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排序方式: 共有119条查询结果,搜索用时 15 毫秒
1.
Marotta E Lapolla A Fedele D Senesi A Reitano R Witt M Seraglia R Traldi P 《Journal of mass spectrometry : JMS》2003,38(2):196-205
The Maillard reaction occurring between sugars and amino groups is important in living systems. When amino groups belonging to protein chains are involved, the Maillard reaction has been invoked as responsible for protein cross-linking and the production of 'toxic' compounds. The reaction leads to the production of a heterogeneous group of substances, usually called advanced glycation end products (AGEs). Classical analytical approaches, such as spectroscopic (ultraviolet, fluorescence) and mass spectrometric (matrix-assisted laser desorption/ionization, liquid chromatography/electrospray ionization mass spectrometry) methods, have shown that the digestion mixture is highly complex. However, there are clear differences between the digestion mixtures of glycated and unglycated human serum albumin (HSA). In the former case, possible glycated peptides belonging to the AGE peptide class may be identified. Tandem mass spectrometric experiments on selected species seemed to be promising as regards structural information, but it was thought of interest to undertake the present investigation, based on liquid chromatography/electrospray ionization Fourier transform mass spectrometry, in order to obtain definitive results on their elemental composition. Using this approach, about 20 glycated peptides were detected and their possible structures were postulated by examining the known sequence of HSA. 相似文献
2.
Giovanni Appendino Giancarlo Cravotto Gian Mario Nano Giovanni Palmisano Rita Annunziata 《Helvetica chimica acta》1993,76(3):1194-1202
The reaction of 4-hydroxycoumarin and certain aliphatic aldehydes affords 1:1 or complex 2:2 adducts besides (or in place) of the expected 2:1 bis(coumarin) adducts. Reaction with heptanal, cyclohexanecarbaldehyde, and pivalaldehyde are reported as representative. The structure of the reaction products was established by spectroscopical techniques, including X-ray analysis, and their formation was mechanistically rationalized. Some of the 1:1 adducts are synthetically useful for the preparation of 3-alkyl-4-hydroxycoumarins. 相似文献
3.
An efficient synthesis of the 4H-quinolone alkaloid graveoline has been achieved by a route featuring an Pd(II)-catalysed reductive N-hetero-cyclisation [CO(3 MPa), Pd(TMB)2, TMPhen, 170°C, 3h] of 2′-nitrochalcone as a key step. 相似文献
4.
Roberta Seraglia Giovanni Sartore Raffaella Marin Silvia Burlina Enzo Manzato Eugenio Ragazzi Pietro Traldi Annunziata Lapolla 《Journal of mass spectrometry : JMS》2013,48(1):105-110
Increased oxidation of low density lipoprotein (LDL) is characteristic of atherosclerosis. In this frame, high density lipoproteins (HDL) play an important role, being able to remove lipid peroxides (LPOs) and cholesterol from oxidized LDL, so exhibiting a protective role against atherosclerosis. A wide range of reactive compounds lead to the oxidation of methionine (Met) residues with the formation of methionine sulphoxide (MetO) in apolipoprotein A‐I (ApoA‐I). Consequently, the determination of MetO level can give both an evaluation of oxidative stress and the reduced capability of ApoA‐I in LPOs and cholesterol transport. For these reasons, the development of analytical methods able to determine the MetO level is surely of interest, and we report here the results obtained by MALDI mass spectrometry. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
Giovanni Appendino Giancarlo Cravotto Giovanni Palmisano Rita Annunziata 《合成通讯》2013,43(18):3359-3371
In the presence of one-electron metal oxidants (CAN, MAH), 4-hydroxycoumarin (1) adds to alkenes to give 2,3-dihydro-4H-furo[3,2-c][1]benzopyran-4-ones. 相似文献
6.
Elisabetta Massolo Maurizio BenagliaDavide Parravicini Davide BrennaRita Annunziata 《Tetrahedron letters》2014
Starting from (E)-β-substituted-β-nitroacrylates and α,β-unsaturated ketones, a stereoselective organocatalyzed one-pot methodology allowed to synthesize highly decorated chiral 2-nitro-cyclohexane carboxylic esters. The reaction is promoted by Cinchona alkaloid-derived primary amines in the presence of an acidic co-catalyst and affords two diastereoisomers, in good yields and high enantiomeric excess (often higher than 90% ee). By replacing conventional heating with microwave irradiation, cleaner reactions in shortened times (from 48 h to 30 min) were obtained, with improved dr (80:20) and high ee (up to 94%). The application of microwave technology to this organocatalytic methodology allowed also employing C1 substituted enones, leading to cyclohexanones with four contiguous stereocenters in two isomers only, and up to 99% enantioselectivity. 相似文献
7.
