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Post-tetanic potentiation (PTP) is a form of short-term plasticity that lasts for tens of seconds following a burst of presynaptic activity. It has been proposed that PTP arises from protein kinase C (PKC) phosphorylation of Munc18-1, an SM (Sec1/Munc-18 like) family protein that is essential for release. To test this model, we made a knock-in mouse in which all Munc18-1 PKC phosphorylation sites were eliminated through serine-to-alanine point mutations (Munc18-1SA mice), and we studied mice of either sex. The expression of Munc18-1 was not altered in Munc18-1SA mice, and there were no obvious behavioral phenotypes. At the hippocampal CA3-to-CA1 synapse and the granule cell parallel fiber (PF)-to-Purkinje cell (PC) synapse, basal transmission was largely normal except for small decreases in paired-pulse facilitation that are consistent with a slight elevation in release probability. Phorbol esters that mimic the activation of PKC by diacylglycerol still increased synaptic transmission in Munc18-1SA mice. In Munc18-1SA mice, 70% of PTP remained at CA3-to-CA1 synapses, and the amplitude of PTP was not reduced at PF-to-PC synapses. These findings indicate that at both CA3-to-CA1 and PF-to-PC synapses, phorbol esters and PTP enhance synaptic transmission primarily by mechanisms that are independent of PKC phosphorylation of Munc18-1. [ABSTRACT FROM AUTHOR]

Assemblies of four three-dimensional (3D) mixed-ligand coordination polymers (CPs) having formulas, {[Zn2(bdc)2(4-bpdh)]·C2H5OH·2h2O}n (1), [Zn(bdc)(4-bpdh)]n (2), {[Zn2(bdc)2(4-bpdh)2]·(4-bpdh)}n (3), and {[Zn(bdc)(4-bpdh)]·C2H5OH}n (4) (bdc2- = dianion of 1,4-benzenedicarboxylic acid, 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) have been synthesized and structurally characterized by single-crystal X-ray diffraction method. Structural determination reveals that the coordination numbers (geometry) of Zn(II) ions in 1, 2, 3, and 4 are five (distorted square-pyramidal (SP)), six (distorted octahedral (Oh)), five (trigonal-bipyramidal (TBP)), and four (tetrahedral (Td)), respectively, and are bridged by 4-bpdh with bis-monodentate coordination mode and bdc2- ligands with bis-bidentate in 1, chelating/bidentate in 2, bis-monodentate and bis-bidentate in 3, and bis-monodentate in 4, to generate two-fold interpenetrating 3D cube-like metal-organic framework (MOF) with pcu topology, non-interpenetrating 3D MOF, two-fold interpenetrating 3D rectangular-box-like MOF with pcu topology and five-fold interpenetrating diamondoid-like MOF with dia topology, respectively. These different intriguing architectures indicate that the coordination numbers and geometries of Zn(II) ions, coordination modes of bdc2- ligand, and guest molecules play important roles in the construction of MOFs and the formation of the structural topologies and interpenetrations. Thermal stabilities, and photoluminescence study of 1-4 were also studied in detail. The complexes exhibit ligands based photoluminescence properties at room temperature. [ABSTRACT FROM AUTHOR]

The performance characteristics of lithium-ion battery cathode materials are governed by the surface structure and chemistry. Synthesis is known to affect the structure of these materials; however, a full understanding of the effects of the surface structure is not well understood. Here, we explore the atomic scale structure of lithium-layered oxides prepared with two different thermal treatments. We show that, under certain thermal treatments, the surface perpendicular to the transition-metal layers is enriched in nickel, which results in Ni occupying the lithium layer of the layered oxide structure. Under both thermal treatments, this surface also shows a reduction of Mn, with some of the reduced Mn occupying sites in the lithium layer. The surface parallel to the transition-metal layers under both treatments shows significant Mn reduction, oxygen loss, and reduced Mn in the lithium layer. The Mn reduction and surface reconstruction are the result of unstable surface terminations and are intrinsic to layered oxides. Synthesis can be tuned to eliminate Ni enrichment at the surface; however, it cannot be tailored to eliminate Mn reduction and surface reconstruction. [ABSTRACT FROM AUTHOR]

