Search

An improved, one-pot Minisci reaction has been developed using visible light, an organic photocatalyst, and carboxylic acids as radical precursors via the intermediacy of in situ-generated N-(acyloxy)phthalimides. The conditions employed are mild, demonstrate a high degree of functional group tolerance, and do not require a large excess of the carboxylic acid reactant. As a result, this reaction can be applied to drug-like scaffolds and molecules with sensitive functional groups, enabling late-stage functionalization, which is of high interest to medicinal chemistry. [ABSTRACT FROM AUTHOR]

Binuclear non-heme iron enzymes activate O2 for diverse chemistries that include oxygenation of organic substrates and hydrogen atom abstraction. This process often involves the formation of peroxo- bridged biferric intermediates, only some of which can perform electrophilic reactions. To elucidate the geometric and electronic structural requirements to activate peroxo reactivity, the active peroxo intermediate in 4 -aminobenzoate N- oxygenase (AurF) has been characterized spectroscopically and computationally. A magnetic circular dichroism study of reduced AurF shows that its electronic and geometric structures are poised to react rapidly with O2. Nuclear resonance vibrational spectroscopic definition of the peroxo intermediate formed in this reaction shows that the active intermediate has a protonated peroxo bridge. Density functional theory computations on the structure established here show that the protonation activates peroxide for electrophilic/single-electron-transfer reactivity. This activation of peroxide by protonation is likely also relevant to the reactive peroxo intermediates in other binuclear non- heme iron enzymes. [ABSTRACT FROM AUTHOR]

A three-dimensional graphene-copper (3D GR-Cu) foam electrode prepared by chemical vapor deposition method exhibited superior electrocatalytic activity toward the dechlorination of trichloroacetic acid (TCAA) as compared to the Cu foam electrode. The cyclic voltammetry and electrochemical impedance spectra analysis confirmed that GR accelerated the electron transfer from the cathode surface to TCAA. With the applied cathode potential of -1.2 V (vs SCE), 95.3% of TCAA (500 µg/L) was removed within 20 min at pH 6.8. TCAA dechlorination at the Cu foam electrode was enhanced at acidic pH, while a slight pH effect was observed at the GR-Cu foam electrode with a significant inhibition for Cu leaching. The electrocatalytic dechlorination of TCAA was accomplished via a combined stepwise and concerted pathway on both electrodes, whereas the concerted pathway was efficiently promoted on the GR-Cu foam electrode. The direct reduction by electrons was responsible for TCAA dechlorination at Cu foam electrode, while at GR-Cu foam electrode, the surface-adsorbed atomic H* also contributed to TCAA dechlorination owing to the chemical storage of hydrogen in the GR structure. Finally, the potential applicability of GR-Cu foam was revealed by its stability in the electrocatalytic dechlorination over 25 cycles. [ABSTRACT FROM AUTHOR]

Three series of lanthanide coordination polymers, {[Ln(L)(H2O)2]·NO3·2H2O }n (Ln = La 1, Pr 2), {[Ln2(L)2(NO3)(H2O)2]·Cl·6H2O}n (Ln = Nd 3), {[Ln(L)(H2O)2]·Cl·3H2O}n (Ln = Sm 4, Eu 5, Gd 6, Tb 7, Dy 8, Ho 9, Er 10, Tm 11, Yb 12, and Lu 13) (H3L = 4-carboxy-1-(3,5-dicarboxy-benzyl)-pyridinium chloride), have been successfully synthesized under hydro(solvo)thermally conditions. Single-crystal X-ray diffraction analyses revealed that compounds 1-3 all crystallize in triclinic space group P1̅, but they display different three-dimensional structures with diverse dinuclear subunits. In contrast, compounds 4-13 display the same layer structures in the triclinic space group P1̅. The structural difference of these two classes of compounds is derived from the effect of lanthanide contraction. Powder X-ray diffraction (PXRD) and thermogravimetric analyses of compounds 1-13 have also been investigated and discussed in detail. The solid-state luminescent properties of compounds 4, 5, 7, and 8 were characterized, and the results revealed that they exhibit characteristic Sm(III), Eu(III), Tb(III), and Dy(III) emissions in the pink, red, green, and yellow light regions, respectively. More interestingly, the luminescence colors of the Tb(1-x)(L):xEu can easily be tuned from green to green-yellow, yellow, orange, and red-orange due to the energy transfer from Tb3+ to Eu3+ ions by adjusting the doping concentration of Eu3+ ions. [ABSTRACT FROM AUTHOR]

A newstrategy for the synthesis of jet fuel range branched alkanes withthe xylose and methyl isobutyl ketone (MIBK) from lignocellulose wasintroduced. C10and C11branched alkanes withlow freezing points were synthesized by three steps: (1) the dehydrationof xylose to furfural over solid acid catalysts in MIBK/water biphasicsolvent systems; (2) solid base catalyzed aldol condensation of furfuralwith MIBK which was also the most effective extracting solvent inthe first step; (3) solvent-free hydrodeoxygenation of aldol condensationproduct to jet fuel range branched alkanes over Ru/H-ZSM-5 catalyst.Alternatively, oxygenated fuel can also be obtained by the low temperaturehydrogenation of aldol condensation product over Ru/C catalyst. [ABSTRACT FROM AUTHOR]

The enormous synthetic efforts on novel solar cell materials require a reliable and fast technique for the rapid screening of novel donor/acceptor combinations in order to quickly and reliably estimate their optimized parameters. Here, we report the applicability of such a versatile and fast evaluation technique for bulk heterojunction (BHJ) organic photovoltaics (OPV) by utilizing a steady-state photoluminescence (PL) method confirmed by electroluminescence (EL) measurements. A strong relation has been observed between the residual singlet emission and the charge transfer state emission in the blend. Using this relation, a figure of merit (FOM) is defined from photoluminescence and also electroluminescence measurements for qualitative analysis and shown to precisely anticipate the optimized blend parameters of bulk heterojunction films. Photoluminescence allows contactless evaluation of the photoactive layer and can be used to predict the optimized conditions for the best polymer–fullerene combination. Most interestingly, the contactless, PL-based FOM method has the potential to be integrated as a fast and reliable inline tool for quality control and material optimization. [ABSTRACT FROM AUTHOR]

