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Three lanthanide coordination polymers, [Ln4(BDC)6(H2O)2] n (Ln = Er, 1; Ln = Tm, 2; BDC = 1,2-benzenedicarboxylate) and {[Nd2(BDC)(EDTA)(H2O)2] · 1.5H2O} n , 3, were prepared by hydrothermal synthesis and characterized by elemental analysis, IR spectra, as well as single-crystal X-ray diffraction. The isostructural coordination polymers 1 and 2 exhibit four different coordination modes, which are rarely found in one lanthanide complex. Complex 3 displays a 2-D wave-like network assembled by two polycarboxylate ligands.

The molecular structure of the title compound, [Zn(C8H7O2)2(C7H6N2)2]·2C8H8O2, is composed of a mononuclear ZnII complex, which possesses twofold rotation symmetry, and two uncoordinated 4-methylbenzoic acid molecules. The ZnII atom displays a four-coordinate distorted tetrahedral configuration, formed by two carboxylate O atoms of two monodentate 4-methylbenzoate ligands and two N atoms of two benzimidazole molecules. In the crystal structure, complex molecules are linked by the 4-methylbenzoic acid molecules via N—H...O and O—H...O hydrogen bonds, giving rise to the formation of a supramolecular structure.

In the title complex, [Mn(C(8)H(9)N(2)O(4))(2)(H(2)O)(2)]·3.5H(2)O, the Mn(II) cation is six-coordinated by two N,O-bidentate H(2)pimda(-) ligands (H(2)pimda(-) = 5-carb-oxy-2-propyl-1H-imidazole-4-carboxyl-ate) and two water mol-ecules in a distorted octa-hedral environment. The complete solid-state structure can be described as a three-dimensional supra-molecular framework stabilized by a wide range of O-H⋯O and N-H⋯O hydrogen bonds. The propyl groups of H(2)pimda(-) are disordered over two sets of sites with refined occupancies of 0.759 (5):0.241 (5) and 0.545 (7):0.455 (7).

In the title complex, [Ca(C(8)H(9)N(2)O(4))(2)(H(2)O)(2)](n), the Ca(II) atom is eight-coordinated in a distorted square-anti-prismatic environment. The water-coordinated Ca atom is N,O-chelated by the monocarboxyl-ate anion; the carboxyl -CO(2) portion engaged in chelation bears an acid hydrogen. The free -CO(2) portion engages in bonding to adjacent Ca atoms. The Ca(II) centres are connected through the ligand, forming a layer structure; the layers are linked by hydrogen bonds into a three-dimensional network.

In the title dinuclear complex, [Ni2(C8H7O2)4(C12H8N2)2(H2O)], each NiII atom is six-coordinated by three carboxylate O atoms from three 4-methylbenzoate ligands, two N atoms from two 1,10-phenanthroline ligands, and one μ2-bridging aqua ligand. The dimeric complex is located on a crystallographic twofold axis and each Ni atom displays a distorted octahedral coordination geometry. The crystal structure is stabilized via intramolecular hydrogen bonding of the bridging water molecule and the uncoordinated carboxylate O atoms, and by C—H...O and À–À stacking interactions [centroid–centroid distances between neighbouring phenanthroline ring systems and between the benzene ring of a 4-methylbenzoate unit and a phenanthroline ring system are 3.662 (2) and 3.611 (3) Å, respectively].

In the title dinuclear complex, [Ni2(C8H7O2)4(C12H8N2)2(H2O)], each NiII atom is six-coordinated by three carboxylate O atoms from three 4-methylbenzoate ligands, two N atoms from two 1,10-phenanthroline ligands, and one μ2-bridging aqua ligand. The dimeric complex is located on a crystallographic twofold axis and each Ni atom displays a distorted octahedral coordination geometry. The crystal structure is stabilized via intramolecular hydrogen bonding of the bridging water molecule and the uncoordinated carboxylate O atoms, and by C—H...O and π–π stacking interactions [centroid–centroid distances between neighbouring phenanthroline ring systems and between the benzene ring of a 4-methylbenzoate unit and a phenanthroline ring system are 3.662 (2) and 3.611 (3) Å, respectively].