Post-tetanic potentiation (PTP) is a widespread form of short-term synaptic plasticity in which a period of elevated presynaptic activation leads to synaptic enhancement that lasts tens of seconds to minutes. A leading hypothesis for the mechanism of PTP is that tetanic stimulation elevates presynaptic calcium that in turn activates calcium-dependent protein kinase C (PKC) isoforms to phosphorylate targets and enhance neurotransmitter release. Previous pharmacological studies have implicated this mechanism in PTP at hippocampal synapses, but the results are controversial. Here we combine genetic and pharmacological approaches to determine the role of classic PKC isoforms in PTP. We find that PTP is unchanged in PKC triple knock-out (TKO) mice in which all calcium-dependent PKC isoforms have been eliminated (PKCα, PKCβ, and PKCγ). We confirm previous studies and find that in wild-type mice 10 µM of the PKC inhibitor GF109203 eliminates PTP and the PKC activator PDBu enhances neurotransmitter release and occludes PTP. However, we find that the same concentrations of GF109203 and PDBu have similar effects in TKO animals. We also show that 2 µM GF109203 does not abolish PTP even though it inhibits the PDBu-dependent phosphorylation of PKC substrates. We conclude that at the CA3 to CA1 synapse Ca2+- dependent PKC isoforms do not serve as calcium sensors to mediate PTP. [ABSTRACT FROM AUTHOR]

Two metal–organic frameworks (MOFs) based on Zn(ii)-squarate bridges associated with non-covalent and covalent bonds of dpe ligands, [Zn(dpe)(C4O4)(H2O)2]n(1), and {[Zn(Hdpe)(C4O4)0.5(H2O)3][Zn(C4O4)2(H2O)2]}n(2) (C4O42−(squarate) = dianion of 3,4-dihydroxycyclobut-3-ene-1,2-dione (H2C4O4); dpe = 1,2-bis(4-pyridyl)ethane), have been synthesized and characterized by spectroscopic analysis and single-crystal X-ray diffraction studies. Compound 1is a two-dimensional (2D) metal–organic framework (MOF), being constructed viathe crosslinkage of one-dimensional (1D) [Zn(μ1,3-squarate)] chains and 1D sinusoidal-like [Zn(gauche-dpe)] chains. Compound 2is a 2D tri-layered composite network composed of one cationic polythreading [Zn(Hdpe)(C4O4)0.5(H2O)3]2+MOF and two anionic [Zn(C4O4)2(H2O)2]2−MOFs with the penetration of the monoprotonated anti-form Hdpe+ligands dangling above and below the 2D Zn(ii)-(μ1,2,3,4-squarate) layer of cationic [Zn(Hdpe)(C4O4)0.5(H2O)3]2+MOF into the windows of two 2D Zn(ii)-(μ1,3-squarate) layers of anionic [Zn(C4O4)2(H2O)2]2−MOFs. Both of their 2D MOFs in compounds 1and 2are then extended to 3D supramolecular architectures viathe intermolecular hydrogen bonding interaction among the squarate, protonated dpe ligands and water molecules. [ABSTRACT FROM AUTHOR]

A new coordination polymer, [Zn(HBTC)(BPE)0.5(H2O)]n·nH2O (1) with an extended 1D ladderlike metal-organic framework (MOF) has been synthesized and structural characterized by single-crystal X-ray diffraction method. Structural determination reveals that, in compound 1, the Zn(II) ion is four-coordinated in a distorted tetrahedral geometry, bonded to one nitrogen atom from one BPE ligand, and three oxygen atoms from two monodentate carboxylate groups of two HBTC2- ligands and one coordinated water molecule. The HBTC2- acts as a bridging ligand with a bis-monodentate coordination mode, connecting the Zn(II) ions to form a one-dimensional (1D) [Zn(HBTC)] chain. Two 1D chains are then interlinked via the connectivity between the ZnII ions and anti-BPE liagnds to complete the 1D ladderlike MOF. Adjacent 1D Ladders are further extended to a 2D hydrogen-bonded layered network through the intermolecular O-H⋯O hydrogen bond between the carboxylic group and carboxylate group of interladder HBTC2- ligand. Adjacent 2D layers are then packed orderly in an ABAB-type array via the intermolecular interactions of combined π-π interaction and O-H⋯O hydrogen bonds to form a 3D supramolecular architecture exhibiting 1D channels intercalated with guest water molecules. The reversible solid-state structural transformation between crystalline 1 with 1D ladderlike framework and its dehydrated powder 2, [Zn(HBTC)(BPE)0.5]n, with 2D framework via the displacement of coordinated water molecule to HBTC2- ligand, by thermal de/rehydrated processes has been verified by PXRD measurements. The emission of 1 and 2 is ascribed to a ligand-based transition. [ABSTRACT FROM AUTHOR]

