Search

Hypochlorite (ClO–) is widely presented in daily life and human body. An appropriate amount of hypochlorite may help the body regulate the immune system, while excessive hypochlorite can cause a variety of diseases. Herein, a novel fluorescence probe PTZ-BT containing a large conjugate plane was designed and synthesized. It exhibited a large Stokes shift of 158 nm and extreme AIE activity and emitted deep-red fluorescence (∼642 nm). Moreover, PTZ-BT showed specific turn-off fluorescent-responsive and high-sensitive detection (detection limit equals to 0.64 μM) toward ClO– in PBS buffer solutions. Job’s plot showed that the binding stoichiometry of PTZ-BT with ClO– was 1:1. It was further demonstrated that sulfur atoms in the phenothiazine groups were oxidized to sulfoxide by ClO–, resulting in fluorescence quenching supported by high-resolution mass spectrometry. In addition, PTZ-BT was used for bioimaging in HepG-2 cells with low cell toxicity and good cell permeability. Furthermore, live cells studies also demonstrated PTZ-BT can detect exogenous ClO– inside live cells. [ABSTRACT FROM AUTHOR]

Metasurfaces, two-dimensional lattices of nanoscale resonators, offer unique opportunities for functional flat optics and allow the control of the transmission, reflection, and polarization of a wavefront of light. Recently, all-dielectric metasurfaces reached remarkable efficiencies, often matching or out-performing conventional optical elements. The exploitation of the nonlinear optical response of metasurfaces offers a paradigm shift in nonlinear optics, and dielectric nonlinear metasurfaces are expected to enrich subwavelength photonics by enhancing substantially nonlinear response of natural materials combined with the efficient control of the phase of nonlinear waves. Here, we suggest a novel and rather general approach for engineering the wavefront of parametric waves of arbitrary complexity generated by a nonlinear metasurface. We design all-dielectric nonlinear metasurfaces, achieve a highly efficient wavefront control of a third-harmonic field, and demonstrate the generation of nonlinear beams at a designed angle and the generation of nonlinear focusing vortex beams. Our nonlinear metasurfaces produce phase gradients over a full 0-2π phase range with a 92% diffraction efficiency. [ABSTRACT FROM AUTHOR]

Herein we reported an efficient palladiumcatalyzed enantioselective arylation of both alkyl and aryl sulfenate anions to deliver various chiral sulfoxides in good yields (up to 98%) with excellent enantioselectivities (up to 99% ee) by the use of our developed chiral O,P-ligands (PCPhos). PC-Phos are easily prepared in short steps from inexpensive commercially available starting materials. The single-crystal structure of the PC4/PdCl2 showed that a rarely observed 11-membered ring was formed via the O,P-coordination with the palladium(II) center. The salient features of this method include general substrate scope, ease of scale-up, applicable to the late-stage modification of bioactive compounds, and the synthesis of a marketed medicine Sulindac. [ABSTRACT FROM AUTHOR]

Reliable and accurate detection of telomerase activity is crucial to better understand its role in cancer cells and to further explore its function in cancer diagnosis and treatment. Here, we construct a smart DNA tweezer (DT) for detection of telomerase activity. The DT is assembled by three specially designed single-stranded oligonucleotides: a central strand dually labeled with donor/acceptor fluorophores and two arm strands containing overhangs complementary to telomerase reaction products (TRPs). It can get closed through hybridization with TRPs and get reopen through strand displacement reaction by TRPs' complementary sequences. First, under the action of telomerase, telomerase binding substrates (TS) are elongated to generate TRPs ended with telomeric repeats (TTAGGG)n. TRPs hybridize with the two arm overhangs cooperatively and strain DT to closed state, inducing an increased fluorescence resonance energy transfer (FRET) efficiency, which is utilized for telomerase activity detection. Second, upon introduction of a removal strand (RS) complementary to TRPs, the closed DT is relaxed to open state via the toeholdmediated strand displacement, inducing a decreased FRET efficiency, which is utilized for determination of TRP length distribution. The detection limit of telomerase activity is equivalent to 141 cells/μL for HeLa cells, and telomerase-active cellular extracts can be differentiated from telomerase-inactive cellular extracts. Furthermore, TRPs owning 1, 2, 3, 4, and ≥5 telomeric repeats are identified to account for 25.6%, 20.5%, 15.7%, 12.5%, and 25.7%, respectively. The proposed strategy will offer a new approach for reliable, accurate detection of telomerase activity and product length distribution for deeper studying its role and function in cancer. [ABSTRACT FROM AUTHOR]

Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical properties in order to disentangle the contributions of distinct properties to the functional electrochemistry. This goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects, and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing. The structural motif most frequently used for insertion type electrodes is based on layered type structures where ion diffusion in two dimensions can be envisioned. However, lattice expansion and contraction associated with the ion movement and electron transfer as a result of repeated charge and discharge cycling can result in structural degradation and amorphization with accompanying loss of capacity. In contrast, tunnel type structures embody a more rigid framework where the inherent structural design can accommodate the presence of cations and often multiple cations. Of specific interest are manganese oxides as they can exhibit a tunneled structure, termed α-MnO2, and are an important class of nanomaterial in the fields of catalysis, adsorption-separation, and ion-exchange. The α-MnO2 structure has one-dimensional 2 × 2 tunnels formed by corner and edge sharing manganese octahedral [MnO6] units and can be readily substituted in the central tunnel by a variety of cations of varying size. Importantly, α-MnO2 materials possess a rich chemistry with significant synthetic versatility allowing deliberate synthetic control of structure, composition, crystallite size, and defect content. This Account considers the investigation of α-MnO2 tunnel type structures and their electrochemistry. Examination of the reported findings on this material family demonstrates that multiple physiochemical properties influence the electrochemistry. The retention of the parent structure during charge and discharge cycling, the material composition including the identity and content of the central cation, the surface condition including oxygen vacancies, and crystallite size have all been demonstrated to impact electrochemical function. The selection of the ^5-MnO2 family of materials as a model system and the ability to control the variables associated with the structural family affirm that full investigation of the mechanisms related to active materials in an electrochemical system demands concerted efforts in synthetic material property control and multimodal characterization, combined with theory and modeling. This then enables more complete understanding of the factors that must be controlled to achieve consistent and desirable outcomes. [ABSTRACT FROM AUTHOR]

Doped motifs offer an intriguing structural pathway toward improving conductivity for battery applications. Specifically, Ca-doped, three-dimensional "flower-like" Li4-xCaxTi5O12 ("x" = 0, 0.1, 0.15, and 0.2) micrometer-scale spheres have been successfully prepared for the first time using a simple and reproducible hydrothermal reaction followed by a short calcination process. The products were experimentally characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge testing. Calcium dopant ions were shown to be uniformly distributed within the LTO structure without altering the underlying "flower-like" morphology. The largest lattice expansion and the highest Ti3+ ratios were noted with XRD and XPS, respectively, whereas increased charge transfer conductivity and decreased Li+-ion diffusion coefficients were displayed in EIS for the Li4-xCaxTi5O12 ("x" = 0.2) sample. The "x" = 0.2 sample yielded a higher rate capability, an excellent reversibility, and a superior cycling stability, delivering 151 and 143 mAh/g under discharge rates of 20C and 40C at cycles 60 and 70, respectively. In addition, a high cycling stability was demonstrated with a capacity retention of 92% after 300 cycles at a very high discharge rate of 20C. In addition, first-principles calculations based on density functional theory (DFT) were conducted with the goal of further elucidating and understanding the nature of the doping mechanism in this study. The DFT calculations not only determined the structure of the Ca-doped Li4Ti5O12, which was found to be in accordance with the experimentally measured XPD pattern, but also yielded valuable insights into the doping-induced effect on both the atomic and electronic structures of Li4Ti5O12. [ABSTRACT FROM AUTHOR]

