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排序方式: 共有466条查询结果,搜索用时 31 毫秒
101.
Ottaviani P Giuliano M Velino B Caminati W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):538-543
The 1:1 molecular complex between oxetane and water has been investigated by using free-jet millimeter-wave spectroscopy. The rotational spectra of five isotopomers (with H(2)O, D(2)O, DOH, HOD and H(2) (18)O) have been assigned. Partial r(0) and r(s) structures of the complex have been derived. The water moiety lies in the plane of symmetry of oxetane, with the "free" hydrogen E with respect to the ring. The oxetane ring appears to be slightly nonplanar, with the C(beta) carbon tilted on the opposite side of the water unity. The three atoms involved in the hydrogen bond adopt a linear arrangement with an O(ring).H distance of about 1.86 A, and the angle between the COC bisector and the O(ring).H bond being congruent with 106 degrees. Additionally, quantum-chemical calculations for the complex were performed and were found to be in agreement with the experimental results. 相似文献
102.
Femoni C Kaswalder F Iapalucci MC Longoni G Mehlstäubl M Zacchini S 《Chemical communications (Cambridge, England)》2005,(46):5769-5771
Carbonylation of Na2PtCl6.6H2O, as well as K2PtCl6, in water under a CO pressure of 900 mm Hg selectively and quantitatively affords [Pt3n(CO)6n]2- (n > 6) salts; conversely, their corresponding carbonylation at reduced CO pressure of 760-800 mm Hg leads to a convenient one-step synthesis of [Pt38(CO)44]2-. 相似文献
103.
Edmund Kwiatkowski Marek Kwiatkowski Aleksandra Olechnowicz Giuliano Bandoli 《Journal of chemical crystallography》1993,23(6):473-480
The Schiffbases 1,9-bis(2-pyrrolyl)-2,5,8-triazanona-1,8-diene (H2L1), 1,10-bis(2-pyrrolyl)-2,5,9-triazaundeca-l,9-diene (H2L2), and 1,11-bis(2-pyrrolyl)-6-methyl-2,6,10-triazaundeca-l,10-diene (H2L4) react with copper(II) nitrate or nickel(II) perchlorate in the presence of triethylamine to give new complexes [Cu(HL1,2,4)]NO3 and [Ni(HL1,2,4)]ClO4. The crystal structures of [Cu(HL2)]NO3 and [Ni(HL2)]CIO4 have been determined from single crystal diffractometer data and refined to finalR factors of 5.09 and 5.3%, respectively. Crystallographic data: [Cu(HL2)]NO3: monoclinic,P21/c,a=10.036(2),b=14.500(2),c=13.317(2) Å,=108.14(1)°,Z=4, andd
c
=11.427 Mg m–3; [Ni(HL2)]ClO4: monoclinic,P21/n,a=10.578(3),b=13.953(3),c=12.394(4) Å,=93.78(2)°,Z=4, andd
c
=1.549 Mg m–3. In both the structures the potentially pentadentate ligand (HL2)– acts as a tetradentate one leaving one pyrrole group uncoordinated. Interesting is the metal dependent sequence of the three chelate rings. While the Ni (II) ion coordinates the (HL2)– ligand to form a 5-5-6-membered ring system, the ring arrangement in the copper complex is of the 5-6-5 type. 相似文献
104.
The hydrogen-bonded complex cyclobutanone-water has been studied by Fourier-transform molecular-beam microwave spectroscopy in the frequency range of 6-18.5 GHz. The rotational spectra of ten isotopomers have been assigned and measured. Five of them have been obtained from different isotopic species (or configurations) of water (H2O, D2O, DOH, HOD, and H2 18O). The remaining five correspond to the four singly substituted 13C and to the 18O species of cyclobutanone, observed in natural abundance. For all species the inertial defect is in the range from -10.44 to -10.50 uA2, showing that the cyclobutanone frame is effectively planar and that the water molecule is coplanar to this frame. The hydrogen bond, almost linear, is formed between a water proton and one of the lone pairs of the cyclobutanone oxygen. 相似文献
105.
Correlation between indoor and outdoor levels of BTX (benzene, toluene and the sum of ethyl benzene, o-xylene, m-xylene and p-xylene) has been investigated at thirteen homes, thirteen classrooms and related outdoor atmospheres. Non smoking people and low polluted sites were chosen for this campaign, in order to highlight if commonly used domestic materials could act as internal sources. Data, obtained by employing long-term diffusive samplers over a three-month period, are compared with a parallel experiment showing the day-night indoor/outdoor trend. The obtained results let us conclude that there is evidence of internal sources at homes whilst in the schools depletion phenomena prevail, probably due to the walls adsorption. 相似文献
106.
The three-dimensional structure of an optically active substituted s-triazine derivative, 2-chloro-4-methoxy-6-[(R)-1-phenylethylamino]-1,3,5-triazine,
has been studied by conformational analysis using density functional theory (DFT) both in vacuo and in acetonitrile solution
in the polarizable continuum model integral equation formalism framework. Time-dependent DFT methods have been used to investigate
the molecular electronic CD and absorption UV spectra. Comparison with experimental results allowed the reliability of the
theoretical predictions to be enhanced and suggested a possible interpretation of the measured data.