Cyanobacterial aldehyde-deformylating oxygenases (ADOs) belong to the ferritin-like diiron-carboxylate superfamily of dioxygen-activating proteins. They catalyze conversion of saturated or monounsaturated Cn fatty aldehydes to formate and the corresponding Cn–1 alkanes or alkenes, respectively. This unusual, apparently redox-neutral transformation actually requires four electrons per turnover to reduce the O2 cosubstrate to the oxidation state of water and incorporates one O-atom from O2 into the formate coproduct. We show here that the complex of the diiron(II/II) form of ADO from Nostoc punctiforme (Np) with an aldehyde substrate reacts with O2 to form a colored intermediate with spectroscopic properties suggestive of a Fe2III/III complex with a bound peroxide. Its Mössbauer spectra reveal that the intermediate possesses an antiferromagnetically (AF) coupled Fe2III/III center with resolved subsites. The intermediate is long-lived in the absence of a reducing system, decaying slowly (t1/2 ~ 400 s at 5 °C) to produce a very modest yield of formate (<0.15 enzyme equivalents), but reacts rapidly with the fully reduced form of 1-methoxy-5-methylphenazinium methylsulfate (MeOPMS) to yield product, albeit at only ~50% of the maximum theoretical yield (owing to competition from one or more unproductive pathway). The results represent the most definitive evidence to date that ADO can use a diiron cofactor (rather than a homo- or heterodinuclear cluster involving another transition metal) and provide support for a mechanism involving attack on the carbonyl of the bound substrate by the reduced O2 moiety to form a Fe2III/III-peroxyhemiacetal complex, which undergoes reductive O–O-bond cleavage, leading to C1–C2 radical fragmentation and formation of the alk(a/e)ne and formate products. [ABSTRACT FROM AUTHOR]

So far, conventional processes that have been employed to delacquer the paints decorated on used beverage cans (UBCs) are less than satisfactory in economic and environmental effect. Therefore, a new method combining vacuum pyrolysis with dilute sulfuric acid leaching to delacquer the paints was investigated. The results of vacuum pyrolysis showed that the decoating rate increased with the increase of temperature and the paints were almost 100% removed from UBCs under the following conditions: temperature of 650 °C, holding time of 20 min, and residual gas pressure lower than 0.1 kPa. The pyrolysis oil was mainly composed of phenol and 2-methy-phenol analyzed by GC-MS. The delacquered UBCs were subsequently leached with 5% H2SO4 for 60 s and TiO2 was recovered by calcining the residuals in muffle furnace at 450 °C for 15 min. This innovative technology offers an effective method to delacquer paints from UBCs, which obtains excellent stripping effect and avoids the production of toxic substances generated in direct combustion process. Furthermore, the pyrolysis oil can be reused as chemical feedstock in other fields. [ABSTRACT FROM AUTHOR]

A solvent- and metal-free process has been developed for the direct methallylboration of ketones employing the stable B-methallylborinane 1, which was accelerated by tertiary alcohols. In the presence of 2.0 equiv of readily available tertiary alcohols such as tert-amyl alcohol, the methallylation products were prepared at room temperature in excellent yields. The salient features of the described process include simple operation, high efficiency, and mild reaction conditions. [ABSTRACT FROM AUTHOR]

Cyanobacterial aldehyde decarbonylases (ADs) catalyze the conversion of Cn fatty aldehydes to formate (HCO2-) and the corresponding Cn-1 alk(a/e)nes. Previous studies of the Nostoc punctiforme (Np) AD produced in Escherichia coli (Ec) showed that this apparently hydrolytic reaction is actually a cryptically redox oxygenation process, in which one O-atom is incorporated from O2 into formate and a protein-based reducing system (NADPH, ferredoxin, and ferredoxin reductase; N/F/FR) provides all four electrons needed for the complete reduction of O2. Two subsequent publications by Marsh and co-workers [Das, et al. (2011) Angew. Chem. Int. Ed.50, 7148-7152; Eser, et al. (2011) Biochemistry 50, 10743-10750] reported that their Ec-expressed Np and Prochlorococcus marinus (Pm) AD preparations transform aldehydes to the same products more rapidly by an O2-independent, truly hydrolytic process, which they suggested proceeded by transient substrate reduction with obligatory participation by the reducing system (they used a chemical system, NADH and phenazine methosulfate; N/PMS). To resolve this discrepancy, we re-examined our preparations of both AD orthologues by a combination of (i) activity assays in the presence and absence of O2 and (ii) 18O2 and H218O isotope-tracer experiments with direct mass-spectrometric detection of the HCO2- product. For multiple combinations of the AD orthologue (Np and Pm), reducing system (protein-based and chemical), and substrate (n-heptanal and n-octadecanal), our preparations strictly require O2 for activity and do not support detectable hydrolytic formate production, despite having catalytic activities similar to or greater than those reported by Marsh and co-workers. Our results, especially of the 18O-tracer experiments, suggest that the activity observed by Marsh and co-workers could have arisen from contaminating O2 in their assays. The definitive reaffirmation of the oxygenative nature of the reaction implies that the enzyme, initially designated as aldehyde decarbonylase when the C1-derived coproduct was thought to be carbon monoxide rather than formate, should be redesignated as aldehyde-deformylating oxygenase (ADO). [ABSTRACT FROM AUTHOR]

