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51.
Garzotti M 《Rapid communications in mass spectrometry : RCM》2003,17(4):272-278
Inflamed tissues are often characterised by the production of *NO and O(2)(-) radicals, which are known to react at an extremely fast rate to produce peroxynitrite (ONOO(-)). This highly oxidising entity reacts with protein-bound tyrosine to give 3-nitrotyrosine, which is considered a biochemical marker of peroxynitrite-induced damage. Lacidipine is a calcium antagonist indicated for the treatment of mild to moderate hypertension. In the present work, electrospray mass spectrometry with and without liquid chromatography was used to evaluate the capability of lacidipine and two other related molecules as ONOO(-) scavengers. This capability is compared with that associated with a number of commercial polyphenols described in the literature as efficient scavengers of this cytotoxic agent. The use of mass spectrometry provided rapid quantitative assessment of both the nitration and its reduction, and showed that lacidipine possesses a reasonable capability for reducing in vitro nitration of superoxide dismutase. 相似文献
52.
Rudolf Schmid Joseph Foricher Marco Cereghetti Peter Schnholzer 《Helvetica chimica acta》1991,74(2):370-389
The new axially dissymmetric diphosphines (R)- and (S)-(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diphenyl phosphine) ((R)- and (S)- 5a ; ‘MeO-BIPHEP’) and the analogues (R)- and (S)- 5b and 5c have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho-lithiation/iodination reaction of the (m-methoxyphenyl)diprienylphosphine oxides 8 and a subsequent Ullmann reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10 . The bis(phosphine oxides) 10 subsequently are resolved with (?)-(2R,3R)- and (+)-(2S,3S)-O-2,3-dibenzoyltartaric acid and reduced to diphosphines 5 . The Ullmann reaction constitutes a new and efficient route to 2,2′-bis(phosphinoyl)-substituted biphenyl systems. Absolute configurations were established for (R)- 5a by X-ray analysis of the derived Pd complex (R,R)- 17a , and for 5b and 5c by means of 1H-NMR comparisons of the derived Pd complexes 16 or 17 , respectively, and by means of CD comparisons. The MeO-BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6′-dimethylbiphenyl-2,2′-diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations. 相似文献
53.
54.
Ford S Hofmann M Morley CP Roberts JL Di Vaira M 《Organic & biomolecular chemistry》2005,3(21):3990-3995
Bis(1,2,3,4-tetramethylcyclopentadienyl)selane (1) has been prepared by the reaction of tetramethylcyclopentadienyllithium (Cp(t)Li) with selenium bis(diethyldithiocarbamate). Treatment of Cp(t)Li with elemental selenium, followed by air oxidation, led to loss of the allylic hydrogen atom, and formation of the novel tricyclic compound 1,4,5,6,7,10,11,12-octamethyltricyclo[7.3.0.0]-2,8-diselenadodeca-3,5,9,11-tetraene (2). The sulfur analogue of 2 has been obtained by a similar procedure. The X-ray crystal structures of compounds 1 and 2 have been determined, and the molecular geometry observed for has been probed using DFT calculations. 相似文献
55.
Alessandra Sussulini Jerusa S. Garcia Márcia F. Mesko Diogo P. Moraes Érico M. M. Flores Carlos A. Pérez Marco A. Z. Arruda 《Mikrochimica acta》2007,158(1-2):173-180
Two methods of protein extraction for soybean seeds were evaluated in terms of preservation of the metal ions bound to proteins
after the extraction and separation procedures. The proteins were firstly separated according to their molar masses by polyacrylamide
gel electrophoresis. Then, the protein bands were mapped by synchrotron radiation X-ray fluorescence in order to establish
which metal ions were present in each one. Finally, some mapped protein bands were decomposed by microwave-assisted combustion
and Ca, Cu, K, Mg, Mn, and Zn were quantified by inductively coupled plasma mass spectrometry or inductively coupled plasma
optical emission spectrometry. The extraction methods studied were Method A (based on the treatment of ground soybean seeds with hexane and their extraction with Tris–HCl and β-mercaptoethanol) and
Method B (based on the treatment of ground soybean seeds with petroleum ether and their extraction with Tris–HCl, dithiothreitol,
phenylmethanesulfonyl fluoride, sodium dodecyl sulfate and potassium chloride). The best method was Method B, in which a 78% higher extraction efficiency was obtained when compared to Method A. Additionally, the metal-protein interactions were more appropriately preserved when Method B was applied, where the most affected ions were those that are bound weakly to proteins, such as Ca, K, and Mg. 相似文献
56.