In this paper, reconstituted high-density lipoprotein (rHDL), a lipoprotein-derived nanovector, was constructed for codelivery of paclitaxel (PTX) and wild-type p53 gene (p53). The particle size and the zeta potential of PTX-DODAB/p53-rHDL nanoparticles were 177.2 nm and -20.06 mV, respectively. Meanwhile, they exhibited great serum stability and satisfactory sustained release characteristics in vitro. PTX-DODAB/pDNA-rHDL nanoparticles simultaneously improved the cellular uptake of PTX and pDNA via scavenger receptor B type I (SR-BI) mediated lysosome-independent internalization and promoted the transfection of pDNA in MCF-7 cells, which were revealed by flow cytometry and confocal laser scanning microscopy analyses. The high p53 protein expression in MCF-7 cells after rHDL-mediated transfection was detected by Western blotting assay. Moreover, PTX-DODAB/p53-rHDL nanoparticles showed superior cytotoxicity and significantly induced apoptosis in SR-BI overexpressed MCF-7 cells. In in vivo studies, PTX-DODAB/p53-rHDL nanoparticles without obvious toxic effects to vessels, blood, or major organs exhibited efficient tumor targeting and encouraging antitumor effects on tumor-bearing nude mice compared with controls. All the results above indicated that PTX-DODAB/p53-rHDL nanoparticles held broad prospects in combination of chemotherapeutics and gene therapeutic agents for cancer-targeted therapy. [ABSTRACT FROM AUTHOR]

Solution-processable organic semiconductors have potentials as visible photoelectrochemical (PEC) water splitting photoelectrodes due to their tunable small band gap and electronic energy levels, but they are typically limited by poor stability and photocatalytic activity. Here, we demonstrate the direct visible PEC water oxidation on solution-processed organic semiconductor thin films with improved stability and performance by ultrathin metal oxide passivation layers. N-type fullerene-derivative thin films passivated by sub-2 nm ZnO via atomic layer deposition enabled the visible PEC water oxidation at wavelengths longer than 600 nm in harsh alkaline electrolyte environments with up to 30 μA/cm2 photocurrents at the thermodynamic water-oxidation equilibrium potential and the photoanode half-lifetime extended to ~1000 s. The systematic investigation reveals the enhanced water oxidation catalytic activity afforded by ZnO passivation and the charge tunneling governing the hole transfer through passivation layers. Further enhanced PEC performances were realized by improving the bottom ohmic contact to the organic semiconductor, achieving ~60 μA/cm2 water oxidation photocurrent at the equilibrium potential, the highest values reported for organic semiconductor thin films to our knowledge. The improved stability and performance of passivated organic photoelectrodes and discovered design rationales provide useful guidelines for realizing the stable visible solar PEC water splitting based on organic semiconductor thin films. [ABSTRACT FROM AUTHOR]

Complex Fe(bpyB)3 (1, bpyB = 5,5′-bis- (dimesitylboranyl)-2,2′-bipyridine) and its reduced species [(18-c-6)K(THF)2]·[Fe(bpyB)3] (2) were synthesized. Their solid state and electronic structures were investigated by single crystal X-ray crystallography, electron paramagnetic resonance and UV-vis spectroscopy, and SQUID measurements. In 1 two bpyB radical anions are fused by a diamagnetic FeII ion, whereas in 2 all three bpyB ligands are in the radical state. Complex 1 possesses an open-shell singlet ground state with a singlet-triplet gap of 0.18 kcal mol-1 and 2 features an open-shell doublet ground state with a doublet-quartet gap of 1.4 kcal mol-1, as determined by SQUID measurements. The unpairedelectrons in 1 and 2 mainly delocalize over the boron atoms and the bipyrdine moieties with negligible spin density at the iron center. Complex 2 represents the first isolable example of boron-based triradicals. [ABSTRACT FROM AUTHOR]

Expansion of the genetic code allows unnatural amino acids (Uaas) to be site-specifically incorporated into proteins in live biological systems, thus enabling novel properties selectively introduced into target proteins in vivo for basic biological studies and for engineering of novel biological functions. Orthogonal components including tRNA and aminoacyl-tRNA synthetase (aaRS) are expressed in live cells to decode a unique codon (often the amber stop codon UAG) as the desired Uaa. Initially developed in E. coli, this methodology has now been expanded in multiple eukaryotic cells and animals. In this Account, we focus on addressing various biological challenges for rewriting the genetic code, describing impacts of code expansion on cell physiology and discussing implications for fundamental studies of code evolution. Specifically, a general method using the type-3 polymerase III promoter was developed to efficiently express prokaryotic tRNAs as orthogonal tRNAs and a transfer strategy was devised to generate Uaa-specific aaRS for use in eukaryotic cells and animals. The aaRSs have been found to be highly amenable for engineering substrate specificity toward Uaas that are structurally far deviating from the native amino acid, dramatically increasing the stereochemical diversity of Uaas accessible. Preparation of the Uaa in ester or dipeptide format markedly increases the bioavailability of Uaas to cells and animals. Nonsense-mediated mRNA decay (NMD), an mRNA surveillance mechanism of eukaryotic cells, degrades mRNA containing a premature stop codon. Inhibition of NMD increases Uaa incorporation efficiency in yeast and Caenorhabditis elegans. In bacteria, release factor one (RF1) competes with the orthogonal tRNA for the amber stop codon to terminate protein translation, leading to low Uaa incorporation efficiency. Contradictory to the paradigm that RF1 is essential, it is discovered that RF1 is actually nonessential in E. coli. Knockout of RF1 dramatically increases Uaa incorporation efficiency and enables Uaa incorporation at multiple sites, making it feasible to use Uaa for directed evolution. Using these strategies, the genetic code has been effectively expanded in yeast, mammalian cells, stem cells, worms, fruit flies, zebrafish, and mice. It is also intriguing to find out that the legitimate UAG codons terminating endogenous genes are not efficiently suppressed by the orthogonal tRNA/aaRS in E. coli. Moreover, E. coli responds to amber suppression pressure promptly using transposon insertion to inactivate the introduced orthogonal aaRS. Persistent amber suppression evading transposon inactivation leads to global proteomic changes with a notable up-regulation of a previously uncharacterized protein YdiI, for which an unexpected function of expelling plasmids is discovered. Genome integration of the orthogonal tRNA/aaRS in mice results in minor changes in RNA transcripts but no significant physiological impairment. Lastly, the RF1 knockout E. coli strains afford a previously unavailable model organism for studying otherwise intractable questions on code evolution in real time in the laboratory. We expect that genetically encoding Uaas in live systems will continue to unfold new questions and directions for studying biology in vivo, investigating the code itself, and reprograming genomes for synthetic biology. [ABSTRACT FROM AUTHOR]