Challenging modeling problems include how to obtain a simple and accurate model for a partial differential equation (PDE) unknown nonlinear distributed parameter system (DPS). In this paper, a time/space separation modeling approach based on the interval type-2 T-S fuzzy model (IT2 T-S model) is proposed for nonlinear DPS. First, the spatial-temporal output is divided into a few dominant spatial basis functions and low-dimensional time series by a linear time/space separation method. Second, the interval type-2 T-S fuzzy model is determined from the low-dimensional time series to reconstruct the system dynamics through the spatial basis functions. As the IT2 T-S model employs an interval linear model in the consequent part, the relationship between the input and spatial output can be determined by linear expressions through type reduction and linear time/space reconstruction. Thus, the obtained model is suitable for control design. The simulation presents the accuracies and effectiveness of the proposed modeling methodologies. [ABSTRACT FROM AUTHOR]

Psychotripine, a trimeric pyrroloindoline derivative with an unprecedented hendecacyclic system bearing a hexahydro-1,3,5-triazine unit, was isolated from the leaves of Psychotria pilifera. The structure was elucidated on the basis of spectroscopic and quantum theory. A possible biogenesis was also postulated. [ABSTRACT FROM AUTHOR]

This paper presents a generalized predictive control (GPC) strategy for a spatially distributed transport-reaction process based on time–space decomposition. First, the Karhunen–Loève (K–L) decomposition is used for time–space decomposition to find the principal spatial structures and to reduce the dimension of the data. Then, an autoregressive exogenous (ARX) model is identified using the excitation input signals and the temporal coefficients obtained by the K–L decomposition. A GPC strategy is investigated based on the ARX model, with or without considering the system constraints. Numerical simulations on a catalytic rod illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Cyanobacterial aldehyde decarbonylase (AD) catalyzes conversion of fatty aldehydes (R-CHO) to alka(e)nes (R-H) and formate. Curiously, although this reaction appears to be redox-neutral and formally hydrolytic, AD has a ferritin-like protein architecture and a carboxylate-bridged dimetal cofactor that are both structurally similar to those found in di-iron oxidases and oxygenases. In addition, the in vitro activity of the AD from Nostoc punctifornie (Np) was shown to require a reducing system similar to the systems employed by these 02-utilizing di-iron enzymes. Here, we resolve this conundrum by showing that aldehyde cleavage by the Np AD also requires dioxygen and results in incorporation of 180 from 1802 into the formate product. AD thus oxygenates, without oxidizing, its substrate. We posit that (i) 02 adds to the reduced cofactor to generate a metal-bound peroxide nucleophile that attacks the substrate carbonyl and initiates a radical scission of the Cl-C2 bond, and (ii) the reducing system delivers two electrons during aldehyde cleavage, ensuring a redox-neutral outcome, and two additional electrons to return an oxidized form of the cofactor back to the reduced, 02-reactive form. [ABSTRACT FROM AUTHOR]

Traditional cell-based systems used to express integral membrane receptors have yet to produce protein samples of sufficient quality for structural study. Herein we report an in vivo method that harnesses the photoreceptor system of the retina to heterologously express G protein-coupled receptors in a biochemically homogeneous and pharmacologically functional conformation. As an example we show that the adenosine A1 receptor, when placed under the influence of the mouse opsin promoter and rhodopsin rod outer segment targeting sequence, localized to the photoreceptor cells of transgenic retina. The resulting receptor protein was uniformly glycosylated and pharmacologically well behaved. By comparison, we demonstrated in a control experiment that opsin, when expressed in the liver, had a complex pattern of glycosylation. Upon solubilization, the retinal adenosine A1 receptor retained binding characteristics similar to its starting material. This expression method may prove generally useful for generating high-quality G protein-coupled receptors for structural studies. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotube (SWNT)−polymer composites have been fabricated to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) of SWNTs. Our results indicate that SWNTs can be used as effective lightweight EMI shielding materials. Composites with greater than 20 dB shielding efficiency were obtained easily. EMI SE was tested in the frequency range of 10 MHz to 1.5 GHz, and the highest EMI shielding efficiency (SE) was obtained for 15 wt % SWNT, reaching 49 dB at 10 MHz and exhibiting 15−20 dB in the 500 MHz to 1.5 GHz range. The EMI SE was found to correlate with the dc conductivity, and this frequency range is found to be dominated by reflection. The effects of SWNT wall defects and aspect ratio on the EMI SE were also studied. [ABSTRACT FROM AUTHOR]

Examines the synthesis of the antitumor agent rhazinilam. Use of chiral auxiliary in the activation of carbon-hydrogen bond; Attachment of chiral platinum complexes to the nitrogen atom; Dehydrogenation of the diethyl group.

Studies the solution structure of the transcriptional activation domain of the bacteriophage T4 protein MotA. Expression and purification of the sample; Gel filtration analysis; Oligomeric state of the MotNF domain in solution; Assignments and secondary structure; Structure of the MotNF.

The article presents results of a research on the molecular reaction of different chemicals including amine, gold and oxygen. The study was designed to identify the specific reaction of the chemicals for better understanding concerning their application and uses. Moreover, the researchers also aim to identify further application of the chemicals.

