [ABSTRACT FROM AUTHOR]

Dimethylzirconocene reacts with 2 molar equiv of the persistent radical TEMPO to give the Cp2Zr(Me)OTMP complex 12 with formation of TEMPOMe. Methyl anion abstraction from 12 with B(C6F5)3 generates the [Cp2ZrOTMP+] cation 13 (with the [MeB(C6F5)3]- anion) that undergoes a typical intramolecular frustrated Zr+/N Lewis pair (FLP) reaction with phenylacetylene. With PtBu3 it reacts as an intermolecular Zr+/P FLP trapping carbon dioxide. Complex 12 reacts with HB(C6F5)2 also by methyl anion abstraction to form the μ-H bridged tight ion pair Cp2ZrOTMP(μ-H)BMe(C6F5)2 (19). It serves as a Cp2Zr(H)OTMP zirconocene hydride source in the reaction with CO2, giving the respective [Zr](μ-formate)[B] complex 23. With carbon monoxide it forms the Zr-(η²-acetaldehyde)[B] complex 30 by transfer of both the hydride and the methyl anion from the Zr/B pair to the carbon atom of the CO molecule. [ABSTRACT FROM AUTHOR]

The first catalytic enantioselective isomerization of secondary allylic alcohols to access ketones with a α-tertiary stereocenter is presented. The racemic allylic alcohol substrates can be converted to the enantioenriched ketone products in a stereoconvergent fashion. The use of commercially available catalysts and mild reaction conditions makes this an attractive method in stereoselective synthesis. [ABSTRACT FROM AUTHOR]

What are the physical laws of the diffusive search of proteins for their specific binding sites on DNA in the presence of the macromolecular crowding in cells? We performed extensive computer simulations to elucidate the protein target search on DNA. The novel feature is the viscoelastic non-Brownian protein bulk diffusion recently observed experimentally. We examine the influence of the protein-DNA binding affinity and the anomalous diffusion exponent on the target search time. In all cases an optimal search time is found. The relative contribution of intermittent three-dimensional bulk diffusion and one-dimensional sliding of proteins along the DNA is quantified. Our results are discussed in the light of recent single molecule tracking experiments, aiming at a better understanding of the influence of anomalous kinetics of proteins on the facilitated diffusion mechanism. [ABSTRACT FROM AUTHOR]

An In-based metal-organic framework, with 1D nanotubular open channels, In2(OH)(btc)(Hbtc)0.4(L)0.6·3H2O (1), has been synthesized via an in situ ligand reaction, in which 1,2,4-H3btc is partially transformed into the L ligand. Compound 1 exhibits exceptional thermal and chemical stability, especially in water or acidic media. The activated 1 presents highly selective sorption of carbon dioxide (CO2) over dinitrogen. Interestingly, diffuse-reflectance infrared Fourier transform spectroscopy with a carbon monoxide probe molecule demonstrates that both Lewis and Brønsted acid sites are involved in compound 1. As a result, as a heterogeneous Lewis and Brønsted acid bifunctional catalyst, 1 possesses excellent activity and recyclability for chemical fixation of CO2 coupling with epoxides into cyclic carbonates under mild conditions. In addition, the mechanism for the CO2 cycloaddition reaction has also been discussed. [ABSTRACT FROM AUTHOR]

Polyethyleneglycol borate (PEG-BAE) toughening agents were preparedfrom the esterification reaction between boric acid and PEG and characterizedby FTIR and NMR. The effect of reaction conditions such as reactiontemperatures, reaction times, and entrainer amounts on the esterificationreaction rate was studied. Incorporation of PEG-BAE into phenolic(PF) foams leads to an improvement in the flexural and compressionstrengths, and a reduced pulverization ratio compared with pure andPEG-toughened foams. The LOI results illustrate the flame-retardingeffect of PEG-BAE is better than that of pure PEG, with LOI in therange 35.5–39.0%, and all PF foams pass UL 94 V-0 rating. Conecalorimeter results indicate that the incorporation of PEG400 increasesthe peak heat-release rate (PHRR) of PF foam by 38%, whereas PEG400-BAEresults in a slightly decreased PHRR. Moreover, thermal decompositionof pure and toughened PF foams was investigated. [ABSTRACT FROM AUTHOR]

