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171.
Janina Gabrielska Stanisaw Przestalski Adam Miszta Monika Soczyska‐Kordala Marek Langner 《应用有机金属化学》2004,18(1):9-14
Organometallic compounds are widely spread in the human environment sometimes, causing a substantial health risk. Their amphiphilic character enables them to intercalate and penetrate cell membranes, potentially affecting various vital cell functions. Compound adsorption onto the membrane depends on the compound properties, as well as on the membrane composition and state. When adsorbing onto the lipidic surface, phenyltins localize at areas where lipid bilayer organization is compatible with compound spatial requirements. The lipid bilayer is a dynamic and laterally nonuniform structure with complex local and global architecture correlated with a variety of cell functions. The selective binding of a toxic compound to selected membrane areas may, therefore, interfere with some types of cellular process. We present experimental results concerning phenyltin adsorption onto the lipid bilayer surface measured with the fluorescent probe fluorescein‐PE. Model lipid bilayers were formed from lipid mixtures mimicking various plasma membrane regions. The adsorption of Ph3SnCl and P2SnCl2 onto the phosphatidylcholine–cholesterol bilayer was qualitatively different from sphingomyelin–cholesterol. The results presented indicate that phenyltins are likely to accumulate in areas containing phosphatidylcholine, outside of lipid rafts. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
172.
New series of phenylantimony chloride and antimony chloride with Schiff base ligands, L1H and L2H having N∩S and N∩O donor systems were synthesized under microwave irradiation using a domestic microwave oven. The reaction time was brought down from hours to a few seconds with improved yield as compared with conventional heating. All the ligands and their antimony(III) derivatives were characterized on the basis of microanalysis, elemental analyses, molecular weight determinations and spectral studies including IR, NMR (1H and 13C) and electronic spectral studies. A distorted trigonal bipyramidal and pseudo‐octahedral geometry around the antimony atom was tentatively proposed for these derivatives. The compounds were screened in vitro against bacteria and fungi to test their antimicrobial property and in vivo in male albino rats to test their antifertility properties. The treatment with the ligands and their phenylantimony derivatives at dose levels of 20 mg per rat per day did not cause any significant change in body weight, but a significant reduction in the weights of reproductive organs was observed. Arrest of spermatogenesis was noted at various stages with production of primary spermatocytes (preleptotene and pachytene), secondary spermatocytes and step‐19 spermatids found to be decreased. Biochemical parameters of tissues, i.e. protein, sialic acid, cholesterol content of testes and seminal vesicular fructose also showed significant reduction. Further, the serum testosterone concentrations were also decreased after treatment with ligands and their antimony(III) derivatives. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
173.
Ivan Fortelný Monika Lapčíková Jana Mikešová Josef Juza 《Journal of Polymer Science.Polymer Physics》2009,47(21):2158-2170
The effect of a small admixture of high‐density polyethylene (HDPE) with a high or low viscosity to polystyrene/polyamide (PS/PA) blends of various compositions was studied. PS/PA blends with composition near 50/50 form sheet‐like or fiber‐like morphology at mixing that passes to the cocontinuous structure during compression molding. Ternary PS/PA/HDPE blends with PS/PA ratio about 50/50 show similar behavior. Generally, neither continuity nor shape of PS and PA phases was changed qualitatively by the addition of a small amount of HDPE. In agreement with existing rules for ternary blends, HDPE particles prefer a contact with PS phase to PA phase. On the other hand, none of these rules explains why a number of small HDPE subinclusions were dispersed into PS particles instead of HDPE‐PS core‐shell structure with a lower Gibbs free energy. Quantitative evaluation of the size of PA particles in blends with PS matrix showed that the previously proposed rule stating, that the addition of a small amount of a third immiscible component leads to a strong decrease in the size of dispersed particles, was not valid for the blends studied in this work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2158–2170, 2009 相似文献
174.
