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Variety Of Ligands (variety + of_ligand)
Selected AbstractsTowards Cationic Gallium Derivatives: Metallacycles from the Reactions of Organogallium Compounds with Tetraorganodichalcogenoimidodiphosphinates and a New N -(Diphenylthiophosphinyl)thioureato LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2004Virginia Montiel-Palma Abstract The organometallic complexes of general formulae [Me2Ga{,2 - E,E, -[R2P(E)NP(E,)R,2]}] [R = R, = Ph, E = E, = O (1); R = R, = Ph, E = E, = S (2); R = R, = Ph, E = E, = Se (3); R = R, = Ph, E = O, E, = S (4); R = Me, R, = Ph, E = S, E, = O (5)] and [Me2Ga{,2 - S,S, -[Ph2P(S)NC(S)(C9H10N)]}] (6) were obtained by facile methane elimination reactions from GaMe3 and the acidic ligands L1H [(XPPh2)2NH (X = O, S, Se), (OPPh2)(SPPh2)NH, and (OPMe2)(SPPh2)NH] and L2H [Ph2P(S)NHC(S)(C9H10N)] in toluene. Replacement of one phosphorus atom by a carbon atom in the ligand skeleton of L1H gave the new ligand L2H, which, upon reaction with GaMe3, gave compound 6, which shows no significant structural differences with respect to 1,5. Therefore, L2H does not induce partial planarity in the six-membered ring, indicating the necessity for replacing both phosphorus atoms of the ligand by carbon atoms, as in the ,-diketonate-type derivatives, in order to impose ring planarity. Thus, despite originating from a variety of ligands with differing donor atoms and substituents at the phosphorus atoms, all complexes show little structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Inactivation of Pten in Osteo-Chondroprogenitor Cells Leads to Epiphyseal Growth Plate Abnormalities and Skeletal Overgrowth,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2007Alice Fiona Ford-Hutchinson Abstract To study the role of the Pten tumor suppressor in skeletogenesis, we generated mice lacking this key phosphatidylinositol 3,-kinase pathway regulator in their osteo-chondroprogenitors. A phenotype of growth plate dysfunction and skeletal overgrowth was observed. Introduction: Skeletogenesis is a complex process relying on a variety of ligands that activate a range of intracellular signal transduction pathways. Although many of these stimuli are known to activate phosphatidylinositol 3,-kinase (PI3K), the function of this pathway during cartilage development remains nebulous. To study the role of PI3K during skeletogenesis, we used mice deficient in a negative regulator of PI3K signaling, the tumor suppressor, Pten. Materials and Methods:Pten gene deletion in osteo-chondrodroprogenitors was obtained by interbreeding mice with loxP-flanked Pten exons with mice expressing the Cre recombinase under the control of the type II collagen gene promoter (Ptenflox/flox:Col2a1Cre mice). Phenotypic analyses included microcomputed tomography and immunohistochemistry techniques. Results: ,CT revealed that Ptenflox/flox:Col2a1Cre mice exhibited both increased skeletal size, particularly of vertebrae, and massive trabeculation accompanied by increased cortical thickness. Primary spongiosa development and perichondrial bone collar formation were prominent in Ptenflox/flox:Col2a1Cre mice, and long bone growth plates were disorganized and showed both matrix overproduction and evidence of accelerated hypertrophic differentiation (indicated by an altered pattern of type X collagen and alkaline phosphatase expression). Consistent with increased PI3K signaling, Pten-deficient chondrocytes showed increased phospho-PKB/Akt and phospho-S6 immunostaining, reflective of increased mTOR and PDK1 activity. Interestingly, no significant change in growth plate proliferation was seen in Pten-deficient mice, and growth plate fusion was found at 6 months. Conclusions: By virtue of its ability to modulate a key signal transduction pathway responsible for integrating multiple stimuli, Pten represents an important regulator of both skeletal size and bone architecture. [source] Regulated expression of syndecan-4 in rat calvaria osteoblasts induced by fibroblast growth factor-2JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2007Shu