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Khoroshko LO Takhistov VV Petrova VN Viktorovskii IV Lahtiperä M Paasivirta J 《European journal of mass spectrometry (Chichester, England)》2004,10(5):731-736
Structures of six cyclic polysulfides, previously unknown as organic environmental pollutants, were analyzed from a sediment sample from the Eastern Gulf of Finland. The determinations were done by gas chromatography connected to mass spectrometry. High resolution (HRMS) measurements of the isotopic composition of four compounds could be done to confirm their molecular formulae. Total low resolution (LRMS) spectra were used to elucidate structures of all six compounds by thermochemical approach, application of fragmentation rules and by ICLU simulation of the spectra. The compounds were deduced to be (in the order of GC- retention) 1,2,4-trithiacycloheptane, tetrathiacyclopentane, 1,2,4,5-tetrathia-cyclohexane, 1,2,3,4- tetrathiacycloheptane, 1,2,3,4-tetrathiacyclohexane and 1,2,4,6-tetrathiacyclooctane. 相似文献
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Stereoselective Synthesis and Retentive Trapping of α‐Chiral Secondary Alkyllithiums Leading to Stereodefined α,β‐Dimethyl Carboxylic Esters 下载免费PDF全文
Varvara Morozova Dr. Kohei Moriya Dr. Peter Mayer Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9962-9965
The treatment of α‐chiral secondary alkyl iodides with tBuLi at ?100 °C leads to the corresponding secondary alkyllithiums with high retention of configuration. Subsequent quenching with various electrophiles such as Bu2S2, DMF, MeOB(OR)2, or Et2CO provides the desired products with retention of configuration. Furthermore, a transmetalation with CuBr?P(OEt)3 also allows retentive trapping with acid chlorides and ethylene oxide. The quenching of the resulting alkyllithiums with ClCO2Et furnishes stereoselectively syn‐ and anti‐ethyl‐2,3‐dimethyl ester carboxylates (d.r.>94 %). Related esters bearing three adjacent stereo‐controlled centers (stereotriads) have also been prepared. This method has been applied to the synthesis of the ant pheromone (±)‐lasiol in 26 % overall yield (four steps) with d.r.=97:3 starting from commercially available cis‐2,3‐epoxybutane. 相似文献
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Varvara S. Stafeeva Alexander S. Mitiaev Artem M. Abakumov Alexander A. Tsirlin Artem M. Makarevich Evgeny V. Antipov 《Polyhedron》2007,26(18):5365-5369
Tin(II) acetate was prepared and its crystal structure was solved from X-ray powder diffraction data. Tin(II) acetate adopts a polymeric structure consisting of infinite Sn(CH3COO)2 chains running along the c-axis which are packed into groups of four. The acetate groups bridge the Sn atoms along the chains. The Sn atoms are asymmetrically surrounded by four oxygen atoms with two short Sn–O distances (2.170(6), 2.207(6) Å) and two longer ones (2.293(7), 2.372(8) Å). The coordination environment of the Sn atoms is completed up to a strongly distorted trigonal bipyramid SnO4E by the sterically active lone electron pair E. The coordination environment of the Sn atoms is virtually identical for Sn(CH3COO)2 in the gaseous and solid phase: the two short Sn–O bonds and the lone electron pair are located in the equatorial plane of the trigonal bipyramid and the two longer Sn–O bonds are directed towards the apical vertexes. Localization of the lone electron pair on Sn(II) was confirmed by electron localization function (ELF) analysis. The polymeric nature of the tin(II) acetate crystal structure was confirmed by a MALDI-TOF experiment. 相似文献
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Journal of Fourier Analysis and Applications - Let G be a discrete group, let $$p\ge 1$$, and let $$\omega $$ be a weight on G. Using the approach from Gröchenig and Klotz (J Lond Math Soc (2)... 相似文献
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Varvara Paderno Vladimir Filippov Alfred Liashchenko 《Journal of solid state chemistry》2004,177(2):523-528
We studied the directional crystallization of different compositions in B4C-NbB2 and B4C-MoB2 systems. The eutectic compositions for both systems are evaluated. It is shown that in the first system the rod-like eutectic structure is formed, in second, the “Chinese hieroglyphics”. In both cases high hardness and high microplasticity are observed, which are much more than for individual component phases. These compositions may be considered as a new kind of self-strengthening composite materials. 相似文献
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Dominic C. Castell Varvara I. Nikolayenko Debobroto Sensharma Kyriaki Koupepidou Katherine A. Forrest Carlos J. Solanilla-Salinas Brian Space Leonard J. Barbour Michael J. Zaworotko 《Angewandte Chemie (International ed. in English)》2023,62(19):e202219039