Coordination polymers of metal-croconate (C5O52−) complex, {[Ni2(bpe)2(C5O5)2]·H2O}n(1) (bpe = 1,2-bis(-4-pyridyl)ethylene)) with two-dimensional (2D) metal–organic frameworks (MOF), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1contains two crystallographically independent Ni(ii) ions which both lie in a distorted octahedral environment bonded to two bpe nitrogen atoms and four oxygen donors from two croconates. The croconate acts as a bridging ligand with two different bridging modes, one presents a bis-bidentate adjacent μ3-coordination mode and the other a bis-bidentate μ4-coordination mode. A 2D brick-wall-like layered framework is formed by using a rectangle grid as a basic building unit through the connectivity of NiIIwith hybrid μ3-, μ4-croconates and bpe ligands. Two layers are then cross-linked by the other bpe ligands to complete a 2D bi-layered MOF. The TGA associated with in situXRD measurements demonstrated that 1have quite high thermo-stability that keep their crystalline forms up to 350 °C. Magnetic measurements show the long range magnetic ordering and spin canting behavior in 1below the critical temperature of 22 K with an approximate canting angle of 0.79°. A large coercivity of 3.5 kOe in the hysteresis loop is observed at 1.8 K, indicating that 1is a weak hard magnet. [ABSTRACT FROM AUTHOR]

Streptococcal pyrogenic exotoxin B (SPE B) is a cysteine protease expressed by Streptococcus pyogenes. The D9N, G163S, G163S/A172S, and G239D mutant proteins were expressed to study the effect of the allelic variants on their protease activity. In contrast to other mutants, the G239D mutant was ∼12-fold less active. The Gly-239 residue is located within the C-terminal S230-G239 region, which cannot be observed in the x-ray structure. The three-dimensional structure and backbone dynamics of the 28-kDa mature SPE B (mSPE B) were determined. Unlike the x-ray structure of the 40-kDa zymogen SPE B (proSPE B), we observed the interactions between the C-terminal loop and the active site residues in mSPE B. The structural differences between mSPE B and proSPE B were the conformation of the C-terminal loop and the orientation of the catalytic His-195 residue, suggesting that activation and inactivation of SPE B is involved in the His-195 side-chain rotation. Dynamics analysis of mSPE B and the mSPE B/inhibitor complexes showed that the catalytic and C-terminal loops were the most flexible regions with low order parameter values of 0.5 to 0.8 and exhibited the motion on the ps/ns timescale. These findings suggest that the flexible C-terminal loop of SPE B may play an important role in controlling the substrate binding, resulting in its broad substrate specificity. [ABSTRACT FROM AUTHOR]

A series of one-dimensional (1D) coordination polymers, {[Cu(en)2][M(C5O5)2(H2O)m]·xH2O}n, (M = Mn (1), m= 4, x= 2; M = Co (2), Ni (3), Cu (4), Zn (5), m= 2, x= 0; en = ethylenediamine; C5O52−= croconate, dianion of 4,5-dihydroxycyclopent-4-ene-1,2,3-trione), using [M(C5O5)2(H2O)n]2−dianion as a building block has been synthesized and characterized by the X-ray diffraction method. Structural determination reveals that, in compounds 1−5, one [M(C5O5)2(H2O)n]2−dianion coordinates via two oxygen (croconate) donors to the axial sites of two Cu(II) centers of [Cu(en)2]2+cations to form one-dimensional (1D) linear (1, 3and 4) or zigzag (2and 5) chains of alternating [M(C5O5)2(H2O)n]2−and [Cu(en)2]2+units. The croconate acts as a bridging ligand with three coordination modes as μ1,3-bismonodentate for 1, μ1,2,3-bidentate/monodentate for 2and 5, and μ1,2,4-bidentate/monodentate for 3and 4, respectively. In addition, a byproduct, [Cu(en)(C5O5)(H2O)]2(6), which is cocrystallized with 4, shows a dimeric structure formed through the croconate bridge with μ1,1,2-bidentate/monodentate coordination mode. All of their 1D frameworks (1−5) and dimeric structure (6) are extended to three-dimensional (3D) supramolecular architectures by the intermolecular π−π interaction among croconates and intermolecular hydrogen bonds among the en, croconate, and coordinated water molecules. [ABSTRACT FROM AUTHOR]

