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31.
We computed by spin-polarized DFT the structure and the electronic properties of an infinite periodic wire constituted of planar Cu-bridged hydroxypyridone chelator base pairs and of a similarly stacked finite dimer. The Cu centers undergo electronic hybridization with the bases. There is an unpaired spin per plane, and the majority-spins manifest ordering: The ferromagnetic and antiferromagnetic phases are energetically degenerate. The total magnetization of the ferromagnetic wire depends linearly on the number of planes in the stack. The combination of interplane spin coupling and intraplane metal-hydroxypyridone coupling makes this system very appealing for electronic and magnetic device exploitation. 相似文献
32.
D'Amelio N Gaggelli E Gaggelli N Molteni E Baratto MC Valensin G Jezowska-Bojczuk M Szczepanik W 《Dalton transactions (Cambridge, England : 2003)》2004,(3):363-368
The complexes formed by kanamycin A at three different pH values (5.5, 7.4 and 12.0) were investigated by NMR and EPR spectroscopy. Paramagnetic relaxation contributions to proton relaxation rates were measured using a combination of the TOCSY sequence with the inversion recovery experiment in order to gain signal resolution in the bulk region. Measured contributions were converted into distances and used for structural determination by restrained simulated annealing where all possible chair and boat conformations of the rings were taken into account. The interaction of the Cu(II) ion with the nitrogen of the C ring is apparent at all pH values. At higher pH also the amino group of ring A starts to be involved in the metal coordination sphere. This is accompanied by a switch in conformation of ring C. Structures are consistent with the involvement in the coordination sphere either of the 2' or 4' hydroxyl oxygens at pH 5.5 and the 5 and the 6' hydroxyl oxygens (or the ring oxygen) at pH 12.0. 相似文献
33.
Energy controlled insertion of polar molecules in dense fluids 总被引:1,自引:0,他引:1
De Fabritiis G Delgado-Buscalioni R Coveney PV 《The Journal of chemical physics》2004,121(24):12139-12142
We present a method to search low energy configurations of polar molecules in the complex potential energy surfaces associated with dense fluids. The search is done in the configurational space of the translational and rotational degrees of freedom of the molecule, combining steepest-descent and Newton-Raphson steps which embed information on the average sizes of the potential energy wells obtained from prior inspection of the liquid structure. We perform a molecular dynamics simulation of a liquid water shell which demonstrates that the method enables fast and energy-controlled water molecule insertion in aqueous environments. The algorithm finds low energy configurations of incoming water molecules around three orders of magnitude faster than direct random insertion. This method represents an important step towards dynamic simulations of open systems and it may also prove useful for energy-biased ensemble average calculations of the chemical potential. 相似文献
34.
Antonio Massa Laura Capozzolo Arrigo Scettri 《Central European Journal of Chemistry》2010,8(6):1210-1215
SiCl4 can be conveniently activated by catalytic amounts of dimethyl sulfoxide or other readily-available sulfoxides for the allylation
of aromatic, hetero-aromatic and unsaturated aldehydes in the presence of allyltributyl stannane. Chiral aryl methyl sulfoxides
have been used to develop asymmetric allylation methods, as well as probe the aldehyde substrate scope. 相似文献
35.
Dr. Caterina Bernacchioni Dr. Cecilia Pozzi Flavio Di Pisa Prof. Stefano Mangani Prof. Paola Turano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16213-16219
Ferritins are iron‐storage nanocage proteins that catalyze the oxidation of Fe2+ to Fe3+ at ferroxidase sites. By a combination of structural and spectroscopic techniques, Asp140, together with previously identified Glu57 and Glu136, is demonstrated to be an essential residue to promote the iron oxidation at the ferroxidase site. However, the presence of these three carboxylate moieties in close proximity to the catalytic centers is not essential to achieve binding of the Fe2+ substrate to the diferric ferroxidase sites with the same coordination geometries as in the wild‐type cages. 相似文献
36.