This paper presents a switched offline multiple model predictive control procedure for nonlinear processes to ease the online computational burden and reduce the number of submodels. We employ the gap metric to characterize the dynamic difference between linear models and establish a linear model bank to approximate the nonlinear system. Based on the robust MPC algorithm, we develop an offline model predictive controller for each submodel. The polyhedral invariant set is utilized to expand the work scope of each local controller. In the offline part, a series of discrete states are selected, the corresponding feedback gains are precomputed, and associated polyhedral invariant sets are constructed. In the online implementation, the control input is simply calculated by calling the feedback gain according to the current state. A switching rule is then designed to integrate the submodels and guarantee the stability of the whole system. Finally, the corresponding simulation example is presented to validate the efficiency of the presented algorithm. [ABSTRACT FROM AUTHOR]

The chiral triazole carbene and Ti(OPr-i)4 cocatalyzed reaction between α,β-unsaturated aldehydes and 2-(aroylvinyl)benzaldehydes was systematically studied. A divergence in reaction pathways was observed under different reaction conditions. In benzene solvent and at ambient temperature, the reaction produced 4,5-dihydro-1,4-methanobenzo[c]oxepin-3-ones, the bridged caprolactones, as the major products in moderate yields with excellent enantioselectivity. The same reaction in dichloroethane and at 50 °C, however, gave 2,8-dihydrocyclopenta[a]indenes as the major products in most cases. The application of the method developed was demonstrated by the transformation of the bridged lactone products into enantiopure 4-hydroxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic acids. [ABSTRACT FROM AUTHOR]

High-density (0.82 g mL-1) jet-fuel range cycloalkanes were synthesized in high overall yields (~80%) by the aldol condensation of cyclopentanone and butanal followed by hydrodeoxygenation (HDO). Among the investigated solid-base catalysts, magnesium-aluminum hydrotalcite (MgAl-HT) exhibited the highest activity for the solvent-free aldol condensation of cyclopentanone and butanal. The excellent performance of MgAl-HT was rationalized by the synergism between strong base and weak acid sites on the surface of this material. The aldol condensation products were further hydrodeoxygenated to butylcyclopentane and 1,3-dibutylcyclopentane over the Ni/SiO2, Pd/SiO2, and bimetallic Ni-Pd/SiO2 catalysts. Compared to the Ni/SiO2 and Pd/SiO2 catalysts, the bimetallic Ni-Pd/SiO2 catalyst exhibited higher activity for the solvent-free HDO reaction. Over the 4%Ni-1%Pd/SiO2 catalyst, high carbon yield (88.0%) of butylcyclopentane and 1,3-dibutylcyclopentane was achieved at 503 K. According to the characterization results, the excellent performance of Ni-Pd/SiO2 catalyst can be explained by the formation of Ni-Pd alloy. [ABSTRACT FROM AUTHOR]

While living systems have developed highly efficient ways to convert chemical energy (e.g., ATP hydrolysis) to mechanical motion (e.g., movement of muscle), it remains a challenge to build muscle-like biomimetic systems to generate mechanical force directly from chemical reactions. Here we show that a continuous flow of reactant solution leads to by far the largest volume change to date in autonomous active gels driven by the Belousov-Zhabotinsky reaction. These results demonstrate that microfluidics offers a useful and facile experimental approach to optimize the conditions (e.g., fabrication methods, counterions, flow rates, concentrations of reagents) for chemomechanical transduction in active materials. This work thus provides much needed insights and methods for the development of chemomechanically active systems based on combining soft materials and microfluidic systems. [ABSTRACT FROM AUTHOR]

The high molecular weight (HMW) size variants present in therapeutic monoclonal antibody (mAb) samples need to be closely monitored and characterized due to their impact on product safety and efficacy. Because of the complexity and often low abundances in final drug substance (DS) samples, characterization of such HMW species is challenging and traditionally requires offline enrichment of the HMW species followed by analysis using various analytical tools. Here, we report the development of a postcolumn denaturation-assisted native SEC-MS method that allows rapid and in-depth characterization of mAb HMW species directly from unfractionated DS samples. This method not only provides high-confidence identification of HMW complexes based on accurate mass measurement of both the intact assembly and the constituent subunits but also allows in-depth analysis of the interaction nature and location. In addition, using the extracted ion chromatograms, derived from high-quality, native-like mass spectra, the elution profiles of each noncovalent and/or nondissociable complex can be readily reconstructed, facilitating the comprehension of a complex HMW profile. The utility of this novel method was demonstrated in different applications, ranging from enriched HMW characterization at late stage development, comparability assessment due to process changes, and forced degradation study of coformulated mAbs. As this method does not require prior enrichment, it is thus desirable for providing both rapid and in-depth characterization of HMW species during the development of therapeutic mAbs. [ABSTRACT FROM AUTHOR]

Because of the importance of the indole framework and the versatile transformation of nitro and formyl groups, the efficient synthesis of optically pure 2-alkyl-3-(1H-indol-3-yl)-4-nitrobutanals, one type of tryptamine precursors are of great interest for pharmaceutical and biological research. Herein, the Michael addition of aliphatic aldehydes to indolylnitroalkenes has been developed using (S)-diphenylprolinol trimethylsilyl ether as an organocatalyst, which provides the desired optically pure syn 2-alkyl-3-(1H-indol-3-yl)-4-nitrobutanal derivatives in up to 98% yield with up to >99:1 dr and >99% ee. To show the synthetic usefulness of this methodology, optically active 2-alkyl-4-nitro-3-(1-tosyl-1H-indol-3-yl)butan-1-ol and tryptamine derivatives are readily obtained by stepwise systematic transformations. [ABSTRACT FROM AUTHOR]

Based on the theory of equivalent transfer functions (ETFs), this work proposes a novel partial decoupling control technique for multivariable processes. By measuring the effect of each ETF element in decoupling control, a partial decoupling control structure selection criterion is proposed with the aims that the decoupler has the least complexity and that overall system performance is satisfied. The ETF parameters are then obtained under certain constraints. Consequently, a systematic design procedure is proposed in order to obtain a stable, proper, and causal partial decoupler matrix. Simulation results of several multivariable processes with different interaction characteristics are provided to demonstrate the simplicity and effectiveness of the design method. [ABSTRACT FROM AUTHOR]

