Search results for "complex"
showing 10 items of 5889 documents
Spatial and short-term temporal variations in runoff, soil aggregation and other soil properties along a Mediterranean Climatological Gradient.
1998
Abstract Physical and chemical soil properties were measured along a mountainous climatological gradient in the province of Alicante (Spain). The objective was to evaluate how the climate affects certain soil properties at different temporal and spatial scales. These properties include infiltration, runoff and sediment concentrations resulting from rainfall simulation experiments performed in winter and in summer. Chemical soil properties like carbonate content, organic matter content and CEC were analysed in reference soil profiles along the gradient. Physical soil properties like soil moisture content, macroaggregation and waterstable microaggregation were measured at monthly intervals du…
Synthesis and Characterization of the Hybrid Clay-Based Material Montmorillonite-Melanoidin: A Potential Soil Model
2010
The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay-based material (HCM), montmorillonite (STx-1)-melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence…
FORMATION OF A SMALL RIBONUCLEOPROTEIN PARTICLE BETWEEN TAT PROTEIN AND TRANS-ACTING RESPONSE ELEMENT IN HUMAN IMMUNODEFICIENCY VIRUS-INFECTED CELLS
1991
The trans-acting response element (TAR) within the long terminal repeat of human immunodeficiency virus (HIV) is present in all 5' termini of HIV mRNAs and is recognized by the viral Tat protein. Now we describe that the 59-nucleotide-long TAR-RNA exists as a ribonucleoprotein particle in polysomal and heterogeneous nuclear RNP fractions of HIV-1-infected HeLa-T4+ cells. Applying an immunoprecipitation technique this Tat.TAR complex could be isolated from total cell extracts as well as from polysomal or heterogeneous nuclear RNP fractions. The chain length and the identity of the TAR-RNA were established by RNase protection assays while the Tat protein was confirmed by Western blotting tech…
MODIFICATION OF HUMIC SUBSTANCES FOR DEVELOPMENT OF MATERIALS FOR ENVIRONMENTAL TECHNOLOGIES
2019
Humic substances are high molecular weight refractory polycationites formed during decay of living organic matter and through biosynthesis of low molecular weight organic substances (metabolites or decay products of living organisms). Presence of many functional groups in the structure of humic substances determines their ability to interact with metal ions forming stable complexes and influencing metal ion speciation in the environment and mobility, behaviour and speciation forms in the environment. Presently humic substances are a product of industrial scale and quantities in amounts of hundreds of tons are produced. The aim of this study is to analyse derivatization possibilities of humi…
ortho-Metalation of aromatic ethers by yttrium alkyl complexes that contain a linked amido-cyclopentadienyl ligand
2003
Abstract The reaction of the half-sandwich alkyl complex [Y(η5:η1-C5Me4CH2SiMe2NtBu)(CH2SiMe3)(THF)] (1) with anisole smoothly gives the ortho-metalation product [Y(η5:η1-C5Me4CH2SiMe2NtBu)(2-C6H4OMe)(THF)] (2). 3- and 4-Methylanisole as well as phenetole analogously undergo ortho-metalation, whereas thioanisole, N,N′-dimethylaniline, fluorobenzene, and trifluorobenzene do not react with yttrium complex 1. 2-Methylanisole reacts with 1 under activation of the ring methyl group to give the 2-methoxybenzyl complex [Y(η5:η1-C5Me4CH2SiMe2NtBu)(CH2C6H4OMe-2)(THF)] (6). A single-crystal X-ray structure analysis of the 2-anisyl complex 2 revealed a four-legged piano-stool configuration with the me…
Oxamato-based coordination polymers: recent advances in multifunctional magnetic materials
2014
The design and synthesis of novel examples of multifunctional magnetic materials based on the so-called coordination polymers (CPs) have become very attractive for chemists and physicists due to their potential applications in nanoscience and nanotechnology. However, their preparation is still an experimental challenge, which requires a deep knowledge of coordination chemistry and large skills in organic chemistry. The recent advances in this field using a molecular-programmed approach based on rational self-assembly methods which fully exploit the versatility of the coordination chemistry of the barely explored and evergreen family of N-substituted aromatic oligo(oxamato) ligands are prese…
Ligand design for multidimensional magnetic materials: a metallosupramolecular perspective.
2008
The aim and scope of this review is to show the general validity of the ‘complex-as-ligand’ approach for the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. This is illustrated herein on the basis of our recent studies on oxamato complexes with transition metal ions looking for the limits of the research avenue opened by Kahn's pioneering research twenty years ago. The use as building blocks of mono-, di- and trinuclear metal complexes with a novel family of aromatic polyoxamato ligands allowed us to move further in the coordination chemistry-based approach to high-nuclearity coordination compounds and high-dimensionality coordination po…
Cluster dirhenium(III) cis-dicarboxylates with α-amino acids ligands as mighty selective G4s binders.
2021
The synthesis of four dirhenium(III) cis-dicarboxylates with the α-amino acids residues Asp (I), Glu (II), Phe (III) and Tyr (IV) is presented. The G-quadruplex stabilization potential was evaluated by fluorescence resonance energy transfer - melting analysis. All derivatives show specific binding to c-kit1 quadruplex, while II and IV have also strong stabilization activity to HTelo21 quadruplex. At the same time, the compounds do not show any stabilization activity for ds26 DNA, which suggests unique mechanisms of molecular DNA recognition for these complexes.
Improved Preparations of Molybdenum Coordination Compounds from Tetrachlorobis(diethyl ether)molybdenum(IV)
2001
International audience; The reduction of MoCl5 with metallic tin in diethyl ether provides a rapid and convenient entry to [MoCl4(OEt2)2] This compound can be transformed easily and in high yields into a variety of other useful synthons. The loss of ether in the solid state affords a new and reactive form of MoCl4. Treatment with THF, PMe3 or LiOtBu affords [MoCl4(THF)2], [MoCl4(PMe3)3] or [Mo(OtBu)4] in high isolated yields. Treatment with metallic tin in THF affords [MoCl3(THF)3] All of these reactions can be carried out under simple experimental conditions and represent significant improvements relative to previously reported syntheses of the same compounds.
Towards Adoptive Immunotherapy Using High Affinity T Cell Receptors
2003
The hdm2 oncoprotein is frequently overexpressed in a variety of human malignancies, including acute myeloid and lymphoblastic leukemia. Synthetic peptides representative of hdm2 sequences were tested for their binding to A2.1. HLA-A2.1. (/Kb)-Tg mice were immunized with A2.1-binding hdm2 peptides in order to induce A2.1-restricted and hdm2-specific CTL. A2.1-restricted CTL lines obtained from both A2.1 and HuCD8 × A2.1/Kb-Tg mice were able to recognize a synthetic 8-mer peptide representative of a N-terminal hdm2 sequence. These CTL were capable of recognizing and lysing Saos-2 cells transfected with the hdm2 gene as opposed to the parental cell line that lacks any detectable hdm2 expressi…