La₆Ba₃[Si₁₇N₂₉O₂]ClAn Oxonitridosilicate Chloride with Exceptional Structural Motifs

The oxonitridosilicate chloride La₆Ba₃[Si₁₇N₂₉O₂]Cl was synthesized by a high-temperature reaction in a radiofrequency furnace starting from LaCl₃, BaH₂, and the ammonolysis product of Si₂Cl₆. Diffraction data of a micrometer-sized single crystal were obtained using microfocused synchrotron radiation at beamline ID11 of the ESRF. EDX measurements on the same crystal confirm the chemical composition. The crystal structure [space group <i>P</i>6₃/<i>m</i> (no. 176), <i>a</i> = 9.8117(14), <i>c</i> = 19.286(6) Å, <i>Z</i> = 2] contains an unprecedented interrupted three-dimensional network of vertex-sharing SiN₄ and SiN₃O tetrahedra. The SiN₄ tetrahedra form <i>dreier</i> rings. Twenty of the latter condense in a way that the Si atoms form icosahedra. Each icosahedron is connected to others via six SiN₄ tetrahedra that are part of <i>dreier</i> rings and via six Q³-type SiN₃O tetrahedra. Rietveld refinements confirm that the final product contains only a small amount of impurities. Lattice energy (MAPLE) and bond-valence sum (BVS) calculations show that the structure is electrostatically well balanced. Infrared spectroscopy confirms the absence of N–H bonds

K₂Hg₂Se₃: Large-Scale Synthesis of a Photoconductor Material Prototype with a Columnar Polyanionic Substructure

K₂Hg₂Se₃, a new photoconducting material with a direct band gap around 1.4 eV, was obtained in nearly quantitative yields and large scale (50 g per batch) by means of solvothermal treatment of a corresponding solid. The compound comprises covalently linked selenidomercurate columns that accommodate potassium counterions. Composition and structure allow for a specific combination of optoelectronic, photophysical, and thermoelectric properties, which initiates a systematic material development within this family of compounds

LAI-1-dependent inhibition of cell migration requires the Cdc42 GEF ARHGEF9.

<p>(A) Confluent cell layers of A549 cells were treated for 2 days with siRNA against the different Cdc42 GEFs or GAPs indicated. The cells were then treated or not with LAI-1 (10 μM, 1.5 h), scratched and let migrate for 24 h. Prior to imaging (0, 24 h), the detached cells were washed off. (B) The scratch area was quantified at 6 different positions per condition using ImageJ software. Means and standard deviations of 3 samples are shown, which are representative of 3 independent experiments (***<i>p</i> < 0.001).</p

LAI-1 reverses Icm/Dot-dependent inhibition of migration by <i>L</i>. <i>pneumophila</i>.

<p>(A) <i>D</i>. <i>discoideum</i> Ax3 amoebae harboring pSW102 (GFP) or (B) RAW 264.7 macrophages were left uninfected or infected (MOI 10, 1 h) with <i>L</i>. <i>pneumophila</i> wild-type or Δ<i>icmT</i> mutant bacteria and treated with different concentrations of LAI-1 (1, 5 and 10 μM) or not. The effect of LAI-1 on migration of amoebae towards folate (1 mM) or macrophages towards CCL5 (100 ng/ml) was monitored in under-agarose assays for 4 hours. Macrophages were stained with Cell Tracker Green BODIPY. Graphs depict the per cent fluorescence intensity versus migration distance. (C) <i>D</i>. <i>discoideum</i> Ax3 amoebae harboring pSW102 (GFP) or (D) RAW 264.7 macrophages were left uninfected or infected (MOI 10, 1 h) with <i>L</i>. <i>pneumophila</i> wild-type or Δ<i>icmT</i> mutant bacteria and treated with LAI-1 (10 μM, 1 h) or not. Single cell migration towards folate (1 mM) or CCL5 (100 ng/ml) was tracked in an under-agarose assay for 15 min or 1 h, respectively. Motility parameters (forward migration index, FMI, and velocity (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005307#ppat.1005307.s007" target="_blank">S7 Fig</a>)) were analyzed using the ImageJ manual tracker and Ibidi chemotaxis software. (E) Confluent cell layers of A549 epithelial cells were left uninfected or infected (MOI 10, 1 h) with <i>L</i>. <i>pneumophila</i> wild-type or Δ<i>icmT</i> mutant bacteria, treated with LAI-1 (10 μM) or not, scratched and let migrate for 24 h. Prior to imaging (0, 24 h), the detached cells were washed off. (F) The scratch area was quantified at 7 different positions per condition using ImageJ software. Means and standard deviations of triplicate samples per condition are shown, which are representative of 3 independent experiments (C, D, F; means and standard deviations; *<i>p</i> < 0.05; **<i>p</i> < 0.01; ***<i>p</i> < 0.001).</p