At present, one of main problems for photodynamic therapy (PDT) is how to improve the treatment depth. Two-photon activated (TPA) developed recently provide a possible solution for it. In this work, we report the energy-transferring assembled cationic dipeptide nanoparticles for two-photon activated photodynamic therapy (TPA-PDT). In the nanoparticles, the coencapsulated two-photon fluorescent dye bis(pyrene) (BP) is an energy donor, and a photosensitizer rose bengal (RB) is an acceptor based on an intraparticle fluorescence resonance energy transfer (FRET) mechanism. BP in the nanoparticles can be excited by one- or two- photon laser. And then, the energy of BP was transferred to RB, which highly enhanced the generation of singlet oxygen. The cellular experiments indicated that this nanosystem can induce the cytotoxicity under one- and two-photon irradiation, which allows further applications of FRET-based biomaterials for TPA-PDT. [ABSTRACT FROM AUTHOR]

The orientational dynamics and microscopic liquid structure of a protic ionic liquid, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide (EhimNTf2), and its aprotic analogue, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2), were studied at various water concentrations using optical heterodyne-detected optical Kerr effect (OHD-OKE) spectroscopy, linear infrared spectroscopy, and atomistic simulations. The OHD-OKE experiments essentially measure the orientational relaxation of the Ehim+ and Emim+ cations. The experiments and simulations show a significant dynamical and structural change in EhimNTf2 between the 2:1 ion pair:water and the 1:1 ion pair:water concentrations. The OHD-OKE data show that EmimNTf2/water mixtures exhibit hydrodynamic behavior at all water concentrations up to saturation. In contrast, EhimNTf2/water mixtures deviate from hydrodynamic behavior at water concentrations above 2:1. At the 1:1 concentration, the orientational randomization of the Ehim+cation is slower than that predicted using viscosity data. Atomistic simulation results reveal the microscopic ionic structures of dry liquids and the preferential hydrogen bonding of water to the H atom of the N-H of Ehim+ over other sites on the Ehim+ and Emim+ cations. Atomistic simulation results demonstrate that in EhimNTf2 RTIL/water mixtures there is a substantial jump in the formation of water-water hydrogen bonds in addition to N-H-water hydrogen bonds upon increasing the water concentration from 2:1 to 1:1. Water-water hydrogen bonding strengthens the spatial coordination of the H atom of the N-H moiety of Ehim+ to neighboring water molecules through preferential hydrogen bonding. The jump in the concentration of water-water hydrogen bonds occurs at the Ehim+/water concentration at which the orientational relaxation deviates from hydrodynamic behavior. This structural observation is confirmed with FT-IR spectra that show asymmetry in the peak for the O-D stretch that is indicative of water clusters. The formation of water clusters and the strengthening of the N-H•••Oh2 hydrogen bonds slow the orientational relaxation of Ehim+ cations as observed by the OHD-OKE experiments. [ABSTRACT FROM AUTHOR]

Cancer angiogenesis is mainly initiated by vascular endothelial growth factors (VEGFs). On the basis of the reported crystal structures of three natural ligands (VEGF-A, -B, and PlGF) with the major receptors VEGFR-1 and VEGFR-2, we scanned receptor-binding epitopes of these ligands by designing linear and cyclic peptides with the aim to disrupt the VEGF-A/VEGFR-1 interaction, which is implicated in cancer development. The ability of peptides to inhibit this interaction was evaluated by an ELISA-based assay. Several peptides, especially those mimicking loop 1 (L1) of these ligands that binds primarily to domain D3 of VEGFRs, have demonstrated higher inhibition for VEGF-A/VEGFR-1 binding. They have also shown inhibitory effects on VEGF-induced tube formation in HUVECs (human umbilical vein endothelial cells). These results validate the domain D3 of VEGFRs as an efficient target for the design of VEGFR antagonists. [ABSTRACT FROM AUTHOR]

Intermolecular features like hydrogen bonding and π-type interactions play pivotal roles in stabilizing molecular structures in ionic liquids with planar rings and hydrogen-bond donors and acceptors. However, the delicate interplay among these interactions is complicated and depends on specific ion types. In this work, ab initio molecular dynamics simulations were performed to reveal competitive and cooperative characteristics among hydrogen bonding and π-type interactions in a typical imidazolium–oxalatoborate ionic liquid. Imidazolium rings take preferential on-top parallel orientations, leading to their particular π–π stacking distributions at short distances. Intermolecular interactions between imidazolium and oxalato rings are manifested by short-range on-top parallel orientations and in-plane hydrogen bonding interactions, promoting their parallel displaced offset stacking arrangements. However, on an intermediate distance scale, attractive Coulombic interactions between imidazolium and oxalato rings dominate and contribute to their perpendicular orientations. Spatial coordination patterns between intermolecular oxalato rings are balanced by repulsive electrostatic interactions and steric hindrance effects, leading to their tilted orientations in local environments. [ABSTRACT FROM AUTHOR]

This study has elucidated the roles of hydration chemistry and reaction sequence of magnesia-phosphate cement (MPC) in the upcycling of construction wood waste into rapid-shaping cement-bonded particleboards. The mineralogy and microstructure were evaluated using thermogravimetry, quantitative X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. The results showed that the magnesia-to-phosphate (M/P) ratio controlled the formation of magnesium potassium phosphate hexahydrate (MgKPO4·6H2O, MKP) for strength development. Low M/P ratios gave ill-formed MKP, whereas high M/P ratios resulted in unreacted magnesia. The optimal M/P ratio of 7 led to a much shorter setting time and greater compatibility with wood waste than for ordinary Portland cement. Wood waste can provide a platform for cement hydration and porosity for harboring crystalline MKP and also regulate water release to maintain a moderate MPC reaction. We also highlight the importance of reaction sequence for promoting matrix homogeneity and MKP crystallinity. Our approach enables fast production of value-added construction products from wood waste. [ABSTRACT FROM AUTHOR]

Precious metals have broad applications in modern industry and renewable energy technologies. The high cost and limited availability of these materials, however, have caused a grand challenge for sustainability. Here, we report on the plating of a precious metal on nonprecious metal nanoparticles for the development of sustainable electrocatalysts. Cobalt/platinum core/shell (denoted as Co@Pt) nanoparticles were synthesized via seed-mediated growth. The Co seeds were first synthesized by thermal decomposition of cobalt carbonyl, and the Pt shell was overgrown in situ by adding platinum acetylacetonate (Pt(acac)2). The galvanic replacement reaction between Co and the Pt precursor was successfully suppressed by taking advantage of CO (generated from the decomposition of cobalt carbonyl) as the stabilizing ligand and/or reducing agent. The obtained Co@Pt nanoparticles were further found to exhibit enhanced catalytic activity for the oxygen reduction reaction (ORR). [ABSTRACT FROM AUTHOR]

