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131.
Silvia Sternativo Francesca Del Verme Antonella Calandriello Lorenzo Testaferri Marcello Tiecco 《Tetrahedron》2010,66(34):6851-9385
Variously substituted aziridines were conveniently prepared by an aza-Michael Initiated Ring Closure (aza-MIRC) reaction starting from vinyl selenones and primary amines, aminoalcohols or diamines. The reactions proceed in very high yields at room temperature in toluene or water. A significant rate acceleration was observed under aqueous conditions. 相似文献
132.
Luigino Troisi Catia Granito Francesca Rosato Valeria Videtta 《Tetrahedron letters》2010,51(2):371-206
Amides can be prepared from allyl or benzyl halides and primary or secondary amines, using Pd(0) catalyst under CO pressure, in a one-pot synthesis. The reaction proceeds through the acyl palladium halide formation which undergoes an acylic nucleophilic substitution from the amine. 相似文献
133.
Francesca Tessore Dr. Elena Cariati Prof. Franco Cariati Prof. Dominique Roberto Prof. Renato Ugo Prof. Patrizia Mussini Prof. Cristiano Zuccaccia Dr. Alceo Macchioni Prof. 《Chemphyschem》2010,11(2):495-507
A series of 4‐X‐1‐methylpyridinium cationic nonlinear optical (NLO) chromophores (X=(E)‐CH?CHC6H5; (E)‐CH?CHC6H4‐4′‐C(CH3)3; (E)‐CH?CHC6H4‐4′‐N(CH3)2; (E)‐CH?CHC6H4‐4′‐N(C4H9)2; (E,E)‐(CH?CH)2C6H4‐4′‐N(CH3)2) with various organic (CF3SO3?, p‐CH3C6H4SO3?), inorganic (I?, ClO4?, SCN?, [Hg2I6]2?) and organometallic (cis‐[Ir(CO)2I2]?) counter anions are studied with the aim of investigating the role of ion pairing and of ionic dissociation or aggregation of ion pairs in controlling their second‐order NLO response in anhydrous chloroform solution. The combined use of electronic absorption spectra, conductimetric measurements and pulsed field gradient spin echo (PGSE) NMR experiments show that the second‐order NLO response, investigated by the electric‐field‐induced second harmonic generation (EFISH) technique, of the salts of the cationic NLO chromophores strongly depends upon the nature of the counter anion and concentration. The ion pairs are the major species at concentration around 10?3 M , and their dipole moments were determined. Generally, below 5×10?4 M , ion pairs start to dissociate into ions with parallel increase of the second‐order NLO response, due to the increased concentration of purely cationic NLO chromophores with improved NLO response. At concentration higher than 10?3 M , some multipolar aggregates, probably of H type, are formed, with parallel slight decrease of the second‐order NLO response. Ion pairing is dependent upon the nature of the counter anion and on the electronic structure of the cationic NLO chromophore. It is very strong for the thiocyanate anion in particular and, albeit to a lesser extent, for the sulfonated anions. The latter show increased tendency to self‐aggregate. 相似文献
134.
Francesca Speroni Lisa Elviri Maria Careri Alessandro Mangia 《Analytical and bioanalytical chemistry》2010,397(7):3035-3042
An innovative enzyme-linked immunosorbent assay (ELISA) format based on antibody-coated magnetic micro-particles (MPs) for
the sensitive detection of Ara h3/4 allergen in food is described. The immunosupport is suspended in the incubation solutions
and the MPs with the captured allergen can be easily harvested on a magnet, separated from the solutions, and washed using
an easy-to-use, fast and selective approach that allows its detection and quantification. Two differently coated MPs, ProteinA-Pn-b
and MP-NH2-PAMAM G 1.5 -Pn-b immunosupports, were tested. The functionalization of the MPs with PAMAM-sodium carboxylate dendrimers
elicits a major stability on the immunoglobulin activity resulting in a threefold enhancement of the analytical sensitivity
for the assay with respect to a ProteinA immobilization. Validation was carried out on two different matrices: corn flakes
and biscuits. In the case of MP-NH2-PAMAM G 1.5 -Pn-b immunosupport, limit of detection was found to be 0.2 mg peanuts/kg matrix in both matrices; the linear
response range was demonstrated from 2.5 to 15 mg peanuts/kg matrix by performing statistical tests (homoscedasticity and
Mandel fitting tests). Good accuracy and recovery (>80 ± 2%) were obtained. Different food samples were tested and the results
were compared with those obtained with a commercially available ELISA kit. The results obtained in this work demonstrated
the applicability of the immunomagnetic ELISA methods on real samples and the possibility to perform the assay with significantly
reduced reagent and sample consumption. 相似文献
135.
