The title hydrated complex, [Cu2(C7H4O3)(C12H8N2)4](C7H5O3)2·7.5H2O, is composed of dinuclear CuII complex cations, noncoordinating 4-hydroxybenzoate anions and water molecules of crystallization. In the dinuclear complex cation, the CuII ions are bridged by a 4-oxidobenzoate ligand and thus each metal ion is five-coordinated by two chelating 1,10-phenanthroline (phen) molecules and one anionic O atom in a distorted trigonal-bipyramid geometry. In the crystal, aromatic π–π stacking occurs between phen rings of neighbouring dinuclear CuII complex cations, forming two-dimensional supramolecular systems parallel to (100).

Fibronectin (FN) purified by gelatin affinity chromatography is unstable and undergoes fragmentation. The cleavage has been ascribed to inherent autolytic protease activities as well as co-purified matrix metalloproteinases (MMP). Understanding the mechanism by which the proteolysis of FN occurs is important, because the FN fragments have biological activities that differ from those of intact FN. Having excluded contributions of other plasma-derived proteases, the present experiments demonstrated that cleavage of FN by MMP-2 to distinct fragments occurred in synergy with inherent FN activities. Limited heat treatment of FN at 56°C for 30 min inactivated the inherent protease activities sharply reducing autolysis of FN in a manner similar to that seen in the presence of serine proteinase inhibitors. Heat treatment did not alter cell attachment to FN, but significantly increased the susceptibility of FN to enzymatic cleavage by MMP-2. The carboxyl-terminal hemopexin-like domain (PEX) of MMP-2 was shown to possess critical exodomain properties required for the interactions of MMP-2 with FN, and FN was cleaved at a significantly reduced rate by an MMP-2 variant with deletion of PEX. Verifying the specificity of interactions, isolated PEX competed FN cleavage by MMP-2 in a concentration-dependent manner. These results have further elucidated the synergistic contributions of inherent autolytic serine protease-like activities and MMP-2 to fragmentation of FN and provide the rationale and basis for modified preparation and handling of FN used in biological research.

In the title centrosymmetric dimeric Cd(II) complex, [Cd(2)(C(7)H(5)O(4))(4)(C(12)H(8)N(2))(2)(H(2)O)(2)], the Cd(II) cation is coord-inated by a bidentate phenanthroline (phen) ligand, three dihy-droxy-benzoate (dhba) anions and one water mol-ecule in a distorted CdN(2)O(4) octa-hedral geometry. Among the dhba anions, two anions bridge two Cd(II) cations to form the dimeric complex with significant different Cd-O bond distances of 2.2215 (19) and 2.406 (2) Å. The centroid-centroid distance of 3.4615 (19) Å between two nearly parallel benzene rings of the dhba and phen ligands coordinating to the same Cd(II) cation indicates the existence of intra-molecular π-π stacking in the complex. Extensive O-H⋯O hydrogen bonding and inter-molecular weak C-H⋯O hydrogen bonding help to stabilize the crystal structure. One hy-droxy group of the monodentate dhba ligand is disordered over two sites with a site-occupancy ratio of 0.9:0.1.

In the title centrosymmetric dimeric CdII complex, [Cd2(C7H5O4)4(C12H8N2)2(H2O)2], the CdII cation is coordinated by a bidentate phenanthroline (phen) ligand, three dihydroxybenzoate (dhba) anions and one water molecule in a distorted CdN2O4 octahedral geometry. Among the dhba anions, two anions bridge two CdII cations to form the dimeric complex with significant different Cd—O bond distances of 2.2215 (19) and 2.406 (2) Å. The centroid–centroid distance of 3.4615 (19) Å between two nearly parallel benzene rings of the dhba and phen ligands coordinating to the same CdII cation indicates the existence of intramolecular π–π stacking in the complex. Extensive O—H...O hydrogen bonding and intermolecular weak C—H...O hydrogen bonding help to stabilize the crystal structure. One hydroxy group of the monodentate dhba ligand is disordered over two sites with a site-occupancy ratio of 0.9:0.1.

Pex14p is a central component of the peroxisomal matrix protein import machinery. In the recently determined crystal structure, a characteristic face consisting of conserved residues was found on a side of the conserved N-terminal domain of the protein. The face is highly hydrophobic, and is also the binding site for the WXXXF/Y motif of Pex5p. We report herein the dimerization of the domain in the isolated state. The homo-dimers are in equilibrium with the monomers. The homo-dimers are completely dissociated into monomers by complex formation with the WXXXF/Y motif peptide of Pex5p. A putative dimer model shows the interaction between the conserved face and the PXXP motif of another protomer. The model allows us to discuss the mechanism of the oligomeric transition of the full-length Pex14p modulated by the binding of other peroxins.