In the title mononuclear complex, [Co(C(8)H(7)O(2))(2)(C(7)H(6)N(2))(2)], the Co(II) atom is coordinated by four carboxylate O atoms from two 4-methyl-benzoate ligands and two N atoms from two benzimidazole ligands in an octa-hedral coordination geometry. The molecules are assembled via inter-molecular N-H⋯O hydrogen-bonding inter-actions into a three-dimensional network.

Oligopeptidase B (OpdB) of Escherichia coli, previously called protease II, has a trypsin-like specificity, cleaving peptides at lysine and arginine residues and belongs to the prolyl oligopeptidase family of new serine peptidases. In this study, we report the fusion expression of E. coli oligopeptidase B with an N-terminal histidine tag using pET28a as the expression vector. Although most of the recombinant OpdB was produced as inclusion bodies, the solubility of the recombinant protease increased significantly when the expression temperature shifted from 37 to 30 degrees C. Recombinant OpdB (approximately 10 mg) could be purified from the soluble fraction of the crude extract of 1L log-phase E. coli culture containing 1.5 g wet bacterial cells. The purified OpdB has a molecular weight of approximately 80 kDa and a specific activity of 4.8 x 10(4) U/mg. OpdB could also be purified from the inclusion bodies with a lower yield. The recombinant enzyme was very stable under 40 degrees C. By comparison of the substrate specificity of the purified OpdB with that of OpdA, another trypsin-like protease in E. coli, we found that Boc-Glu-Lys-Lys-MCA is a specific substrate for E. coli OpdB. We also found that compared to OpdA, OpdB is much more sensitive to GMCHA-OPh(t)Bu, a synthetic trypsin inhibitor that can retard the growth of E. coli.

In the title complex, [Mn(C8H9N2O4)2(H2O)2]·3.5H2O, the MnII cation is six-coordinated by two N,O-bidentate H2pimda− ligands (H2pimda− = 5-carb­oxy-2-propyl-1H-imidazole-4-carboxyl­ate) and two water mol­ecules in a distorted octa­hedral environment. The complete solid-state structure can be described as a three-dimensional supra­molecular framework stabilized by a wide range of O—H⋯O and N—H⋯O hydrogen bonds. The propyl groups of H2pimda− are disordered over two sets of sites with refined occupancies of 0.759 (5):0.241 (5) and 0.545 (7):0.455 (7).

In the title complex, [Cd(C(8)H(9)N(2)O(4))(2)(H(2)O)(2)]·3.5H(2)O, the Cd(II) is coordinated by two water mol-ecules and N,O-chelated by two 5-carb-oxy-2-propyl-1H-imidazole-4-carboxyl-ate anions in a distorted octa-hedral geometry. The two imidazole rings are oriented to each other with a dihedral angle of 75.1 (2)°. Strong O-H⋯O hydrogen bonds between protonated and deprotonated carboxyl-ate groups occur in the mol-ecular structure. In the crystal structure extensive O-H⋯O and N-H⋯O hydrogen bonds help to stabilize the three-dimensional supra-molecular framework. The propyl groups of anions are disordered over two sites with refined occupancies of 0.768 (6):0.232 (6) and 0.642 (8):0.358 (8).

In the title dinuclear complex, [Ni(2)(C(8)H(7)O(2))(4)(C(12)H(8)N(2))(2)(H(2)O)], each Ni(II) atom is six-coordinated by three carboxylate O atoms from three 4-methyl-benzoate ligands, two N atoms from two 1,10-phenanthroline ligands, and one μ(2)-bridging aqua ligand. The dimeric complex is located on a crystallographic twofold axis and each Ni atom displays a distorted octa-hedral coordination geometry. The crystal structure is stabilized via intra-molecular hydrogen bonding of the bridging water mol-ecule and the uncoordinated carboxyl-ate O atoms, and by C-H⋯O and π-π stacking inter-actions [centroid-centroid distances between neighbouring phenanthroline ring systems and between the benzene ring of a 4-methyl-benzoate unit and a phenanthroline ring system are 3.662 (2) and 3.611 (3) Å, respectively].

