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71.
Favero G Campanella L Cavallo S D'Annibale A Perrella M Mattei E Ferri T 《Journal of the American Chemical Society》2005,127(22):8103-8111
The realization of a reliable receptor biosensor requires stable, long-lasting, reconstituted biomembranes able to supply a suitable biomimetic environment where the receptor can properly work after incorporation. To this end, we developed a new method for preparing stable biological membranes that couple the biomimetic properties of BLMs (bilayer lipid membranes) with the high stability of HBMs (hybrid bilayer membranes); this gives rise to an innovative assembly, named MHBLM (mixed hybrid bilayer lipid membrane). The present work deals with the characterization of biosensors achieved by embedding an ionotropic glutamate receptor (GluR) on MHBLM. Thanks to signal (transmembrane current) amplification, which is typical of natural receptors, the biosensor here produced detects glutamate at a level of nmol L(-1). The transmembrane current changes linearly vs glutamate up to 100 nmol L(-1), while the limit of detection is 1 nmol L(-1). In addition, the biosensor response can be modulated both by receptor agonists (glycine) and antagonists (Mg(2+)) as well, and by exploiting the biosensor response, the distribution of different kinds of ionotropic GluR present in the purified sample, and embedded in MHBLM, was also evaluated. Finally, one of the most important aspects of this investigation is represented by the high stability of the biomimetic system, which allows the use of biosensor under flowing conditions, where the solutions flow on both biomembrane faces. 相似文献
72.
Agnese Abate Elisabetta Brenna Giovanni Fronza Claudio Fuganti FrancescoG. Gatti Stefano Serra Enrica Zardoni 《Helvetica chimica acta》2004,87(4):765-780
All the enantiomerically enriched stereoisomers of Clarycet ® ( 1 ), Florol ® ( 2 ), and Rhubafuran ® ( 3 ) were prepared by biocatalysis routes. Their absolute configurations were established, and their olfactory properties were fully evaluated. 相似文献
73.
The structure of a 1,7,7-triaryl norbornane (compound 3) has been determined by X-ray diffraction and was found essentially equal to that predicted by molecular mechanics calculations. Restricted rotation of the aryl groups also has been observed by dynamic NMR spectroscopy in this compound and in a number of analogously substituted norbornanes. The aryl-norbornane bond rotation barriers were measured by line shape analysis of the (13)C NMR spectra obtained at temperatures lower than -100 degrees C and were found to cover the range 6.0 to 7.9 kcal mol(-1). An exception was the rotation involving the o-anisyl group in compound 5, which occurs near ambient temperature since the corresponding barrier is much higher (14.4 kcal mol(-1)). In one case (compound 4) configurational enantiomers could be separated by chiral HPLC and the corresponding CD spectra recorded. 相似文献
74.
In this work we illustrate an extension of the polarizable continuum model to describe solvation effects on molecules at the interface between two fluid phases (liquid/liquid, liquid/vapor). This extension goes beyond the naive picture of the interface as a plane dividing two distinct dielectrics, commonly employed in continuum models. The main feature of the model is the use of a diffuse interface with an electric permittivity depending on the position. This characteristic clearly allows the study of simple interfaces as well as more complex membrane or multilayer structures. Moreover the smooth variation of the permittivity in the diffuse interface, in contrast to the sharp boundary between two regions, overcomes the numerical divergences due to charges placed at the boundary. The implementation of the model relies on the integral equation formalism, which allows one to calculate the reaction field acting on a molecule immersed in a dielectric environment once the proper Green's function is known. In the present case, such a Green's function is obtained numerically, allowing a large flexibility in the choice of the dielectric permittivity profile. The applications have been selected with the aim of illustrating the capabilities of the model; its present limitations are also discussed. 相似文献
75.
The composition of volatile compounds produced by fruit during growth and post-harvest storage and ripening has been studied and the different headspace methods compared. Static and dynamic headspace sampling have been compared and evaluated according to their capacity to collect and concentrate volatiles from the atmosphere surrounding the fruits, and FID, MSD, and organoleptic detection have been compared. The results emphasize that the headspace sampling procedure selected is crucial to the performance of subsequent analysis. 相似文献
76.
Michele Sacerdoti Maria Chiara Dalconi Barbara Cavicchi Stefano Colonna 《Journal of solid state chemistry》2004,177(6):1781-1788
Sol-gel routes were used to prepare Ta 10 at% and Nb 5 at% and 10 at% doped titania nanosized powders. When fired between 410°C and 850°C the doped titania powders are in the anatase phase; further heating up to 1050°C is required to obtain the rutile phase. The presence of dopant atoms delays the rate of transformation as compared with pure titania powders. Doping also affects the rate of grain growth and increases the conductance response to gas. To better understand the role played by dopant atoms in inhibiting both phase transformation to rutile and grain growth, X-ray Absorption Spectroscopy measurements were performed at the LIII-LI absorption edges of Ta and Nb K absorption edge. Analysis was restricted to the anatase phase because the transformation to rutile phase, obtained by firing at 1050°C, is accompanied by the formation of undesired Ta and Nb oxides (Ta2O5 and Nb2TiO7, respectively). Extended X-ray Absorption Fine Structure and X-ray Absorption Near-Edge Spectroscopy analysis results indicate that in nanostructured anatase both tantalum and niobium atoms substitute Ti cations with +5 valence state. 相似文献
77.