We investigate the alignment properties of nematic liquid crystal on polyimide films bombarded by Ar ion beams with a small diode sputter type ion-beam source. The alignments of nematic liquid crystal 4'-n-pentyl-4-cyanobiphenyl (5CB) on treated polyimide surface are characterized by using polarizing optical microscope and conoscope. The polyimide surfaces are also studied by using atomic force microscope and x-ray photoemission spectroscopy. We have demonstrated that the polyimide surface treated by Ar ion beams can give both homogeneous and homeotropic alignments with the same ion beam apparatus but varying the energy of ion beam and the bombarding time. [ABSTRACT FROM AUTHOR]

Two metal−croconate (C5O52-) complexes, Cd2(bpe)(C5O5)2(H2O)·2H2On(1) and Zn2(bpe)2(C5O5)2·H2On(2) (bpe 1,2-bis(4-pyridyl)ethylene)) with two-dimensional (2-D) metal−organic frameworks (MOFs), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1possesses a 2-D layered MOF with two rectangular boxes as the basic building units through the connectivity of CdIIwith 3-croconates, 5-croconates, and bpe ligands. In compound 2, a 2-D brick-wall-like layered framework is formed by using a rectangular grid as the basic building unit through the connectivity of ZnIIwith hybrid 3-croconates, 4-croconates, and bpe ligands. Two layers are then cross-linked by the other bpe ligands to complete a 2-D bilayered MOF. Both of the 2-D MOFs are extended to three-dimensional supramolecular architectures through − and C−H···O interactions between the croconate and the pyridyl rings of bpe, which exhibit high thermal stability and retain their crystalline forms up to 350 °C. [ABSTRACT FROM AUTHOR]

Two extended networks of Cd(II) with 2,2‘-bipyrimidine (bpym) and cyclic oxocarbon dianions CnOn2-(n4, 5) with formulas Cd(C4O4)(bpym)0.5(H2O) (1) and Cd(C5O5)(bpym)0.5(H2O) (2) have been synthesized and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that, in compounds 1, each Cd center lies in a seven-coordinate environment bonded to two bpym nitrogen atoms and five oxygen donors from four squarate and one water molecules. The squarate acts as a bridging ligand with two different binding modes, a tetramonodentate (4) and a bis-bridging (4) coordination mode, linking the Cd(II) ions to form a two-dimensional (2D) metal−squarate layer. Adjacent layers are then mutually linked via bridges of bis-bidentate bpym ligands constructing a three-dimensional (3D) triangular metal−organic framework (MOF). In compound 2, each Cd center lies in an eight-coordinate environment bonded to two bpym nitrogen atoms and six oxygen donors from three croconate ligands and one water molecule. Each croconate (C5O52-) adopts a new bis-bidentate/monodentate (5) bridging mode and links crystallographically identical Cd ions, forming a one-dimensional (1D) bichain. Adjacent bichains are then mutually linked via the bridges of bis-bidentate bpym ligands constructing a 2D layered MOF, which is then extended to a 3D supramolecular architecture by two intermolecular − interactions between the pyrimidyl rings of bpyms and between cyclic five-membered rings of croconates. Both MOFs are thermally stable, as evidenced by thermogravimetric analysis and in-situ powder X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

Alumina nanotubes were fabricated by a template method. Tris-(8-hydroxyquinoline) gallium (GaQ3) organic nanowires were used as a soft template for coating with alumina using an atomic layer deposition technique. The deposition was conducted at 25 °C by using trimethylaluminum and distilled water as the precursors of Al2O3. Amorphous alumina nanotubes were obtained after removing the GaQ3by dissolving in toluene or by heat treatment at 350 °C. The amorphous nanotubes could be crystallized by heating at 900 °C for 1 h in vacuum. [ABSTRACT FROM AUTHOR]

Topological analyses of experimental and theoretical calculated electron densities of 1,3,5,7-tetra-tert-butyl-s-indacene provide bond characterizations of the chemical bond and of the π-delocalization. A weak Csp³—H···H—Csp²type intramolecular dihydrogen interaction (DHI) is identified through this analysis. [ABSTRACT FROM AUTHOR]