Dibenzo-24-crown-8-based cryptand 4 forms 1:1 inclusion complexes with three paraquat derivatives, P1, P2, and P3, as demonstrated by proton NMR spectroscopy and X-ray analysis. However, it was found that methyl-substituted paraquat derivatives, P2 and P3, can bind cryptand 4 more strongly than non-methyl-substituted paraquat derivative P1. The association constants (Ka) were determined in acetone by using a UV-vis titration method to be 5.0 x 103 M-1 for 4·P1, 1.0 x 105 M-1 for 4·P2, and 1.2 x 105 M-1 for 4·P3, respectively. In the solid state, 4·P2 and 4·P3 have similar T-type inclusion complexation conformations, which are very different from the pseudorotaxane-type complexation conformation of 4·P1. Theoretical calculations were done to explain these experimental results. [ABSTRACT FROM AUTHOR]

An amorphous solid (glass) may crystallize faster at the surface than through the bulk, making surface crystallization a mechanism of failure for amorphous pharmaceuticals and other materials. An ultrathin coating of gold or polyelectrolytes inhibited the surface crystallization of amorphous indomethacin (IMC), an anti-inflammatory drug and model organic glass. The gold coating (10 nm) was deposited by sputtering, and the polyelectrolyte coating (3−20 nm) was deposited by an electrostatic layer-by-layer assembly of cationic poly(dimethyldiallyl ammonium chloride) (PDDA) and anionic sodium poly(styrenesulfonate) (PSS) in aqueous solution. The coating also inhibited the growth of existing crystals. The inhibition was strong even with one layer of PDDA. The polyelectrolyte coating still permitted fast dissolution of amorphous IMC and improved its wetting and flow. The finding supports the view that the surface crystallization of amorphous IMC is enabled by the mobility of a thin layer of surface molecules, and this mobility can be suppressed by a coating of only a few nanometers. This technique may be used to stabilize amorphous drugs prone to surface crystallization, with the aqueous coating process especially suitable for drugs of low aqueous solubility. [ABSTRACT FROM AUTHOR]

Due to the unique optical properties, colloidal quantum dots (QDs) are excellent candidates for developing next-generation display and solid-state lighting technologies. However, some factors including photoluminescence blinking and Förster resonance energy transfer (FRET) still affect their practical applications. Herein, a series of ZnCdSe-based core/shell QDs with low optical polydispersity have been successfully synthesized by a “low-temperature injection and high-temperature growth” precisely controlled method. The alloyed ZnCdSe core with a certain ratio of Cd and Zn was presynthesized first. Followed by accurate ZnS shell growth, the as-synthesized core/shell QDs are nonblinking with the nonblinking threshold volume of ∼137 nm3. The PL decay dynamics are all single-exponential for both QDs in solutions and close-packed solid films when ZnS shell thickness varying from 2 to 20 monolayers. FRET can be effectively suppressed after growing 10 monolayers of ZnS shell. All of these superb characteristics including nonblinking, single-exponential PL decay dynamics and suppressed FRET can be beneficial to high-quality QD-based light-emitting devices (QLEDs). By applying the ZnCdSe-based core/shell QDs with 10 monolayers ZnS shell, the highest external quantum efficiency of ∼17% was reached, which could compare favorably with the highest efficiency of green QLEDs with traditional multilayered structures. [ABSTRACT FROM AUTHOR]

An efficient synthesis of quinazolines based on an iron-catalyzed C(sp³)-H oxidation and intramolecular C-N bond formation using tert-BuOOH as the terminal oxidant is described. The reaction of readily available 2-alkylamino benzonitriles with various organometallic reagents led to 2-alkylamino N-H ketimine species. The FeCl2-catalyzed C(sp³)-H oxidation of the alkyl group employing tert-BuOOH followed by intramolecular C-N bond formation and aromatization afforded a wide variety of 2,4-disubstituted quinazolines in good to excellent yields. [ABSTRACT FROM AUTHOR]

A chromatography-free, asymmetric synthesis of the C2-symmetric P-chiral diphosphine t-Bu-SMS-Phos was developed using a chiral auxiliary-based approach in five steps from the chiral auxiliary in 36% overall yield. Separtion and recovery of the auxiliary were achieved with good yield (97%) to enable recycling of the chiral auxiliary. An air-stable crystalline form of the final ligand was identified to enable isolation of the final ligand by crystallization to avoid chromatography. This synthetic route was applied to prepare up to 4 kg of the final ligand. The utility of this material was demonstrated in the asymmetric hydrogenation of trifluoromethyl vinyl acetate at 0.1 mol % Rh loading to access a surrogate for the pharmaceutically relavent chiral trifluoroisopropanol fragment in excellent yield and enantiomeric excess (98.6%). [ABSTRACT FROM AUTHOR]

The opioid and neuropeptide FF pharmacophore-containing chimeric peptide 0 (BN-9) was recently developed and produced potent nontolerance forming analgesia. In this study, 11 analogues of 0 were designed and synthesized. An in vitro cAMP assay demonstrated that these analogues behaved as multifunctional agonists at both opioid and NPFF receptors. In mouse tail-flick test, most of the analogues produced potent nontolerance forming antinociception. Notably, 11 (DN-9) was 33-fold more potent than 0 at analgesic effects, which was mediated by μ- and κ-opioid receptors. In addition, 11 also produced powerful analgesic effects in the formalin pain and CFA-induced chronic inflammatory pain models. Strikingly, following its repeated administration for 6 days, 11 did not produce antinociceptive tolerance in the tail-flick test and CFA-induced pain model. The present work indicates that it is reasonable to design multifunctional peptide ligands for opioid and NPFF receptors in a single molecule producing effective nontolerance forming antinociception. [ABSTRACT FROM AUTHOR]

