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941.
Ugo Cosentino Demetrio Pitea Giorgio Moro Vincenzo Barone Alessandra Villa Robert N. Muller Francois Botteman 《Theoretical chemistry accounts》2004,111(2-6):204-209
The conformational behavior in aqueous solution of four complexes of the Eu(III) ion with bis (R–amide) derivatives (R=H, methyl, ethyl, butyl) of diethylentriamine pentacetate ligands has been characterized at the ab initio level to rationalize the experimentally observed influence of alkyl substituents on the rate of the exchange process of the water molecule coordinated to the ion with the bulk water. Calculations were performed in vacuo and for aqueous solution, the latter by using the polarizable continuum model. Geometry optimizations provide, for each system, four isomers as stable conformations, all presenting a distorted tricapped trigonal prism coordination geometry around the ion. No significant influence of the alkyl substitution on the coordination geometry, nor on the europium–water distance, was observed. Moreover, increasing the length of the alkyl chain had no significant effect on the relative isomer population in solution. Thus, these results lead us to suppose that other effects, like those deriving from lateral chain folding in solution, should be considered to explain the increased rate of the water-exchange process with alkyl chain lengthening.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
942.
Quantitative proteomics: a review of different methodologies 总被引:5,自引:0,他引:5
Righetti PG Campostrini N Pascali J Hamdan M Astner H 《European journal of mass spectrometry (Chichester, England)》2004,10(3):335-348
The present review attempts to cover the vast array of methods which have appeared in the last few years for performing quantitative proteome analysis. These methods are divided into two classes: those applicable to conventional two-dimensional map analysis, coupling orthogonally a charge-based step (isoelectric focusing) to a size-based separation [sodium dodecylsulfate (SDS)-electrophoresis] and those applicable to two-dimensional chromatographic protocols. The first method, although being by and large the most popular approach, can offer differential display of paired samples with relatively few methods, the oldest one being based on statistical analysis performed on sets of gels via powerful software packages, such as the MELANIE, PDQuest, Z3 and Z4000, Phoretix and Progenesis. Recent developments comprise analysis performed on a single gel containing mixed samples differentially labeled, either with fluorophors (Cy3 and Cy5) or with d(0)/d(3) acrylamide. Conversely, chromatographic approaches, which mostly rely on analysis not of intact proteins but of their tryptic digests, offer a panoply of differential labeling protocols, most of which rely on stable isotope tagging. Essentially, all possible reactions have been described, such as those involving Lys, Asp, Glu, Cys residues, as well as a number of methods exploiting differential derivatization of amine and carboxyl groups generated during proteolysis. All such methods are described and evaluated. 相似文献
943.
[reaction: see text] The stereoselective synthesis of a novel proline-containing dipeptide isostere is described. Starting from l-valine, three new contiguous stereocenters are generated by asymmetric induction and epoxide chemistry, while the pyrrolidine ring of proline is introduced in the final step via intramolecular ring opening of the amino acid derived epoxyamine. Proline-containing peptidomimetics are potentially attractive as selective inhibitors of proline-specific enzymes, such as PPIases and retroviral proteases, and as analogues of bioactive peptides. 相似文献
944.
Silvio Franz Marc Mézard Giorgio Parisi Luca Peliti 《Journal of statistical physics》1999,97(3-4):459-488
We discuss the response of aging systems with short-range interactions to a class of random perturbations. Although these systems are out of equilibrium, the limit value of the free energy at long times is equal to the equilibrium free energy. By exploiting this fact, we define a new order parameter function, and we relate it to the ratio between response and fluctuation, which is in principle measurable in an aging experiment. For a class of systems possessing stochastic stability, we show that this new order parameter function is intimately related to the static order parameter function, describing the distribution of overlaps between clustering states. The same method is applied to investigate the geometrical organization of pure states. We show that the ultrametric organization in the dynamics implies static ultrametricity, and we relate these properties to static separability, i.e., the property that the measure of the overlap between pure states is essentially unique. Our results, especially relevant for spin glasses, pave the way to an experimental determination of the order parameter function. 相似文献
945.
