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Colloidosomes have attracted great interest in recent years because of their capability for storage and delivery of small molecules for medical and pharmaceutical applications. However, traditional polymer shell colloidosomes leak low molecular weight drugs due to their intrinsic shell permeability. Here, we report aqueous core colloidosomes with a silver shell, which seals the core and makes the shell impermeable. The silver-coated colloidosomes were prepared by reacting l-ascorbic acid in the microcapsule core with silver nitrate in the wash solution. The silver shell colloidosomes were then modified by using 4,4'-dithiodibutyric acid and cross-linked with rabbit Immunoglobulin G (IgG). Label-free surface plasmon resonance was used to test the specific targeting of the functional silver shell with rabbit antigen. To break the shells, ultrasound treatment was used. The results demonstrate that a new type of functional silver-coated colloidosome with immunoassay targeting, nonpermeability, and ultrasound sensitivity could be applied to many medical applications. [ABSTRACT FROM AUTHOR]

Sulfhydryl-containing proteins play critical roles in various physiological and biological processes, and the activities of those proteins have been reported to be susceptible to thiol oxidation. Therefore, the development of protein thiol target fluorescent probe is highly desirable. In the present work, a biotinylated coumarin fluorescence "off-on" probe SQ for selectively detecting protein thiols in biotin receptor-positive cancer cells was designed with a 2,4-dinitrobenzenesulfony as the thiol receptor. The probe exhibited dramatic fluorescence responses toward sulfhydryl-containing proteins (ovalbumin (OVA), bovine serum albumin (BSA)): up to 170-fold fluorescence enhancement with 70 nm blue-shift was observed with the addition of OVA. However, low molecular weight thiols (Cys, glutathione (GSH), Hey) caused negligible fluorescence changes of SQ In addition, biotin receptor-positive Hela cells displayed strong red and green fluorescence after incubation of SQfor 1 h; neither red nor green fluorescence signal could be visualized in biotin-negative normal lung Wi38 cells. These results imply that the probe has potential application in fluorescent imaging protein thiols on the surface of Hela cells. [ABSTRACT FROM AUTHOR]

Combustionheats of FOX-7 and its five closed-loop derivativeswere determined and the standard molar enthalpies of formation (ΔfH°m) were obtained. The sequenceof combustion heat for the six compounds is DNDH > MDNZ > DNDX> DNDZ> DDNI > FOX-7. Combustion heat tends to rise with the increaseofthe number of C atoms in the molecule. Specific heat capacities weremeasured, and the standard molar heat capacities of the six compoundsare (176.59, 205.41, 207.76, 218.89, 217.76, and 215.40) J·mol–1·K–1, respectively. The specificheat capacity presents an opposite change rule with combustion heat.To the isomers and the introduction of hydroxyl group, the changerule is the same. Moreover, the introduction of hydroxyl group canmarkedly decrease the combustion heat and specific heat capacity. [ABSTRACT FROM AUTHOR]

Transformation of bisphenol A (BPA) by ammonia-oxidizing bacteria (AOB) Nitrosomonas europaea ATCC 19718 was investigated. On the basis of the ultraperformance liquid chromatography (UPLC) coupled to quadrupole time-of-flight mass spectrometry (Q-TOF MS) and nuclear magnetic resonance analysis, we found N. europaea could transform BPA into nitro- and dinitro-BPA, suggesting that abiotic nitration between the biogenic nitrite and BPA played a major role in the transformation of BPA in the batch AOB system. Nitrite concentrations, temperature, and pH values were the major factors to influence the reaction rate. Furthermore, the yeast estrogenic screening assay showed that the formed nitro- and dinitro-BPA had much less estrogenic activity as compared with its parent compound BPA. Similar reactions of abiotic nitration were considered for 4-n-nonylphenol (nNP) and 4-n-octylphenol (nOP) since nitro-nNP and nitro-nOP were detected by UPLC-Q-TOF MS. In addition, results from the local wastewater treatment plant (WWTP) showed the occurrence of nitro-BPA and dinitro-BPA during the biological treatment process and in the effluent, indicating that nitration of BPA is also a pathway for removal of BPA. Results of this study provided implication that AOB in the WWTPs might contribute to removal of selected endocrine-disrupting compounds (EDCs) through abiotic nitritation. [ABSTRACT FROM AUTHOR]