Electronic Supplementary Material The online version of this article doi:contains supplementary material, which is available to authorized users. 相似文献
107.
Gian Maria D'Amici Anna Maria Timperio Federica Gevi Giuliano Grazzini Lello Zolla 《Electrophoresis》2010,31(16):2730-2739
Factor VIII is an important glycoprotein involved in hemostasis. Insertion of expression vectors containing either the full‐length cDNA sequence of human factor VIII (FLrFVIII) or B‐domain deleted (BDDrFVIII) into mammalian cell lines results in the production of recombinant factor VIII (rFVIII) for therapeutic usage. Three commercially available rFVIII concentrates (Advate®, Helixate NexGen® and Refacto®), either FLrFVIII or BDDrFVIII, were investigated by 1‐ and 2‐DE and MS. The objective of this study was to compare the heterogeneity and the high purity of both rFVIII preparations before and after thrombin digestion. In particular, the 2‐D gel was optimized to better highlight the presence of contaminants and many unexpected proteins. Recombinant strategies consisting of insertion of expression vectors containing BDDrFVIII and FLrFVIII resulted in homogeneous and heterogeneous protein products, respectively, the latter consisting in a heterogeneous mixture of various B‐domain‐truncated forms of the molecule. Thrombin digestion of all the three rFVIII gave similar final products, plus one unexpected fragment of A2 domain missing 11 amino acids. Regarding the contaminants, Helixate NexGen® showed the presence of impurities, such as Hsp70 kDa, haptoglobin and proapolipoprotein; Refacto® showed glutathione S‐transferase and β‐lactamase, whereas Advate® apparently did not contain any contaminants. The proteomic approach will contribute to improving the quality assurance and manufacturing processes of rFVIII concentrates. In this view, the 2‐DE is mandatory for revealing the presence of contaminants. 相似文献
108.
Giuliano Augusti 《Meccanica》1970,5(2):74-84
Summary The one-degree-of-freedom response of rigid-plastic structures is investigated for a variety of single-parameter dynamic loading-functions. Specific results, valid for any structure under the set assumptions, are obtained for single-pulse and periodic loading. The possibility of linear strain-hardening or reduction of strength with deformation is introduced. In the concluding section, the results are reviewed, and possible future researches are indicated.
(on leave at the Division of Engineering, Brown University, Providence, R. I., 1968/69). 相似文献
Sommario Si sviluppa uno studio teorico del comportamento di strutture rigido-plastiche sottoposte a vari tipi di carichi dinamici; sia la deformazione che il carico si suppongono dipendenti da un singolo parametro, funzione del tempo. Si approfondisce lo studio dei carichi impulsivi e periodici, per cui si forniscono risultati più dettagliati (p. es. riguardo alla più pericolosa forma dell'impulso, ed allastabilizzazione delle oscillazioni sotto carichi periodici), validi per qualsiasi struttura che rispetti le ipotesi. Si introduce quindi la possibilità di variazione (in aumento o in diminuzione) della resistenza con la deformazione, e si studia in particolare la possibilità di completocollasso. Infine, nel paragrafo conclusivo si riassumono e discutono i risultati ottenuti, e si indicano alcuni possibili sviluppi di questa ricerca.
(on leave at the Division of Engineering, Brown University, Providence, R. I., 1968/69). 相似文献
109.
110.
All possible combinations of stable dihedral values have been considered in vacuo at the B3LYP/6-31G level for 3,9-dihydroxy-4,8-diprenylpterocarpan (erybraedin C), whose hydroxy out-out conformation had been examined earlier together with the conformational preferences of 3,9-dimethoxy-4-prenylpterocarpan (bitucarpin A) at the same level (Phys. Chem. Chem. Phys. 2004, 6, 2849). The structure with O5 trans with respect to H6a (O(t)) is about 2 kcal/mol less stable in vacuo than that with one of the H6 trans to it (H(t)); in aqueous solution its energy gap is nearly conserved. The in-in arrangement of the hydroxyl groups of erybraedin turns out to be preferred in vacuo (even considering zero point and thermal effects), where pseudo H-bonds are formed between hydroxy hydrogens and pi electron distributions of prenyl groups. The continuum solvent effect (water) at the IEF-PCM/B3LYP/6-31G level on the relative stability of the various rotamers is very limited both on bitucarpin and erybraedin. Considering the dihydrated derivatives, significant differences in the solvation energy are found between the distinct hydration sites, increasing in the order: methoxy O, ring O, hydroxy O, and hydroxy H. In hydroxy-water interactions, in fact, water prefers to behave as an H-bond acceptor unless nearby bulky groups prevent its approach. Interestingly enough, a bridging water molecule between the hydroxy H of erybraedin and the prenyl group can be found. The inclusion of BSSE corrections in hydroxy-water interactions decidedly favors out-out hydrated arrangements, followed by out-in and in-out ones. Bulk solvent effects with IEF-PCM about the dihydrated systems almost invert the stability order found in vacuo. When a four-water cluster is considered using QM methods, waters gather in H-bonded pairs around the solute OH groups. MD simulations, carried out on a pterocarpan solute (J. Phys. Chem. B 2005, 109, 16918), supply water adducts consistent with a liquid state that have also been embedded in the continuum solvent. 相似文献