In the present work, polyelectrolyte multilayers (PEMs) and graphene sheets are applied to sequentially coat on the surface of hollow carbon spheres/sulfur composite by a flexible layer-by-layer (LBL) self-assembly strategy. Owing to the strong electrostatic interactions between the opposite charged materials, the coating agents are very stable and the coating procedure is highly efficient. The LBL film shows prominent impact on the stability of the cathode by acting as not only a basic physical barrier, and more importantly, an ion-permselective film to block the polysulfides anions by Coulombic repulsion. Furthermore, the graphene sheets can help to stabilize the polyelectrolytes film and greatly reduce the inner resistance of the electrode by changing the transport of the electrons from a "point-to-point" mode to a more effective "plane-to-point'' mode. On the basis of the synergistic effect of the PEMs and graphene sheets, the fabricated composite electrode exhibits very stable cycling stability for over 200 cycles at 1 A g-1, along with a high average Coulombic efficiency of 99%. With the advantages of rapid and controllable fabrication of the LBL coating film, the multifunctional architecture developed in this study should inspire the design of other lithium-sulfur cathodes with unique physical and chemical properties. [ABSTRACT FROM AUTHOR]

Nine cholinium ionic liquids (ILs) were synthesized. A high solubility of lignin (up to 483 mg g-1) and xylan (up to 721 mg g-1) was observed in four ILs containing organic anions, while cellulose, chitosan, and keratin were scarcely soluble in all ILs. These ILs were used for wheat straw pretreatment. Among the nine ILs tested, cholinium taurate ([Ch][Tau]) was the best. The effects of biomass particle sizes, water contents, and biomass loadings on the IL pretreatment were studied. Readily digestible residues were obtained after wheat straw up to 2 mm size was pretreated. Additionally, this IL pretreatment process was highly tolerant toward moisture. A good reducing sugar yield (79.7%) was achieved in the enzymatic hydrolysis of wheat straw pretreated by [Ch][Tau] at a biomass loading of 10% under 80 °C for 6 h. Therefore, renewable sulfonate-based cholinium ILs may be promising solvents for pretreatment and fractionation of lignocelluloses [ABSTRACT FROM AUTHOR]

This paper proposes a gap-metric-basedmultiple model predictivecontrol (MMPC) method for nonlinear systems with a wide operatingrange. The gap metric theory, integrated into a neighborhood estimationalgorithm, is utilized to partition the whole operating range intosubregions corresponding to operating points. A local controller isthen designed in each subregion and is composed of a constant feedbackcontrol and a receding infinite-horizon control with an estimatedpolyhedral stable region. To guarantee the global stability of thewhole system, we design a novel switching rule activating betweenlocal controllers. The simulation study on a continuous stirred-tankreactor (CSTR) is presented to validate the proposed methods. [ABSTRACT FROM AUTHOR]

An inherent challenge in using metal-organic frameworks (MOFs) for catalysis is how to access the catalytic sites generally confined inside the porous structure, in particular for substrates larger than the pores. We present here a promising solution to bypass this roadblock by modulating the facets of a crystalline MOF NENU-3a to enhance the facet exposure of the catalytic sites and the adsorption of substrates. Specifically, by transforming it with encapsulated catalysis-responsible polyoxometalate from octahedron characterized entirely by {111} facets to cube with only {100} facets, much enhanced catalytic activities were observed, especially for sterically demanding substrates that are otherwise hard to diffuse into the pores. Crystallographic analysis and adsorption/desorption experiments collectively established the critical effects of morphological control on the enhanced catalysis. The cubic crystals were then applied for biodiesel production, reaching more than 90% conversion of fatty acids (C12-C22) in comparison to <22% using octahedral crystals. [ABSTRACT FROM AUTHOR]

Aldehyde-deformylating oxygenase (ADO) is a ferritin-like nonheme-diiron enzyme that catalyzes the last step in a pathway through which fatty acids are converted into hydrocarbons in cyanobacteria. ADO catalyzes conversion of a fatty aldehyde to the corresponding alk(a/e)ne and formate, consuming four electrons and one molecule of O2 per turnover and incorporating one atom from O2 into the formate coproduct. The source of the reducing equivalents in vivo has not been definitively established, but a cyanobacterial [2Fe-2S] ferredoxin (PetF), reduced by ferredoxin-NADP+ reductase (FNR) using NADPH, has been implicated. We show that both the diferric form of Nostoc punctiforme ADO and its (putative) diferric-peroxyhemiacetal intermediate are reduced much more rapidly by Synechocystis sp. PCC6803 PetF than by the previously employed chemical reductant, 1-methoxy-5-methylphenazinium methyl sulfate. The yield of formate and alkane per reduced PetF approaches its theoretical upper limit when reduction of the intermediate is carried out in the presence of FNR. Reduction of the intermediate by either system leads to accumulation of a substrate-derived peroxyl radical as a result of off-pathway trapping of the C2-alkyl radical intermediate by excess O2, which consequently diminishes the yield of the hydrocarbon product. A sulfinyl radical located on residue Cys71 also accumulates with short-chain aldehydes. The detection of these radicals under turnover conditions provides the most direct evidence to date for a free-radical mechanism. Additionally, our results expose an inefficiency of the enzyme in processing its radical intermediate, presenting a target for optimization of bioprocesses exploiting this hydrocarbon-production pathway. [ABSTRACT FROM AUTHOR]