A series of nanosheet MgO-based sorbents promoted by mixed-alkali-metal nitrate and carbonate were prepared by a simple precipitation-deposition method and applied to CO2 capture. The structural properties of these sorbents were characterized by various techniques, and their CO2 capture performance was evaluated using a thermogravimetric analyzer. Compared to the sorbent derived from commercial MgO, the nanosheet MgO-based sorbent had faster and higher CO2 uptake, because of its thin-sheet structure. Among various alkali-metal-salt-promoted nanosheet MgO, the sorbents promoted with mixed-alkali-metal nitrates (LiNO3 and KNO3) and carbonates (Na2CO3 and K2CO3) exhibited a high total CO2 uptake at a respectable rate. In particular, the sorbent with a MgO content of 73 wt% and a nitrate/carbonate molar ratio of 2 possessed the highest total CO2 uptake and the best cyclic stability, with a total uptake of 0.52 gCO2 /gsorbent and MgO conversion of 65% after 20 cycles (60 min of absorption in 40% CO2/60% N2 at 350 °C, 15 min of regeneration in 100% N2 at 400 °C). Based on the structure-activity relationship of the sorbents, a possible mechanism consisting of three stages was presented for the CO2 absorption process, in which the dissolution of CO2 and carbonation in the molten nitrate played an important role. [ABSTRACT FROM AUTHOR]

Excellent durable antifogging film, which is composed of hollow microspheres and ZnO nanorods, is fabricated via combining airless spray and crystal growth methods. Because the thermal insulation effect of hollow microspheres strengthens the superhydrophobicity of the micro- and nanostructure composite film at lower temperatures, durable antifogging is realized successfully. When the film is placed in a low-temperature, high-humidity environment, supercooled tiny water droplets cannot spread on it and can easily coalesce and jump off from the surface, exhibiting the robust superhydrophobic and antifogging performance for a significantly long time. This investigation provides insight into designing structured thermal insulation surface materials to realize antifogging that can be applied into microdevices used in cold, high-humidity environments. [ABSTRACT FROM AUTHOR]

Dynamic covalent surfactants were designed to prepare pH switchable emulsions. A dynamic covalent bond between nonamphiphilic building blocks (polyethylenimine (PEI) and benzaldehyde (B)) was introduced to form the dynamic covalent surfactant PEI-B. The dynamic nature of covalent bond in PEI-B was confirmed by 1H NMR and fluorescence probe analysis. Stable emulsions were successfully prepared with interfacial active PEI-B at pH 7.8 with various water/paraffin oil ratios under sonication. When lowering the pH to 3.5, a complete phase separation was observed as a result of breaking dynamic covalent bond in the interfacial active PEI-B. After tuning the pH back to 7.8, stable emulsion was obtained again due to the reformation of the dynamic covalent bond and hence interfacial active PEI-B. The emulsification and demulsification were dependent on the formation and breaking of dynamic covalent bond in PEI-B. Such pH-triggered emulsification and demulsification can be switched at least three times. Application of dynamic covalent surfactants will open up a novel route for preparing responsive emulsions. [ABSTRACT FROM AUTHOR]

The limitation for the biomedical application of porous organic polymers (POPs) is the big size and poor dispersibility in aqueous media. Herein, a nanoscale metal-organic framework (MOF)@POP composite, named UNM, has been synthesized by epitaxial growth of the photoactive porphyrin-POPs (H2P-POP) on the outer surface of amine containing UiO-66 (UiO-AM). After the growth of POPs, the crystallization, pore structure, and size distribution of UNM are retained well. The formed UNM possesses a small size of less than 200 nm and could be internalized by cancer cells. Such light-activated UNM exhibits efficient ability to generate ¹O2 under various experimental conditions, which can be further applied for PDT efficacy. The present work demonstrates the great potential of nanoscale porous polymers in biomedical fields and cancer treatment. [ABSTRACT FROM AUTHOR]

A series of Cs(NH4)xH3-xPMo11VO40 with different x values were synthesized to catalyze the selective oxidation of methacrolein to methacrylic acid. The effects of ammonium on both structure and catalytic activity were explored in this study. Compared with CsH3PMo11VO40, the surface area, amount of acid sites, and active species (V4+/VO2+) were found to be strongly dependent on the content of ammonium. The optimum structure of Cs(NH4) 1.5H1.5PMo11VO40 shows comparable large surface area of 50.33 m²/g, large amount of acid sites, and active species (V4+/VO2+), consequently offering a higher methacrolein conversion (83%) and methacrylic acid selectivity (93%). Furthermore, the steady activity of Cs(NH4)1.5H1.5PMo11VO40 was not affected much by the decomposition of ammonium, and the catalyst exhibited good stability. [ABSTRACT FROM AUTHOR]

In this work, we develop a modified mussel-inspired method to enhance interfacial adhesion of aramid fiber to a rubber matrix. Through a simple dip-coating procedure, catechol and polyamine could initially codeposit as a poly(catechol-polyamine) (PCPA) coating on the surface of the aramid fiber. Then, the PCPA layer could be further grafted with silane coupling agent γ-(glycidyloxypropyltrimethoxysilane) (GPTMS). Results indicated that GPTMS was successfully grafted onto the aramid fiber surface via the bridging of the PCPA layer. The interfacial adhesion between the aramid fibers and the rubber matrix was improved compared to that achieved by polydopamine in our previous study. In addition, this method is more applicable to the rubber industry than polydopamine coating because of its cost-effectiveness and short reaction time. [ABSTRACT FROM AUTHOR]

A new method for generating nanobubbles via microwave irradiation was verified and quantified. AFM measurement showed that nanobubbles with diameters ranging from 200 to 600 nm were generated at a water-HOPG surface by applying microwave radiation to aqueous solutions with 9.0-30.0 mg/L dissolved oxygen. Graphite displays strong microwave absorption and transmits high thermal energy to the surface. Because of the high dielectric constant (20 °C, 80 F/m) and dielectric loss factor, water molecules have a strong ability to absorb microwave radiation. The thermal and nonthermal effects of microwave radiation made contributions to decreasing the gas solubility, thus facilitating nanobubble nucleation. The yield of nanobubbles increased about 10-fold when the irradiation time increased from 60 to 120 s at 200 W of microwave radiation. The nanobubble density increased from 0.8 to 15 μm-2 by improving the working power from 200 to 600 W. An apparent improvement in nanobubbles yield was obtained between 300 and 400 W, and the resulting temperature was 34-52 °C. When the initial dissolved oxygen increased from 11.3 to 30.0 mg/L, the density of nanobubbles increased from 1.2 to 13 μm-2. The generation of nanobubbles could be well controlled by adjusting the gas concentration, microwave power, or irradiation time. The method may be valuable in preparing surface nanobubbles quickly and conveniently for various applications, such as catalysis, hypoxia/anoxia remediation, and templates for preparing nanoscale materials. [ABSTRACT FROM AUTHOR]

A wide range of analytical techniques in bioanalysis relies on surface-based biomolecular detection, which requires the confinement of probes onto a heterogeneous surface to react with targets. Probe arrangement on the interface is critical for target recognition and determines assay performance. Much effort has been devoted to screen the optimized probe arrangement according to experimental tests. Such a data-driven posteriori pattern faces low efficiency, ambiguous orientation, and possible deviated tested ranges from the best case. Herein, we demonstrate that a model can effectively guide probe arrangement onto the interface to facilitate probe--target recognition, embodied by the assay of human telomerase activity with DNA-conjugated gold nanoparticles (AuNPs). Both theoretical calculation and experimental results indicate that telomerase activity is maximized on the AuNP surface under guidance of the model The detection limit is at least 1 order of magnitude lower than that of AuNP bearing densely packed DNA, comparable to that of the telomeric repeat amplification protocol (TRAP). The model-guided interface probe arrangement is proved to be highly useful in regulating interface recognition and may offer a new paradigm to promote surface-based biomolecular detection. [ABSTRACT FROM AUTHOR]