Cornucopia of Structures in the Pseudobinary System (SnSe)_<i>x</i>Bi₂Se₃: A Crystal-Chemical Copycat

Pseudobinary phases (SnSe)_<i>x</i>Bi₂Se₃ exhibit a very diverse structural chemistry characterized by different building blocks, all of which are cutouts of the NaCl type. For SnSe contents between <i>x</i> = 5 and <i>x</i> = 0.5, several new phases were discovered. Next to, for example, Sn₄Bi₂Se₇ (<i>x</i> = 4) in the NaCl structure type and SnBi₄Se₇ (<i>x</i> = 0.5) in the layered defect GeSb₂Te₄ structure type, there are at least four compounds (0.8 ≤ <i>x</i> ≤ 3) with lillianite-like structures built up from distorted NaCl-type slabs (L4,4-type Sn_2.22Bi_2.52Se₆, L4,5-type Sn_9.52Bi_10.96Se₂₆, L4,7-type Sn_11.49Bi_12.39Se₃₀, and L7,7-type Sn_3.6Bi_3.6Se₉). For two of them (L4,7 and L7,7), the cation distributions were determined by resonant X-ray scattering, which also confirmed the presence of significant amounts of cation vacancies. Thermoelectric figures of merit ZT range from 0.04 for Sn₄Bi₂Se₇ to 0.2 for layered SnBi₄Se₇; this is similar to that of the related compounds SnBi₂Te₄ or PbBi₂Te₄. Compounds of the lillianite series exhibit rather low thermal conductivities (∼0.75 W/mK for maximal ZT). More than other “sulfosalts”, compounds in the pseudobinary system SnSe-Bi₂Se₃ adapt to changes in the cation–anion ratio by copying structure types of compounds containing lighter or heavier homologues of Sn, Bi, or Se and can incorporate significant amounts of vacancies. Thus, (SnSe)_<i>x</i>Bi₂Se₃ is a multipurpose model system with vast possibilities for substitutional and structural modification aiming at the optimization of thermoelectric or other properties

Model of LA1-1-dependent inter-kingdom signaling through IQGAP1, Cdc42 and ARHGEF9.

<p>In eukaryotic cells, LAI-1 (directly or indirectly) inhibits or prevents the activation of the Cdc42-specific GEF ARHGEF9, which in turn prevents the IQGAP1-dependent activation of Cdc42. The host cell might detect extracellular and/or intracellular LAI-1.</p

Effect of <i>L</i>. <i>pneumophila lqs</i> genes on host cell migration.