Two {Ni6} cluster-containing inorganic-organic hybrid compounds have been successfully synthesized in the presence of organic amine under hydrothermal conditions, and they were characterized by powder and single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, and IR spectroscopy. Structural analysis indicates that [Ni0.5(H2O)3][{Ni6(µ3-OH)3en(H2O)10}(H2P2W15O56)]·10H2O (1, en = ethylenediamine) is a triangular inorganic {Ni6} cluster substituted polyoxotungstate with only one en to stabilize the {Ni6} cluster. However, [Ni(dap)2]{[Ni1.5(dap)1.5-(H2O)3][Ni6(µ3-OH)3(dap)2(en)(H2O) {O2C(CH2)2CO2}0.5-(CH3COO)(P2W15O56)]}·15H2O (2, dap = 1,2-diaminopropane) is a three-dimensional inorganic-organic hybrid compound linked by succinic acid. The magnetic properties of both compounds were studied. In addition, the adsorption properties of compound 2 have also been investigated. [ABSTRACT FROM AUTHOR]

The tandem oxo-Michael-IED/HDA and oxo-Michael-IED/HDA-Michael-Aldol condensation transformations between (E)-2-hydroxyaryl-2-oxobut-3-enoate derivatives with enals have been developed in the presence of (S)-diphenylprolinol trimethylsilyl ether as an organocatalyst. Two types of tricyclic chroman derivatives were, respectively, obtained, by adjusting the reactant ratio and reaction temperature, in good yields (up to 96%) with excellent enantioselectivities (up to >99%) and good diastereoselecdvities (up to >30/1). It should be noted that the divergent chiral chroman derivatives were obtained by successive reaction of (E)-2-hydroxyaryl-2-oxobut-3-enoate derivatives with two different enal substrates in highly catalytic results. [ABSTRACT FROM AUTHOR]

We report a facile route to reversibly tune surface wettability of InxGa(1–x)N (InGaN) nanotip arrays by octylphosphonic acid (OPA) modification and ultraviolet–visible (UV–vis) light illuminations. Well-aligned InGaN nanotip arrays were grown by chemical vapor deposition (CVD). OPA was covalently attached to the InGaN nanotip surface, which was initially oxidized in Piranha solution. Because of the high surface energy of polar groups, OPA-coated InGaN nanotip arrays demonstrated superhydrophobic properties (contact angle of 154°). Transitions between superhydrophobicity and hydrophilicity were obtained through OPA adsorption and UV–vis light illumination. The InGaN nanotip surface chemistry was further characterized by X-ray photoelectron spectroscopy (XPS), which suggested a scission mechanism at P–C and MO–P (M = In and Ga) bonds of bound OPA molecules. Meanwhile, no significant surface degradation was observed after the OPA modification and phototreatments. [ABSTRACT FROM AUTHOR]

Taco complex templation based on the bis(m-phenylene)-32-crown-10/paraquat recognition motif is used to develop a general method for preparing mechanically interlocked molecules. A [2]rotaxane and a [2]catenane were synthesized in high yields by a ring-closing metathesis reaction, which was owed to the impactful template effect. Due to the high symmetry of (5,5′)-difunctional bis(m-phenylene)-32-crown-10 derivatives, this taco complex templated synthesis has potential to be a tempting method to solve a symmetry-based problem in the fabrication of complicated mechanically interlocked structures. [ABSTRACT FROM AUTHOR]

Two bis(m-phenylene)-32-crown-10 derivatives containing two pyridyl or carboxyl groups were made. They were used to prepare three bis(m-phenylene)-32-crown-10-based discrete rhomboids by coordination-driven self-assembly with high yields. The formation of these crown ether-based rhomboids was confirmed by NMR, UV-vis, CSI-TOF-MS, and elemental analysis. The complexation of these crown ether-based assemblies with paraquat (N,N′-dimethyl-4,4′-bipyridinium) was studied. The complexation of neutral bis(crown ether) rhomboid 1 with paraquat was found to be statistical with a 1:2 stoichiometry. The average apparent association constant Kav of the complexation of rhomboid 1 with paraquat was found to be about 8.8(±0.8) × 10³ M-1 in acetone, about 17 times higher than the reported association constant value for the complexation of the corresponding simple bis(m-phenylene)-32-crown-10 with paraquat. This is possibly because the carboxylate groups provide additional noncovalent interactions between the host and guest. No obvious complexation was observed between the cationic rhomboids and paraquat when studied by NMR, UV-vis, and CSI-TOF-MS analysis. This could be attributed to the combination of the charge repulsion between cationic pyridinium rings and cationic platinum atoms and the weak π-π stacking and charge transfer interactions between the phenyl rings and the pyridinium rings caused by the electron-withdrawing effect of the cationic platinum atoms. [ABSTRACT FROM AUTHOR]

Five new polyoxovanadate-based cluster compounds, (Et 4N) 4[HV 15O 39(acac)Cl]·3CH 3CN ( 1), (Et 4N) 5[V 16O 40X] (X = Br 2a; X = Cl 2b), (Me 2NH 2) 8[H 2V 16O 42(ClO 4)]·4H 2O ( 3), and (Me 2NH 2) 2(Et 4N) 2[H 2V 10O 28] ( 4), having different types of vanadium oxide shells are isolated in organic media. Compounds 1− 3are hollow structures with different encapsulated anions in their centers. The surfaces of four compounds are constituted by vanadium and oxygen atoms, showing large 10-membered -O−V−O−V- rings and/or eight-membered -O−V−O−V- rings, which distinguish vanadium-oxide clusters from the common hollow clusters built up with closed surfaces. [ABSTRACT FROM AUTHOR]

