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141.
Jaromír Plešek Jan Machá?ek Ivana Císa?ová 《Journal of organometallic chemistry》2007,692(22):4801-4804
The synthesis of a new, paramagnetic closo-[(8-(-CH2CH2O)2-1,2-C2B9H10)(1′,2′-C2B9H11)-3,3′-Fe]0 (3) is reported. This compound can serve as a versatile building block for construction of both anionic and zwitterionic derivatives, as exemplified by the synthesis of a series of compounds of general formula closo-[(8-X-(CH2CH2O)2-1,2-C2B9H10)(1′,2′-C2B9H11)-3,3′-Fe], bearing organic end groups (X = NC5H5 (4), (C6H5)3P (5), OH (6), and 2-O(1-CH3O-C6H4) (7)) attached to the cluster by a diethyleneglycol spacer. Molecular structures of 3, 4, 5 and 7 were determined by single-crystal X-ray diffraction analysis and by the long-time neglected method of paramagnetic, high field NMR (1H, 13C and 11B) spectroscopy. 相似文献
142.
Ivana Generali Mekini Martina agalj Giulia Tabanelli Chiara Montanari Federica Barbieri Danijela Skroza Vida imat 《Molecules (Basel, Switzerland)》2021,26(21)
Marine macroalgae are well known to release a wide spectrum of volatile organic components, the release of which is affected by environmental factors. This paper aimed to identify the essential oil (EO) compounds of the brown algae Cystoseira compressa collected in the Adriatic Sea monthly, from May until August. EOs were isolated by hydrodistillation using a Clavenger-type apparatus and analyzed by gas chromatography coupled with mass spectrometry (GC–MS). One hundred four compounds were identified in the volatile fraction of C. compressa, accounting for 84.37–89.43% of the total oil. Samples from May, June, and July were characterized by a high share of fatty acids (56, 69, and 34% respectively) with palmitic acid being the dominant one, while in the August sample, a high content of alcohols (mainly phytol and oleyl alcohol) was found. Changes in the other minor components, which could be important for the overall aroma and biological activities of the algal samples, have also been noted during the vegetation periods. The results of this paper contribute to studies of algal EOs and present the first report on C. compressa EOs. 相似文献
143.
On the field method in non-holonomic mechanics 总被引:1,自引:0,他引:1
This paper deals with the generalization of the field method to non-holonomic systems whose motion is subject to either non-linear constraints or those of a higher order, while their motion is modeled by the generalized Lagrange equations of the second kind. Two examples are given to illustrate the theory.The project supported by the Ministry of Science, Technologies and Development, Republic of Serbia (1874) 相似文献
144.
Gabriela Kuzderov Michaela Rendoov Rbert Gyepes Simona Sovov Danica Sabolov Mria Vilkov Petra Olejníkov Ivana Ba
ov Simonida Stoki
Martin Kello Zuzana Vargov 《Molecules (Basel, Switzerland)》2021,26(21)
Three silver(I) dipeptide complexes [Ag(GlyGly)]n(NO3)n (AgGlyGly), [Ag2(GlyAla)(NO3)2]n (AgGlyAla) and [Ag2(HGlyAsp)(NO3)]n (AgGlyAsp) were prepared, investigated and characterized by vibrational spectroscopy (mid-IR), elemental and thermogravimetric analysis and mass spectrometry. For AgGlyGly, X-ray crystallography was also performed. Their stability in biological testing media was verified by time-dependent NMR measurements. Their in vitro antimicrobial activity was evaluated against selected pathogenic microorganisms. Moreover, the influence of silver(I) dipeptide complexes on microbial film formation was described. Further, the cytotoxicity of the complexes against selected cancer cells (BLM, MDA-MB-231, HeLa, HCT116, MCF-7 and Jurkat) and fibroblasts (BJ-5ta) using a colorimetric MTS assay was tested, and the selectivity index (SI) was identified. The mechanism of action of Ag(I) dipeptide complexes was elucidated and discussed by the study in terms of their binding affinity toward the CT DNA, the ability to cleave the DNA and the ability to influence numbers of cells within each cell cycle phase. The new silver(I) dipeptide complexes are able to bind into DNA by noncovalent interaction, and the topoisomerase I inhibition study showed that the studied complexes inhibit its activity at a concentration of 15 μM. 相似文献
145.