Ranjbarzadeh Ramin Akhgar Alireza Taherialekouhi Roozbeh DOrazio Annunziata Mohammad Sajadi S. Ghaemi Ferial Baleanu Dumitru 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7509-7521
Journal of Thermal Analysis and Calorimetry - In this research, the effect of using GO/ water nanofluid as a coolant fluid in an isothermal heat transfer system was studied. At first, to evaluate... 相似文献
8.
We report the four diffusion coefficients for the lysozyme-MgCl2-water ternary system at 25 degrees C and pH 4.5. The comparison with previous results for the lysozyme-NaCl-water ternary system is used to examine the effect of salt stoichiometry on the transport properties of lysozyme-salt aqueous mixtures. We find that the two cross-diffusion coefficients are very sensitive to salt stoichiometry. One of the cross-diffusion coefficients is examined in terms of common-ion, excluded-volume, and protein-preferential hydration effects. We use the four ternary diffusion coefficients to extract chemical-potential cross-derivatives and protein-preferential interaction coefficients. These thermodynamic data characterize the protein-salt thermodynamic interactions. We demonstrate the presence of the common-ion effect (Donnan effect) by analyzing the dependence of the preferential-interaction coefficient not only with respect to salt concentration but also with respect to salt stoichiometry. We conclude that the common-ion effect and the protein-preferential hydration are both important for describing the lysozyme-MgCl2 thermodynamic interaction. 相似文献
9.
Maria Annunziata M. Capozzi Andrea Bottoni Matteo Calvaresi Cosimo Cardellicchio 《Tetrahedron》2018,74(16):2041-2047
Pentafluorobenzyl pentafluorophenyl sulfide is oxidised with moderate e.e. value and a low yield by the usually highly successful oxidation protocol based upon tert-butyl hydroperoxide (TBHP) in the presence of a titanium/hydrobenzoin complex. This disappointing result resisted until the present work, in which the switch of the oxidation agent (from TBHP to cumene hydroperoxide), suggested by our previous computations, yielded the enantiopure sulfoxide. This valuable chiral compound was obtained in good yields (76%) without resorting to a chromatographic separation. DFT computations uncovered that this favourable reactivity was originated by a stabilizing π?π?stacking between the phenyl group of the oxidant and the pentafluorophenyl moiety of the substrate. 相似文献
10.
Rayleigh interferometry has been extensively used for the precise determination of diffusion coefficients for binary and ternary liquid mixtures. For ternary mixtures, the 2x2 matrix of multicomponent diffusion coefficients is obtained. Polydispersity adds complexity to the meaning of these measured diffusion coefficients. Here we discuss three important issues of polydispersity regarding the diffusion measurements extracted from this interferometric technique. First, we report novel equations for the extraction of diffusion moments from the Rayleigh interferometric pattern. These moments are used to define polydispersity parameters for macromolecular systems. We have experimentally determined mean diffusion coefficients and polydispersity parameters for aqueous solutions of poly(ethylene glycol) and poly(vinyl alcohol) at 25 degrees C. Aqueous solutions of poly(ethylene glycol) mixtures were used to examine the accuracy of the polydispersity parameters. Second, we compare Rayleigh interferometry to dynamic light scattering. Specifically, we have performed diffusion measurements on the same system using both techniques. To our knowledge, no direct experimental comparison between dynamic light scattering and classical methods for the measurements of diffusion coefficients has been previously reported in relation to polydispersity. We find that substantial discrepancies (i.e., 1 order of magnitude) between the mean diffusion coefficients obtained from these two different techniques can be observed when polydispersity is large. Third, for two-solute mixtures with one polydisperse solute, we report a novel corrective procedure for extracting accurate ternary diffusion coefficients from Rayleigh interferometry. Computer simulations were used to examine the accuracy of the extracted ternary diffusion coefficients. 相似文献