A new cadmium croconate (C[sub5]O[sup2-],[sub5]) complex, [Cd[sub2](C[sub5]O[sub5])[sub2](4,4'-bpy)(H[sub2]O)][sub∞] (4,4-bpy = 4,4'-bipyridine) with an extended network has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. The title compound crystallizes in the monoclinic system, space group P2[sub1]/n[sub1] with empirical formula C[sub20]H[sub12]Cd[sub2]N[sub2]O[sub12], a = 15.9623(3) Å, b = 7.5837(1) Å, c = 18.1181(3) Å, β = 99.95(2)°, and Z= 4. Structural determination reveals that the title compound has a bilayered network, containing two crystallographically independent Cd(II) ions in different coordination environments. Cd(1) lies in a distorted pentagonal bipyramidal environment, consisting of three croconate ions and one 4,4'-bpy nitrogen donor, while Cd(2) lies in a distorted octahedral environment, consisting of two croconate anions, one 4,4'-bpy nitrogen donor, and one water molecule. Of the two crystallographic independent croconate ligands, one presents a bis-bidentate adjacent μ[sub3]-coordination mode and the other a new bidentate/three-adjacent μ[sub5]-coordination mode. A two-dimensional hybrid layer is formed by two rectangular boxes as the building units through the connectivity between Cd(II) and croconate and 4,4'-bpy ligands. [ABSTRACT FROM AUTHOR]

Examines the synthesis and structural characterization of monocyclic aromatic oxocarbon dianions. Ability of croconate ligands to act as a terminal or as a bridging ligand; Outcome of the reaction of sodium croconate and metal chloride in aqueous solution; Formation of a three-dimensional structure.

Examines the hydrothermal synthesis and structural characterization of a two-dimensional polymeric copper(II) complex containing an unusual bridged H[sub 2]edta[sup2-] ligand. Formation of a six-coordinate octahedron; Discussion of the X-ray single-crystal structure of [Cu(edtaH[sub 2])][sub n]; Performance of a magnetic measurement.

Titanium dioxide nanotubes were prepared by refluxing TiO2 in 10 M NaOH at 200 °C for 12 h. The light absorption edge was slightly shifted to a longer wavelength when 0.025 mol % of iron was incorporated to TiO2 nanotubes. A turn-on field at 12 V/μm and a maximum current density of 12 mA/cm2 at 19 V/μm was observed for the Fe-doped but not for pure TiO2. The field emission behavior can be correlated with the geometry and electronic states of the nanotubes. [ABSTRACT FROM AUTHOR]

Two supramolecular isomers of [Ni(4-bpd)2(NCS)2] (4-bpd = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene) with 2D 44 square-grid and 3D 65·8 frameworks are co-crystallized in a one-pot reaction, both of which exhibit interesting luminescence properties and reversible adsorption–desorption with respect to guest solvents. [ABSTRACT FROM AUTHOR]

A new polymeric silver complex, [Ag2(L2)(ClO4)2] (L = 4,5-diazospirobifluorene), has been synthesized and shown to exhibit interesting luminescence properties in a single crystal. Structural analysis reveals a one-dimensional chain, which contains a [Ag2-(L2)]2+ dimer bridged with ClO4-. The Ag…Ag distances are 2.776-(1) and 4.575(1) Å incorporated by two L ligands and by a ClO4- bridge, respectively. [ABSTRACT FROM AUTHOR]

The effects of hydrogen thermal and plasma treatment on the formation and photocatalytic activities of black TiO2 nanowire arrays were investigated and discussed. After either the hydrogen thermal or plasma treatment, the TiO2 nanowires remained. However, in contrast to the plasma treated nanowires, the diameter of the thermal treated TiO2 nanowires reduced more significantly, which was attributed to a thicker surface amorphous layer and more oxygen vacancies. A higher photoresponse in both UV and visible light regions and more hydroxide groups were also observed for the thermal treated nanowires. In addition, the black nanowires possessed greater carrier concentration, leading to a more efficient separation of electron–hole pairs. As a consequence, much enhanced photoelectrochemical water splitting and photocatalytic degradation of methylene blue were obtained. [ABSTRACT FROM AUTHOR]

TiO2-based nanowires were prepared by a hydrothermal method, and Pt nanoparticles were deposited on the nanowires by atomic layer deposition (ALD). The size and loading of Pt nanoparticles with very good uniformity could be controlled by the ALD cycle number, along with acid or water treatment of the nanowires. The lower growth rate and the loading of Pt nanoparticles were obtained with water treatment. With acid treatment, the growth rate and loading were increased, and this increase was attributed to the formation of higher density of hydroxide groups on the nanowires. The photocatalytic activities of Pt-deposited nanowires were investigated. The deposition of Pt on the nanowires resulted in both enhanced light absorption in the visible region and electron–hole separation efficiency. The water-treated nanowires exhibited the highest degradation rate of rhodamine B and the highest hydrogen evolution rate. A maximum amount of hydrogen evolution, 13.8 mmol g−1 in 6 h, was achieved. [ABSTRACT FROM AUTHOR]