Atomistic molecular dynamics simulations have been performed to investigate volumetric quantities and dynamic properties of binary trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL)/water mixtures with different water concentrations. The predicted liquid densities for typical [P6,6,6,14][BOB] IL/water mixtures are consistent with available experimental data with a relative discrepancy of less than 3%. The liquid densities and excess molar volumes of all studied [P6,6,6,14][BOB] IL/water mixtures are characterized by concave and convex features, respectively, within full water concentration range. The dynamic properties of [P6,6,6,14] cations, [BOB] anions, and water molecules are particularly analyzed through calculation of velocity autocorrelation functions, diffusion coefficients, and reorientational autocorrelation functions and correlation times. The translational and reorientational mobilities of three species become faster upon increasing water concentration in [P6,6,6,14][BOB] IL/water mixtures and present complex dynamical characteristics arising from three distinct microscopic diffusion features within the full water concentration range. The obtained striking volumetric quantities and particular dynamic properties are well correlated to microscopic liquid structural organization and distinct local ionic environment of all studied [P6,6,6,14][BOB] IL/water mixtures. [ABSTRACT FROM AUTHOR]

Low molecular weight (MW) charged organic matter is poorly removed by conventional coagulants but contributes to disinfection byproduct formation during chlorination of drinking waters. We hypothesized that CIEX, a new Al-based hybrid coagulant with ion-exchange functional groups, would be new mechanistic approach to remove low MW organic matter during coagulation and would perform better than polyaluminum chloride (PACl) or metal-salt based coagulants. We measured coagulation performance using dissolved organic carbon (DOC) in a high hardness surface water. CIEX achieved excellent turbidity removal and removed 20% to 46% more DOC than FeCl3, Al2(SO4)3, or PACl, depending on dose. The improved DOC removal was attributable to better removal of low MW organic matter (<2 kDa). We further studied removal mechanisms in a model water containing a low MW organic acid (salicylic acid (SA)). CIEX achieved high removal of organic acids (>90% of SA) independent of pH, whereas removal by metal salts was lower (<15%) and was strongly pH dependent. CIEX ion-exchange capability is facilitated by its covalently bound quaternary ammonium group, which conventional coagulants lack. Plus, unlike other cationic polymers that react with chloramines to form N-nitrosodimethylamine (NDMA), CIEX has a low molar yield (9.3 x 10-7 mol NDMA per mol CIEX-N). [ABSTRACT FROM AUTHOR]

Here, we explored a modular strategy for rational design of nuclease-responsive three-way junctions (TWJs) and fabricated a dynamic DNA device in a "plug-and-play" fashion. First, inactivated TWJs were designed, which contained three functional domains: the inaccessible toehold and branch migration domains, the specific sites of nucleases, and the auxiliary complementary sequence. The actions of different nucleases on their specific sites in TWJs caused the close proximity of the same toehold and branch migration domains, resulting in the activation of the TWJs and the formation of a universal trigger for the subsequent dynamic assembly. Second, two hairpins (HI and H2) were introduced, which could coexist in a metastable state, initially to act as the components for the dynamic assembly. Once the trigger initiated the opening of HI via TWJs-driven strand displacement, the cascade hybridization of hairpins immediately switched on, resulting in the formation of the concatemers of H1/H2 complex appending numerous integrated G-quadruplexes, which were used to obtain label-free signal readout. The inherent modularity of this design allowed us to fabricate a flexible DNA dynamic device and detect multiple nucleases through altering the recognition pattern slightly. Taking uracil-DNA glycosylase and CpG methyltransferase M.SssI as models, we successfully realized the butt joint between the uracil-DNA glycosylase and M.Sssl recognition events and the dynamic assembly process. Furthermore, we achieved ultrasensitive assay of nuclease activity and the inhibitor screening. The DNA device proposed here will offer an adaptive and flexible tool for clinical diagnosis and anticancer drug discovery. [ABSTRACT FROM AUTHOR]

Despite the frequent detection of benzotriazoles (BTRs) and benzothiazoles (BTHs) in groundwater and surface-water environments, knowledge on their occurrence and profile in tap water is still scarce. This study demonstrates widespread occurrence of these compounds in tap water from 51 major cities in China, which have ranges of

The finding of the periodic law is a milestone in chemical science. The periodicity of light elements in the Periodic Table is fully accounted for by quantum mechanics. Here we report that relativistic effects change the bond multiplicity of the group 6 diatomic molecules M2 (M = Cr, Mo, W, Sg) from hextuple bonds for Cr2, Mo2, W2 to quadruple bonds for Sg2, thus breaking the periodicity in the nonrelativistic domain. The same trend is also found for other superheavy-element diatomics Rf2, Db2, Bh2, and Hs2. [ABSTRACT FROM AUTHOR]

This study characterizes two of the primary photodissociation channels of 2-bromoethyl nitrite, BrCH2CH2ONO, at 193 nm and the subsequent unimolecular dissociation channels of the nascent vibrationally excited BrCH2CH2O radicals produced from the O-NO bond photofission. We use a crossed laser-molecular beam scattering apparatus with electron bombardment detection. Upon photodissociation of BrCH2CH2ONO at 193 nm, the measured branching ratio between primary O-NO photofission and C-Br photofission is 3.9:1 (O-NO/C-Br). The measured O-NO photofission recoil kinetic energy distribution (P(ET)) peaks near 30 kcal/mol and extends from 20 to 50 kcal/mol. We use the O-NO photofission P(ET) to characterize the internal energy distribution in the nascent ground-electronic-state BrCH2CH2O radicals. At 193 nm, all of the BrCH2CH2O radicals are formed with enough internal energy to unimolecularly dissociate to CH2Br + H2CO or to BrCH2CHO + H. We also investigated the possibility of the BrCH2CH2O → CH2CHO + HBr reaction arising from the vibrationally excited BrCH2CH2O radicals produced from O-NO primary photodissociation. Signal strengths at HBr+, however, demonstrate that the vinoxy product does not have HBr as a cofragment, so the BrCH2CH2O → HBr + vinoxy channel is negligible compared to the CH2Br + H2CO channel. We also report our computational prediction of the unimolecular dissociation channels of the vibrational excited CH2CH2ONO radical resulting from C-Br bond photofission. Our theoretical calculations on the ground-state CH2CH2ONO potential energy surface at the G4//B3LYP/6-311++G(3df,2p) level of theory give the energetics of the zero-point corrected minima and transition states. The lowest accessible barrier height for the unimolecular dissociation of CH2CH2ONO is a 12.7 kcal/mol barrier from the cis-ONO conformer, yielding NO2 + ethene. Our measured internal energy distribution of the nascent CH2CH2ONO radicals together with this computational result suggests that the CH2CH2ONO radicals will dissociate to NO2 + ethene, with a small possible branching to NO + oxirane. [ABSTRACT FROM AUTHOR]