cis-Dibenzo-30-crown-10 (cis-DB30C10) diester and trans-dibenzo-30-crown-10 (trans-DB30C10) diester were synthesized regioselectively with reasonable yields. These two isomers were further reduced to cis-dibenzo-30-crown-10 diol (1) and trans-DB30C10 diol (2), respectively. The complexations of cis- and trans-DB30C10 diols with paraquat (3) and diquat (4) were investigated by ¹H NMR, mass spectrometry, UV-vis spectroscopy, and single-crystal X-ray analysis. The reversible control of complexations of 1·3 and 2·3 by adding small molecules (KPF6 and dibenzo-18-crown-6) was demonstrated by ¹H NMR. The addition of 2 molar equiv of KPF6 is enough to dissociate 2·3 and 1·3 completely while the subsequent addition of 2 molar equiv of DB18C6 allows the two complexes to reform. However, 2 molar equiv of KPF6 cannot dissociate 1·4 and 2·4 completely. Because the DB30C10 cavity has a better geometry fit with paraquat 3 than with diquat 4, 4-based complexes have much higher association constants than the corresponding 3-based complexes. In the crystal structure of 1·4, the two hydroxymethyl groups of the crown ether 1 were joined by a "water bridge" to form a "supramolecular cryptand" while this kind of supramolecular cryptand structure was not observed in the crystal structure of 2·4. This is a possible reason for the increase in association constant from 2·4 (3.3 × 104 M-1) to 1·4 (5.0 × 104 M-1). [ABSTRACT FROM AUTHOR]

Shell−core nanostructured carbon materials with a nitrogen-doped graphitic layer as a shell and pristine carbon black particle as a core were synthesized by carbonizing the hybrid materials containing in situ polymerized aniline onto carbon black. In an N-doped carbon layer, the nitrogen atoms substitute carbon atoms at the edge and interior of the graphene structure to form pyridinic N and quaternary N structures, respectively. As a result, the carbon structure becomes more compact, showing curvatures and disorder in the graphene stacking. In comparison with nondoped carbon, the N-doped one was proved to be a suitable supporting material to synthesize high-loading Pt catalysts (up to 60 wt %) with a more uniform size distribution and stronger metal−support interactions due to its high electrochemically accessible surface area, richness of disorder and defects, and high electron density. Moreover, the more rapid charge-transfer rates over the N-doped carbon material are evidenced by the high crystallinity of the graphitic shell layer with nitrogen doping as well as the low charge-transfer resistance at the electrolyte/electrode interface. Beneficial roles of nitrogen doping can be found to enhance the CO tolerance of Pt catalysts. Accordingly, an improved performance in methanol oxidation was achieved on a high-loading Pt catalyst supported by N-doped carbon. The enhanced catalytic properties were extensively discussed based on mass activity (Pt utilization) and intrinsic activity (charge-transfer rate). Therefore, N-doped carbon layers present many advantages over nondoped ones and would emerge as an interesting supporting carbon material for fuel cell electrocatalysts. [ABSTRACT FROM AUTHOR]

We demonstrate that secondary dialkylammonium salts can thread through the cavity of benzo-21-crown-7 to form 2pseudorotaxanes with binding constants (527−1062 M-1in acetone) higher than the corresponding values (135−261 M-1in acetone) of the analogous complexes with their traditionally used host, dibenzo-24-crown-8. Based on this new benzo-21-crown-7/secondary dialkylammonium salt recognition motif, a 2rotaxane was successfully prepared. The formation of these threaded structures was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray single crystal analysis. [ABSTRACT FROM AUTHOR]

A first-principle theoretical protocol was developed that could predict the absolute pKavalues of over 250 structurally unrelated compounds in DMSO with a precision of 1.4 pKaunits. On this basis we developed the first theoretical protocol that could predict the standard redox potentials of over 250 structurally unrelated organic anions in DMSO with a precision of 0.11 V. Using the two new protocols we systematically reevaluated the bond dissociation enthalpies (BDEs) measured previously by the electrochemical methods. It was confirmed that for most compounds the empirical equation (BDE 1.37 pKHA23.1Eoconstant) was valid. The constant in this equation was determined to be 74.0 kcal/mol, compared to 73.3 kcal/mol previously reported.Nevertheless, for a few compounds the empirical equation could not be used because the solvation energy changed dramatically during the bond cleavage, which resulted from the extraordinary change of dipole moment during the reaction. In addition, we found 40 compounds (mostly oximes and amides) for which the experimental values were questionable by over 5 kcal/mol. Further analyses revealed that all these questionable BDEs could be explained by one of the three following reasons:  (1) the experimental pKavalue is questionable; (2) the experimental redox potential is questionable; (3) the solvent effect cannot be neglected. Thus, by developing practical theoretical methods and utilizing them to solve realistic problems, we hope to demonstrate that ab initio theoretical methods can now be developed to make not only reliable, but also useful, predictions for solution-phase organic chemistry. [ABSTRACT FROM AUTHOR]

G protein-coupled receptors (GPCRs) constitute the largest superfamily of transmembrane signaling proteins; however, the only known GPCR crystal structure is that of rhodopsin. This disparity reflects the difficulty in generating purified GPCR samples of sufficient quantity and quality. Rhodopsin, the light receptor of retinal rod neurons, is produced in large amounts of homogeneous quality in the vertebrate retina. We used transgenic Xenopus laevis to convert these retina rod cells into bioreactors to successfully produce 20 model GPCRs. The receptors accumulated in rod outer segments and were homogeneously glycosylated. Ligand and [35S]GTPγS binding assays of the 5HT1A and EDG1 GPCRs confirmed that they were properly folded and functional. 5HT1AR was highly purified by taking advantage of the rhodopsin C-terminal immunoaffinity tag common to all GPCR constructs. We have also developed an automated system that can generate hundreds of transgenic tadpoles per day. This expression approach could be extended to other animal model systems and become a general method for the production of large numbers of GPCRs and other membrane proteins for pharmacological and structural studies. [ABSTRACT FROM AUTHOR]

The article reports on the self-sorting organization of two heteroditopic monomers to supramolecular alternating copolymers. It states that self-sorting is the process whereby molecules can find and self-assemble their recognition units within a complex mixture. It is also said to be a commonplace and vital in biological systems.