<p><i>D</i>. <i>discoideum</i> strain Ax3 producing GFP (pSW102) was infected (MOI 10, 1 h) with (A) <i>L</i>. <i>pneumophila</i> wild-type, Δ<i>icmT</i>, Δ<i>lqsS</i>, Δ<i>lqsT</i>, <i>ΔlqsS-lqsT</i>, Δ<i>lqsR</i> or Δ<i>lqsA</i> mutant strains harboring pSW001 (DsRed), or with (D) the strains harboring pNT28 (GFP) or pNT36 (GFP, LqsA). An under-agarose assay was used to monitor the migration towards folate (1 mM) for another 4 h. The white lines represent the edge of the sample wells. (B, E) Graphs of the data from (A, D) plotted as per cent GFP fluorescence intensity versus migration distance. (C) Murine RAWs 264.7 macrophages were infected (MOI 10, 1 h) with <i>L</i>. <i>pneumophila</i> wild-type, Δ<i>icmT</i>, Δ<i>lqsS</i>, Δ<i>lqsT</i>, <i>ΔlqsS-lqsT</i>, Δ<i>lqsR</i> or Δ<i>lqsA</i> mutant strains. Cells were stained with Cell Tracker Green BODIPY and let migrate towards CCL5 (100 ng/ml) in an under-agarose assay for another 4 h. Graphs show the per cent fluorescence intensity versus migration distance. (F) Confluent cell layers of A549 epithelial cells were left uninfected or infected (MOI 10, 1 h) with <i>L</i>. <i>pneumophila</i> wild-type, Δ<i>icmT</i> or Δ<i>lqsA</i> mutant strains harboring pNT28 (GFP) or pNT36 (GFP, LqsA), scratched and let migrate for 24 h. Prior to imaging (0, 24 h), the detached cells were washed off. (G) The scratch area was quantified using ImageJ software at 7 different positions per condition in triplicate samples. Means and standard deviations of the triplicate samples are shown (pNT28 vs. pNT36: ***<i>p</i> < 0.001). The data shown are representative of at least 3 independent experiments.</p

Dose-dependent inhibition of chemotaxis and cell migration by LAI-1.

<p><i>D</i>. <i>discoideum</i> amoebae harboring pSW102 (GFP) were treated for 1 h with different concentrations of (A) racemic LAI-1, (B) 10 μM (<i>R</i>)-LAI-1, (<i>S</i>)-LAI-1, (<i>R</i>)-amino-LAI-1 or (<i>S</i>)-amino-LAI-1, or (C) different concentrations of CAI-1, and cell migration towards folate (1 mM) was monitored in under-agarose assays for 4 h. Graphs depict per cent GFP fluorescence intensity versus migration distance. (D) <i>D</i>. <i>discoideum</i> amoebae harboring pSW102 (GFP) were treated with LAI-1 (10 μM, 1 h). Single cell migration towards folate (1 mM) was monitored in under-agarose assays for 15 min. Motility parameters (forward migration index, FMI; and velocity) were analyzed using the ImageJ manual tracker and Ibidi chemotaxis software. (E) Murine RAW 264.7 macrophages were treated for 1 h with different concentrations of racemic LAI-1, cell migration towards CCL5 (100 ng/ml) was monitored in under-agarose assays for 4 h, and the cells were stained with Cell Tracker Green BODIPY. Macrophages treated for 1 h with 10 μM LAI-1 were immuno-labeled for (F) α-tubulin (green) or (G) actin (red) and, as a control, the production of cellular α-tubulin or actin was quantified by Western blot. Microtubule fibers per cell were counted along cross-sections (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005307#ppat.1005307.s003" target="_blank">S3 Fig</a>), and the actin architecture was analyzed by quantifying the number of cells displaying cortical actin. The graphs show means and standard deviations of 3 independent experiments (n > 25 (α-tubulin) or > 40 (actin) single cells; Student´s t-test, *<i>p</i> < 0.05, **<i>p</i> < 0.01). Bars (F, G), 5 μm.</p

LAI-1-dependent inhibition of cell migration requires IQGAP1 and Cdc42.

<p>(A) Confluent cell layers of A549 epithelial cells were treated with siRNA against IQGAP1, Cdc42, RhoA or Rac1 for 2 days. The cells were then treated or not with LAI-1 (10 μM, 1.5 h), scratched and let migrate for 24 h. Prior to imaging (0, 24 h), the detached cells were washed off. (B) The scratch area was quantified using ImageJ software at 7 different positions per condition in triplicate samples. Means and standard deviations of triplicate samples are shown (**<i>p</i> < 0.01). The data is representative of 3 independent experiments.</p

Chemical synthesis of LAI-1 and amino-LAI-1.

<p>The chemical synthesis of the putative <i>L</i>. <i>pneumophila</i> small molecule compounds (A) LAI-1 and (B) amino-LAI-1 is shown.</p