Effect of metal oxides on the evolution of aromatic hydrocarbons in the thermal decomposition of PVC
Alberto Ballistreri Salvatore Foti Pietro Maravigna Giorgio Montaudo Emilio Scamporrino 《Journal of polymer science. Part A, Polymer chemistry》1980,18(10):3101-3110
The thermal decomposition of poly(vinyl chloride) (PVC) mixed with several metal oxides was investigated by direct pyrolysis in a mass spectrometer (MS) and flash pyrolysis–gas chromatography. Our results show that the thermal decomposition of PVC occurs in two stages. Unsubstituted aromatic hydrocarbons (benzene, naphthalene, and anthracene) are evolved mainly in the first stage, alkyl-aromatics (e.g., toluene) in the second. Although the addition of some metal oxides results in an overall suppression of aromatic hydrocarbons, the unsubstituted aromatics are much more suppressed with respect to alkyl-aromatics. Furthermore, the formation of ZnCl2 and SnCl4 was revealed by the mass spectra of PVC–metal oxide pyrolysates. This suggests that, at least in these two cases, metal chlorides are responsible for aromatic hydrocarbon suppression. With this information a detailed reaction mechanism could be formulated for the thermal degradation of PVC. 相似文献
946.
Giorgio Talenti 《Annali di Matematica Pura ed Applicata》1965,69(1):285-304
Sunto Si considera una equazione lineare a derivate parziali di tipo ellittico del secondo ordine, a coefficienti reali misurabili.
Con una ipotesi conveniente sugli autovalori della forma quadratica associata, si dimostrano una limitazione a priori per
soluzioni dotate di derivate seconde di quadrato sommabile, e un teorema di esistenza-unicità per il problema di Dirichlet.
Questo lavoro fa parte dell'attività del gruppo di ricerca n. 23 del C. N. R., a. a. 1964–1965. 相似文献
947.
948.
Giorgio Pidello Wlodzimierz M. Tulczyjew 《Annali di Matematica Pura ed Applicata》1987,147(1):249-265
Summary The theory of derivations of differential forms, originally formulated by Frölicher and Nijenhuis [2], is generalized to include derivations which connect differential forms on two different manifolds. This generalized theory is then used to analyze derivations of direct limits of exterior algebras of forms on jet bundles. Such derivations have found applications in the analysis of Lie equations [3], [4] and in the inverse problem of the calculus of variations [6], [7], [8], [9].
This work is a part of a program conducted jointly with ProfessorBenenti at Istituto di Fisica Matematica «J. L. Lagrange» of Torino. The authors are greatly indebted to the Director of the Institute Professor D.Galletto for his interest and encouragement.This work has been supported by Gruppo Nazionale per la Fisica Matematica del Consiglio Nazionale delle Ricerche. 相似文献
Résumé On présente une généralization de la théorie des dérivations des formes extérieures, formulée par Frölicher et Nijenhuis [2], au cas des dérivations qui relient les formes extérieurs sur deux variétés différentes. On utilize ensuite cette théorie généralizée pour étudier les dérivations des limites directes des algèbres des formes extérieures sur les fibrés des jets. Ces dérivations ont été appliquées dans l'analyse des équations de Lie [3], [4] et dans le problème inverse du calcul des variations [6], [7], [8], [9].
This work is a part of a program conducted jointly with ProfessorBenenti at Istituto di Fisica Matematica «J. L. Lagrange» of Torino. The authors are greatly indebted to the Director of the Institute Professor D.Galletto for his interest and encouragement.This work has been supported by Gruppo Nazionale per la Fisica Matematica del Consiglio Nazionale delle Ricerche. 相似文献
949.
Giorgio Raspi Antonino Lo Moro Maria Spinetti 《Fresenius' Journal of Analytical Chemistry》1988,332(1):48-51
Summary Human urines contain a family of trypsin inhibitors (UTIs) in small quantities, which seem to be involved in important biological processes. A procedure for separation and quantitative determination of such endogenous inhibitors in human urine has been developed. The urine sample is adjusted to pH 8.3 and percolated through a trypsin-Sepharose 4B column: the inhibitors are eluted with acid solution. The eluate (1000 l) is analysed by RP-HPLC with programmed elution and ultraviolet detection (200 nm). Three principal peaks have been evidenced: they are due to the elution of urinary trypsin inhibitors (UTIs) having apparent m.w. of ca. 6000, 72000, 18000 daltons, respectively. Characteristics of the procedure are: limited sample volume (ca. 200 ml) and recovery of the global inhibition activity (95%). For each UTI determination reproducibility and linearity ranges are reported.
Trennung und Bestimmung von Trypsin-Inhibitoren im Harn durch Umkehrphasen-HPLC相似文献
950.
Sergio Di Liberto Franco Meddi Giorgio Romano Giovanni Rosa Claudio Sgarbi 《Nuclear Physics A》1978,296(3):519-532
The disintegration of aluminium nuclei by 800 MeV electrons is studied using plastic detectors. Angular and energy distributions of emitted Li, Be and B isotopes are presented. The compatibility of the results with a two-stage process (cascade and evaporation) is studied with the aid of a Monte Carlo calculation. 相似文献