Attilio Citterio Anna Gentile Francesco Minisci Marco Serravalle Susanna Ventura 《Tetrahedron》1985,41(3):617-620
The homolytic decomposition of hydroxylamine-O-sulphonic acid in alcoholic solvents was investigated in the presence or absence of protonated heteroaromatic bases and Fe(II) salt. The addition of the α-hydroxyalkyl radicals to the base and their oxidation by Fe(III) salt to the corresponding alkyl cyanide were competitive processes. A redox chain process involving the amino radical cation, NH3t., is suggested and the factors affecting the yields of the homolytic substitution are discussed. 相似文献
57.
Marco Arfelli Giovanni Cossu Giulia Mattogno Carla Ferragina Maria Antonietta Massucci 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(2):161-170
X-ray photoelectron spectroscopy provides evidence that when [Cu(phen)2]2+(phen = 1,10-phenanthroline) is diffused between the layers of -zirconium phosphate, the complex species does not remain intact after intercalation, but some Cu-N bonds are broken, replaced with Cu-O bonds and the released nitrogen atoms can now interact with the PO3-OH groups of the host. XPS also provides evidence for coordination of the Cu2+ ions when they are diffused by ion exchange in the phenanthroline--zirconium phosphate intercalation compound. Although Cu2+ and phen are in a 1 : 1 molar ratio in the interlayer region of the host, so that a 1 : 1 coordination could be expected between the two species, the characteristic peaks of the uncoordinated phenanthroline, even though at a low intensity, are still present. The differences between the two Cu(II)-intercalation compounds are discussed. 相似文献
58.
Yu. I. Aristov G. Di Marco M. M. Tokarev V. N. Parmon 《Reaction Kinetics and Catalysis Letters》1997,61(1):147-154
In this communication we present a low-temperature “solidification-melting” phase diagram for CaCl2/H2O solutions confined in KSK and KSM silica gels. At salt concentrations of 0–48 wt. %, the diagram has been found to lie below
the diagram reported for the bulk system by 15–30°C. It shows a depression of the solution melting point due to its confinment
to the pores. Several other peculiarities of melting and solidification in this system are also reported and discussed. Beside
fundamental interest, the data obtained could be of importance in many commercial areas such as refrigeration, accumulation
of low temperature heat, frost prevention in building materials,etc. 相似文献
59.
Accurate and efficient calculations of absorption spectra of molecules and materials are essential for the understanding and rational design of broad classes of systems. Solving the Bethe–Salpeter equation (BSE) for electron–hole pairs usually yields accurate predictions of absorption spectra, but it is computationally expensive, especially if thermal averages of spectra computed for multiple configurations are required. We present a method based on machine learning to evaluate a key quantity entering the definition of absorption spectra: the dielectric screening. We show that our approach yields a model for the screening that is transferable between multiple configurations sampled during first principles molecular dynamics simulations; hence it leads to a substantial improvement in the efficiency of calculations of finite temperature spectra. We obtained computational gains of one to two orders of magnitude for systems with 50 to 500 atoms, including liquids, solids, nanostructures, and solid/liquid interfaces. Importantly, the models of dielectric screening derived here may be used not only in the solution of the BSE but also in developing functionals for time-dependent density functional theory (TDDFT) calculations of homogeneous and heterogeneous systems. Overall, our work provides a strategy to combine machine learning with electronic structure calculations to accelerate first principles simulations of excited-state properties.Machine learning can circumvent explicit calculation of dielectric response in first principles methods and accelerate simulations of optical properties of complex materials at finite temperature. 相似文献
60.
Oxidation of 5×10−3 M noradrenaline in aqueous phosphate buffer, pH 7.4, with K3Fe(CN)6, NaIO4 or Fe2+/EDTA/H2O2 followed by extraction with ethyl acetate and acetylation with Ac2O/Pyr led to a main reaction product which was isolated and identified as 4-[bis-(1H-5,6-diacetoxyindol-2-yl)methyl]-1,2-diacetoxybenzene, an unprecedented [bis-(indol-2-yl)methyl]-benzene derivative unsubstituted on the 3-position of the indole rings. This product was also obtained in 40% yield by reaction of 5,6-dihydroxyindole with 3,4-dihydroxybenzaldehyde. Other components of the oxidation mixture were 1-acetyl-3,5,6-triacetoxyindole, derived from noradrenolutin, and 5,6-diacetoxyindole, originating from cyclisation/dehydration of the o-quinone of noradrenaline, along with some 3,4-diacetoxybenzaldehyde. Inspection of the aqueous phase revealed the presence of 3,4-dihydroxymandelic acid and 3,4-dihydroxybenzaldehyde, derived from oxidative breakdown of the 2-amino-1-hydroxyethyl chain via a p-quinomethane intermediate. These results disclose new aspects of the oxidative chemistry of noradrenaline beyond the aminochrome stage and provide a route to novel [bis-(indol-2-yl)methyl]-benzene derivatives of potential pharmacological interest. 相似文献