The application of the Skorokhod representation of martingales and of the local asymptotic normality to derive limit inequalities for the cost in controlled finite state Markov chains is reviewed. The inequalities are usable in self-optimizing control. The methods are taken from the references listed but, with the exception of proposition 4, the results are formulated for Markov chains for the first time. 相似文献
175.
Monika Backhaus-Ricoult 《Interface Science》1997,4(3-4):285-302
Metal precipitation occuring during internal reduction of various mixed oxides, such as magnesia or alumina, doped with more noble transition metal oxides, is investigated for different doping contents, reaction temperature and driving forces. The precipitate morphology developing inside the solid oxide matrix and the corresponding orientation relationships between the metal and the oxide phase are analysed by transmission electron microscopy. The evolution of precipitate shape across the reduction scale is interpreted in terms of ageing of the metal inclusions; the various morphologies identified are ascribed to different stages of nucleation, diffusional growth and final equilibration.Precipitate morphology is analysed in terms of diffusion-controlled growth of small metal particles in their local and long range diffusion field. The influence of interfacial energy and related anisotropy is experimentally demonstrated for selected examples. The general role played by these parameters during growth and final equilibration is also discussed. The implications of the elastic strain fields building up during growth of the metal inside the oxide matrix are analysed in view of our experimental results. Shape changes taking place during the growth process are considered to be controlled by local matter transport properties. The influence of the reaction mechanism at an atomic scale and the relative fit of the crystallographic lattices are briefly summarised. 相似文献
176.
Gregory Fridman Alexey Shereshevsky Monika M. Jost Ari D. Brooks Alexander Fridman Alexander Gutsol Victor Vasilets Gary Friedman 《Plasma Chemistry and Plasma Processing》2007,27(2):163-176
Initiation of apoptosis, or programmed cell death, is an important issue in cancer treatment as cancer cells frequently have
acquired the ability to block apoptosis and thus are more resistant to chemotherapeutic drugs. Targeted and perhaps selective
destruction of cancerous tissue is desirable for many reasons, ranging from the enhancement of or aid to current medical methods
to problems currently lacking a solution, i.e., lung cancer. Demonstrated in this publication is the inactivation (killing)
of human Melanoma skin cancer cell lines, in vitro, by Floating Electrode Dielectric Barrier Discharge (FE-DBD) plasma. Not
only are these cells shown to be killed immediately by high doses of plasma treatment, but low doses are shown to promote
apoptotic behavior as detected by TUNEL staining and subsequent flow cytometry. It is shown that plasma acts on the cells directly and not by
“poisoning” the solution surrounding the cells, even through a layer of such solution. Potential mechanisms of interaction
of plasma with cells are discussed and further steps are proposed to develop an understanding of such systems. 相似文献
177.
Influence of the soft segment length on the properties of water‐cured poly(carbonate‐urethane‐urea)s
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Magdalena M. Mazurek Karolina Tomczyk Monika Auguścik Joanna Ryszkowska Gabriel Rokicki 《先进技术聚合物》2015,26(1):57-67
Poly(carbonate‐urethane‐urea)s (PCUU) based on oligocarbonate diols (Mn ≈ 2000) with different length of the hydrocarbon chain as soft segments were synthesized and investigated. Carbonate oligomerols were obtained in a two‐step method from dimethyl carbonate (DMC) and linear α,ω‐diols (1,4‐butanediol, 1,5‐pentanediol, 1,6‐hexanediol, 1,9‐nonanediol, 1,10‐dekanediol and 1,12‐dodecanediol). Oligo(trimethylene carbonate) diol was synthesized using ring‐opening polymerization of trimethylence carbonate. PCUUs were obtained by prepolymer method using isophorone diisocyanate (IPDI) and water as a chain extender. Changes in polymers properties with increase of methylene group number between carbonate linkages were investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile strength and hardness measurements. The thermal stability was also analyzed by means of thermogravimetric analysis (TGA). Based on FTIR analysis influence of methylene groups number between carbonate linkages on phase separation and concentration of allophanate and biuret groups in the samples were investigated. The obtained poly(carbonate‐urethane‐urea)s exhibited very good mechanical properties. Tensile strength and elongation at break were 40 MPa and 400–600%, respectively, depending on the oligocarbonate used. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
178.