Three isomorphous metal-organic frameworks of formula [M(ppdc)(H2O)2]n [M = Mn(II), Fe(II), and Co(II)] were synthesized from sodium p-phenylenediacrylic (Na2ppdc). Crystallographic studies revealed that the compounds are layer-pillared 3D frameworks in which the square-grid M(II) layers with single carboxylate bridges are interlinked by long organic spacers with large interlayer separations of about 13 Å. Magnetic investigations indicated that they all display intralayer antiferromagnetic interactions through the carboxylate bridges in the unusual skew-skew coordination mode but the bulk behaviors are quite different. The Co(II) compound, like most compounds containing similar M-O-C-O-M layers, shows no 3D magnetic ordering down to 2 K, while the Mn(II) and Fe(II) compounds exhibit spin-canted ordering, behaving as a weak ferromagnet (TC = 3.8 K) and a metamagnet (TN = 3.8 K, Hc = 650 Oe), respectively. Spin-canted ordering is still a rarity in this series of materials. Magnetostructural comparisons with analogous compounds indicate that the occurrence of spin-canted ordering can be related to the uncommon skew-skew and anti-anti coordination modes of carboxylate bridges, which induce stronger antiferromagnetic interactions than the common syn-anti mode. [ABSTRACT FROM AUTHOR]

A 2-fold interpenetrated metal−organic framework displaying intense yellow fluorescence is constructed from [Zn4O(COO)6] clusters and a new dicarboxylate ligand bearing the fluorene chromophore fluorene-2,7-dicarboxylic acid. The [Zn4O(COO)6] secondary building unit exhibits unusual coordination features and leads to the rare 3D pillared kagomé net topology (324865). [ABSTRACT FROM AUTHOR]

The microtubule-associated protein tau, in a hyperphosphorylated form, aggregates into insoluble paired-helical filaments (PHFs) in Alzheimer's disease (AD) and other tauopathies. In AD, there is approximately 8 mol of phosphate per mole of tau distributed among approximately 30 PHF phosphorylation sites as compared to 2-3 mol of phosphate per mole in normal brain. In AD, kinases such as glycogen synthase kinase-3β (GSK-3β) are believed to be involved in the generation of hyperphosphorylated tau. However, the functional consequences of hyperphosphorylation on the microtubule binding and polymerization of tau are not well understood. To address this question, we have generated pseudohyperpho-sphorylation mutants consisting of six and seven sites in the proline-rich region and carboxy terminus of tau by amino acid substitution. In addition, several single, double, and triple pseudophosphorylation mutants were also generated. Pseudophosphorylation of tau decreases its affinity for microtubules, and pseudohyperphosphorylated forms of tau do not have significantly decreased levels of microtubule binding as compared to single and double sites. Three pseudohyperphosphorylated forms of tau with altered sodium dodecyl sulfate-polyacrylamide gel electrophoresis migration have a greater effect on its inducer-mediated polymerization, slowing the rate of nucleation and elongation. On the basis of the observations that pseudohyperphosphorylated tau has decreased affinity for microtubules and reduced inducer-initiated rates of nucleation and polymerization, we propose that this combination could be the cause of the increased cytotoxicity of hyperphosphorylated tau in Alzheimer's disease and also explain the potentially beneficial role of tau polymerization and NFT formation. [ABSTRACT FROM AUTHOR]

Focuses on the use of enhanced-fluidity liquid chromatography for chiral separations. Comparison of the technique to high performance liquid chromatography and supercritical fluid chromatography; Applicability of fluoroform as fluidity-enhancing solvent for chiral separations.