In the title compound, [Mn(C7H3N2O7)(C12H8N2)2(H2O)](C7H2N2O7), the MnII ion is chelated by two phenanthroline ligands, a water mol­ecule and a carboxyl­ate group in an octa­hedral geometry; the two O atoms involved in bonding are cis to each other. The coordinated water mol­ecule links the cation and the carboxyl­ate anion into a linear chain through hydrogen bonds.

In the title complex, [Ni(C(8)H(9)N(2)O(4))(2)(H(2)O)(2)]·2C(3)H(7)NO, the Ni(II) atom is six-coordinated by two N,O-bidentate 5-carb-oxy-2-propyl-1H-imidazole-4-carboxyl-ate ligands and two water mol-ecules in a distorted octa-hedral environment. The methyl C and H atoms of the two ligands are disordered over two sets of sites in 0.74 (2):0.26 (2) and 0.57 (8):0.43 (8) ratios. A supra-molecular network is stabilized by intra- and inter-molecular N-H⋯O and O-H⋯O hydrogen bonds involving the ligands, coordinated water mol-ecules and dimethyl-formamide solvent mol-ecules.

In the title complex, [Ca(C8H9N2O4)2(H2O)2]n, the CaII atom is eight-coordinated in a distorted square-anti­prismatic environment. The water-coordinated Ca atom is N,O-chelated by the monocarboxyl­ate anion; the carboxyl –CO2 portion engaged in chelation bears an acid hydrogen. The free –CO2 portion engages in bonding to adjacent Ca atoms. The CaII centres are connected through the ligand, forming a layer structure; the layers are linked by hydrogen bonds into a three-dimensional network.

In the title complex, [Mn(C(8)H(9)N(2)O(4))(2)(H(2)O)(2)]·2C(3)H(7)NO, the Mn(II) atom, lying on an inversion centre, is six-coordinated by two N,O-bidentate 5-carb-oxy-2-propyl-1H-imidazole-4-carb-oxyl-ate ligands and two water mol-ecules in a distorted octa-hedral environment. In the crystal structure, the complex mol-ecules and dimethyl-formamide solvent mol-ecules are linked by N-H⋯O and O-H⋯O hydrogen bonds into a two-dimensional supra-molecular network parallel to (001).

In the title coordination polymer, {[Ca(C(8)H(5)Cl(2)O(3))(2)(H(2)O)(2)]·H(2)O}(n), the Ca(II) atom is eight-coordinated by six O atoms from four different (2,4-dichloro-phen-oxy)acetate ligands and two water mol-ecules, and displays a distorted square-anti-prismatic coordination geometry. The compound forms an infinite zigzag chain through connection of the metal centers by (2,4-dichlorphen-oxy)acetate ligands and hydrogen bonding of coordinated and inter-stitial water mol-ecules. These chains are further hydrogen bonded with neighboring chains, forming a supra-molecular network.

In the title mononuclear complex, [Cu(C8H7O2)2(C7H6N2)2], the CuII atom lies on an inversion centre and is coordinated by two O atoms of two monodentate 4-methyl­benzoate ligands and two N atoms of two benzimidazole ligands in a square-planar geometry. The mol­ecules are linked into chains running parallel to the b axis by inter­molecular N—H⋯O hydrogen bonds and by π–π stacking inter­actions [centroid–centroid distance = 3.669 (2) A] involving centrosymmetrically related imidazole rings.

In the title compound, [Ag(C4H4N2)]ClO4, pyrazine ligands bridge two symmetry-related Ag atoms [Ag—N = 2.222 (3) Å] to form linear polycationic chains which run along the c axis of the orthorhombic unit cell. The AgI ion has m2m site symmetry. The N atoms of the pyrazine ligand lie on a crystallographic mirror plane and each C atom of this ligand possesses crystallographically imposed disorder with two components of equal occupancy. The Cl atom of the perchlorate anion has m2m site symmetry and the two unique O atoms of this anion lie on a mirror plane. In addition, in the crystal structure, one-dimensional chains are linked through weak interactions involving perchlorate anions [Ag...O = 2.726 (2) Å] into a motif that can be described as a 4(4).6(2) sheet.