Home About us Contact
|
Home About us Contact | ||
|
|
||
Metal Chelators (metal + chelator)
Selected AbstractsSpectral Properties of Pro-multimodal Imaging Agents Derived from a NIR Dye and a Metal ChelatorPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2005Zongren Zhang ABSTRACT Monomolecular multimodal imaging agents (MOMIAs) are able to provide complementary diagnostic information of a target diseased tissue. We developed a convenient solid-phase approach to construct two pro-MOMIAs (before incorporating radiometal) derived from 1,4,7,10-tetraazacy-clododecane-1,4,7,10-tetraacetic acid (DOTA) and cypate, a near-infrared (NIR) fluorescent dye analogous to indocyanine green (ICG). The possible interaction between d orbitals of transition metal DOTA complexes or free metals and the p orbitals of cypate chromophore could quench the fluorescence of pro-MOMIAs. However, we did not observe significant changes in the spectral properties of cypate upon conjugation with DOTA and subsequent chelation with metals. The fluorescence intensity of the chelated and nonmetal-chelated PRO-MOMIAs remained fairly the same in dilute 20% aqueous dimethylsulfoxide (DMSO) solution (1 × 10,6M). Significant reduction in the fluorescence intensity of pro-MOMIAs occurred in the presence of a large excess of metal ions (> 1 molar ratio for indium and 20-fold for a copper relative to pro-MOMIA). This study suggests the feasibility of using MOMIAs for combined optical and radioisotope imaging. [source] Efficient stabilization of bulk fish oil rich in long-chain polyunsaturated fatty acidsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 4 2008Stephan Drusch Abstract The aim of the present study was to systematically investigate the possibilities of stabilizing a bulk oil rich in long-chain polyunsaturated fatty acids under ambient conditions. Combinations of different antioxidants (,-, ,- and/or ,-tocopherol, rosmarinic acid and rosemary extract rich in carnosic acid) as well as lecithin and citric acid were systematically investigated. Efficient stabilization was achieved by choosing a combination of tocopherols rich in ,- or ,-tocopherol and low in ,-tocopherol, by including tocopherol-sparing synergists like ascorbyl palmitate and carnosic acid from rosemary extract and metal-chelating agents. For carnosic acid, a concentration of 400,mg/kg oil provides sufficient protection; the concentration of the metal chelator should be adapted to the concentration of metal ions present in the oil. As an alternative ingredient with metal-chelating and tocopherol-sparing activity, lecithin may be included in the formulation, but its poor solubility in bulk oils limits its use. [source] Desorption of zinc by extracellularly produced metabolites of Trichoderma harzianum, Trichoderma reesei and Coriolus versicolorJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007P. Adams Abstract Aims:, To determine the role of fungal metabolites in the desorption of metals. Methods and Results:, Desorption of Zn from charcoal by three different fungi was compared against metal desorption with reverse osmosis water, a 0·1% Tween 80 solution and a 0·1 mol l,1 CaCl2 solution. All three fungal filtrates desorbed three times more Zn than either 0·1% Tween 80 or 0·1 mol l,1 CaCl2. Metal chelator production in Trichoderma harzianum and Coriolus versicolor was constitutively expressed while chelator production in Trichoderma reesei was induced by Zn. The presence of Zn inhibited the production of metal chelators by C. versicolor. Only C. versicolor was found to produce oxalic acid (a strong metal chelator). All fungi caused a marked decrease in pH, although this was not enough to explain the increased desorption of the metals by the different fungal filtrates. Conclusions:, Metal chelation via organic acids and proteins are the main mechanisms by which the fungal filtrates increase zinc desorption. Significance and Impact of the Study:, The results of this study explain why plants inoculated with T. harzianum T22 take up more metal from soil, than noninoculated plants while metabolites produced by fungi could be used for metal leaching from contaminated soils. [source] Self-assembly and recrystallization of bacterial S-layer proteins at silicon supports imaged in real time by atomic force microscopyJOURNAL OF MICROSCOPY, Issue 3 2003E. S. Györvary Summary The self-assembly of bacterial surface-layer (S-layer) proteins (SbpA of Bacillus sphaericus CCM 2177) at silicon supports (hydrophobic, non-plasma-treated and hydrophilic, O2 plasma-treated silicon supports) was imaged in real time by atomic force microscopy (AFM). A closed mosaic layer consisting of small crystals (less than 200 nm in diameter) was formed at a hydrophobic silicon support, whereas a coherent crystalline lattice consisting of large domains (2,10 µm in size) was generated at O2 plasma-treated, hydrophilic silicon wafers. The structure of the formed layers was a monolayer (9 nm in height) at the hydrophobic silicon and a bilayer (15 nm in height) at the hydrophilic silicon. In situ AFM measurements confirmed the importance of ionic bonds in the formation of crystalline SbpA layers at silicon supports. Rupture of the protein subunits with a metal chelator from the crystalline lattice of SbpA was visualized in situ by AFM. The stability of solid-supported SbpA layers could be enhanced by cross-linking the S-layers with amino,amino or amino,carboxyl group directed