Ricardo Bossio Stefano Marcaccini Valerio Parrini Roberto Pepino 《Journal of heterocyclic chemistry》1985,22(4):1147-1148
2-(Benzimidazol-2-ylamino)pyridine (4a) , 2-(benzimidazol-2-ylamino)pyrazine (4b) , and 2-(benzimidazol-2-ylamino)thiazole (4c) underwent a ring-closure reaction on treatment with phosgene affording 6H-pyrimido-[1′,2′:5,4][1,3,5]triazino[1,2-a]benzimidazol-6-one (1a) , 6H-pyrazino[1′,2′:5,4][1,3,5]triazino[1,2-a]benzimidazol-6-one (1b) , and 5H-thiazolo[2′,3′:4,5][1,3,5]triazino[1,2-a]benzimidazol-5-one (1c) respectively. The structure of these hitherto unknown heterocyclic systems was confirmed by their ir and mass spectra. 相似文献
78.
Franco Cecconi Carlo A. Ghilardi Stefano Midollini Annabella Orlandini Piero Zanello 《Polyhedron》1986,5(12):2021-2031
The reaction of hydrogen sulphide with [Co(H2O)6](BF4)2 and triethylphosphine in the presence of sodium tetraphenylborate or tetrabutylammonium hexafluorophosphate gave the paramagnetic clusters [Co6(μ3-S)8(PEt3)6](Y) (Y = BPh4, (1), PF6, (2)). These compounds can be easily reduced by sodium napthalenide to the diamagnetic species [Co6(μ3-S)8(PEt3)6] · 2C4H8O (3). The molecular structures of 1 and 3 have been established by single-crystal X-ray diffraction methods. Crystal data: (1) space group P
, a = 19.481(9), b = 15.562(7), c = 12.390(b) Å, α = 92.70(8), β = 94.50(7), γ = 94.10(9)°, Z = 2, (3) space group R
, a = 11.780(6) Å, α = 92.50(7)°, Z = 1. Both structures were solved by the heavy atom method and refined by full-matrix least-squares techniques to the conventional R factors values of 0.050 for 1 and 0.044 for 3 on the basis of 4251 and 1918 observed reflections, respectively. The two clusters [Co6(μ3-S)8)(PEt3)6]1+,0 are isostructural, the inner core consisting of an octahedron of cobalt atoms with all the faces symmetrically capped by triply bridging sulphur atoms. Each metal centre is additionally linked to a triethylphosphine group so that each cobalt atom is co-ordinated by four sulphur atoms and one phosphorus in a distorted square pyramidal environment. The addition of one electron whilst leaving unchanged the geometry of the inner framework, induces small changes in the structural parameters, the average Co---Co and Co---P distances being 2.794 (3) and 2.162 (2) Å for 1 and 2.817 (3) and 2.138 (2) Å for 3 respectively. Electrochemistry in non-aqueous solvents shows the electron-transfer sequence
The tricationic species is stable only in the short time of cyclic voltammetric tests. 相似文献
Full-size image (3K)
79.
Alessandra Gentili Fulvia Caretti Giuseppe D’Ascenzo Lucia Mainero Rocca Stefano Marchese Stefano Materazzi Daniela Perret 《Chromatographia》2007,66(9-10):669-676
Two new methods of analysis, based on liquid chromatography–tandem mass spectrometry, for simultaneous determination of trichothecenes A, B, and D in maize flour and oil have been developed and validated in accordance with European Commission decision 2002/657/EC (recovery, CCα, CCβ, and precision). The trichothecenes were extracted from maize flour by matrix solid-phase dispersion, with recoveries ≥79%, and from maize oil by liquid–liquid extraction, with recoveries ≥78%. Limits of quantitation ranged between 0.03 and 50 μg kg?1, depending on the electrospray response to each analyte and on the matrix. Monitoring of flour and oil samples with this HPLC–MS–MS method revealed the presence of deoxynivalenol, T-2 toxin, and diacetoxyscirpenol at very low concentrations. 相似文献
80.
Irradiation of esters
derived from carboxylic acids and
-hydroxypyridine-2-thione
in the presence of anhydrous camphorsulphonic acid and various heteroaromatic systems including purines affords the corresponding adducts in moderate to good yield. 相似文献