Lithium-sulfur (Li-S) battery is a promising high energy storage candidate in electric vehicles. However, the commonly employed ether based electrolyte does not enable to realize safe high-temperature Li-S batteries due to the low boiling and flash temperatures. Traditional carbonate based electrolyte obtains safe physical properties at high temperature but does not complete reversible electrochemical reaction for most Li-S batteries. Here we realize safe high temperature Li-S batteries on universal carbon-sulfur electrodes by molecular layer deposited (MLD) alucone coating. Sulfur cathodes with MLD coating complete the reversible electrochemical process in carbonate electrolyte and exhibit a safe and ultrastable cycle life at high temperature, which promise practicable Li-S batteries for electric vehicles and other large-scale energy storage systems. [ABSTRACT FROM AUTHOR]

An efficient and practical method has been developed for the diversity-oriented synthesis of polysubstituted 2-piperidinones via four-component reaction between substituted nitrostyrenes, aromatic aldehydes, ammonium acetate, and dialkyl malonates for the generation of a wide range of structurally interesting and pharmacologically significant compounds. It is worth mentioning that in the course of this reaction, the formation of products was highly stereoselective. Two differently stereochemical classes of polysubstituted 2-piperidinones depended on the substitutent position of aromatic aldehyde. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of Zn(II), Cd(II), Mn(II), Co(II), or Ni(II) salts and 2-pyrimidinecarbonitrile (pymCN) in the presence of NaN3in DMF yielded seven metal−organic coordination polymers formulated as [Zn(pymtz)2]n(1), [NaMII(pymtz)3]n·G (M = Zn 2, Cd 3, Mn 4, Co for 5, and Ni for 6; G = DMF and/or H2O) and [Cd(pymtz)2]n(7) [pymtz = 5-(2′-pyrimidyl)tetrazolato]. Compounds 2−6are isomorphous and all contain neutral honeycomb layers in which pymtz serves as a bis(chelating) bridge between M(II) (M = Zn for 2, Cd for 3, Mn for 4, Co for 5, and Ni for 6) and Na, and the ellipse stacking of the layers generates one-dimensional hexagonal channels. Compounds 1and 7exhibit different (4,4) square grid networks. In 1, the Zn ions are octahedrally coordinated and linked by pymtz ligands in the μ2tridentate bridging mode, while in 7, the Cd(II) ions are eight-coordinated with a square prismatic geometry and bridged by bis(chelating) pymtz ligands. Compounds 2and 3can transform into 1and 7, respectively, by immersing the sample in appropriate solvents. Interestingly, photoluminescence measurements on Zn(II) and Cd(II) compounds show that the emission bands can be correlated to the coordination modes of the pymtz ligands. [ABSTRACT FROM AUTHOR]

Metallic Na anode is considered as a promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to its high specific capacity, and low potential. However, the unstable solid electrolyte interphase layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we first demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as a protective layer for metallic Na anode. By protecting Na anode with controllable alucone layer, the dendrites and mossy Na formation have been effectively suppressed and the lifetime has been significantly improved. Moreover, the molecular layer deposition alucone coating shows better performances than the atomic layer deposition Al2O3 coating. The novel design of molecular layer deposition protected Na metal anode may bring in new opportunities to the realization of the next-generation high energy-density NIBs and NMBs. [ABSTRACT FROM AUTHOR]

Thedevelopment of hydraulic fracturing has created a huge demandfor fracturing fluids with high performance and low formation damagein recent years. In this paper, a foam stabilized by partially hydrophobicmodified SiO2nanoparticles and sodium dodecyl benzenesulfonate(SDBS) was studied as a fracturing fluid. The properties of SiO2/SDBS foam such as rheology, proppant suspension, filtration,and core damage were investigated. The experimental data showed thatthe stability and thermal adaptability of sodium dodecyl benzenesulfonate(SDBS) foam increased when silica (SiO2) nanoparticleswere added. The surface tension of SDBS dispersion almost did notchange after SiO2nanoparticles were added; however, thedilational viscoelasticity of the interface increased, indicatingthat the SiO2nanoparticles attached to the interface andformed a stronger viscoelasticity layer to resist the external disturbance.The proppant settling velocity in the SiO2/SDBS foam wasfound to be 2 orders of magnitude lower than that in a pure SDBS foam.The total leakoff coefficient of the SiO2/SDBS foam wasfound to be lower than that of an SDBS foam. Although the core damageratio of the SiO2/SDBS foam was slightly larger than thatof an SDBS foam, compared to GEL/SDBS, the core damage caused by theSiO2/SDBS foam remained at a low level. SiO2nanoparticle–surfactant-stabilized foam is superior to asurfactant-stabilized foam and causes lower core permeability damagethan a gel–surfactant-stabilized foam. It is recommended foruse in hydraulic fracturing, particularly for fracturing stimulationin tight and shale gas reservoirs. [ABSTRACT FROM AUTHOR]