The effects of medicine on the biomolecular interaction have been given increasing attention in biochemistry and affinity-based analytics since the environment in vivo is complex especially for the patients. Herein, myoglobin, a biomarker of acute myocardial infarction, was used as a model, and the medicine effects on the interactions of myoglobin/aptamer and myoglobin/antibody were systematically investigated using atomic force microscopy (AFM) for the first time. The results showed that the average binding force and the binding probability of myoglobin/aptamer almost remained unchanged after myoglobin-modified gold substrate was incubated with promazine, amoxicillin, aspirin, and sodium penicillin, respectively. These parameters were changed for myoglobin/antibody after the myoglobin-modified gold substrate was treated with these medicines. For promazine and amoxicillin, they resulted in the change of binding force distribution of myoglobin/antibody (i.e., from unimodal distribution to bimodal distribution) and the increase of binding probability; for aspirin, it only resulted in the change of the binding force distribution, and for sodium penicillin, it resulted in the increase of the average binding force and the binding probability. These results may be attributed to the different interaction modes and binding sites between myoglobin/aptamer and myoglobin/antibody, the different structures between aptamer and antibody, and the effects of medicines on the conformations of myoglobin. These findings could enrich our understanding of medicine effects on the interactions of aptamer and antibody to their target proteins. Moreover, this work will lay a good foundation for better research and extensive applications of biomolecular interaction, especially in the design of biosensors in complex systems. [ABSTRACT FROM AUTHOR]

A new uranyl silicate, K2Ca4[(UO2)(Si2O7)2], with a 1D chain structure has been synthesized from a solution of mixed alkali- and alkaline-earth-metal cations under hydrothermal conditions at 550 °C and 1400 bar and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. It crystallizes in the triclinic space group P1̅ (No. 2) with a = 6.6354(2) Å, b = 6.6791(2) Å, c = 9.6987(3) Å, α = 98.324(2)°, β = 93.624(2)°, γ = 112.310(2)°, and Z = 1. Its crystal structure consists of a 1D chain of uranyl disilicate formed of corner-sharing UO6 tetragonal bipyramids and Si2O7 double groups. The adjacent chains are separated by K+ and Ca2+ cations. It is the first example of uranyl silicate with a 1D chain structure. [ABSTRACT FROM AUTHOR]

Herein, two stable lead(II) molecular-bowl-based metal-organic frameworks and their micro- and nanosized forms with open metal sites were presented. These materials could act as Lewis acid catalysts to cyanosilylation reaction. Moreover, the catalytic performances are size-dependent, with the catalyst with nanosized form being 1 order of magnitude more efficient than those with micro- and millisized forms. [ABSTRACT FROM AUTHOR]

Brønstedacid p-TsOH·H2O-catalyzedhydrovinylation of styrenes with internal olefins α-oxo ketenedithioacetals was efficiently achieved in the presence of N-phenylselenophthalimide (N-PSP), regioselectivelyaffording Markovnikov phenylselenative hydrovinylation products throughPhSe transfer of the phenylseleno ketene dithioacetal intermediates.Radical reduction of the resultant PhSe-alkyl-substituted ketene dithioacetalswith AIBN/n-Bu3SnH gave the corresponding anti-Markovnikov hydrovinylation products formally fromthe linear codimerization of styrenes and the internal olefins. [ABSTRACT FROM AUTHOR]