NMDA receptor signaling plays a complex role in CREB activation and CREB-mediated gene transcription, depending on the subcellular location of NMDA receptors, as well as how strongly they are activated. However, it is not known whether Rac1, the prototype of Rac GTPase, plays a role in neuronal CREB activation induced by NMDA receptor signaling. Here, we report that NSC23766, a widely used specific Rac1 inhibitor, inhibits basal CREB phosphorylation at S133 (pCREB) and antagonizes changes in pCREB levels induced by NMDA bath application in rat cortical neurons. Unexpectedly, we found that NSC23766 affects the levels of neuronal pCREB in a Rac1-independent manner. Instead, our results indicate that NSC23766 can directly regulate NMDA receptors as indicated by their strong effects on both exogenous and synaptically evoked NMDA receptor-mediated currents in mouse and rat neurons, respectively. Our findings strongly suggest that Rac1 does not affect pCREB signaling in cortical neurons and reveal that NSC23766 could be a novel NMDA receptor antagonist. [ABSTRACT FROM AUTHOR]

Single-crystalline Zn 2GeO 4nanorods were formed by submerging Zn-containing Ge nanoparticles (ZCGNs) in water at room temperature. These nanorods with the diameter ranging from several tens to more than 100 nm and the length of several micrometers exhibit a blue-green luminescence peak at 450 nm. Due to the surface instability of Ge in water, the agglomerates of crystalline ZCGNs keep oxidizing, and gradually transform into amorphous membranes composed of Zn, Ge, and oxygen. Zn 2GeO 4nanorods then grow out directly from the amorphous membranes after further aging. This novel transformation route may provide a new thinking for preparing similar 1-D Ge-based ternary oxides or other 1-D nanomaterials. [ABSTRACT FROM AUTHOR]

Reaction of Kpmf (pmf− = anion of N,N′-bis(pyrimidyl-2-yl)formamidine, Hpmf) with divalent copper salt CuX2 afforded the linear trinuclear complexes of the type [Cu3(pmf)4](X)2 (X = BF4, 1; NO3, 2; ClO4, 3), while reaction of Kpmf with monovalent copper salt CuX gave the linear tetranuclear complexes of the type Cu4(pmf)4X2 (X = Cl, 4; Br, 5). The copper atoms of complexes 1–5 are helically bridged by four pmf− ligands, resulting in three different coordination modes for the pmf− ligands. In complexes 1–3, one pmf− ligand adopts a new coordination mode with the two amine nitrogen atoms chelating to the central copper atom, while the other three feature chelation by one pyrimidyl and one adjacent amine nitrogen atoms. The Cu(ii)⋯Cu(ii) distances are 2.729(2) and 2.825(2) Å for 1, 2.762(1) and 2.832(1) Å for 2 and 2.732(1) and 2.827(1) Å for 3. In complexes 4 and 5, the pmf− ligands are coordinated to the copper atoms in tetradentate fashion with each nitrogen atom coordinating to one Cu atom. The Cu⋯Cu distances are 2.580(1) and 2.549(1) Å for 4 and 2.582(1) and 2.561(1) Å for 5. Antiferromagnetic interactions between the copper ions are observed with calculated g and J values of 2.03(1) and −188(2) cm−1 for 1, 2.09(1) and −268(3) cm−1 for 2, and 2.09(1) and −486(2) cm−1 for 5. By comparing the magnetic data it can be shown that the bonding mode of the pmf− ligand is one of the important factors in determining the strengths of the Cu⋯Cu interactions in linear trinuclear and tetranuclear copper complexes. [ABSTRACT FROM AUTHOR]

Examines the role of hydrogen-bonding system in nonpolar solvents. Identification of the carbonyl compounds; Observation of the electrostatic interactions; Formation of the polydimers.

