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41.
Matthias Engleder Dr. Tea Pavkov‐Keller Dr. Anita Emmerstorfer Altijana Hromic Sabine Schrempf Dr. Georg Steinkellner Dr. Tamara Wriessnegger Prof. Erich Leitner Dr. Gernot A. Strohmeier Dr. Iwona Kaluzna Dr. Daniel Mink Dr. Martin Schürmann Dr. Silvia Wallner Prof. Peter Macheroux Prof. Karl Gruber Dr. Harald Pichler 《Chembiochem : a European journal of chemical biology》2015,16(12):1730-1734
Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration. 相似文献
42.
Terry D. Humphries Keelie T. Munroe Tamara M. DeWinter Craig M. Jensen G. Sean McGrady 《International Journal of Hydrogen Energy》2013
Aluminum hydride (alane; AlH3) has been identified as a leading hydrogen storage material by the US Department of Energy. With a high gravimetric hydrogen capacity of 10.1 wt.%, and a hydrogen density of 1.48 g/cm3, AlH3 decomposes cleanly to its elements above 60 °C with no side reactions. This study explores in detail the thermodynamic and spectroscopic properties of AlH3; in particular the α, α′ and γ polymorphs, of which α′-AlH3 is reported for the first time, free from traces of other polymorphs or side products. Thermal analysis of α-, α′-, and γ-AlH3 has been conducted, using DSC and TGA methods, and the results obtained compared with each other and with literature data. All three polymorphs were investigated by 1H MAS-NMR spectroscopy for the first time, and their 27Al MAS-NMR spectra were also measured and compared with literature values. AlH3·nEt2O has also been studied by 1H and 27Al MAS-NMR spectroscopy and DSC and TGA methods, and an accurate decomposition pathway has been established for this adduct. 相似文献
43.
Archambault D Munzner T Auber D 《IEEE transactions on visualization and computer graphics》2006,12(5):813-820
We extend the popular force-directed approach to network (or graph) layout to allow separation constraints, which enforce a minimum horizontal or vertical separation between selected pairs of nodes. This simple class of linear constraints is expressive enough to satisfy a wide variety of application-specific layout requirements, including: layout of directed graphs to better show flow; layout with non-overlapping node labels; and layout of graphs with grouped nodes (called clusters). In the stress majorization force-directed layout process, separation constraints can be treated as a quadratic programming problem. We give an incremental algorithm based on gradient projection for efficiently solving this problem. The algorithm is considerably faster than using generic constraint optimization techniques and is comparable in speed to unconstrained stress majorization. We demonstrate the utility of our technique with sample data from a number of practical applications including gene-activation networks, terrorist networks and visualization of high-dimensional data 相似文献
44.
Tamara Elzein Ahmad Fahs Amina Elhiri Bénédicte Lepoittevin Philippe Roger 《The Journal of Adhesion》2013,89(5):416-432
The present paper focuses on a simplified method to study the orientation and the anisotropy of two different alkanethiols self-assembled monolayers on gold surfaces. The alkanethiols of interest vary only by their terminal functionalities (COOH and COOCH3), thus allowing one to highlight the influence of these ending chemical groups on the final orientation of the adsorbed molecules. 11-Mercaptoundecanoic acid [HS-(CH2)10-COOH] and the methyl-11-mercaptoundecanoate [HS-(CH2)10-COOCH3] were grafted under adequate conditions to obtain a high grafting density on gold substrates. These latter, before and after the alkanethiol adsorption, were analyzed mainly by the polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) technique to access orientation angles, and by atomic force microscopy (AFM) to check the homogeneity of the grafted layer. By applying an original PM-IRRAS simplified method, the results showed an orientation closer to the normal of the surface plane in the case of the acid thiol compared with the ester one, which is probably because of the lateral hydrogen bonds established between the adjacent COOH functions. This method offers a direct and simple way to quantify the orientation angles in the alkanethiol nanofilms. 相似文献
45.
46.