Two series of OAc–-dependent unique homoleptic nonanuclear [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] (1–7) and hexanuclear {[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (8–14) are obtained from the self-assembly of the partially deprotonated OH-H2Salen ligand H3L1 (N,N′-bis(salicylidene)(propylene-2-ol)-1,3-diamine) or OH-MeO-H2Salen ligand H3L2 (N,N′-bis(3-methoxysalicylidene)(propylene-2-ol)-1,3-diamine) with Ln(OAc)3 (Ln = La, Eu, Tb, Gd, Nd, Yb, or Er), respectively. The result of their photophysical properties shows that the sensitization for single-component near-white-light of complex 2, efficient Eu3+-centered red-light (ΦLEu = 13.4%) of complex 9, or or Tb3+-centered yellowish-green-light (ΦLTb = 8.1% and 21.3%) of complexes 3 and 10, and Nd3+- or Yb3+-centered NIR luminescence (η = ΦLLn/ΦLnLn = 67–75% and 76–85%) for complexes 5–6 and 12–13, arose from the ligands’ 3π–π* excited state, due to effective intramolecular energy transfer and multiple Ln3+-to-Ln3+ electron-communications. [ABSTRACT FROM AUTHOR]

Black phosphorene (BP)/carbon nanotube (CNT) heterostructures can be classified as either type I or II, depending on the size of the CNTs. An external electric field (Eext) can modulate the interfacial electronic structures and separate the electron and hole carriers of the BP/CNT heterostructures. The giant Stark effect is observed, and the band gap of the semiconducting heterostructures can vary several-fold. The intercalation of 3d transition metals can strongly bond BP and CNTs together. Furthermore, strong ferromagnetism with Curie temperature (TC) above room temperature is predicted. It is expected that these BP/CNT heterostructures will provide new opportunities and applications in the fields of optoelectronics and electronics as well as spintronics. [ABSTRACT FROM AUTHOR]

Knowledge of lectin and glycosidase specificities is fundamental to the study of glycobiology. The primary specificities of such molecules can be uncovered using well-established tools, but the complex details of their specificities are difficult to determine and describe. Here we present a language and algorithm for the analysis and description of glycan motifs with high complexity. The language uses human-readable notation and wildcards, modifiers, and logical operators to define motifs of nearly any complexity. By applying the syntax to the analysis of glycan-array data, we found that the lectin AAL had higher binding where fucose groups are displayed on separate branches. The lectin SNA showed gradations in binding based on the length of the extension displaying sialic acid and on characteristics of the opposing branches. A new algorithm to evaluate changes in lectin binding upon treatment with exoglycosidases identified the primary specificities and potential fine specificities of an α1- 2-fucosidase and an α2-3,6,8-neuraminidase. The fucosidase had significantly lower action where sialic acid neighbors the fucose, and the neuraminidase showed statistically lower action where α1-2 fucose neighbors the sialic acid or is on the opposing branch. The complex features identified here would have been inaccessible to analysis using previous methods. The new language and algorithms promise to facilitate the precise determination and description of lectin and glycosidase specificities. [ABSTRACT FROM AUTHOR]

Development of underwater superoleophobic surfaces has captured the imagination of researchers because of their applications; especially, oil manipulation based on such surfaces has attracted much attention. Here, we show a simple and effective way to fabricate an underwater transparent miniature "mechanical hand" based on controllable oil-adhesive patterned glass using a femtosecond laser. The underwater oil-adhesive force of the patterned glasses that compose the "mechanical hand" device can be controlled from ultralow to ultrahigh by adjusting the ratio of the untreated flat glass area to the laser-ablated rough area. These surfaces also showed favorable transparency in water. Various oils such as chloroform, hexadecane, n-dodecane, decane, liquid paraffin, and petroleum ether were tested, and their repellency against the as-prepared surfaces in water medium was confirmed. Moreover, the "mechanical hand" was used to implement oil transportation, fusion, and rapid capture, which can be applied in the construction of microfluidic devices, in situ detectors, and bioreactors. [ABSTRACT FROM AUTHOR]

