Search results for "Trimer"
showing 10 items of 76 documents
Ab initio determination of the ionization potentials of water clusters (H2O)n (n = 2-6).
2012
High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic ionization potentials of several water clusters: dimer, trimer, tetramer, pentamer, hexamer book, hexamer ring, hexamer cage, and hexamer prism. The present results establish reference values at a level not reported before for these systems, calibrating different computational strategies and helping to discard less reliable theoretical and experimental data. The systematic study with the increasing size of the water cluster allows obtaining some clues on the structure and reductive properties of liquid water.
Synthesis, crystal structures and magnetic properties of picolinate-bridged copper(II) chains
2018
The paper reports the synthesis, crystal structures, and magnetic properties of two copper(II) coordination polymers, Cu2(L1)4 (1) and Cu3(L2)6 (2), based on rigid ethynylene-bridged ditopic ligands containing one picolinate subunit (L1 = 5-(pyridin-3-ylethynyl)picolinate anion; L2 = 5-((4-(methoxycarbonyl)phenyl)ethynyl)picolinate anion). Both 1 and 2 have a chain structure. In 1, the repeating unit in the chain is a doubly bridged picolinate dicopper(II) complex, whereas 2 is built upon trimeric units where the Cu2+ ions are also connected by double picolinate bridges. Both compounds exhibit antiferromagnetic interactions in the solid state. The magnetic properties of 1 and 2 were analyze…
Selective Metal–Ligand Bond-Breaking Driven by Weak Intermolecular Interactions: From Metamagnetic Mn(III)-Monomer to Hexacyanoferrate(II)-Bridged Me…
2020
Metal–ligand coordination interactions are usually much stronger than weak intermolecular interactions. Nevertheless, here, we show experimental evidence and theoretical confirmation of a very rare...
Nonanuclear Spin-Crossover Complex Containing Iron(II) and Iron(III) Based on a 2,6-Bis(pyrazol-1-yl)pyridine Ligand Functionalized with a Carboxylat…
2016
The synthesis and magnetostructural characterization of [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](ClO4)13·(CH3)2CO)6·(solvate) (2) are reported. This compound is obtained as a secondary product during synthesis of the mononuclear complex [Fe(II)(bppCOOH)2](ClO4)2 (1). The single-crystal X-ray diffraction structure of 2 shows that it contains the nonanuclear cluster of the formula [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](13+), which is formed by a central Fe(III)3O core coordinated to six partially deprotonated [Fe(II)(bppCOOH)(bppCOO)](+) complexes. Raman spectroscopy studies on single crystals of 1 and 2 have been performed to elucidate the spin and oxidation states of iron …
Solving the Puzzle of Taxonomic Position of the Petroleum Fly by Resurrection of Diasemocera Bezzi from Psilopa Fallén (Diptera: Ephydridae) with Pro…
2018
Diasemocera Bezzi, 1895 (Type species: Psilopa nigrotaeniata Bezzi, 1895 [= Psilopa roederi Girschner, 1889]) is resurrected from synonymy with Psilopa and the following four new synonyms of Diasemocera are proposed: Domina Hutton (Type species: Domina metallica Hutton), Discocerinella Mercier (Type species: Discocerinella omonvillea Mercier, 1927 [= Notiphila pulicaria Haliday, 1839]), Trimerinoides Cresson (Type species: Trimerina adfinis Cresson) and Helaeomyia Cresson, 1941 (Type species: Psilopa petrolei Coquillett). Diasemocera is placed close to the genus Trimerina and it differs from the highly specialized Psilopa and related genera by the number of pseudotracheae (6–7), vestiture o…
Associating HIV-1 envelope glycoprotein structures with states on the virus observed by smFRET
2019
The HIV-1 envelope glycoprotein (Env) trimer mediates cell entry and is conformationally dynamic1-8. Imaging by single-molecule fluorescence resonance energy transfer (smFRET) has revealed that, on the surface of intact virions, mature pre-fusion Env transitions from a pre-triggered conformation (state 1) through a default intermediate conformation (state 2) to a conformation in which it is bound to three CD4 receptor molecules (state 3)8-10. It is currently unclear how these states relate to known structures. Breakthroughs in the structural characterization of the HIV-1 Env trimer have previously been achieved by generating soluble and proteolytically cleaved trimers of gp140 Env that are …
Exploration of the Activation Mechanism of the Epigenetic Regulator MLL3: A QM/MM Study
2021
The mixed lineage leukemia 3 or MLL3 is the enzyme in charge of the writing of an epigenetic mark through the methylation of lysine 4 from the N-terminal domain of histone 3 and its deregulation has been related to several cancer lines. An interesting feature of this enzyme comes from its regulation mechanism, which involves its binding to an activating dimer before it can be catalytically functional. Once the trimer is formed, the reaction mechanism proceeds through the deprotonation of the lysine followed by the methyl-transfer reaction. Here we present a detailed exploration of the activation mechanism through a QM/MM approach focusing on both steps of the reaction, aiming to provide new…
Mutation spectrum and clinical investigation of achromatopsia patients with mutations in the GNAT2 gene
2019
Achromatopsia (ACHM) is a hereditary cone photoreceptor disorder characterized by the inability to discriminate colors, nystagmus, photophobia, and low-visual acuity. Six genes have been associated with this rare autosomal recessively inherited disease, including the GNAT2 gene encoding the catalytic α-subunit of the G-protein transducin which is expressed in the cone photoreceptor outer segment. Out of a cohort of 1,116 independent families diagnosed with a primary clinical diagnosis of ACHM, we identified 23 patients with ACHM from 19 independent families with likely causative mutations in GNAT2, representing 1.7% of our large ACHM cohort. In total 22 different potentially disease-causing…
Concentration dependence of amplified spontaneous emission in two oligo-(p-phenylenevinylene) derivatives
2005
Amplified spontaneous emission sASEd in optically pumped polystyrene sPSd films doped with two different oligo-sp-phenylenevinylened derivatives sOPVsd, with three s3-OPVd and five s5-OPVd monomer units is reported. It is observed that there is a maximum content of oligomer s25 wt. % for 3-OPV and 20 wt. % for 5-OPVd that can be introduced in the films, due to degradation sin 3-OPVd and ASE quenching sin 5-OPVd. Optimal concentrations swith minimum pump-intensity thresholds for the observation of ASEd of 15 wt. % and 9 wt. % are measured for the trimer and the pentamer, respectively. The concentration dependence of the ASE threshold is discussed in terms of the optical absorption spectra. G…
Electrochemical molecular recognition of silver cation by electropolymerised thieno[3′,4′:5,6][1,4]dithiino[2,3-b]quinoxaline: a joint experimental a…
2000
The novel annelated monomer thieno[3′,4′:5,6][1,4]dithiino[2,3-b]quinoxaline 1 has been electropolymerised on a variety of electrodes, resulting in films which are electroactive in non-aqueous and aqueous solution. The polymer films exhibit a transformation in voltammetric response corresponding to a positive shift in redox potential in the presence of silver cation, the maximum shift being ca. 150 mV in acetonitrile and ca. 400 mV in aqueous LiClO4 solution. Mercury dication demonstrates a similar, but smaller (ca. 130 mV) shift in aqueous solution. Theoretical calculations clearly show the potential of poly(1) as a metal complexation agent. The Ag+ ion coordinates with 1 in two ways: (i) …