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1.
Nobuoki Eshima Claudio Giovanni Borroni Minoru Tabata Takeshi Kurosawa 《Entropy (Basel, Switzerland)》2021,23(2)
This paper proposes a method for deriving interpretable common factors based on canonical correlation analysis applied to the vectors of common factors and manifest variables in the factor analysis model. First, an entropy-based method for measuring factor contributions is reviewed. Second, the entropy-based contribution measure of the common-factor vector is decomposed into those of canonical common factors, and it is also shown that the importance order of factors is that of their canonical correlation coefficients. Third, the method is applied to derive interpretable common factors. Numerical examples are provided to demonstrate the usefulness of the present approach. 相似文献
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Christian Lerner Romain Siegrist Eliane Schweizer Franois Diederich Volker Gramlich Roland Jakob‐Roetne Gerhard Zürcher Edilio Borroni 《Helvetica chimica acta》2003,86(4):1045-1062
Inhibition of the enzyme catechol O‐methyltransferase (COMT) is of significant interest in the therapy of Parkinson's disease. Described herein are structural analogs of the potent bisubstrate inhibitor (?)‐ 1 (IC50=9 nM ; Table 1) for COMT, with target modifications of the central ribose moiety. Their synthesis involves, as key intermediates, adenosine derivatives, which are transformed to the potential bisubstrate inhibitors by a similar sequence of six steps (Schemes 1–4). The compounds were submitted to an enzymatic assay for determination of their in vitro inhibitory activity against COMT, and the inhibition mechanism with respect to the binding side of the cofactor S‐adenosylmethionine (SAM) was analyzed by kinetics measurements (Fig. 3). Both binding affinity and binding mode were exceedingly sensitive towards modifications of the ribose moiety (Table 1). Removal of the 2′‐OH group upon changing from (?)‐ 1 to (?)‐ 2 (IC50=28 μM ) led to a reduction in binding affinity by more than three orders of magnitude. At the same time, competitive inhibition kinetics with respect to the SAM binding site was maintained, thereby supporting a bisubstrate binding mode. Unlike (?)‐ 2 , the dideoxyribose inhibitor (?)‐ 3 (IC50=3 μM ) showed a mixed and the cyclopentane derivative (+)‐ 4 (IC50=1 μM ) an uncompetitive inhibition mechanism with respect to the SAM binding site. In the complex of the latter, the adenine‐substituted cyclopentane ring orients most probably towards the surface of the enzyme into the surrounding solution. The enantiomeric compounds (?)‐ 5 (IC50=43 μM ) and (+)‐ 5 (IC50=141 μM ), wherein the ribose had been replaced by a pyrrolidine ring, showed only low binding affinity. 相似文献
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M. T. Valentini Ganzerli V. Crespi Caramella L. Maggi P. A. Borroni 《Journal of Radioanalytical and Nuclear Chemistry》1998,229(1-2):B39-41
Two new simple methods were studied for the analysis of radium in fresh waters by concentration and purification. Both methods
are based on the use of an inorganic selective adsorber, namely basic lead rhodizonate, LERHO, and partially reduced tin dioxide
(PRTD). The procedures were checked by using filtered fresh waters spiked with 0.1 Bq of226Ra, and in the presence of few μg/l of barium. In each experiment133Ba radioisotope was added to water samples to measure the yield of the overall procedure by γ-counting. Barium and radium
were adsorbed from basic solutions on LERHO packed chromatographic column in the first procedure, while batch experiments
were preferred for the adsorption on PRTD. After separation,226Ra and barium were eluted from the exchangers and co-precipitated onto small filters as thin film, supported on an inactive
barium sulphate substrate, to be submitted to alpha-and gamma-spectrometry. Both methods gave promising results. 相似文献
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M. T. Ganzerli-Valentini S. Meloni V. Caramella-Crespi P. A. Borroni 《Journal of Radioanalytical and Nuclear Chemistry》1976,34(1):103-112
The adsorption of about 50 ions on molybdenum dibromide, (Mo6Br8)Br4·2H2O, in nitric acid was investigated. The preparation of the adsorber and its characterization is presented and discussed. Adsorption
mechanism studies were carried out for some noble metals and chromium. Sorption cannot be ascribed to ion exchange mechanism
but to formation of insoluble species, and to settlement of few ions into surface sorption sites or into a limited number
of cavities in the cluster crystal structure of the adsorber. 相似文献
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In strip theory analysis the vessel is represented by a series of 2D transverse sections. For 2D arbitrary-shaped sections either floating in the free surface or totally submerged, a higher-order boundary element analysis has been developed to permit determination of the associated radiation and diffraction velocity potentials. In this paper the formulation of the cited interaction problems is reworked to reflect the new capability of permitting curved boundary elements to represent the geometry and a higher-order functional behaviour of the unknown velocity potentials over that geometry. This is in direct contrast to the usual technique of using straight-line geometric panels and invariant behaviour of the required potentials over these simple panels. Applications to representative sections of floating ships and the fully submerged pontoon section of a semi-submersible are presented. Within these applications the results of the standard Frank close-fit technique, of linear panels and constant behaviour, are compared with different combinations of higher-order representations of the geometry and the determined velocity potentials. Conclusions regarding the advantages and limitations of the procedures developed are discussed. 相似文献
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Lerner C Masjost B Ruf A Gramlich V Jakob-Roetne R Zürcher G Borroni E Diederich F 《Organic & biomolecular chemistry》2003,1(1):42-49
Inhibition of the enzyme catechol-O-methyltransferase (COMT) is an important approach in the treatment of Parkinson's disease. A series of new potent bisubstrate inhibitors for COMT, resulting from X-ray structure-based design and featuring adenosine and catechol moieties have been synthesised. Biological results show a large dependence of binding affinity on inhibitor preorganisation and the length of the linker between nucleoside and catechol moieties. The most potent bisubstrate inhibitor for COMT has an IC50 value of 9 nM. It exhibits competitive kinetics for the SAM and mixed inhibition kinetics for the catechol binding site. Its bisubstrate binding mode was confirmed by X-ray structure analysis of the ternary complex formed by the inhibitor, COMT and a Mg2+ ion. 相似文献
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M. T. Ganzerli-Valentini V. Caramella-Crespi S. Meloni L. Maggi P. Borroni 《Journal of Radioanalytical and Nuclear Chemistry》1977,38(1-2):513-521
Copper, iridium, platinum and gold content was determined in 15 italian chondritic meteorites by destructive neutron activation
analysis. The chemical procedure involves few steps: sample dissolution, group separation of noble metals on inorganic adsorbers
and gamma-ray spectrometry. Element content and atomic abundances (Si=106 atoms) are presented and discussed. Precision and accuracy of the analytical method are given as well. Copper, platinum and
gold content is within the reported ranges for ordinary chondrites, whereas the iridium content is located on the low side
of reported values. 相似文献