Radmila Krupkov Jan Fbry Pemysl Vank Ivana Císaov 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(8):i79-i82
The structures of two modifications, (I) and (II), of potassium dihydrogenphosphate–hydrofluoric acid (1/1), KH2PO4·HF, were determined at 250 and 150 K, and at 292 and 150 K, respectively. Modifications (I) and (II) crystallize from stoichiometric aqueous solutions at 295 (1) and 308 (3) K, respectively. The H atoms were located clearly from the difference Fourier maps in each modification. The two modifications differ mainly in the arrangement of the dihydrogenphosphate anions, i.e. (I) contains looped dimeric and tetrameric units of the dihydrogenphosphate ions, whereas (II) contains two types of looped tetrameric unit. In addition, both structures contain a very short F—H⃛O hydrogen bond (2.38–2.40 Å). The K+ ions are coordinated by O and F atoms, with similar K⃛O and K⃛F distances in both modifications. 相似文献
146.
Petr Holý Jií Zvada Ivana Císaov Jaroslav Podlaha 《Angewandte Chemie (International ed. in English)》1999,38(3):381-383
D 4 ‐symmetric chiral hydrogen‐bonded cyclotetramers (see the structure in the picture) are present in the self‐assembled achiral title compound in the solid state. The unilayered network set up from the chiral “square” blocks is achiral as a consequence of the crystal symmetry. 相似文献
147.
Iva ikuten Petra tambuk Jasminka Karoglan Konti Edi Maleti Ivana Tomaz Darko Preiner 《Molecules (Basel, Switzerland)》2021,26(23)
(1) Background: Solid phase microextraction (SPME)-Arrow is a new extraction technology recently employed in the analysis of volatiles in food materials. Grape volatile organic compounds (VOC) have a crucial role in the winemaking industry due to their sensory characteristics of wine.; (2) Methods: Box–Behnken experimental design and response surface methodology were used to optimise SPME-Arrow conditions (extraction temperature, incubation time, exposure time, desorption time). Analyzed VOCs were free VOCs directly from grape skins and bound VOCs released from grape skins by acid hydrolysis.; (3) Results: The most significant factors were extraction temperature and exposure time for both free and bound VOCs. For both factors, an increase in their values positively affected the extraction efficiency for almost all classes of VOCs. For free VOCs, the optimum extraction conditions are: extraction temperature 60 °C, incubation time 20 min, exposure time 49 min, and desorption time 7 min, while for the bound VOCs are: extraction temperature 60 °C, incubation time 20 min, exposure time 60 min, desorption time 7 min.; (4) Conclusions: Application of the optimized method provides a powerful tool in the analysis of major classes of volatile organic compounds from grape skins, which can be applied to a large number of samples. 相似文献
148.
Pavić Kristina Rajić Zrinka Michnová Hana Jampílek Josef Perković Ivana Zorc Branka 《Molecular diversity》2019,23(3):657-667
Molecular Diversity - Here, we describe design and synthesis of twelve novel compounds bearing primaquine motif and hydroxy- or halogenamine linked by an urea or bis-urea spacer. Preparation of... 相似文献
149.
The Einstein evolution of a dust shell universe with spatial spherical symmetry is analyzed. The implicit and parametric solutions
of Tolman–Bondi equations are proposed in order to show its agreement with the rectilinear solutions of Kepler’s problem.
Finally, a complete systematization of Tolman–Bondi models is obtained through the classical Weierstrass approach. 相似文献
150.
Ivana Kiov Zdenk To
ík Milo Budínský Ondej imk Radek Liboska Dominik Rejman Ondej Pa
es Ivan Rosenberg 《Tetrahedron letters》2009,50(49):6745-6747
A straightforward procedure leading to the new phosphonylating reagent, methyl 4-toluenesulfonyloxymethylphosphonate, requiring no chromatographic purification is described. This stable reagent works with the same efficiency as dimethyl and other dialkyl esters for the introduction of an O-phosphonomethyl moiety while, in contrast to dimethyl ester, it does not cause any unwanted methylation of sensitive functionalities. Its utility for the alkylation of protected nucleosides in high yield is exemplified. 相似文献