One-pot solvothermal reactions of 2-aminopyridine, triethylorthoformate and sodium hydroxide with CuX (X = Br, and I) in dimethylformamide (DMF) and methanol (MeOH) afforded extended metal chains based on the linear tetracopper units, {[Cu4Br2(Dpyf)2]·DMF}n, 1, and [Cu4I2(Dpyf)2]n, 2, which were structurally identified by X-ray crystallography. Complexes 1 and 2 present closed-shell Cu(I)–Cu(I) interactions that are supported by formamidinate ligands, resulting in a face-to-side configuration and a face-to-face configuration, respectively, for the tetranuclear units. Complexes 1 and 2 represent the first example of one-dimensional (1D) coordination polymers that are based on linear tetracopper units. Moreover, complexes 1 and 2 can be regarded as copper(I) halide aggregates with the unique Cu4Br2 2+ and Cu4I2 2+ cations extending into a 1D zigzag chain and a looped chain, respectively. Complexes 1 and 2 show broad emissions at 570 and 549 nm, respectively, which can most probably be ascribed to 3d(Cu) → π* metal to ligand charge transfer. Reversible crystal-to-crystal transformation and luminescence change were observed for complex 1 upon solvent exchange, which can be regarded as a potential luminescent sensor for selective detection of water and methanol. [ABSTRACT FROM AUTHOR]

TiO2 with different morphology was deposited on acid-treated multi-walled carbon nanotubes (CNTs) by atomic layer deposition at 100 °C–300 °C to form a TiO2@CNT structure. The TiO2 fabricated at 100 °C was an amorphous film, but became crystalline anatase nanoparticles when fabricated at 200 °C and 300 °C. The saturation growth rates of TiO2 nanoparticles at 300 °C were about 1.5 and 0.4 Å/cycle for substrate-enhanced growth and linear growth processes, respectively. It was found that the rate constants for methylene blue degradation by the TiO2@CNT structure formed at 300 °C were more suitable to fit with second-order reaction. The size of 9 nm exhibited the best degradation efficiency, because of the high specific area and appropriate diffusion length for the electrons and holes. [ABSTRACT FROM AUTHOR]

The 2D protuberant-grid-type Zn(II)-organic framework consists of unusual racemic interdigitated bilayers and comprises a 3D intersecting channel system. The framework is thermally stable and the channels contain multiple water aggregates. Accompanying the migration of guest water molecules, only the specific channels in the bilayers along the b axis can easily and efficiently absorb guest benzene molecules in a regular manner. [ABSTRACT FROM AUTHOR]

The level and integrity of glutamate transmission during critical periods of postnatal development plays an important role in the refinement of pyramidal neuron dendritic arbor, synaptic plasticity, and cognition. Presently, it is not clear how excitatory transmission via the two predominant isoforms of the vesicular glutamate transporter (VGLUT1 and VGLUT2) participate in this process. To assess a neurodevelopmental role for VGLUT2 in pyramidal neuron maturation, we generated recombinant VGLUT2 knock-out mice and inactivated VGLUT2 throughout development using Emxl-Cre+/+ knock-in mice. We show that VGLUT2 deficiency in corticolimbic circuits results in reduced evoked glutamate transmission, release probability, and LTD at hippocampal CA3-CA1 synapses during a formative developmental period (postnatal days 11-14). In adults, we find a marked reduction in the amount of dendritic arbor across the span of the dendritic tree of CA1 pyramidal neurons and reduced long-term potentiation and levels of synaptic markers spinophilin and VGLUT1. Loss of dendritic arbor is accompanied by corresponding reductions in the number of dendritic spines, suggesting widespread alterations in synaptic connectivity. Conditional VGLUT2 knock-out mice exhibit increased open-field exploratory activity yet impaired spatial learning and memory, endophenotypes similar to those of NMDA receptor knock-down mice. Remarkably, the impairment in learning can be partially restored by selectively increasing NMDA receptor-mediated glutamate transmission in adult mice by prolonged treatment with D-serine and a D-amino acid oxidase inhibitor. Our data indicate that VGLUT2 expression is pivotal to the proper development of mature pyramidal neuronal architecture and plasticity, and that such glutamatergic deficiency leads to cognitive malfunction as observed in several neurodevelopmental psychiatric disorders. [ABSTRACT FROM AUTHOR]

A novel porous metal–organic framework, Mn9(btt)2(HCOO)12·0.7DMF·0.9H2O, was synthesized solvothermally in mixed H2O–DMF. Its structure was characterized by single-crystal X-ray diffraction techniques, which reveal that it is constructed by cross-linking Mn2誉 with 1,3,5-benzenetristetrazolates and formates, which formed in situfrom the hydrolysis of dimethylformamide, to form a 3D framework with parallel hexagonal channels. Although the Mn2誉 at 4f Wyckoff sites are 75% occupied, the framework remains robust and porous upon evacuation of solvent molecules, with 264 m2g−1BET surface area and hydrogen adsorption capacity of ca.0.9 wt% at 77 K and 1 atm. Photoluminescence studies exhibit a blue band with λmax= 418 nm. [ABSTRACT FROM AUTHOR]