Metal nanoclusters (NCs) as a new type of fluorescent material have been extensively explored because of their attractive set of features such as their ultrafine size, low toxicity, and excellent photostability. However, little progress has been made in producing water-soluble, homogeneous, and ultrabright metal NCs. In this study, gold NCs (AuNCs) with a photoluminescence quantum yield (QY) as high as 65% are synthesized in water through a simple blending route. Weak emission is observed from the 6-aza-2-thiothymine-protected AuNCs (ATT-AuNCs); however, the fluorescence intensity can be prominently enhanced by introducing l-arginine (Arg) into the capping layer. The fluorescence enhancement mechanism is systematically investigated by the measurements of ultraviolet-visible absorption spectroscopy, photoluminescence spectroscopy, fluorescence lifetime spectroscopy, transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, ¹H nuclear magnetic resonance, and calculations from density functional theory, with results isolating the vital role of the ligand shell and ruling out the effect of the gold core. The supramolecular host-guest assemblies formed between ATT capped on the gold core and the guanidine group of Arg make the capping ligands of ATT rigid. Subsequently, the intramolecular vibration and rotation of ATT are greatly suppressed, which reduce the nonradiative relaxation of excited states and, as a result, predominantly increase the luminescence QY of ATT-AuNCs. Further experiments demonstrate that a small change in guanidine substituents can arouse obvious changes in the photoluminescence features of NCs. We envision that this work will substantively contribute to the process of developing efficient synthetic routes to high-quality metal NCs. [ABSTRACT FROM AUTHOR]

Carcinoma-associated fibroblasts (CAFs) are found in many types of cancer and play an important role in tumor growth and metastasis. Fibroblast-activation protein (FAP), which is overexpressed on the surface of CAFs, has been proposed as a universal tumor targeting antigen. However, recent studies show that FAP is also expressed on multipotent bone marrow stem cells. A systematic anti-FAP therapy may lead to severe side effects and even death. Hence, there is an urgent need of a therapy that can selectively kill CAFs without causing systemic toxicity. Herein we report a nanoparticle-based photoimmunotherapy (nano-PIT) approach that addresses the need. Specifically, we exploit ferritin, a compact nanoparticle protein cage, as a photosensitizer carrier, and we conjugate to the surface of ferritin a FAP-specific single chain variable fragment (scFv). With photoirradiation, the enabled nano-PIT efficiently eliminates CAFs in tumors but causes little damage to healthy tissues due to the localized nature of the treatment. Interestingly, while not directly killing cancer cells, the nano-PIT caused efficient tumor suppression in tumor-bearing immunocompetent mice. Further investigations found that the nano-PIT led to suppressed C-X-C motif chemokine ligand 12 (CXCL12) secretion and extracellular matrix (ECM) deposition, both of which are regulated by CAFs in untreated tumors and mediate T cell exclusion that prevents physical contact between T cells and cancer cells. By selective killing of CAFs, the nano-PIT reversed the effect, leading to significantly enhanced T cell infiltration, followed by efficient tumor suppression. Our study suggests a new and safe CAF-targeted therapy and a novel strategy to modulate tumor microenvironment (TME) for enhanced immunity against cancer. [ABSTRACT FROM AUTHOR]

Capecitabine, an oral prodrug of 5-fluorouracil, inhibits DNA synthesis and has received FDA approval for treatment of metastatic colorectal and breast cancers. Hand-foot syndrome (HFS) is a serious dose-limiting toxicity and the most frequently reported side effect of capecitabine. Because of the lack of knowledge about the causative mechanism of HFS, scarce information is available for effective treatment or prevention. Data are based on published literatures and reports available from the HFS development program database. The purpose of this Review is to provide information regarding definition, clinical manifestation, and the possible mechanisms of HFS induced by capecitabine. Ethnic variations in the clinical presentation of HFS warrant further attention. Several physiological and pharmacological mechanisms have been investigated, such as cyclooxygenase (COX) inflammatory-type reaction, accumulation of capecitabine metabolites, and enzymes and transporters involved in the metabolism and absorption. Although current studies describe the possible mechanisms of HFS induced by capecitabine, much remains to be determined. It appears from this scientific evidence that additional study is needed to determine the effect of skin-mediated metabolism in the possible mechanism of HFS induced by capecitabine. [ABSTRACT FROM AUTHOR]

