1,286 research outputs found
Coordination chemistry of 2-pyrimidinolate: Synthesis and characterization of a neutral tetrameric rhodium(I) derivative
No full textA novel metal-organic complex of analytical Rh(COD)(2-pymo) formulation (COD = 1,5-cyclooctadiene, 2-Hpymo = 2-hydroxypyrimidine) has been prepared by reacting [Rh(COD)Cl]2 with 2-Hpymo. While direct syntheses in a variety of solvents (acetone, toluene or methanol) typically afforded amorphous powders, recrystallization from methanol allowed to perform a single crystal data collection on the CH3OH solvate. The crystal structure of the latter [tetragonal, P-42c, a = 13.9780(2), c = 14.4980(10) Å, V = 2832.7(6) Å^3] contains cyclic [Rh(COD)(2-pymo)]4 tetramers, in which distorted square planar metal atoms are bridged by n1-μ2-N,N′-exo-bidentate 2-pymo ligands in 1,3-alternate disposition. Upon dissolving both the amorphous and the crystalline (solvated) species in CD2Cl2, variable temperature NMR spectra confirmed the presence of identical (tetrameric) species, thus excluding the existence of other oligomers of different nuclearity in the amorphous powders
Elucidating the CO2 adsorption mechanisms in the triangular channels of the bis(pyrazolate) MOF Fe2(BPEB)3 by in situ synchrotron X-ray diffraction and molecular dynamics simulations
No full textThe structural origin of the remarkable performance of the metal–organic framework Fe2(BPEB)3 as a CO2 adsorbent (40.5% of the host weight at 298 K and 10 bar) was investigated by combining advanced experimental and computational tools.</p
Deconstructing destruction: A rapid route to proteasomal fate
No full textIn this issue of Molecular Cell, Kiss et al.1 introduce UbiREAD, a technology that deciphers ubiquitin chain-mediated degradation in living cells, revealing a hierarchy where K48 chains of at least three ubiquitins drive rapid proteasomal degradation and branched K48/K63 chains follow substrate-anchored rules
Ab-initio XRPD structural characterization of coordination polymers: The case of [Ag(C3H3N2CS2)]
No full textThe crystal structure of the one-dimensional polymer [Ag(C3H3N2CS2)] has been determined from conventional X-ray powder diffraction methods, through simulated annealing and Rietveld refinement techniques [Ag(C3H3N2CS2)] is monoclinic, P21/c; a = 8.409(1), b = 11.740(1), c = 6.721(1) Å, β = 101.86(2)°, V = 649.3(2) Å^3; Z = 4; ρ = 2.566 g cm^-3. Final Rwp, Rp and RF agreement factors, for 3100 data points collected in the 8-70° 2θ range, are 0.091, 0.071 and 0.058, respectively. Anisotropic peak shapes and high-angle tails for the 0k0 (and neighboring) reflections suggest that the polymeric chains, aligned along b, suffer from a partial disorder, in that packing of adjacent molecules does not conform to a rigorous crystalline, truly periodic, tiling
Synthesis and characterisation of new polynuclear copper(I) pyrazolate complexes and their catalytic activity in the cyclopropanation of olefins
No full textThe reaction of [Cu(CH3CN)4](BF4) with racemic pyrazole-3,5-dicarboxylic acid di-sec-butyl ester (3,5-dicarbo-sec-butoxypyrazole, Hdcsbpz) or with pyrazole-3,5-di-ter-butyl (3,5-di-ter-butylpyrazole, Hdtbpz) quantitatively yields the new [Cu(dcsbpz)]4 and [Cu(dtbpz)]4 complexes, respectively. Crystals of [Cu(dcsbpz)]4 are triclinic, P1̄, a = 10.9748(7), b = 11.8399(8), c = 26.5575(17) Å, α =100.605(2), β = 90.783(2), γ = 105.362(2)°; [Cu(dtbpz)]4·CH2Cl2 is monoclinic, P21/n, a = 10.902(3), b = 19.200(3), c = 25.772(4) Å, β = 93.86(2)°. Both species contain cyclic tetrameric molecules, with the heterocyclic ligands binding in the common N,N′-exo-bidentate mode; however, the shape and geometry of the inner Cu4 moiety is remarkably different, as highlighted, for example, by the absolute values of the 1,2 and 1,3 (non-bonding) Cu⋯Cu interactions. These polynuclear copper(I) pyrazolate complexes catalyse the conversion of alkenes into the corresponding cyclopropane derivatives with interesting diastereomeric excesses. Aiming at the evaluation of their catalytic activities, a systematic study of the cyclopropanation reactions in the presence of ethyl diazoacetate has been performed
Facile Preparation of Polytopic Azoles: Synthesis, Characterization, and X-ray Powder Diffraction Studies of 1,4-Bis(pyrazol-4-yl)- and 1,4-Bis(tetrazol-5-yl)benzene