cross-linkers. [source] The induction of HIF-1 reduces astrocyte activation by amyloid beta peptideEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2009David Schubert Abstract Reduced glucose metabolism and astrocyte activation in selective areas of the brain are pathological features of Alzheimer's disease (AD). The underlying mechanisms of low energy metabolism and a molecular basis for preventing astrocyte activation are not, however, known. Here we show that amyloid beta peptide (A,)-dependent astrocyte activation leads to a long-term decrease in hypoxia-inducible factor (HIF)-1, expression and a reduction in the rate of glycolysis. Glial activation and the glycolytic changes are reversed by the maintenance of HIF-1, levels with conditions that prevent the proteolysis of HIF-1,. A, increases the long-term production of reactive oxygen species (ROS) through the activation of nicotinamide adenine dinucleotide phosphate oxidase and reduces the amount of HIF-1, via the activation of the proteasome. ROS are not required for glial activation, but are required for the reduction in glycolysis. These data suggest a significant role for HIF-1,-mediated transcription in maintaining the metabolic integrity of the AD brain and identify the probable cause of the observed lower energy metabolism in afflicted areas. They may also explain the therapeutic success of metal chelators in animal models of AD. [source] Synthesis of Isoxazolopyridobicyclooxacalix[4]arenes: A New Family of Heteracalixarene SystemsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 32 2008Serena Ferrini Abstract A new family of isoxazolopyridobicyclooxacalix[4]arenes was obtained by reaction of dichloroisoxazolopyridines with phloroglucinol. X-ray crystallography and density functional calculations were used for their structural determination and evaluation of their chemical properties. Their role as metal chelators was studied by mass spectrometry. This new family of heteracalixarenes is of potential interest for host,guest interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Desorption of zinc by extracellularly produced metabolites of Trichoderma harzianum, Trichoderma reesei and Coriolus versicolorJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007P. Adams Abstract Aims:, To determine the role of fungal metabolites in the desorption of metals. Methods and Results:, Desorption of Zn from charcoal by three different fungi was compared against metal desorption with reverse osmosis water, a 0·1% Tween 80 solution and a 0·1 mol l,1 CaCl2 solution. All three fungal filtrates desorbed three times more Zn than either 0·1% Tween 80 or 0·1 mol l,1 CaCl2. Metal chelator production in Trichoderma harzianum and Coriolus versicolor was constitutively expressed while chelator production in Trichoderma reesei was induced by Zn. The presence of Zn inhibited the production of metal chelators by C. versicolor. Only C. versicolor was found to produce oxalic acid (a strong metal chelator). All fungi caused a marked decrease in pH, although this was not enough to explain the increased desorption of the metals by the different fungal filtrates. Conclusions:, Metal chelation via organic acids and proteins are the main mechanisms by which the fungal filtrates increase zinc desorption. Significance and Impact of the Study:, The results of this study explain why plants inoculated with T. harzianum T22 take up more metal from soil, than noninoculated plants while metabolites produced by fungi could be used for metal leaching from contaminated soils. [source] ,Sulfo-click' for ligation as well as for site-specific conjugation with peptides, fluorophores, and metal chelatorsJOURNAL OF PEPTIDE SCIENCE, Issue 1 2010Dirk T. S. Rijkers Abstract The ,sulfo-click' reaction, which is a chemoselective amidation reaction involving the reaction of an aminoethane sulfonyl azide with a thio acid, encompasses a new approach for ligation and conjugation. Detailed protocols are provided for decorating biologically active peptides or dendrimers with biophysical tags, fluorescent probes, metal chelators, and small peptides by using this reaction as a novel, metal-free ,sulfo-click' approach. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source] Characterization of an exosite binding inhibitor of matrix metalloproteinase 13PROTEIN SCIENCE, Issue 1 2008Lata T. Gooljarsingh Abstract Matrix metalloproteinase 13 (MMP13) is a key enzyme implicated in the degradation of the extracellular matrix in osteoarthritis. Clinical administration of broad spectrum MMP inhibitors such as marimastat has been implicated in severe musculo-skeletal side effects. Consequently, research has been focused on designing inhibitors that selectively inhibit MMP13, thereby circumventing musculo-skeletal toxicities. A series of pyrimidine dicarboxamides were recently shown to be highly selective inhibitors of MMP13 with a novel binding mode. We have applied a molecular ruler to this exosite by dual inhibition studies involving a potent dicarboxamide in the presence of two metal chelators of different sizes. A larger hydroxamate mimic overlaps and antagonizes binding of the dicarboxamide to the exosite whereas the much smaller acetohydroxamate synergizes with the dicarboxamide. These studies elucidate the steric requirement for compounds that fit exclusively into the active site, a mandate for generating highly selective MMP13 inhibitors. [source] | |||||||||||||