Jun Song Abstract Fibroblast growth factor-2 (FGF2) is a member of a prominent growth factor family that drives proliferation in a wide variety of cell types, including osteoblasts. The binding and signal transduction triggered by these mitogens is dependent on glycosaminoglycan (GAG) sugars, particularly of the heparan sulfate (HS) class. These are secreted in proteoglycan (PG) complexes, some of which become FGF co-receptors. The syndecans, the transmembrane forms of HSPG of which there are four members, act as multifunctional receptors for a variety of ligands involved in cell-extracellular matrix (ECM) adhesion as well as growth factor binding. To understand the role of syndecans in developing osteoblasts, the effects of exogenous FGF2 on syndecan expression were examined using primary rat calvarial osteoblasts. All four syndecan mRNAs were expressed in the osteoblasts, although only syndecan-4 was upregulated by FGF2 treatment in a dose-dependent manner. This upregulation could be abrogated by pretreatment with the protein synthesis inhibitor cycloheximide, suggesting that the upregulation of syndecan-4 by FGF2 is not a primary response. Osteoblast proliferation and mineralization were enhanced by exogenous FGF2 treatment, but could be specifically diminished by anti-syndecan-4 antibody pretreatment. This treatment also blocked FGF2-induced extracellular signal-regulated kinase activation, but not the expression of the bone-specific transcription factor Runx2. These results demonstrate that mitogen-triggered syndecan-4 expression is an intrinsic part of the pathways subtending osteoblast proliferation and mineralization. J. Cell. Biochem. 100: 402,411, 2007. © 2006 Wiley-Liss, Inc. [source] Binding of Warfarin Influences the Acid-Base Equilibrium of H242 in Sudlow Site I of Human Serum AlbuminPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2006Jennifer L. Perry ABSTRACT Sudlow Site I of human serum albumin (HSA) is located in subdomain IIA of the protein and serves as a binding cavity for a variety of ligands. In this study, the binding of warfarin (W) is examined using computational techniques and isothermal titration calorimetry (ITC). The structure of the docked warfarin anion (W,) to Site I is similar to that revealed by X-ray crystallography, with a calculated binding constant of 5.8 × 105M,1. ITC experiments (pH 7.13 and I = 0.1) carried out in three different buffers (MOPs, phosphate and Tris) reveal binding of W, is accompanied by uptake of 0.30 ± 0.02 protons from the solvent. This measurement suggests that the binding of W, is stabilized by an ion-pair interaction between protonated H242 and the phenoxide group of W,. [source] A Robust Protein Host for Anchoring Chelating Ligands and OrganocatalystsCHEMBIOCHEM, Issue 4 2008Manfred T. Reetz Prof. Dr. Abstract In order to put the previously proposed concept of directed evolution of hybrid catalysts (proteins that harbor synthetic transition-metal catalysts or organocatalysts) into practice, several prerequisites must be met. The availability of a robust host protein that can be expressed in sufficiently large amounts, and that can be purified in a simple manner is crucial. The thermostable enzyme tHisF from Thermotoga maritima, which constitutes the synthase subunit of a bi-enzyme complex that is instrumental in the biosynthesis of histidine, fulfills these requirements. In the present study, fermentation has been miniaturized and parallelized, as has purification of the protein by simple heat treatment. Several mutants with strategically placed cysteines for subsequent bioconjugation have been produced. One of the tHisF mutants, Cys9Ala/Asp11Cys, was subjected to bioconjugation by the introduction of a variety of ligands for potential metal ligation, of a ligand/metal moiety, and of several organocatalytic entities that comprise a flavin or thiazolium salts. Characterization by mass spectrometry and tryptic digestion was achieved. As a result of this study, a platform for performing future directed evolution of these hybrid catalysts is now available. [source] | |||||||||||||