Pex14p is a central component of the peroxisomal protein import machinery, in which the conserved N-terminal domain mediates dynamic interactions with other peroxins including Pex5p, Pex13p, and Pex19p. Here, we report the crystal structure of the conserved N-terminal domain of Pex14p with a three-helix bundle. A hydrophobic surface is composed of the conserved residues, of which two phenylalanine residues (Phe-35 and Phe-52) protrude to the solvent. Consequently, two putative binding pockets suitable for recognizing the helical WXXXF/Y motif of Pex5p are formed on the surface by the two phenylalanine residues accompanying with positively charged residues. The structural feature agrees well with our earlier findings where F35A/L36A and F52A/L53A mutants were impaired in the interactions with other peroxins such as Pex5p and Pex13p. Pex14p variants each with Phe-to-Ala mutation at positions 35, 52, and 35/52, respectively, were defective in restoring the impaired peroxisomal protein import in pex14 Chinese hamster ovary mutant ZP161 cells. Moreover, in GST pull-down assays His6-Pex5pL bound only to GST-Pex14p(25–70), not to any of GST-Pex14p(25–70)F35A, GST-Pex14p(25–70)F52A, and GST-Pex14p(25–70)F35A/F52A. Endogenous Pex5p was recruited to FLAG-Pex14p on peroxisomes in vivo but barely to FLAG-Pex14pF35A, FLAG-Pex14pF52A, and FLAG-Pex14pF35A/F52A. Collectively, Phe-35 and Phe-52 are essential for the Pex14p functions, including the interaction between Pex14p and Pex5p.

Peroxisome is an organelle in eukaryotic cells, which functions in various metabolisms such as β-oxidation of very long fatty acids. Peroxisomal matrix proteins synthesized in cytosol are imported into the peroxisome by a dynamic system consisting of over a dozen peroxins, Pex1p to Pex26p. Pex14p is a central component of the peroxisomal matrix protein import machinery. Until now, any structural information of Pex14p has not been elucidated at all. We describe here the crystal structure of the conserved domain of mammalian Pex14p at 1.8 Å resolution. A hydrophobic surface is composed of the conserved residues, of which two phenylalanine residues (Phe35 and Phe52) protrude to the solvent. Consequently, two putative binding pockets suitable for recognizing the helical WxxxF/Y motif of Pex5p are formed on the surface by the two phenylalanine residues accompanying with positively charged residues. Other structural studies for peroxins are also reviewed in this report.

The title compound, [Co-4(C4H4O5)(4)(C7H6N2)(8)]center dot 20H(2)O, consists of tetranuclear Co-II complexes and disordered uncoordinated water molecules. The tetrameric complex molecule has (4) over bar symmetry. While two benzimidazole molecules and a tridentate malate dianion coordinate a Co-II ion, the carboxylate O atom from an adjacent malate dianion bridges the Co-II ions to complete a distorted octahedral coordination geometry. The tridentate malate dianion chelates the Co-II ion, and the chelate six- and five-membered rings show half-chair and envelope configurations, respectively. A face-to-face separation of 3.494 (9) angstrom between parallel benzimidazole ligands indicates the existence of pi-pi stacking between adjacent complexes. The crystal structure also involves N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds.

The title compound, [Ni2(C7H5O3)4(C7H6N2)4][Ni(C7H5O3)2(C7H6N2)2]·6H2O, is a mononuclear/dinuclear nickel(II) cocrystal, the two molecular species interacting through hydrogen bonds that involve the uncoordinated water molecules. In the mononuclear species, the NiII ion, located on an inversion center, is coordinated by two 1H-benzimidazole (bzim) ligands and two 3-hydroxybenzoate (hba) anions in a square-planar geometry. In the centrosymmetric dinuclear species, the NiII ion is coordinated by two bzim ligands and three hba anions in a square-pyramidal geometry; of the two independent hba anions, one bridges two NiII ions with both carboxylate and hydroxyl groups whereas the other coordinates in a unidentate manner to the NiII ion. The apical Ni—Ohydroxyl bond is 0.39 Å longer than the basal Ni—Ocarboxyl bonds. The face-to-face separation of 3.326 (9) Å indicates the existence of π–π stacking between parallel bzim ligands of adjacent dinuclear entities. Extensive N—H...O and O—H...O hydrogen bonds help to stabilize the crystal structure.

The title compound, [Co4(C4H4O5)4(C7H6N2)8]·20H2O, consists of tetranuclear CoII complexes and disordered uncoordinated water molecules. The tetrameric complex molecule has overline{4} symmetry. While two benzimidazole molecules and a tridentate malate dianion coordinate a CoII ion, the carboxylate O atom from an adjacent malate dianion bridges the CoII ions to complete a distorted octahedral coordination geometry. The tridentate malate dianion chelates the CoII ion, and the chelate six- and five-membered rings show half-chair and envelope configurations, respectively. A face-to-face separation of 3.494 (9) Å between parallel benzimidazole ligands indicates the existence of π–π stacking between adjacent complexes. The crystal structure also involves N—H...O and O—H...O hydrogen bonds.

The crystal structure of the title compound, [Co(C(7)H(5)O(3))(C(12)H(8)N(2))(2)(H(2)O)](C(7)H(5)O(3))·5H(2)O, consists of Co(II) complex cations, uncoordinated hydroxy-benzoate anions and uncoord-inated water mol-ecules. The Co(II) ion is coordinated by two phenanthroline ligands, a water mol-ecule and a 3-hydroxy-benzoate anion, and displays a distorted octa-hedral geometry. π-π stacking is observed between parallel phenanthroline ligands, the face-to-face separations being 3.454 (19) and 3.435 (7) Å. An extensive hydrogen-bonding network helps to stabilize the crystal structure. The hydroxybenzoate ligand is disordered over two positions, with site occupancy factors 0.6 and 0.4. One solvent water molecule is also disordered over two positions, with site occupancy factors 0.6 and 0.4.