Francesca Zavarise Encarnació Companys Josep Galceran Giancarla Alberti Antonella Profumo 《Analytical and bioanalytical chemistry》2010,397(1):389-394
Absence of gradients and Nernstian equilibrium stripping (AGNES) is a recently developed electroanalytical technique specifically designed for the direct determination of free concentrations of metal ions. AGNES is applied here to the determination of free Zn concentration in a river water sample. The method has been validated with synthetic solutions of low ionic strengths containing Zn and 2,6-pyridinedicarboxylic acid and then applied to synthetic river waters and to a natural sample collected from Besòs River in Montcada i Reixac (Catalonia, North-Eastern Spain). In the river sample, an average free Zn concentration of 12.8(4) nM was obtained, while the total dissolved Zn concentration was 0.51(8)?μM. To control and maintain pH and pCO2 constant during AGNES measurements, a novel device for N2/CO2 mixed purging has been developed. 相似文献
136.
137.
Samantha Reale Dr. Francesca Attanasio Dr. Nicoletta Spreti Prof. Francesco De Angelis Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):6077-6087
Model coniferyl alcohol lignin (the so‐called dehydrogenative polymerisate, DHP) was produced in water under homogeneous conditions guaranteed by the presence of a micellised cationic surfactant. A complete study of the activity of the enzymatic system peroxidase/H2O2 under our reaction conditions was reported and all the reaction products up to the pentamer were characterised by 1H NMR spectroscopy and ESI mass spectrometry. Our system, and the molecules that have been generated in it, represent a closer mimicry of the natural microenvironment since an enzyme, under micellar conditions, reproduces the cell system better than in buffer alone. On the basis of the oligomers structures a new biosynthetic perspective was proposed that focused attention on a coniferyl alcohol dimeric quinone methide as the key intermediate of the reaction. A formal, strictly alternate sequence of a radical and an ionic step underlines the reaction, thus generating ordered oligolignols structures. Alternatively to other model lignins, our olignols present a lower degree of radical coupling between oligomeric units. This offers a closer biosynthetic situation to the observation of a low rate of radical generation in the cell wall. 相似文献
138.
Reineri F Bouguet-Bonnet S Canet D 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,210(1):107-112
When a hydrogenation reaction is carried out with gaseous hydrogen enriched in its para- isomer in the earth magnetic field (prior to adiabatic insertion of the sample in the NMR magnet), enhanced proton longitudinal order (represented by 2I(z)(A)I(z)(B)) is created but also difference of enhanced polarizations (I(z)(A)-I(z)(B)). In a first part, it is shown theoretically and experimentally that the longitudinal relaxation time of this polarization difference is roughly twice the ones of individual polarizations. The second part is devoted to a pulse sequence designed for transforming this difference into net hyperpolarization. The evolution of this global hyperpolarization is studied experimentally in a third part and it is observed that a fraction of hyperpolarization possesses an effective longitudinal relaxation time similar to the one of the initial polarization difference. Those experimental results are interpreted by numerical calculations based on Solomon-type equations including the longitudinal order and possibly dipolar-csa cross correlation rates. 相似文献
139.
The surface composition of 18th century papers was investigated by means of ToF-SIMS and XPS. The aim of the present study was to explore the possibility of using these surface sensitive methods to obtain information which can help to determine the manufacturing process, provenance and state of conservation of ancient papers. The ToF-SIMS results indicate that the analyzed papers were sized by gelatin and that alum was added as hardening agent. The paper sheets produced in near geographical areas but in different paper mills exhibit a similar surface composition and morphology of the fibers as shown by the ToF-SIMS measurements. The ToF-SIMS and the XPS results indicate that a significant fraction of the cellulose fibers is not covered by the gelatin layer. This was observed for the ancient papers and for a modern handmade paper manufactured according to the old recipes. 相似文献
140.
Freudenthal duality, introduced in Borsten et al. (2009) [1] and defined as an anti-involution on the dyonic charge vector in d=4 space-time dimensions for those dualities admitting a quartic invariant, is proved to be a symmetry not only of the classical Bekenstein-Hawking entropy but also of the critical points of the black hole potential.Furthermore, Freudenthal duality is extended to any generalized special geometry, thus encompassing all N>2 supergravities, as well as N=2 generic special geometry, not necessarily having a coset space structure. 相似文献