Structural Characterization of O‐ and C‐Glycosylating Variants of the Landomycin Glycosyltransferase LanGT2
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Dr. Heng Keat Tam Dr. Johannes Härle Dr. Stefan Gerhardt Prof. Dr. Jürgen Rohr Guojun Wang Prof. Dr. Jon S. Thorson Dr. Aurélien Bigot Monika Lutterbeck Dr. Wolfgang Seiche Prof. Dr. Bernhard Breit Prof. Dr. Andreas Bechthold Prof. Dr. Oliver Einsle 《Angewandte Chemie (International ed. in English)》2015,54(9):2811-2815
The structures of the O‐glycosyltransferase LanGT2 and the engineered, C? C bond‐forming variant LanGT2S8Ac show how the replacement of a single loop can change the functionality of the enzyme. Crystal structures of the enzymes in complex with a nonhydrolyzable nucleotide‐sugar analogue revealed that there is a conformational transition to create the binding sites for the aglycon substrate. This induced‐fit transition was explored by molecular docking experiments with various aglycon substrates. 相似文献
179.
180.
Amir Hossein Alamdar Mehrdad Pourayoubi Anahid Saneei Michal Duek Monika Ku
erkov Margarida S. Henriques 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(9):824-833
Hirshfeld surfaces and two‐dimensional fingerprint plots are used to analyse the intermolecular interactions in two new phosphorothioic triamide structures, namely N,N′,N′′‐tris(3,4‐dimethylphenyl)phosphorothioic triamide acetonitrile hemisolvate, P(S)[NHC6H3‐3,4‐(CH3)2]3·0.5CH3CN or C24H30N3PS·0.5CH3CN, (I), and N,N′,N′′‐tris(4‐methylphenyl)phosphorothioic triamide–3‐methylpiperidinium chloride (1/1), P(S)[NHC6H4(4‐CH3)]3·[3‐CH3‐C5H9NH2]+·Cl− or C21H24N3PS·C6H14N+·Cl−, (II). The asymmetric unit of (I) consists of two independent phosphorothioic triamide molecules and one acetonitrile solvent molecule, whereas for (II), the asymmetric unit is composed of three components (molecule, cation and anion). In the structure of (I), the different components are organized into a six‐molecule aggregate through N—H...S and N—H...N hydrogen bonds. The components of (II) are aggregated into a two‐dimensional array through N—H...S and N—H...Cl hydrogen bonds. Moreover, interesting features of packing arise in this structure due to the presence of a double hydrogen‐bond acceptor (the S atom of the phosphorothioic triamide molecule) and of a double hydrogen‐bond donor (the N—H unit of the cation). For both (I) and (II), the full fingerprint plot of each component is asymmetric as a consequence of the presence of three fragments. These analyses reveal that H...H interactions [67.7 and 64.3% for the two symmetry‐independent phosphorothioic triamide molecules of (I), 30.7% for the acetonitrile solvent of (I), 63.8% in the phosphorothioic triamide molecule of (II) and 62.9% in the 3‐methylpiperidinium cation of (II)] outnumber the other contacts for all the components in both structures, except for the chloride anion of (II), which only receives the Cl...H contact. The phosphorothioic triamide molecules of both structures include unsaturated C atoms, thus presenting C...H/H...C interactions: 17.6 and 21% for the two symmetry‐independent phosphorothioic triamide molecules in (I), and 22.7% for the phosphorothioic triamide molecule of (II). Furthermore, the N—H...S hydrogen bonds in both (I) and (II), and the N—H...Cl hydrogen bonds in (II), are the most prominent interactions, appearing as large red spots on the Hirshfeld surface maps. The N...H/H...N contacts in structure (I) are considerable, whereas for (II), they give a negligible contribution to the total interactions in the system. 相似文献