Unique Topology Analysis by ToposPro for a Metal-Organic Framework with Multiple Coordination Centers.

The reactions of 2-(4-pyridyl) thiazole-4-carboxylic acid (Hptca) and CuCl2·6H2O have led to a novel 3D mixed-valence, four-copper-center, metal-organic framework (MOF) [Cu8Cl2(ptca)10·17H2O] n (1). The topology analysis using ToposPro software package for 1 resulted in three chain-based topology types of sra (42, 63, 8), pcu (412, 63), and dia (66) via choosing corresponding connection atoms as central atoms. The study indicates that connection atoms associated directly with multiple coordination centers are applicable to act as central atoms. This unique topology analysis approach is conceptually different from the current analytical methods which use node atoms as central atoms. In addition, complex 1 exhibits significant selective adsorption of CO2 over N2. This study provides a great example of the topological analysis of MOFs with multiple coordination centers.

Shape-Asymmetry Supramolecular Isomerism in Asymmetrical Ligand PCPs and the Expression Method of Three-Level Isomerism.

We show here the supramolecular isomerism, with respect to shape-asymmetry of ligand and the new hierarchical classification for supramolecular isomerism, the three-level isomerism, which was advanced based on a thorough investigation for the four new Ni/dpt24 polymorphs [Hdpt24 = 3-(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole)]. Compounds 1, 2, and 3 are three-dimensional twofold interpenetrated porous coordination polymers with NbO topology, while 4 with two-dimensional grid structure is termed as the primary isomer of 1/2/3 due to the difference of dimensionality. Complex 3 possessing different shape-asymmetry of single networks from 1 and 2, is called as the secondary isomer of 1 and 2. Complexes 1 and 2 possess the same topology, single shape-asymmetry networks, but different interpenetration-orientation and interpenetration-asymmetry, and are defined as the tertiary isomers. Distinct differences in H2 and CO2 adsorption capacity were observed among each level of isomers. In addition, the hierarchical classification's relationship with characteristic classifications has been discussed.

Synthesis, structure and adsorption properties of lanthanide-organic frameworks with pyridine-3,5-bis(phenyl-4-carboxylate).

Under solvothermal conditions, reactions of pyridine-3,5-bis(phenyl-4-carboxylic acid) (H2L) with lanthanide metal salts give rise to three new metal-organic frameworks (MOFs) with the formula {[Ln4(L)3(µ3-OH)4(H2O)4]·(NO3)2·solvent}n [Ln = Er (1), Yb (2) and Lu (3)]. The complexes were characterized by single crystal and powder X-ray diffraction, IR and thermogravimetric analyses. They have the same two-fold interpenetrating three-dimensional (3D) framework structures with [Ln4(COO)6(µ3-OH)4(H2O)4] clusters as secondary building units (SBUs) and a rare 6-connected lcy topology with the point (Schläfli) symbol of {3(3)·5(9)·6(3)}. Interestingly, 1-3 show selective and hysteretic sorption of CO2 over N2, and the photoluminescence properties of the complexes were also investigated.

Expression and one-step purification of the antimicrobial peptide cathelicidin-BF using the intein system in Bacillus subtilis.

The intein expression system has been widely applied in Escherichia coli to express various proteins and peptides. However, the removal of endotoxin from the recombinant proteins expressed in E. coli is very difficult and therefore complicates the purification process. In this study, we constructed an intein-based expression vector for an antimicrobial peptide (cathelicidin from Bungarus fasciatus) and expressed the intein fusion peptide in a Bacillus subtilis expression system. The fusion peptide was secreted into the culture medium, identified by Western blot and purified by affinity chromatography and intein self-cleavage in just one step. Approximately, 0.5 mg peptide was obtained from 1 litre of culture medium. The purified peptide showed antimicrobial activity. Our results indicate that the intein expression system may be a safe and efficient method to produce soluble peptides and proteins in B. subtilis.

DMF/H2O volume ratio controls the syntheses and transformations of a series of cobalt complexes constructed using a rigid angular multitopic ligand.

Through middle-temperature solvothermal reactions of CoCl(2).6H(2)O with the rigid-angled ligand 3-(2'-pyridyl)-5-(4''-pyridyl)-1,2,4-triazole (Hdpt24), we obtained the three cobalt complexes {[Co(dpt24)(2))](3).4DMF.1.5H(2)O}(n) (1), {[Co(dpt24)(2))](2).H(2)O}(n) (2), and Co(dpt24)(2)(Hdpt24).H(2)O] (4) at N,N-dimethylformamide (DMF)/H(2)O volume ratios of 9:1, 1:1, and 0:1, respectively. Interestingly, 1 underwent transformations into 2, {[Co(dpt24)(2)].0.5DMF}(n) (3), and 4 when treated with DMF/H(2)O at volume ratios of 1:1, 1:9, and 0:1, respectively. Moreover, 3 and 4 converted back to 1 in 9:1 DMF/H(2)O and to 2 in 1:1 DMF/H(2)O; 3 transformed into 4 in H(2)O and vice versa in 1:9 DMF/H(2)O. Structurally, 1 is a three-dimensional (3D) 2-fold interpenetrating distorted NbO-type complex, 2 possesses a two-dimensional layer metal-organic framework, 3 is a 3D 2-fold interpenetrating typical NbO-type complex, and 4 is a wheel-shaped mononuclear neutral complex. This approach, using a mixed solvent's component ratio to direct the syntheses and conversions of four cobalt complexes, provides unprecedented control for crystal engineering.