Search results for "Dimer"

Hydro-dimerization of Pt2Cl2(C2H4)2: model reaction to capture details on catalytic mechanisms

2005

Abstract The density functional theory was employed to mimic the homogeneous hydro-dimerization of the Zeise-similar dichloro-bis(ethene)-platinum(II), PtCl 2 ( C 2 H 4 ) 2 . Three energy minima and four transition-states were involved in the reaction mechanism, which was even characterized by a catalytic cycle. The minima were fully optimized at B3LYP level whereas the transition-states were first individuated at the same level, by the synchronous transit-guided quasi-Newton method, then fully optimized. The mechanistic hypotheses on the PtCl 2 ( C 2 H 4 ) 2 dimerization implied the displacement of two ethene or two ethane molecules, respectively, occurring in absence or in presence of mol…

Species-specific mechanisms for cholesterol 7alpha-hydroxylase (CYP7A1) regulation by drugs and bile acids.

2005

The gene encoding cholesterol 7alpha-hydroxylase (CYP7A1) is tightly regulated in order to control intrahepatic cholesterol and bile acid levels. Ligands of the xenobiotic-sensing pregnane X receptor inhibit CYP7A1 expression. To retrace the evolution of the molecular mechanisms underlying CYP7A1 inhibition, we used a chicken hepatoma cell system that retains the ability to be induced by phenobarbital and other drugs. Whereas bile acids regulate CYP7A1 via small heterodimer partner and liver receptor homolog-1, mRNA expression of these nuclear receptors is unchanged by xenobiotics. Instead, drugs repress chicken hepatic nuclear factor 4alpha (HNF4alpha) transcript levels concomitant with a …

Cytoplasmic STAT proteins associate prior to activation

2000

The commonly accepted model of STAT factor activation at the cytoplasmic part of the receptor assumes that signal transducers and activators of transcription (STATs) are recruited from a cytoplasmic pool of monomeric STAT proteins. Based on a previous observation that non-phosphorylated STAT3-Src homology 2 domains dimerize in vitro, we investigated whether the observed dimerization is of physiological relevance within the cellular context. We show that STAT1 and STAT3 are pre-associated in non-stimulated cells. Apparently, these complexes are not able to translocate into the nucleus. We provide evidence that the event of STAT activation is more complex than previously assumed.

Cystic Fibrosis Transmembrane Conductance Regulator Interacts with Multiple Immunoglobulin Domains of Filamin A

2010

Mutations of the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) that impair its apical localization and function cause cystic fibrosis. A previous report has shown that filamin A (FLNa), an actin-cross-linking and -scaffolding protein, interacts directly with the cytoplasmic N terminus of CFTR and that this interaction is necessary for stability and confinement of the channel to apical membranes. Here, we report that the CFTR N terminus has sequence similarity to known FLNa-binding partner-binding sites. FLNa has 24 Ig (IgFLNa) repeats, and a CFTR peptide pulled down repeats 9, 12, 17, 19, 21, and 23, which share sequence similarity yet differ from the other FLN…

1,2,4-Triazole Schiff base directed synthesis of polynuclear iron complexes: Investigating the magnetic properties going from a dimer to a 1D chain t…

2018

Abstract Based on two functionalized Schiff base ligands 4-(1H-imidazol-5-ylmethylene-amino)-4H-1,2,4-triazole (imztrz) and 4-(p-tolylidene-amino)-4H-1,2,4-triazole (toltrz), a series of three triazole based polynuclear Fe complexes has been prepared. Compounds {[FeII(toltrz)2(C2O4)]·10H2O}n (1) and {[FeII(5-imztrz)(C2O4)]·2H2O}n (2) are oxalate bridged FeII complexes with 1 showing a linear 1D chain structure and 2 exhibiting a zigzag chain based 3D interpenetrating framework. Both structures show rather big voids in the 3D architecture (∼15% of the crystal volume). Compound (5-imztrzH)2[FeIII2(cit4−)2(H2O)2]·6H2O (3) is a binuclear FeIII complex bridging by two citrate ligands to form a f…

Fe II Complexes with Triple N 1, N 2‐Triazole Bridge Schiff Base Ligand: Antiferromagnetic Dimer vs. Spin Conversion Trimer

2018

A unique example of structural and magnetic diversity in four interconvertible copper(II)-azide complexes with the same schiff base ligand: a monomer…

2010

Four new Cu(II)-azido complexes of formula [CuL(N(3))] (1), [CuL(N(3))](2) (2), [Cu(7)L(2)(N(3))(12)](n) (3), and [Cu(2)L(dmen)(N(3))(3)](n) (4) (dmen = N,N-dimethylethylenediamine) have been synthesized using the same tridentate Schiff base ligand HL (2-[1-(2-dimethylaminoethylimino)ethyl]phenol, the condensation product of dmen and 2-hydroxyacetophenone). The four compounds have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Complex 1 is mononuclear, whereas 2 is a single mu-1,1 azido-bridged dinuclear compound. The polymeric compound 3 possesses a 2D structure in which the Cu(II) ions are linked by phenoxo oxygen atoms and t…

Ferromagnetic exchange coupling in a new bis(μ-chloro)-bridged copper(II) Schiff base complex: Synthesis, structure, magnetic properties and catalyti…

2009

Abstract A new (μ-chloro)-bridged complex [Cu(HL)Cl]2 · H2O (1) with the Schiff base ligand H2L, [2-((E)-(2-hydroxyethylimino)methyl)-4-bromophenol], has been synthesized and characterized by elemental analysis, IR, UV–Vis and EPR spectroscopic studies. X-ray diffraction studies show that 1 is a binuclear CuII complex with a pair of chlorine atoms bridging the copper atoms in a central Cu2Cl2 core. Each copper atom in 1 adopts a distorted square-pyramidal geometry with the imine nitrogen atom, alkoxy and phenoxy oxygen atoms from the Schiff base ligand and a bridging chlorine atom constructing the basal plane, while the apical position of the pyramid is occupied by the other bridging chlori…

A ferromagnetic methoxido-bridged Mn(III) dimer and a spin-canted metamagnetic μ(1,3)-azido-bridged chain.

2012

Two new Mn(III) complexes of formulas [MnL(1)(N(3))(OMe)](2) (1) and [MnL(2)(N(3))(2)](n) (2) have been synthesized by using two tridentate NNO-donor Schiff base ligands HL(1){(2-[(3-methylaminoethylimino)-methyl]-phenol)} and HL(2) {(2-[1-(2-dimethylaminoethylimino)methyl]phenol)}, respectively. Substitution of the H atom on the secondary amine group of the N-methyldiamine fragment of the Schiff base by a methyl group leads to a drastic structural change from a methoxido-bridged dimer (1) to a single μ(1,3)-azido-bridged 1D helical polymer (2). Both complexes were characterized by single-crystal X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The ma…

Synthesis, X-ray crystal structure and magnetic study of a novel μ2-1,1-azido bridged dimeric copper(II) complex

2007

Abstract A new azido derivative of tridentate Schiff base copper(II) complex has been synthesized and characterized. X-ray single crystal structure analysis reveals that the complex [Cu2L2(N3)2(NO3)2] (1), containing 1-(N-pyridylimino)-3-aminopropane (L) as co-ligand, is a dimer in which copper(II) ions are bridged by two azido groups in end-on fashion. The coordination environment around copper(II) is distorted octahedral which is rarely observed among these types of azido bridged copper(II) dimers. Three among the four coordination sites of the basal plane of the octahedron are occupied by the nitrogen atoms of the Schiff base and the fourth site is occupied by a nitrogen atom of a μ2-1,1…