8,8'-(1,4,10,13-Tetrathia-7,16-diazacyclooctadecane-7,16-diyl)-bis(mefhytene)diquinotin-7-ol (TTBQ) was synthesized and proved to selectively recognize Hg2+, forming a Hg2+/TTBQ complex with an association constant (Ks) as large as ∼1.3 x 104 ± 520 M-1 in aqueous solution. Single clystals of TTBQ and a TTBQ-Hg2+ complex have also been successfully grown, in which the fatter unambiguously revealed a cagelike configuration consisting of thiol-crown and dual 7-hydroxyquinoline moieties to firmly trap Hg2+. This 3D-comptexation stwcture accounts for ∼25-fold luminescence enhancement and a detection limit of sub-μM in water for sensing Hg2+. Great selectivity toward Hg2+ has been exhibted over atkali- and alkaline-earth metal ions, first-row transition-metal ions, and other cations studied. This chemosensor is particulady suited for the detection of Hg2+ in a pH range of 5.5 to 7.5. This, in combination with its fine biocompatibility, leads to the success toward in vitro mercury recognition based on fluorescence imaging. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and fundamental of the dual excited-state proton-transfer properties of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one (1a) are reported. In the electronic ground state, there exist two competitive hydrogen bonding (HB) isomers for 1a. Conformer 1a(O)reveals a five-membered ring HB structure between O−H and carbonyl oxygen, while conformer 1a(N)possesses a six-membered ring HB formation between O−H and pyridyl nitrogen. In a single crystal, the X-ray crystallography unveils an exclusive formation of conformer 1a(N). In solution such as CH2Cl2, 1a(O)and 1a(N)are in equilibrium, and their respective absorption chromophores are significantly different due to different degrees of hydrogen-bond induced π electron delocalization. Upon excitation, both conformers 1a(O)and 1a(N)undergo excited-state intramolecular proton transfer (ESIPT) reaction. Following ESIPT, 1a(O)gives rise to a tautomer emission maximized at 534 nm in CH2Cl2. Conversely, due to dominant radiationless quenching processes the tautomer emission for 1a(N)cannot be obtained with a steady-state manner but can be resolved from time-resolved fluorescence. Time resolved fluorescence estimates an equilibrium constant of 27 ± 5 in favor of 1a(N)in CH2Cl2. Ultrafast ESIPT also takes place for the unique 1a(N)form in the crystal. Due to the prohibition of quenching processes in the solid state, bright tautomer emission maximized at 540 nm is resolved for 1a(N)(Φf∼ 0.3). The interplay between two HB conformers with on(1a(O))/off(1a(N)) character in tautomer emission may find future applications such as the recognition of organic Lewis acid/base in organic solvents. [ABSTRACT FROM AUTHOR]

Group A Streptococcus is a common pathogen that causes pharyngitis, impetigo, myositis, and lethal streptococcal toxic shock syndrome. Streptococcal pyrogenic exotoxin B (SPE B) is strongly associated with the severity of disease. SPE B is a cysteine protease and matures itself by autocatalysis. We found that SPE B was directly associated with human S-adenosylhomocysteine hydrolase (AdoHcyase), an essential factor for a delayed-type immune response. AdoHcyase protein levels and enzymatic activities were significantly higher inhumancells infected with the Streptococcus pyogenes SW510 speB mutant strain than in cells infected with the NZ131 wild-type strain. SPE B also inactivated AdoHcyase, shown by a decrease in homocysteine, the main product of AdoHcyase. We found that in vivo and in vitro, SPE B induced hypermethioninemia, which is caused by an AdoHcyase defect. We also found that AdoHcyase is a substrate of SPE B cysteine protease. SPE B, therefore, potentially causes immunosuppression by cleaving AdoHcyase. [ABSTRACT FROM AUTHOR]

Examines the proton-lithium binding behavior of tris(2-((pyrid-2-ylmethyl)uredio)ethyl)amine. Stability constants; Formation of the complexes; Increased Columbic repulsion occurring on complexation.

8,8′-(1,4,10,13-Tetraoxa-7,16-diazacyclooctadecane-7,16-diyl)bis(methylene)diquinolin-7-ol (TDBQ) was synthesized and proved to recognize Hg2+via reducing Hg2+ to Hg+, forming a unique Hg22+–TDBQ complex. [ABSTRACT FROM AUTHOR]