Synthesis, spectroscopy, thermal and X-structure studies of a seven coordinated hydrated Ca(II)-<i>para</i>-nitrobenzoate complex showing mono and bidentate carboxylate ligation^ψ

2392-2399The reaction of CaCo3 with 4-nitrobenzoic acid (4-nhaH) results in the formation of a seven coordinated Ca (II) complex [Ca(H2O)4(4-nba)2] 1, (4-nba being 4-nitrobenzoate). The compound has been characterized by elemental analysis, IR and UV-Vis spectra and its structure determined. The complex can be dehydrated to the corresponding anhydrous Ca(II)bis-4-nitrobenzoate Ca(4-nba)2 2, and the anhydrous complex thus formed can he rehydrated as evidenced by IR spectra. The structure of 1 exhibits both monodentate and bidentate carboxylate ligation of the 4-nitrobenzoate ligand. The coordination by the O atom from four water molecules completes the heptacoordination around Ca(II). The free O atoms of the monodentate 4-nba and one of the coordinated O atom of the bidentate 4-nba in 1 are linked via H-bonding to one of the coordinated waters of a neighbouring Ca(II) resulting in the formation of psuedo dimers. The dimers thus formed are further linked with the aid of II bonds, along a as well as b resulting in the formation of an intricate supramolecular network

On the distorted {NiN₆} octahedron in hexakis(imidazole)nickel(II) bis(4-nitrobenzoate) dihydrate

181-188The reaction of [Ni(H₂O)₆]Cl₂ with the sodium salt of 4-nitrobenzoic acid (4-nbaH) in the presence of imidazole results in the formation of the title compound hexakis(imidazole)nickel(II) bis(4-nitrobenzoate) dihydrate (1). Compound (1) is dehydrated to hexakis(imidazole)nickel(II) bis(4-nitrobenzoate) (2) by heating at 100oC. Both compounds are characterized by elemental analysis, infrared spectra, X-ray powder pattern and thermal studies. The title compound [Ni(Im)₆](4-nba)₂.2H₂O (1) crystallizes in the centrosymmetric triclinic space group P₁⁻ with the Ni(II) situated on an inversion center. The structure of (1) consists of a distorted octahedral hexakis(imidazole)nickel(II) cation, a free uncoordinated 4-nba anion and a lattice water with half of the molecule accounting for the asymmetric unit. In the complex cation the central metal is bonded to six neutral terminal Im ligands. The distortion of the {NiN6}octahedron in (1) is discussed in terms of the difference between the longest and shortest Ni-N bonds. A comparative study of several [Ni(Im)6]2+ compounds in different structural environments is described. In the crystal structure, the cation, anion and lattice water are linked by three types of H-bonding interactions comprising two O-H•••O, three N-H•••O and three C-H•••O interactions. Each hexacoordinated Ni(II) complex cation is linked to eight symmetry related 4-nba anions and four different lattice water molecules via N-H•••O and C-H•••O interactions, while each 4-nba anion is H-bonded to four complex cations and two symmetry related lattice water molecules. Pairs of [Ni(Im)₆]²⁺ cations and 4-nba anions are linked to lattice water molecules via O-H•••O and C-H•••O interactions. As a result of the hydrogen bonding interactions, the cations and anions are organized into alternating layers

Loss of keratin 8 phosphorylation leads to increased tumor progression and correlates with clinico-pathological parameters of OSCC patients.

BACKGROUND: Keratins are cytoplasmic intermediate filament proteins expressed in tissue specific and differentiation dependent manner. Keratins 8 and 18 (K8 and K18) are predominantly expressed in simple epithelial tissues and perform both mechanical and regulatory functions. Aberrant expression of K8 and K18 is associated with neoplastic progression, invasion and poor prognosis in human oral squamous cell carcinomas (OSCCs). K8 and K18 undergo several post-translational modifications including phosphorylation, which are known to regulate their functions in various cellular processes. Although, K8 and K18 phosphorylation is known to regulate cell cycle, cell growth and apoptosis, its significance in cell migration and/or neoplastic progression is largely unknown. In the present study we have investigated the role of K8 phosphorylation in cell migration and/or neoplastic progression in OSCC. METHODOLOGY AND PRINCIPAL FINDINGS: To understand the role of K8 phosphorylation in neoplastic progression of OSCC, shRNA-resistant K8 phospho-mutants of Ser73 and Ser431 were overexpressed in K8-knockdown human AW13516 cells (derived from SCC of tongue; generated previously). Wound healing assays and tumor growth in NOD-SCID mice were performed to analyze the cell motility and tumorigenicity respectively in overexpressed clones. The overexpressed K8 phospho-mutants clones showed significant increase in cell migration and tumorigenicity as compared with K8 wild type clones. Furthermore, loss of K8 Ser73 and Ser431 phosphorylation was also observed in human OSCC tissues analyzed by immunohistochemistry, where their dephosphorylation significantly correlated with size, lymph node metastasis and stage of the tumor. CONCLUSION AND SIGNIFICANCE: Our results provide first evidence of a potential role of K8 phosphorylation in cell migration and/or tumorigenicity in OSCC. Moreover, correlation studies of K8 dephosphorylation with clinico-pathological parameters of OSCC patients also suggest its possible use in prognostication of human OSCC