The crystal structure of the title compound, [Co(C7H5O3)(C12H8N2)2(H2O)](C7H5O3)·5H2O, consists of CoII complex cations, uncoordinated hydroxybenzoate anions and uncoordinated water molecules. The CoII ion is coordinated by two phenanthroline ligands, a water molecule and a 3-hydroxybenzoate anion, and displays a distorted octahedral geometry. π–π stacking is observed between parallel phenanthroline ligands, the face-to-face separations being 3.454 (19) and 3.435 (7) Å. An extensive hydrogen-bonding network helps to stabilize the crystal structure. The hydroxybenzoate ligand is disordered over two positions, with site occupancy factors 0.6 and 0.4. One solvent water molecule is also disordered over two positions, with site occupancy factors 0.6 and 0.4.

The title compound, [Ni(2)(C(7)H(5)O(3))(4)(C(7)H(6)N(2))(4)][Ni(C(7)H(5)O(3))(2)(C(7)H(6)N(2))(2)]·6H(2)O, is a mononuclear/dinuclear nickel(II) cocrystal, the two mol-ecular species inter-acting through hydrogen bonds that involve the uncoordinated water mol-ecules. In the mononuclear species, the Ni(II) ion, located on an inversion center, is coordinated by two 1H-benzimidazole (bzim) ligands and two 3-hydroxy-benzoate (hba) anions in a square-planar geometry. In the centrosymmetric dinuclear species, the Ni(II) ion is coordinated by two bzim ligands and three hba anions in a square-pyramidal geometry; of the two independent hba anions, one bridges two Ni(II) ions with both carboxylate and hydroxyl groups whereas the other coordin-ates in a unidentate manner to the Ni(II) ion. The apical Ni-O(hydrox-yl) bond is 0.39 Å longer than the basal Ni-O(carbox-yl) bonds. The face-to-face separation of 3.326 (9) Å indicates the existence of π-π stacking between parallel bzim ligands of adjacent dinuclear entities. Extensive N-H⋯O and O-H⋯O hydrogen bonds help to stabilize the crystal structure.

The title compound, [Co(4)(C(4)H(4)O(5))(4)(C(7)H(6)N(2))(8)]·20H(2)O, consists of tetra-nuclear Co(II) complexes and disordered uncoordinated water mol-ecules. The tetra-meric complex mol-ecule has symmetry. While two benzimidazole mol-ecules and a tridentate malate dianion coordinate a Co(II) ion, the carboxylate O atom from an adjacent malate dianion bridges the Co(II) ions to complete a distorted octa-hedral coordination geometry. The tridentate malate dianion chelates the Co(II) ion, and the chelate six- and five-membered rings show half-chair and envelope configurations, respectively. A face-to-face separation of 3.494 (9) Å between parallel benzimidazole ligands indicates the existence of π-π stacking between adjacent complexes. The crystal structure also involves N-H⋯O and O-H⋯O hydrogen bonds.

In the title compound, [Sr(C 7 H 5 O 3 ) 2 (C 12 H 8 N 2 ) 2 (H 2 O) 2 ], the Sr II ion is located on a twofold rotation axis and assumes a distorted square-antiprism SrN 4 O 4 coordination geometry, formed by two phenanthroline (phen) ligands, two 2-hydroxybenzoate anions and two water molecules. Within the mononuclear complex molecule, intramolecular π–π stacking is observed between nearly parallel coordinated phen ligands, while normal intermolecular π–π stacking occurs between parallel phen ligands of adjacent complex molecules. Classic O—H...O and weak C—H...O hydrogen bonding helps to stabilize the crystal structure.

In the title compound, [Sr(C7H5O3)2(C12H8N2)2(H2O)2], the Sr(II) ion is located on a twofold rotation axis and assumes a distorted square-antiprism SrN4O4 coordination geometry, formed by two phenanthroline (phen) ligands, two 2-hydroxybenzoate anions and two water molecules. Within the mononuclear complex molecule, intramolecular pi-pi stacking is observed between nearly parallel coordinated phen ligands, while normal intermolecular pi-pi stacking occurs between parallel phen ligands of adjacent complex molecules. Classic O-H...O and weak C-H...O hydrogen bonding helps to stabilize the crystal structure.

In the crystal structure of the title compound, [Cd(C 7 H 5 O 3 ) 2 (C 12 H 8 N 2 ) 2 ]·H 2 O, the Cd II ion is coordinated by two 1,10-phenanthroline (phen) ligands and two 2-hydroxy­benzoate anions, resulting in a distorted CdN 4 O 2 octa­hedral coordination geometry. A partially overlapped arrangement and short face-to-face separation of 3.47 (2) Å indicate the existence of π–π stacking between parallel phen ligands.