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11.
Ramirez E Cabeza M Heuze I Gutiérrez E Bratoeff E Membrillo M Lira A 《Chemical & pharmaceutical bulletin》2002,50(1):15-20
The pharmacological activity of several new pregnane derivatives 15-19 were determined on gonadectomized male hamster flank organs, seminal vesicles and in vitro conversion of testosterone (T) to dihydrotestosterone (DHT) as 5alpha-reductase inhibitors. Steroids 15-19 decreased the diameter of the pigmented spot in the flank organs as compared to the T treated animals; in this model, steroids 16 and 19 showed a higher activity than the commercially available finasteride 3. Injection of T increased the weight of the seminal vesicles. Compounds 15-19 when injected together with T decreased the weight of the seminal vesicles thus showing an antiandrogenic effect. The trienone 19 exhibited a considerably higher activity than finasteride. Steroids 15-19 inhibited the in vitro metabolism of [3H]T to [3H]DHT in seminal vesicles homogenates of gonadectomized male hamsters. Compounds 18 and 19 showed a much higher antiandrogenic effect than finasteride. This enhancement of the biological activity could probably be attributed to the coplanarity of the steroidal skeleton as previously observed by our group. The high antiandrogenic activity of the epoxy compound 16 is probably the result of the ring opening of the oxiran ring with the nucleophilic part of the enzyme 5alpha-reductase thus leading to a stable adduct with concomitant deactivation of this enzyme. 相似文献
12.
The essential features (geometries of the minima and of the saddle points, energy barriers) of the potential energy surface of the four hydrides YXH4 mentioned in the title have been determined with two basis sets, of minimal and DZ quality respectively. The importance of the different extent of the deformation of the XH4 group in the different structures of the four hydrides is brought out and discussed. The aspects of charge distribution and bonding are examined drawing on population analysis, comparison of the electrostatic molecular potentials and decomposition of the interaction energy (this last referred to the Y+ + XH
4
–
YXH4 process). The capability of XH3 in effecting the etherolytic disruption of the Y-H bond is finally brought out. 相似文献
13.
The cis-decalin based gamma-amino alcohols, 1-5, were synthesized, resolved, and employed as catalysts in the addition of organozincs to benzaldehyde. Despite large facial differentiation in the RZn adducts of the ligands, the enantioselectivities were found to be moderate. Transition structure calculations were done using several quantum chemical methods to examine the underlying causes of the selectivity for three gamma-amino alcohols, 1, 2, and 3. The tricyclic mu-oxo (6/4/4), rather than the bicyclic six-membered (6/6), transition structures were found to explain the observed enantioselectivity for 2 and 3. MP2 calculations gave the best correlation to the experimental results compared to B3LYP and HF calculations. The conformational flexibility of the chiral ligands was found to be an important factor in the selectivity. 相似文献
14.
In this paper we propose a system, based on-calculus, where the restriction of Church's to normal forms is dropped, while the monotony properties are weakened. The main feature of such a system is that the Church-Rosser property is maintained and all provable equalities between closed terms are semidecidable within it. 相似文献
15.
Almeida CM Vasconcelos MT Barbaste M Medina B 《Analytical and bioanalytical chemistry》2002,374(2):314-322
A comparison of the performance of the methodologies used in two distinct laboratories (Lab A and Lab B) for multi-element analysis in different wines was carried out. ICP-MS apparatus (quadrupole mass analyzers) of different brands as well as different wine pre-treatments were used. At Lab A, a pre-treatment by UV-irradiation was performed. At Lab B, a micro-concentric nebulizer was used for direct analysis of the wine. Twenty-six elements (Li, V, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) were measured in common at the two labs in three different wine samples (red and white Bordeaux table wines and Port wine) and the results were compared. The two methodologies provided similar LODs and similar precisions, with RSDs of 0.5-5%, for most of the elements. The recovery percentages were 85-120% at Lab A for the three wines, and 78-119% at Lab B for the Bordeaux wines, validating the accuracy of the methods used. Comparable results were obtained at both labs for ten elements (Li, V, Co, Ni, Cu, Zn, Rb, Sr, Ba, and Pb) in the three selected wines; the differences were lower than 10% in most cases. For REEs, the differences observed were slightly higher, but still in the acceptable range due to the sub-ppb levels involved. The results obtained for As and Ga were not comparable, due to methodological influence. A comparison through linear least-squares adjustment indicated that the results obtained by the two labs were linearly correlated (correlation coefficient =0.997) but statistically different as the slope was slightly, but significantly different from one, for a confidence level of 95% (the intercept was statistically identical to zero in any case). In the future, strictly more identical results can be achieved by using a reference wine sample. 相似文献
16.