Knowledge of human exposure to imidacloprid, the most extensively used insecticide, and para-hydroxybenzoic acid esters (parabens), the most extensively used preservative, is insufficient. In this study, 295 urine samples collected from subjects in rural and urban areas in China were analyzed for imidacloprid and four parabens (namely, methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) as well as their major metabolites (namely, 6-chloronicotinic acid (6-ClNA) and para-hydroxybenzoic acid (p-HB)). Imidacloprid was detected in 100% of the urine samples from rural Chinese subjects and 95% of the urine samples from urban Chinese subjects. Concentrations of urinary imidacloprid detected in rural Chinese subjects (geometric mean (GM) = 0.18 ng/mL) were slightly higher than those detected in urban Chinese subjects (GM = 0.15 ng/mL) when the effect of pesticide spraying was excluded. However, concentrations of urinary imidacloprid detected in rural adults increased significantly in the subsequent days of pesticide spraying (GM = 0.62 ng/mL), which could return to the normal levels within 3 days. In contrast, concentrations of urinary parabens detected in rural Chinese subjects (GM = 6.90 ng/mL) were lower than that in urban Chinese subjects (GM = 30.5 ng/mL). In addition, the metabolism characteristics of imidacloprid to 6-ClNA and parabens to p-HB were discussed preliminarily. [ABSTRACT FROM AUTHOR]

High-valent iron imido species are implicated as reactive intermediates in many iron-catalyzed transformations. However, isolable complexes of this type are rare, and their reactivity is poorly understood. Herein, we report the synthesis, characterization, and reactivity studies on novel three-coordinate iron(IV) bisimido complexes with aminocarbene ligation. Using our recently reported synthetic method for [LFe(NDipp)2] (L = IMes, 1; Me2-cAAC, 2), four new iron(IV) imido complexes, [(IPr)Fe(NDipp)2] (3) and [(Me2-cAAC)Fe(NR)2] (R = Mes, 4; Ad, 5; CMe2CH2Ph, 6), were prepared from the reactions of three-coordinate iron(0) compounds with organic azides. Characterization data acquired from ¹H and 13C NMR spectroscopy, 57Fe Mössbauer spectroscopy, and X-ray diffraction studies suggest a low-spin singlet ground state for these iron(IV) complexes and the multiple-bond character of their Fe-N bonds. A reactivity study taking the reactions of 1 as representative revealed an intramolecular alkane dehydrogenation of 1 to produce the iron(II) complex [(IMes)Fe(NHDipp)(NHC6H3-2-Pri-6-CMe-CH2)] (7), a Si-H bond activation reaction of 1 with PhSiH3 to produce the iron(II) complex [(IMes)Fe(NHDipp)(NDippSiPhH2)] (8), and a [2+2]-addition reaction of 1 with PhNCNPh and p-PriC6H4NCO to form the corresponding open-shell formal iron(IV) monoimido complexes [(IMes)Fe(NDipp)(N(Dipp)C(NPh)(-NPh))] (9) and [(IMes)Fe(NDipp)(N(Dipp)C(O)N(p-PriC6H4))] (10), as well as [NDipp]-group-transfer reactions with CO and ButNC. Density functional theory calculations suggested that the alkane chain dehydrogenation reaction starts with a hydrogen atom abstraction mechanism, whereas the Si-H activation reaction proceeds in a [2p+2s]-addition manner. Both reactions have the pathways at the triplet potential energy surfaces being energetically preferred, and have formal iron(IV) hydride and iron(IV) silyl species as intermediates, respectively. The low-coordinate nature and low d-electron count (d4) of iron(IV) imido complexes are thought to be the key features endowing their unique reactivity. [ABSTRACT FROM AUTHOR]

Supramolecular vesicles, also referredto as polymersomes, self-assembledfrom amphiphilic polymers capable of synchronically loading with bothhydrophilic and hydrophobic payloads have shown promising potentialin drug delivery application. Herein, we report the fabrication ofpH-responsive polymersomes via supramolecular self-assembly of amphiphilicdiblock copolymers, poly(ethylene oxide)-b-poly(2-((((5-methyl-2-(2,4,6-trimethoxyphenyl)-1,3-dioxan-5-yl)methoxy)carbonyl)amino)ethylmethacrylate) (PEO-b-PTTAMA), which were synthesizedvia reversible addition–fragmentation chain transfer (RAFT)polymerization of a pH-responsive monomer (i.e., TTAMA) using a PEO-basedmacroRAFT agent. The resultant amphiphilic diblock copolymer thenself-assembled into vesicles consisting of hydrophilic PEO coronasand pH-responsive hydrophobic bilayers, as confirmed by TEM and DLSmeasurements. The polymersomes containing cyclic benzylidene acetalsin the hydrophobic bilayers were relatively stable under neutral pH,whereas they underwent hydrolysis with the liberation of hydrophobic2,4,6-trimethoxybenzaldehyde and the simultaneous generationof hydrophilic diol moieties upon exposure to acidic pH milieu, whichcould be monitored by UV/vis spectroscopy, SEM, and TEM observations.By loading hydrophobic model drug (Nile red) as well as hydrophilicchemotherapeutic drug (doxorubicin hydrochloride, DOX·HCl) intothe bilayer and aqueous interior of the polymersomes, the subsequentrelease of Nile red and DOX·HCl payloads was remarkably regulatedby the solution pH values, and a lower pH value led to a faster drugrelease profile. In vitroexperiment, observed bya confocal laser scanning microscope (CLSM), revealed that the pH-responsivepolymersomes were easily taken up by HeLa cells and were primarilylocated in the acidic organelles after internalization, where thepH-responsive cyclic acetal moieties were hydrolyzed and the embeddedpayloads were therefore released, allowing for on-demand release ofthe encapsulants mediated by intracellular pH. In addition to smallmolecule chemotherapeutic drugs, biomacromolecules (alkaline phosphatase,ALP) can also be encapsulated into the aqueous lumen of the polymersomes.Significantly, the pH-triggered degradation of polymersomes couldalso regulate the release of encapsulated ALP, as confirmed by ALP-activatedfluorogenic reaction. [ABSTRACT FROM AUTHOR]

2-Amino-4-oxo-6-substituted-pyrrolo[2,3-d]pyrimidine antifolate thiophene regioisomers of AGF94 (4) with a thienoyl side chain and three-carbon bridge lengths [AGF150 (5) and AGF154 (7)] were synthesized as potential antitumor agents. These analogues inhibited proliferation of Chinese hamster ovary (CHO) sublines expressing folate receptors (FRs) α or β (IC50s < 1 nM) or the proton-coupled folate transporter (PCFT) (IC50 < 7 nM). Compounds 5 and 7 inhibited KB, IGROV1, and SKOV3 human tumor cells at subnanomolar concentrations, reflecting both FRα and PCFT uptake. AGF152 (6) and AGF163 (8), 2,4-diamino-5-substituted-furo[2,3-d]pyrimidine thiophene regioisomers, also inhibited growth of FR-expressing CHO and KB cells. All four analogues inhibited glycinamide ribonucleotide formyltransferase (GARFTase). Crystal structures of human GARFTase complexed with 5 and 7 were reported. In severe combined immunodeficient mice bearing SKOV3 tumors, 7 was efficacious. The selectivity of these compounds for PCFT and for FRα and β over the ubiquitously expressed reduced folate carrier is a paradigm for selective tumor targeting. [ABSTRACT FROM AUTHOR]