No full textTwo polytopic azoles, 1,4-bis(pyrazol-4-yl)benzene and 1,4-bis(tetrazol-5-yl)benzene, were prepared in sizable amounts by high yield syntheses employing, in mild conditions, cheap reactants and, whenever possible, aqueous Solutions. The two species were characterized by H-1 and (CNMR)-C-13 spectroscopy and by thermal analyses, the latter evidencing their high chemical and thermal stability. X-ray powder diffraction methods disclosed their non isomorphous crystal structures. in which individual molecules interact via hydrogen bonds to form two-dimensional sheets
First person – Simona Amodeo
No full textABSTRACT
First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Simona Amodeo is the first author on ‘Characterization of the novel mitochondrial genome replication factor MiRF172 in Trypanosoma brucei’, published in Journal of Cell Science. Simona is a PhD student in the lab of Torsten Ochsenreiter at the Institute of Cell Biology, University of Bern, Switzerland, investigating mitochondrial genome anchoring, replication and inheritance in Trypanosoma brucei.</jats:p
In vitro ubiquitination: self-ubiquitination, chain formation, and substrate ubiquitination assays
No full textUbiquitination of proteins in vitro has evolved as an indispensable tool for the functional analysis of this posttranslational modifi cation. In vitro ubiquitination is particularly helpful to study conjugation mechanisms. The effi ciency of the ubiquitination reaction depends in part on the quality of the enzymes utilized. Here we introduce the assay developed in our lab to study HECT E3 ligases. It involves bacterially expressed E1, His-tagged Ube2D3 (also called UbcH5c, the best E2 for Nedd4), untagged Nedd4, and untagged ubiquitin (Ub). As tags may impair specifi c activity of the enzymes or even interfere with the enzymatic reaction, they should be avoided, removed, or kept to a minimal size whenever possible, unless proven to be without consequence. The protocol described here is suitable for other E3 ligases capable of forming Ub chains as pseudo-product of the enzyme reaction. It is also adapted to include substrates. In this case, substrates should be tagged and purifi ed after the reaction is completed to allow the detection of the ubiquitinated products
HECT E3 Ligases : a Tale With Multiple Facets
Get PDFUbiquitination plays a pivotal role in several cellular processes and is critical for protein degradation and signaling. E3 ubiquitin ligases are the matchmakers in the ubiquitination cascade, responsible for substrate recognition. In order to achieve selectivity and specificity on their substrates, HECT E3 enzymes are tightly regulated and exert their function in a spatially and temporally controlled fashion in the cells. These characteristics made HECT E3s intriguing targets in drug discovery in the context of cancer biology
Theoretical and experimental characterization of pyrazolato-based Ni(II) metal–organic frameworks
Get PDFThe structural, electronic, dielectric and vibrational features of two metal–organic frameworks with bi-pyrazolate ligands are investigated by combining ab initio periodic calculations and experimental techniques. UV-Vis spectroscopy has been used to study the electronic structure, while FTIR spectroscopy to obtain information about the vibrational features of the samples and their adsorptive properties. The examined MOFs contain square-planar Ni(II) nodes bridged either by the 4,4'-bi-pyrazolato (bpz) or by the 1,4-bis(4-pyrazolato)benzene (bpb) spacers. As expected, they are diamagnetic solids, with Ni(II) in low spin state. This has been confirmed through computations, other magnetic phases being predicted as remarkably less stable. Both materials possess a band gap of 3.4 eV and show interesting dielectric properties due to the microporous structure and the low dielectric constant. Although Ni(II) is coordinatively unsaturated, it does not show any specific interaction with the probe molecules tested, as evidenced by FTIR measurements. This unexpected behavior is explained on the basis of computed results. The high stability of the low spin state of Ni(II) in square planar coordination and a reduced accessibility of the metal sites due to steric effects are considered to be the reasons for the absence of preferential interactions between the metal centers and the probe molecules adopted
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