A binder-free three-dimensional (3D) nanostructured air electrode composed of vertically grown nitrogen doped carbon nanotubes on carbon paper (NCNT-CP) is developed and applied to Na-O2 cells. The 3D architecture of the air electrode results in increased discharge capacity by optimizing the utilized area of the electrode material. The chemical and electrochemical reaction mechanisms of the cell are also explored with the use of synchrotron-based X-ray absorption spectroscopy (XAS). Investigation of the discharge product of Na-O2 cells during discharge and charge cycles using X-ray absorption near-edge structure (XANES) indicates that both sodium superoxide and peroxide are produced under various physicochemical conditions and can be subsequently decomposed with different overpotentials. Furthermore, formation of carbonate-based parasitic products is also shown to restrict the cyclability of the cell. [ABSTRACT FROM AUTHOR]

Mn(II) and Fe(II) compounds derived from azide and the zwitterionic l-carboxylatomethylpyridinium-4-carbox)date ligand are isomorphous three-dimensional metal--organic frameworks (MOFs) with the sra net, in which the metal ions are connected into anionic chains by mixed (μ-l, l-azide)bis(μ-carboxylate) triple bridges and the chains are cross-linked by the cationic backbones of the zwitterionic ligands. The Mn(ll) MOFs display typical one-dimensional antiferromagnetic behavior. In contrast, with one more d electron per metal center, the Fe(n) counterpart shows intrachain ferromagnetic interactions and slow relaxation of magnetization attributable to the single-chain components. The activation energies for magnetization reversal in the infinite- and finite-chain regimes are Δτ1, = 154 K and Δτ2 = 124 K, respectively. Taking advantage of the isomorphism between the Mn(II) and Fe(II) MOFs, we have prepared a series of mixedmetal Mn1-xIIFexII MOFs with x = 0.41, 0.63, and 0.76, which intrinsically feature random isotropic/anisotropic sites and competing antiferromagnetic--ferromagnetic interactions. The materials show a gradual antiferromagnetic-to-ferromagnetic evolution in overall behaviors as the Fe(II) content increases, and the Fe-rich materials show complex relaxation processes that may arise for mixed SCM and spin-glass mechanisms. A general trend is that the activation energy and the blocking temperature increase with the Fe(II) content, emphasizing the importance of anisotropy for slow relaxation of magnetization. [ABSTRACT FROM AUTHOR]

Hydrothermal reactions of Cu(II) salts and 2,2′,4,4′-biphenyltetracarboxylic acid (2,2′,4,4′-H4bptc) in the presence of pyridyl ligands yielded three isomorphous 3D metal–organic coordination polymers formulated as [Cu2(2,2′,4,4′-bptc)(L)x]·H2O [x= 2 for L = pyridine; x= 1 for L = bis(4-pyridyl)ethene and bis(4-pyridyl)ethane]. In the structure, the distorted paddlewheel [Cu2(COO)4] motif and the twisted Π-shaped 2,2′,4,4′-bptc serve as dissimilar 4-connected SBUs to generate a 3D [Cu2(2,2′,4,4′-bptc)] mother framework with the PtS topology, which selectively accommodates pyridine or bis(pyridyl) ligands of appropriate size. [ABSTRACT FROM AUTHOR]

A series of transition metal coordination polymers with azide and flexible zwitterionic dicarboxylate ligands was synthesized and structurally and magnetically characterized. These compounds are formulated as [M2(L¹)(N3)4] (L¹ = 4,4'-trimethylenedipyridinio-N,N'-diacetate and M = Mn, 1; Co, 2; and Ni, 3) and [ML²(N3)6(H2O)2] (L² = 4,4'-dipyridinio-N,N'-diacetate and M = Mn, 4; Co, 5). The isomorphous compounds 1-3 consist of two-dimensional coordination layers in which the anionic chains with mixed triple bridges (two end-on (EO) azides and a syn-syn carboxylate) are cross-linked by the flexible cationin 4,4'-trimethylenedipyridinium spacers, while the isomorphous compounds 4 and 5 consist of alternating chains with triple (two EO azides plus a carboxylate) and double (two end-to-end azides) bridges, the 4,4'-dipyridinium spacers serving as side bridges along the chain. Magnetic studies demonstrated that the triple bridge transmits antiferromagnetic coupling in the Mn(II) compounds (1 and 4) but ferromagnetic coupling in the Co(II) and Ni(II) species (2, 3, and 5). The differences have been discussed in terms of the collaboration or competition between the carboxylate and azide pathways. Compound 4 exhibits alternating antiferromagnetic interactions, while alternating ferromagnetic-ferromagnetic-antiferromagnetic interactions with spin canting are suggested for 5. [ABSTRACT FROM AUTHOR]