2-Amino-4-oxo-6-substituted-pyrrolo[2,3-d]pyrimidine antifolate thiophene regioisomers of AGF94 (4) with a thienoyl side chain and three-carbon bridge lengths [AGF150 (5) and AGF154 (7)] were synthesized as potential antitumor agents. These analogues inhibited proliferation of Chinese hamster ovary (CHO) sublines expressing folate receptors (FRs) a or β (IC50s < 1 nM) or the proton-coupled folate transporter (PCFT) (IC50 < 7 nM). Compounds 5 and 7 inhibited KB, IGROV1, and SKOV3 human tumor cells at subnanomolar concentrations, reflecting both FRa and PCFT uptake. AGF152 (6) and AGF163 (8), 2,4-diamino-5-substituted-furo[2,3-d]pyrimidine thiophene regioisomers, also inhibited growth of FR-expressing CHO and KB cells. All four analogues inhibited glycinamide ribonucleotide formyltransferase (GARFTase). Crystal structures of human GARFTase complexed with 5 and 7 were reported. In severe combined immunodeficient mice bearing SKOV3 tumors, 7 was efficacious. The selectivity of these compounds for PCFT and for FRa and β over the ubiquitously expressed reduced folate carrier is a paradigm for selective tumor targeting. [ABSTRACT FROM AUTHOR]

Severalcyclized indole derivatives have been synthesized, andtheir structures been determined. The C3-symmetric single-chiral N-phenyltriindole (Tr-Ph3)crystallized in the P1 space group, and the S4-symmetric saddle-like tetraindole (TTr) crystallizedin the I4̅ space group. The Tr-Ph3 and TTrcrystals exhibit remarkable powder SHG intensities 5 and 11 timesthat of KH2PO4(KDP), respectively. TTr is auseful octupolar core to build S4-symmetricmolecules and crystals for second-NLO materials. [ABSTRACT FROM AUTHOR]

Activation parameters are reported for additions of phenylchlorocarbene (PhCCl), pentafluorophenylchlorocarbene (F5-PhCCl), and 3,5-dinitrophenyl-chlorocarbene (3,5-DN-PhCCl) to tetramethylethylene (TME), cyclohexene, and 1-hexene. The order of activation enthalpies is F5-PhCCl > PhCCl > 3,5-DN-PhCCl. Activation enthalpies also increase as the degree of alkene alkylation decreases. In general, the entropies of activation increase in tandem with the enthalpies of activation. [ABSTRACT FROM AUTHOR]

The oxygen evolving complex (OEC) of the naturalphotosynthesis system II (PSII) oxidizes water to produce oxygen andreducing equivalents (protons and electrons). The oxygen releasedfrom PSII provides the oxygen source of our atmosphere; the reducingequivalents are used to reduce carbon dioxide to organic products,which support almost all organisms on the Earth planet. The firstphotosynthetic organisms able to split water were proposed to be cyanobacteria-likeones appearing ca. 2.5 billion years ago. Since then, nature has chosena sustainable way by using solar energy to develop itself. Inspiredby nature, human beings started to mimic the functions of the naturalphotosynthesis system and proposed the concept of artificial photosynthesis(AP) with the view to creating energy-sustainable societies and reducingthe impact on the Earth environments. Water oxidation is a highlyenergy demanding reaction and essential to produce reducing equivalentsfor fuel production, and thereby effective water oxidation catalysts(WOCs) are required to catalyze water oxidation and reduce the energyloss. [ABSTRACT FROM AUTHOR]

To determine further the enhancement and mitigation mechanisms of protein fouling, filtration experiments were carried out with polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes and bovine serum albumin (BSA) over a range of ionic strengths. The interaction forces, the adsorption behavior of BSA on the membrane surface, and the structure of the BSA adsorbed layers at corresponding ionic strengths were investigated. Results indicate that when the ionic strength increased from 0 to 1 mM, there was a decrease in the PVDF-BSA and BSA-BSA electrostatic repulsion forces, resulting in a higher deposition rate of BSA onto the membrane surface, and the formation of a denser BSA layer; consequently, membrane fouling was enhanced. However, at ionic strengths of 10 and 100 mM, membrane fouling and the BSA removal rate decreased significantly. This was mainly due to the increased hydration repulsion forces, which caused a decrease in the PVDF-BSA and BSA-BSA interaction forces accompanied by a decreased hydrodynamic radius and increased diffusion coefficient of BSA. Consequently, BSA passed more easily through the membrane and into permeate. There was less accumulation of BSA on the membrane surface. A more nonrigid and open structure BSA layer was formed on the membrane surface. [ABSTRACT FROM AUTHOR]

Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations. [ABSTRACT FROM AUTHOR]

Conspectus: Molecular photochromic compounds are those that interconvert between two isomeric forms with light. The two isomeric forms display distinct electronic and molecular structures and must not be in equilibrium with one another. These light-activated molecular switch compounds have found wide application in areas of study ranging from chemical biology to materials science, where conversion from one isomeric form to another by light prompts a response in the environment (e.g., protein or polymeric material). Certain ruthenium and osmium polypyridine sulfoxide complexes are photochromic. The mode of action is a phototriggered isomerization of the sulfoxide from S- to O-bonded. The change in ligation drastically alters both the spectroscopic and electrochemical properties of the metal complex. Our laboratory has pioneered the preparation and study of these complexes. In particular, we have applied femtosecond pump-probe spectroscopy to reveal excited state details of the isomerization mechanism. The data from numerous complexes allowed us to predict that the isomerization was nonadiabatic in nature, defined as occurring from a S-bonded triplet excited state (primarily metal-to-ligand charge transfer in character) to an O-bonded singlet ground state potential energy surface. This prediction was corroborated by high-level density functional theory calculations. An intriguing aspect of this reactivity is the coupling of nuclear motion to the electronic wave function and how this coupling affects motions productive for isomerization. In an effort to learn more about this coupling, we designed a project to examine phototriggered isomerization in bis-sulfoxide complexes. The goal of these studies was to determine whether certain complexes could be designed in which a single photon excitation event would prompt two sulfoxide isomerizations. We employed chelating sulfoxides in this study and found that both the nature of the chelate ring and the R group on the sulfoxide affect the photochemical reactivity. For example, this reactivity may be tuned such that two sulfoxide ligands isomerize sequentially following two successive excitations or that two sulfoxide ligands isomerize following a single excitation. This Account explains our understanding to date of this photochemistry. [ABSTRACT FROM AUTHOR]

Ta3N5nanostructuresare widely explored as anodesfor photoelectrochemical (PEC) water splitting. Although the materialshows excellent semiconductive properties for this purpose, the keychallenge is its severe photocorrosion when used in typical aqueousenvironments. In the present work we introduce a NiFe layered doublehydroxide (LDH) cocatalyst that dramatically reduces photocorrosioneffects. To fabricate the Ta3N5electrode, weuse through-template anodization of Ta and obtain oxide nanorod arraysthat then are converted to Ta3N5by high temperaturenitridation. After modification with our cocatalyst system, we obtainedsolar photocurrents of 6.3 mA cm–2at 1.23 VRHEin 1 M KOH, and an electrode maintains about 80% of theinitial activity for extended irradiation times. [ABSTRACT FROM AUTHOR]

