4,4′-Bipyridine-1,1′-diium 2,3,5,6-tetra­bromo­terephthalate dihydrate

The title compound, C10H10N2 2+·C8Br4O4 2−·2H2O, consists of a tetra­bromo­terephthalate dianion, a 4,4′-bipyridinium dication and two solvent water mol­ecules. Crystallographic inversion centers are situated at the center of the aromatic ring of the dianion as well as at the midpoint of the carbon–carbon bond connecting the pyridine rings in the dication. In the crystal, inter­molecular N—H⋯O hydrogen-bonding inter­actions between tetra­bromo­terephthalate dianions and protonated 4,4′-bipyridinium dications result in the formation of a chain-like structure. Further O—H⋯O hydrogen bonds between carboxyl­ate O atoms and water mol­ecules lead to the formation of a two-dimensional network in the crystal structure

Structure and non-blocking properties of bidirectional unfolded two-stage switches

Two-stage switch networks are an emerging design option for relatively small-capacity space switches. They are classified into two categories: folded and unfolded. Although folded switches have been well studied, research on unfolded two-stage switch networks (UTSNs) remains limited. Here, non-blocking UTSNs are considered. First, a new UTSN design is presented that consists of input and output switch modules (ISMs and OSMs) using bidirectional switching techniques. The proposed UTSN is represented by B(n, m, r), where n, m, and r denote the number of input ports of the ISM, number of OSMs, and number of ISMs, respectively. Second, the maximum number of rearrangements for B(n, n, r) is proved to be L(r-1)/2(n-1) RIGHT FLOOR in general, whereas it is limited to two when n >= r. The strictly non-blocking condition for B(n, m, r) to be m >= n + 1 is also determined. Finally, it is shown that the switch hardware complexity becomes minimal at n=N/2 and saturates at N-2/2 as N -> infinity

Cloning and Characterization of a Streptomyces Single Module Type Non-ribosomal Peptide Synthetase Catalyzing a Blue Pigment Synthesis

In the present study, we cloned a gene, designated bpsA, which encodes a single module type non-ribosomal peptide synthetase (NRPS) from a d-cycloserine (DCS)-producing Streptomyces lavendulae ATCC11924. A putative oxidation domain is significantly integrated into the adenylation domain of the NRPS, and the condensation domain is absent from the module. When S. lividans was transformed with a plasmid carrying bpsA, the transformed cells produced a blue pigment, suggesting that bpsA is responsible for the blue pigment synthesis. However, to produce the blue pigment in Escherichia coli, the existence of the 4′-phosphopantetheinyl transferase (PPTase) gene from Streptomyces was necessary, in addition to bpsA. The chemical structure of the pigment was determined as 5,5′-diamino-4,4′-dihydroxy-3,3′-diazadiphenoquinone-(2,2′), called indigoidine. The bpsA gene product, designated BPSA, was overproduced in an E. coli host-vector system and purified to homogeneity, demonstrating that the recombinant enzyme prefers l-Gln as a substrate. The in vitro experiment using l-Gln also showed that the blue pigment was formed by the purified BPSA only when the enzyme was phosphopantetheinylated by adding a Streptomyces PPTase purified from E. coli cells. Each site-directed mutagenesis experiment of Lys598, Tyr601, Ser603, and Tyr608, which are seen in the oxidation domain of BPSA, suggests that these residues are essential for the binding of FMN to the protein and the synthesis of the blue pigment

Poly[[dodeca­aqua­(μ4-benzene-1,4-dicarboxyl­ato)(μ2-4,4′-bipyridine-κ2 N:N′)dicerium(III)] bis­(benzene-1,4-dicarboxyl­ate)]

The asymmetric unit of the title compound, {[Ce2(C8H4O4)(C10H8N2)(H2O)12](C8H4O4)2}n, consists of half a CeIII cation, a quarter of a coordinated benzene-1,4-dicarboxyl­ate (bdc2−) dianion, a quarter of a 4,4′-bipyridine (bpy) mol­ecule, three water mol­ecules and a half of an uncoordinated benzene-1,4-dicarboxyl­ate dianion. The CeIII ion is located on a twofold rotation axis and exhibits a distorted trigonal prism square-face tricapped coordination geometry. The coordinated and uncoordinated bdc2− ions and the bpy mol­ecule lie about special positions of site symmetries 2/m, m and 2/m, respectively. The CeIII ions are bridged by the bdc2− and bpy ligands, giving a sheet structure parallel to the ac plane. The uncoordinated bdc2− dianion exists between the sheets and links the sheets by inter­molecular O—H⋯O hydrogen bonds between the uncoordinated bdc2− and coordinated water mol­ecules. A π–π stacking inter­action between the uncoordinated bdc2− dianion and the bpy ligand [centroid–centroid distance = 3.750 (4) Å] is also observed

Colorectal Carcinoma: Local Tumor Staging and Assessment of Lymph Node Metastasis by High-Resolution MR Imaging in Surgical Specimens

Purpose. To assess the accuracy of high-resolution MR imaging as a means of evaluating mural invasion and lymph node metastasis by colorectal carcinoma in surgical specimens. Materials and Methods. High-resolution T1-weighted and T2-weighted MR images were obtained in 92 surgical specimens containing 96 colorectal carcinomas. Results. T2-weighted MR images clearly depicted the normal colorectal wall as consisting of seven layers. In 90 (94%) of the 96 carcinomas the depth of mural invasion depicted by MR imaging correlated well with the histopathologic stage. Nodal signal intensity on T2-weighted images (93%) and nodal border contour (93%) were more accurate than nodal size (89%) as indicators of lymph node metastasis, and MR imaging provided the highest accuracy (94%–96%) when they were combined. Conclusion. High-resolution MR imaging is a very accurate method for evaluating both mural invasion and lymph node metastasis by colorectal carcinoma in surgical specimens

Bis[μ-3,5-bis­(2-pyrid­yl)pyrazolato]bis­(hydrogensulfato)­dicopper(II) methanol disolvate

The title compound, [Cu2(C13H9N4)2(HSO4)2]·2CH3OH, consists of discrete centrosymmetric dinuclear complex mol­ecules and methanol solvent mol­ecules. The CuII atom shows a square-pyramidal coordination geometry and is bonded to four N atoms of the two bis-chelating 3,5-bis­(2-pyrid­yl)pyrazol­ate ions (bpypz−) and one O atom of the hydrogensulfate ion. The bpypz− ligands in the complex mol­ecule are virtually coplanar [dihedral angle between the mean ligand planes = 0.000(1)°] with the CuII atom deviating in opposite directions from their best plane by 0.2080 (12) Å. π–π stacking inter­actions between the pyridyl and pyrazole rings [centroid–centroid distance = 3.391 (3) Å] and strong O—H⋯O hydrogen bonds between the hydrogensulfate ligands and the methanol mol­ecules assemble the mol­ecules into a one-dimensional polymeric structure extending along the a axis. The methanol mol­ecule acts both as an accepter and a donor in the hydrogen bonding