An emerging strategy in the design of efficient gas storage technologies is the development of stimuli-responsive physisorbents which undergo transformations in response to a particular stimulus, such as pressure, heat or light. Herein, we report two isostructural light modulated adsorbents (LMAs) containing bis-3-thienylcyclopentene (BTCP), LMA-1 [Cd(BTCP)(DPT)2] (DPT=2,5-diphenylbenzene-1,4-dicarboxylate) and LMA-2 [Cd(BTCP)(FDPT)2] (FDPT=5-fluoro-2,diphenylbenzene-1,4-dicarboxylate). Both LMAs undergo pressure induced switching transformations from non-porous to porous via adsorption of N2, CO2 and C2H2. LMA-1 exhibited multi-step adsorption while LMA-2 showed a single-step adsorption isotherm. The light responsive nature of the BTPC ligand in both frameworks was exploited with irradiation of LMA-1 resulting in a 55 % maximum reduction of CO2 uptake at 298 K. This study reports the first example of a switching sorbent (closed to open) that can be further modulated by light. 相似文献
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Tsilia V Devreese B de Baenst I Mesuere B Rajkovic A Uyttendaele M Van de Wiele T Heyndrickx M 《Analytical and bioanalytical chemistry》2012,404(6-7):1691-1702
Enterotoxins produced by different species of the Bacillus cereus group, such as cytotoxin K1 (CytK1) and non-haemolytic enterotoxin (NHE), have been associated with diarrhoeal food poisoning incidents. Detection of CytK1 is not possible with commercial assays while NHE is recognised by an immunological kit (TECRA) that does not specifically target this protein because it is based on polyclonal antibodies. It is evident that the lack of suitable tools for the study of enterotoxins hampers the possibilities for accurate hazard identification and characterisation in microbial food safety risk assessment. We applied matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS) for the detection of CytK1 and NHE produced by pathogenic strains of the B. cereus group using protein digests from 1D gel electrophoresis. Secretion of CytK1 and two of the three components of NHE was confirmed in supernatants of different B. cereus cultures. For each protein, we introduce biomarkers that could be used for the screening of food poisoning or food/environmental isolates that can secrete enterotoxins. For example, tryptic peptides of 2,310.2 and 1,192.5?Da (calculated mass) can be indicators for CytK1 and NheA, respectively, although a simultaneous detection of other enterotoxin-specific peptides is recommended to assure the presence of a toxin in an unknown sample. Comparison of MALDI-TOF/MS with the TECRA kit showed that our methodological strategy performed well and it had the competitive advantage of specifically detecting NheA. Therefore, MALDI-TOF/MS can be successfully incorporated into risk assessment procedures in order to determine the involvement of strains of the B. cereus group in foodborne outbreaks, including the recently described cytK1 producing species, Bacillus cytotoxicus. 相似文献
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Nikolaos Naziris Natassa Pippa Varvara Chrysostomou Stergios Pispas Costas Demetzos Marcin Libera Barbara Trzebicka 《Journal of nanoparticle research》2017,19(10):347
Different in nature biomaterials, which are used for the development of drug delivery nanosystems, could be mixed, in order to produce chimeric/mixed nanostructures. Their morphological characteristics and biophysical properties depend on the degree of association and interactions between the self-assembling biomaterials. For the purpose of this study, chimeric nanosystems composed of phospholipid and amphiphilic diblock copolymers were developed, at different molar ratios. Light scattering and imaging techniques were employed, in order to extract information on the nanostructure physicochemical characteristics and their morphology. Certain morphological characteristics were assessed for vesicle membranes, which are considered to be of paramount importance for their fate inside the physiological environment and their biophysical behavior. Besides vesicles, a variety of structures appeared in the phospholipid/copolymer chimeric systems, depending on both the composition and the concentration of the utilized polymer, declaring the lyotropic effect on the self-assembly of the biomaterials. The size range of most objects, including vesicles, was around 100 nm. Membrane irregularities, such as domains and rafts, are considered as functional biophysical factors, rendering liposomes appropriate artificial models for approaching various diseases on the level of living cell membranes. Such information is of paramount importance for the utilization of chimeric nanostructures in drug delivery and in therapy. 相似文献