The simplest chiral portion of sparteine, N,N'-dimethyl-2-endo-methylbispidine, was prepared and evaluated in the asymmetric lithiation-substitution of N-Boc-pyrrolidine. The results indicate that the complete A-ring of sparteine is essential for high levels of asymmetric induction. DFT-QSSR analyses of the diamine/Li(+) complexes and DFT calculations of the pertinent i-PrLi/diamine/N-Boc-pyrrolidine complexes are predictive and provide complementary pictures of the stereochemical features critical to this transformation. 相似文献
17.
Long chain alkanethiols self-assembled monolayers (SAMs) formed on Au microelectrodes showed higher sensitivity towards defects than the same monolayers on macroelectrodes. The analysis of cyclic voltammetry and electrochemical impedance spectroscopy (EIS) experiments performed on covered microelectrodes were consistent with the formation of pinholes of about 10 nm in diameter. Moreover, the EIS data exhibited a specific behavior that was interpreted invoking the short circuiting of the pinholes impedance by the surrounding surface of the microelectrode in the high frequency domain, whereas in the low frequencies, the surface covered by the SAM was assume to act as an insulator. 相似文献
18.
19.
Rosanna Bonaccorsi Carlo Petrongolo Eolo Scrocco Jacopo Tomasi 《Theoretical chemistry accounts》1969,15(4):332-343
The C.I. method is applied to already published double- SCF wave functions for OF2, NO
2
–
and CN–. All doubly excited configurations are considered. The second order approximation values presented for those cases are compared with the exact energy values in some minor cases. An attempt has been made to improve the rate of convergency of the process by transforming the canonical SCF occupied orbitals into localized ones and the virtual canonical orbitals into a particular type of localized orbitals. These latter show also an intuitively acceptable spatial conformation.
Work supported by the Consiglio Nazionale delie Ricerche. 相似文献
Zusammenfassung Die CI Methode wird auf bereits bekannte Doppel-Zeta-SCF-Wellenfuntionen für die Systeme OF2, NO 2 – und CN– angewandt. Dabei werden alle doppelt angeregten Konfigurationen berücksichtigt. Um die Konvergenz zu verbessern, werden versuchsweise die kanonischen und besetzten SCF-Orbitale in lokalisierte Orbitale und die virtuellen kanonischen Orbitale in einen besonderen Typ von lokalisierten Orbitalen transformiert. Die letzteren zeigen eine besonders geeignete räumliche Anpassung.
Résumé Pour un calcul de intéraction de configurations, comprenant toutes le configurations à double excitation, on a employé des fonctions d'onde SCF sur une base doublée. Pour le calcul complet on a essayé des formules d'approximation, qu'on a pu vérifier avec le calcul exact sur des cas réduits.Pour améliorer la vélocité de convergence du procés on a transformé les orbitales canoniques SCF en orbitales localisées et aprés on a construit, selon un procedé particulier, des orbitales virtuelles localisées qui montrent une conformation dans l'espace qui est intuitivement satisfaisante.
Work supported by the Consiglio Nazionale delie Ricerche. 相似文献
20.
Valentina Noemi Madia Walter Toscanelli Daniela De Vita Marta De Angelis Antonella Messore Davide Ialongo Luigi Scipione Valeria Tudino Felicia Diodata DAuria Roberto Di Santo Stefania Garzoli Annarita Stringaro Marisa Colone Magda Marchetti Fabiana Superti Lucia Nencioni Roberta Costi 《Molecules (Basel, Switzerland)》2022,27(12)
Influenza viruses are transmitted from human to human via airborne droplets and can be transferred through contaminated environmental surfaces. Some works have demonstrated the efficacy of essential oils (EOs) as antimicrobial and antiviral agents, but most of them examined the liquid phases, which are generally toxic for oral applications. In our study, we describe the antiviral activity of Citrus bergamia, Melaleuca alternifolia, Illicium verum and Eucalyptus globulus vapor EOs against influenza virus type A. In the vapor phase, C. bergamia and M. alternifolia strongly reduced viral cytopathic effect without exerting any cytotoxicity. The E. globulus vapor EO reduced viral infection by 78% with no cytotoxicity, while I. verum was not effective. Furthermore, we characterized the EOs and their vapor phase by the head-space gas chromatography–mass spectrometry technique, observing that the major component found in each liquid EO is the same one of the corresponding vapor phases, with the exception of M. alternifolia. To deepen the mechanism of action, the morphological integrity of virus particles was checked by negative staining transmission electron microscopy, showing that they interfere with the lipid bilayer of the viral envelope, leading to the decomposition of membranes. We speculated that the most abundant components of the vapor EOs might directly interfere with influenza virus envelope structures or mask viral structures important for early steps of viral infection. 相似文献