The first Pd-catalyzed multisite-selective acetoxylation reactions are disclosed at an unactivated alkene sp² C-H bond versus secondary allylic sp³ C-H bond in cyclic olefins via the modulation of directing groups. The different directing groups overcome the key challenge in differentiating C-H bonds and provide a new controlling approach for site-specific C-H activation. A wide variety of substrates are readily acetoxylated under operationally simple conditions. Mechanistic studies suggest that different Pd (IV) intermediates were involved in the multisite-selective acetoxylation reactions. [ABSTRACT FROM AUTHOR]

A visible-light-promoted, mild, and direct difunctionalization of alkynoates has been accomplished. This procedure provides a new strategy toward synthesis of the coumarin core structure by photoredox-mediated oxidation to generate the α-oxo radical, which supervenes a domino radical addition/cyclization reaction in moderate to good yields with high regioselectivity at ambient temperature. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) is a compelling candidate for next-generation electronics beyond conventional silicon-based devices due to the exhibition of a sharp metal-insulator transition. In this study, in order to realize functional VO2 film for flexible electronics, the growth of VO2 film directly on a transparent and flexible muscovite via van der Waals epitaxy is established. The heteroepitaxy and structural transition of VO2 films on muscovite are examined by a combination of high-resolution X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The unique metal-insulator transition of VO2 is further revealed with a change in electrical resistance over 10³ and a more than 50% variation of optical transmittance. Furthermore, due to the nature of muscovite, the VO2/muscovite heterostructure possesses superior flexibility and optical transparence. The approach developed in this study paves an intriguing way to fabricate functional VO2 film for the applications in flexible electronics. [ABSTRACT FROM AUTHOR]

Ethylene glycol (EG) is an essential chemical and forms mixtures with water or methanol in the production processes. Its purification is imperative in the production of pure EG from its water/methanol mixtures. Conventionally, distillation is employed in this separation process at the expense of massive energy consumption. Here water/methanol-EG mixtures are separated by the highly permeable PIM-1 membrane via pervaporation to produce the pure EG product. PIM-1 is one of most representative polymers of intrinsic microporosity (PIMs) that are attractive membrane materials. The overall separation performances for water/methanol-EG mixtures are investigated systematically. The membrane shows good separation performances as well as high purifying efficiency. Typically, the membrane has a high flux of 10.40 kg µm m-2 h-1 and separation factor of 24.2 in the pervaporation of methanol (18.50 wt %)-EG mixtures at 30 °C. In addition, effects of feed composition and temperature are investigated respectively on the separation performances. The flux and separation factor increases simultaneously with the water/methanol content in feed, whereas the separation factor decreases with increasing feed temperature for the methanol-EG mixture and the opposite for the water-EG mixture. The PIM-1 membrane shows a great potential in the EG purification industries. [ABSTRACT FROM AUTHOR]

Exciplex systems have become increasingly important due to their good performance in devices. Considering their bipolar transporting properties, exciplex systems with strong blue fluorescence and high triplet energies could potentially be ideal hosts for fluorescenceâ€"phosphorescence hybrid (Fâ€"P) white organic light-emitting diodes (WOLEDs). Here we achieved an efficient blue exciplex system formed with a new material (4-dimesitylboryl)phenyltriphenylamine (TPAPB) and 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi), which exhibited a high photoluminescence quantum yield of 44.1%. Using only these two organic materials, a high performance blue-emitting OLED was fabricated with a maximum external quantum efficiency (EQE) of 7.0 ± 0.4%. Such high efficiency is not only among the highest results of blue fluorescent organic light-emitting diodes (OLEDs) but also indicates that high Ï (fraction of excitons that can potentially radiatively decay) can be as well achieved via a TTA triplet up-conversion process. By simply doping an orange phosphor, the first Fâ€"P WOLED using an exciplex host system was realized with a single-emission-layer structure and merely three organic materials. The WOLED exhibits a maximum power efficiency, current efficiency, and EQE of 29.6 ± 0.2 lm Wâ€"1, 42.5 ± 0.3 cd Aâ€"1, and 15.7 ± 0.3%, respectively. To the best of our knowledge, this highly efficient and structurally simplified exciplex-based Fâ€"P WOLED is truly unprecedented. [ABSTRACT FROM AUTHOR]