Zoccatelli G Dalla Pellegrina C Mosconi S Consolini M Veneri G Chignola R Peruffo A Rizzi C 《Electrophoresis》2007,28(3):460-466
Wheat proteinaceous alpha-amylase inhibitors (alpha-AIs) are increasingly investigated for their agronomical role as natural defence molecules of plants against the attack of insects and pests, but also for their effects on human health. The wheat genomes code for several bioactive alpha-AIs that share sequence homology, but differ in their specificity against alpha-amylases from different species and for their aggregation states. Wheat alpha-AIs are traditionally classified as belonging to the three classes of tetrameric, homodimeric and monomeric forms, each class being constituted by a number of polypeptides that display different electrophoretic mobilities. Here we describe a proteomic approach for the identification of bioactive alpha-AIs from wheat and, in particular, a 3-D technique that allows to best identify and characterize the dimeric fraction. The technique takes advantage of the thermal resistance of alpha-AIs (resistant to T > 70 degrees C) and consists in the separation of protein mixtures by 2-D polyacrylamide/starch electrophoresis under nondissociating PAGE (ND-PAGE, first dimension) and dissociating (urea-PAGE or U-PAGE second dimension) conditions, followed by in-gel spontaneous reaggregation of protein complexes and identification of the alpha-amylase inhibitory activity (antizymogram, third dimension) using enzymes from human salivary glands and from the larvae of Tenebrio molitor coleopter (yellow mealworm). Dimeric alpha-AIs from Triticum aestivum (bread wheat) were observed to exist as heterodimers. The formation of heterodimeric complexes was also confirmed by in vitro reaggregation assays carried out on RP-HPLC purified wheat dimeric alpha-AIs, and their bioactivity assayed by antizymogram analysis. The present 3-D analytical technique can be exploited for fast, full-fledged identification and characterization of wheat alpha-AIs. 相似文献
37.
Stańczak P Valensin D Juszczyk P Grzonka Z Valensin G Bernardi F Molteni E Gaggelli E Kozłowski H 《Chemical communications (Cambridge, England)》2005,(26):3298-3300
The interaction between the single hexarepeat unit of chicken prion protein [ChPrP(54-59)] and Cu(II) was investigated by NMR, finding different coordination modes for the trans/trans and cis/trans isomers. 相似文献
38.
Carlo Bruno Eleonora Ussano Gianni Barucca Davide Vanossi Giovanni Valenti Edward A. Jackson Andrea Goldoni Lucio Litti Simona Fermani Luca Pasquali Moreno Meneghetti Claudio Fontanesi Lawrence T. Scott Francesco Paolucci Massimo Marcaccio 《Chemical science》2021,12(23):8048
The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure.A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene. 相似文献
39.
Carlo Anchisi Luciana Corda Antonio Maccioni Gianni Podda 《Journal of heterocyclic chemistry》1982,19(1):141-144
The action of acyl halides on heterocyclic compounds of five-membered rings containing an O-M-O (M ? P, As, Sb) linkage is described. The reactions were either carried out in the presence of a solvent (benzene or toluene) or by direct heating of the reagent with the substrate. In the case of arsole, stibole and stannole derivatives, the cleavage of O-M bond and the formation of the respective mono- and diesters were always obtained, while with the phospholes, no cleavage of the compounds was observed. The products IIa-c (M = Sb) have been obtained in excellent yields starting from VIa-c and antimony trichloride. The structure of the compounds which were prepared was determined by analytical and spectroscopic methods and also by comparations with authentic samples where possible. 相似文献
40.
Tanvir Miah Palmarita Demoro Izuchika Nduka Federica De Luca Dr. Salvatore Abate Dr. Rosa Arrigo 《Chemphyschem》2023,24(7):e202200589
We report a green, wet chemistry approach towards the production of C-supported Cu electrocatalysts active in the CO2 reduction to formic acid. We use citrus peels as a C support precursor and as a source of reducing agents for the Cu cations. We show that orange peel is a suitable starting material compared to lemon peel for the one-pot hydrothermal synthesis of Cu nanostructures affording better Cu dispersion as well as productivity and selectivity towards formic acid. We rationalize this finding in terms of the beneficial chemical composition of the orange peel, which favors both the reduction of the Cu precursor as well as the carbon matrix. This work demonstrates new viable opportunities for the reuse of citrus waste on a rational basis. 相似文献