The effect of monovalent ions on both the reactivity and global folding of the 8-17 DNAzyme is investigated, and the results are compared with those of the hammerhead ribozyme, which has similar size and secondary structure. In contrast to the hammerhead ribozyme, the 8-17 DNAzyme activity is not detectable in the presence of 4 M K+, Rb+, or Cs+ or in the presence of 80 mM, [Co(NH3)6]3+. Only 4 M Li+, NH4+ and, to a lesser extent, Na+ conferred detectable activity. The observed rate constants (Kobs ≈ 10-3 min-1 for Li+ and NH4+) are ~1000-fold lower than that in the presence of 10mM Mg2+, and ~200,000- fold slower than that in the presence of 100 μM Pb2+. Since the hammerhead ribozyme displays monovalent ion-dependent activity that is often within ~10-fold of divalent metal ion-dependent activity, these results suggest that the 8-17 DNAzyme, obtained by in vitro selections, has evolved to have a more stringent divalent metal ion requirement for high activity as compared to the naturally occurring ribozymes, making the 8-17 DNAzyme an excellent choice as a Pb2+ sensor with high selectivity. In contrast to the activity data, folding was observed in the presence of all the monovalent ions investigated, although those monovalent ions that do not support DNAzyme activity have weaker binding affinity (Kd ~ 0.35 M for Rb+ and Cs+), while those that confer DNAzyme activity possess stronger affinity (Kd 0.22 M for Li+, Na+ and NH4+). In addition, a correlation between metal ion charge density, binding affinity and enzyme activity was found among mono- and divalent metal ions except Pb2+ higher charge density resulted in stronger affinity and higher activity, suggesting that the observed folding and activity is at least partially due to electrostatic interactions between ions and the DNAzyme. Finally, circular dichroism (CD) study has revealed Z-DNA formation with the monovalent metal ions, Zn2+ and Mg2+ the Kd values obtained using CD were in the same range as those obtained from folding studies using FRET. However, Z-DNA formation was not observed with Pb2+. These results indicate that Pb2+-dependent function follows a different mechanism from the monovalent metal ions and other divalent metal ions; in the presence of latter metal ions, metal- ion dependent folding and structural changes, including formation of Z-DNA, play an important role in the catalytic function of the 8-17 DNAzyme. [ABSTRACT FROM AUTHOR]

The accumulation of polymers of the microtubule associated protein tau is correlative with increased neurodegeneration in Alzheimer' s disease and other related tauopathies. In vitro models have been developed in order to investigate molecular mechanisms that regulate the polymerization of tau. Arachidonic acid and heparin have been proposed to induce tau polymerization via a ligand dependent nucleation—elongation mechanism. However, certain aspects of these in vitro results are inconsistent with a classic nucleation—elongation mechanism. Using steady state and kinetic analyses of tau polymerization at a variety of protein and inducer concentrations, we have found that the thermodynamic barrier for nucleation in the presence of inducers is negligible, which was manifested by increases in protein polymerization at low tau concentrations and very rapid kinetics of polymerization. However, the mechanism of polymerization is complicated by the observation that high concentrations of inducer molecules result in the inhibition of tau fibril formation through different mechanisms for arachidonic acid and heparin. These observations indicate that the molar ratio of inducer to protein is a greater determinant of the rate and extent of tau polymerization than the concentration of tau itself. Our results are therefore not consistent with a canonical nucleation—elongation reaction but rather are more consistent with an allosteric regulation model in which the presence of small molecules induce a conformational change in the protein that decreases the thermodynamic barrier for polymerization essentially to zero. [ABSTRACT FROM AUTHOR]