Toxicological studies have shown that phthalates, a class of widely used chemicals, can impair male reproductive function, but epidemiological evidence is in consistent This study aimed to investigate the associations of semen phthalate metabolites with sperm apoptosis and DNA damage in a Chinese population. We assessed sperm apoptosis markers with Annexin V/PI analysis and sperm DNA integrity with comet assay before measuring eight phthalate metabolites in semen by high-performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS ) among 463 men from Wuhan, China. We found a suggestive do se-response relationship between semen mono-(2-ethylhexyl) phthalate (MEHP) and an increased percentage of Annexin V7PF sperm (p for trend of <0.10). We also observed that semen monomethyl phthalate (MMP) and monoethyl phthalate (MEP) were associated with significant dose-related increases in tail length of the comet (both p for trend of < 0.01). In conclusion, our data indicate that semen MEHP is associated with increased sperm apoptosis and that semen MMP and MEP are associated with increased sperm DNA damage in a Chinese population. [ABSTRACT FROM AUTHOR]

An easily prepared platinum nanoparticle (PtNP) probe for the sensitive and selective detection of Hg2+ ions is developed here. The PtNPs with an average size of approximately 2.5 nm were prepared by a reduction method with sodium borohydride and trisodium citrate serving as reductant and stabilizer, respectively. The resulting PtNPs could catalyze the reduction of Hg2+ by surface-capping citrate. The effect of Hg2+ uptake implies amalgam formation, which leads to remarkable inhibition of the peroxidase-like activity of citrate-capped PtNPs. On the basis of this effect, a colorimetric mercury sensor was established through the use of citrate-capped PtNPs to catalyze the colorimetric system of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2. The high specificity of the Hg-Pt interaction provides the excellent selectivity for Hg2+ over interfering metal ions. The sensitivity of this smart probe to Hg2+ is extremely excellent with a limit of detection (LOD) as low as 8.5 pM. In view of these advantages, as well as the cost-effectiveness, minimized working steps, and naked-eye observation, we expect that this colorimetric sensor will be a promising candidate for the field detection of toxic Hg2+ ions in environmental, biological, and food samples. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing is expanding rapidly in the US to meet increasing energy demand and requires high volumes of hydroffacking fluid to displace natural gas from shale. Accidental spills and deliberate land application of hydroffacking fluids, which return to the surface during hydroffacking, are common causes of environmental contamination. Since the chemistry of hydroffacking fluids favors transport of colloids and mineral particles through rock cracks, it may also facilitate transport of in situ colloids and associated pollutants in unsaturated soils. We investigated this by subsequendy injecting deionized water and flowback fluid at increasing flow rates into unsaturated sand columns containing colloids. Colloid retention and mobilization was measured in the column effluent and visualized in situ with bright field microscopy. While <5% of initial colloids were released by flushing with deionized water, 32-36% were released by flushing with flowback fluid in two distinct breakthrough peaks. These peaks resulted from l) surface tension reduction and steric repulsion and 2) slow kinetic disaggregation of colloid floes. Increasing the flow rate of the flowback fluid mobilized an additional 36% of colloids, due to the expansion of water filled pore space. This study suggests that hydroffacking fluid may also indirectly contaminate groundwater by remobilizing existing colloidal pollutants. [ABSTRACT FROM AUTHOR]