Two molecular assemblies with one Ru(II)-polypyridine photosensitizer covalently linked to one Ru(II)(bda)L2 catalyst (1) (bda = 2,2'-bipyridine-6,6'-dicarboxylate) and two photosensitizers covalently linked to one catalyst (2) have been prepared using a simple C-C bond as the linkage. In the presence of sodium persulfate as a sacrificial electron acceptor, both of them show high activity for catalytic water oxidation driven by visible light, with a turnover number up to 200 for 2. The linked photocatalysts show a lower initial yield for light driven oxygen evolution but a much better photostability compared to the three component system with separate sensitizer, catalyst and acceptor, leading to a much greater turnover number. Photocatalytic experiments and time-resolved spectroscopy were carried out to probe the mechanism of this catalysis. The linked catalyst in its Ru(II) state rapidly quenches the sensitizer, predominantly by energy transfer. However, a higher stability under photocatalytic condition is shown for the linked sensitizer compared to the three component system, which is attributed to kinetic stabilization by rapid photosensitizer regeneration. Strategies for employment of the sensitizer-catalyst molecules in more efficient photocatalytic systems are discussed. [ABSTRACT FROM AUTHOR]

A convergent strategy was developed for the stereoselective synthesis of four unusual N-acylated monosaccharides (5-8), which are fragments of lipooligosaccharide IV (LOS-IV) from Mycobacterium marinum. A critical substrate-controlled asymmetric cyclization of an amino acid derived oxazolidine provided a key lactam intermediate 11, which was successfully converted to targets 5-7. The key step in die synthesis of 8 was a one-pot cascade oxidation--cyclization--oxidation reaction of a Boc-protected amino alcohol, prepared from 3-butynol, which led to the formation of lactam 15. The five-membered ring lactam intermediates in these synthetic routes were sensitive to elimination side reactions, but careful manipulation of the reaction sequence allowed for the stereoselective synthesis of the targets. This work represents the first synthesis of these unusual motifs, which have been shown to be essential to the bioactivity of LOS-IV. [ABSTRACT FROM AUTHOR]

Despite the widespread use of bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE) in various consumer products, studies on human exposure to these compounds are scarce. In this study, BADGE, BFDGE, and seven of their derivatives were determined in human adipose fat and blood plasma samples collected from New York City, NY. Bisphenol A bis (2,3-dihydroxypropyl) ether [BADGE-2H20 ] was the major BADGE derivative found in 60% of the adipose samples and 70% of the plasma samples analyzed. High concentrations and detection frequencies of BFDGE were found in both adipose and plasma samples. BFDGE concentrations in adipose fat ranged from 19.1 to 4500 ng/g wet weight A significant correlation between BADGE or BFDGE and their derivatives in adipose and plasma samples suggested hydration of these reactive compounds in humans. A significant positive correlation existed between BADGEs (i.e., the sum of BADGE and its five derivatives) and BFDGEs in adipose samples, which suggested similar exposure sources and pathways for these compounds in humans. Bisphenol A (BPA) also was analyzed in adipose fat and plasma, and its concentrations were positively correlated with those of BADGEs, which confirmed coexposure of BADGEs and BPA in humans. [ABSTRACT FROM AUTHOR]

Axons are very sensitive to molecular gradients and can discriminate extremely small differences in gradient steepness. Microfluidic devices capable of generating chemical gradients and adjusting their steepness could be used to quantify the sensitivity of axonal response. Here, we present a versatile and robust microfluidic device that can generate substrate-bound molecular gradients with evenly varying steepness on a single chip to precisely quantify axonal response. In this device, two solutions are perfused into a central channel via two inlets while partially flowing into two peripheral channels through interconnecting grooves, which gradually decrease the fluid velocity along the central channel. Molecular gradients with evenly and gradually decreased steepness can therefore be generated with a high resolution that is less than 0.05%/mm. In addition, the overall distribution range and resolution of the gradient steepness can be highly and flexibly controlled by adjusting various parameters of the device. Using this device, we quantified the hippocampal axonal response to substrate-bound laminin and ephrin-A5 gradients with varying steepnesses. Our results provided more detailed information on how and to what extent different steepnesses guide hippocampal neuron development during the initial outgrowth. Furthermore, our results show that axons can sensitively respond to very shallow laminin and ephrin-A5 gradients, which could effectively initiate biased differentiation of hippocampal neurons in the steepness range investigated in this study. [ABSTRACT FROM AUTHOR]

Reaction of multidentate 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole (L) ligand with Ag(I) ions in the existence of H3PW12O40 as anionic template under hydrothermal conditions results in tridecanuclear silver cluster-polyoxometalates hybrid: {Ag13L12}{PW12O40}4·30H2O (1). X-ray single crystal diffraction analysis indicates that the main structural feature of 1 is a nanosized molecular windmill-shaped polynuclear Ag cluster with intriguing {M@M12}-type cuboctahedral topology. The as-synthesized compound exhibits effective photocatalytic activity in the photodegradation of Rhodamine-B (RhB) and antibacterial activity against Escherichia coli, respectively. [ABSTRACT FROM AUTHOR]

A series of isostructural 2-fold interpenetrating 2D Cd(II)-MOFs, namely G⊂CdL2(OTs)2 (G = THF (1), PhF (2), PhCl (3), PhBr (4), PhI (5), L = 1,2-bis[(3-(pyridin-4-yl)phenoxy]ethane, and OTs- = p-toluenesulfonate anion), have been successfully synthesized from the flexible ethylene glycol ether-bridging ligand L and Cd(OTs)2 in solution. The CdL2(OTs)2 framework contains squarelike nonpolar channels, and the encapsulated guest molecules can be removed by heating (150 °C) to generate a guest-free host framework which is able to reversibly adsorb monohalobenzenes PhX (X = F, Cl, Br, I) in the liquid phase under ambient conditions without loss of framework integrity. Furthermore, it can effectively separate these monohalobenzenes and exhibits a clear affinity for monohalobenzenes according to the following order: PhI > PhBr > PhCl > PhF. In addition, PhX⊂CdL2(OTs)2 exhibits guest-dependent luminescence properties. [ABSTRACT FROM AUTHOR]

Computational and experimental results demonstrate that adamantanylidene (1) behaves as a highly reactive nucleophile toward common alkenes. It is the only known saturated nucleophilic carbene that lacks direct or vinylogous heteroatomic substitution. The activation energy and enthalpy for addition of 1 to methyl acrylate are the most negative values yet encountered in any carbene–alkene addition. [ABSTRACT FROM AUTHOR]

A base-promoted formal arylation of benzo[d]-oxazoles with acyl chloride was achieved in moderate to good yields. This reaction was triggered by the N-acylation of oxazole to form an iminium intermediate. Then, the addition of H2O to the iminium formed the hemiacetal intermediate. After the sequential ring-opening, extrusion of CO, the ring closure, the dehydration delivered the formal arylation product. In comparison with the transition-metal-catalyzed methodology, it represents an alternative arylation memod leading to 2-arylbenzooxazole [ABSTRACT FROM AUTHOR]