Nadezhda S. Tian Tamara K. Meleshko Galina A. Polotskaya Iosif V. Gofman Anna V. Kashina Nina V. Kukarkina Elena N. Vlasova Zoolsho F. Zoolshoev Alexander V. Yakimansky 《Polymer Engineering and Science》2020,60(3):481-490
Composite films based on polyamide (poly(m-phenylene-iso-phthalamide)) (PA) and a brush-like polymer with polyimide (PI) backbone and side poly(methyl methacrylate) chains (PI-PMMA) were prepared by mixing individual solutions of PA and PI-PMMA and subsequent film casting. Macromolecular brushes with the same backbone length and density of side chains but with various lengths of side PMMA chains were synthesized via activator generated by electron transfer atom transfer radical polymerization. Interactions between PA and PI-PMMA, as well as distribution of PI-PMMA filler inside the PA matrix, were studied by viscometry, dynamic light scattering, differential scanning calorimetry, scanning electron microscopy, and IR spectroscopy. The mechanical properties of polymer samples were also investigated. Microphase separation was revealed in PA/PI-PMMA films. The length of side chains influences interactions between PA and PI-PMMA. At the same time, the degree of reduction in the rigidity parameters and in the elasticity parameter depends on the side chain length. Diffusion membranes were prepared on the basis of compositions with the best mechanical properties; these membranes proved to be highly efficient in pervaporation of methanol–hexane mixture. It was established that the fluxes and separation factors of the studied membranes are several times higher as compared to the corresponding characteristics of known commercial membranes. POLYM. ENG. SCI., 60:481–490, 2020. © 2019 Society of Plastics Engineers 相似文献
47.
Svetlana Pavlova Tamara Kharlamova Vladislav Sadykov Tamara Krieger Vitaly Muzykantov Yulia Bespalko 《传热工程》2013,34(11-12):904-916
Mixed ionic?electronic conducting nanocomposites comprising complex oxides - perovskite (lanthanum-strontium nickelate-ferrite [LSFN]) and gadolinium-doped ceria (GDC) have been prepared via ultrasonic dispersion of nanocrystalline powders of LSFNx and GDC in organic solvent with addition of surfactant, followed by drying and sintering up to 1300°C. Their structural and surface properties have been studied by x-ray diffraction, ultraviolet–visible (UV-vis) electron spectroscopy, transmission electron microscopy with elemental analysis, and x-ray photoelectron spectroscopy. Results of impedance spectroscopy, oxygen isotope exchange, O2 temperature-programmed desorption, weight, and conductivity relaxation experiments have revealed a strong positive effect of perovskite?fluorite nanodomain interfaces in composite on the oxygen mobility and reactivity. Testing in wet H2/air feeds for a button-size cell with functionally graded LSFN0.4–GDC cathode layer supported on a thin YSZ layer covering Ni/YSZ cermet has demonstrated high and stable performance, promising for the practical application in the intermediate temperature range. 相似文献
48.
This study examined connections between college students' adjustment and success and characteristics of their relationships with their parents. A sample of 236 students completed the Student Attitudes and Perceptions Survey, a 135-item anonymous self-report instrument. Students' grades, confidence level, persistence, task involvement, and rapport with their teachers were generally predicted by both current and childhood levels of parental autonomy granting, demandingness, and supportiveness. Ratings of parenting characteristics were equally predictive of adjustment and success among students living with their parents and those living on their own. They were somewhat less predictive of seniors' adjustment and success than they were for freshmen, sophomores, and juniors. These findings suggest that parenting style continues to play an important role in the academic lives of college students. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
49.
Omari Mukbaniani Tamara Tatrishvili Giorgi Titvinidze Sopho Patsatsia 《应用聚合物科学杂志》2009,114(2):892-900
The synthesis of polysiloxanes with pendant unsaturated cyclic fragments have been successfully performed by hydrosilylation reactions of polymethylhydrosiloxane with 4‐vinyl‐1‐cyclohexene in the presence of platinum hydrochloric acid (0.1 M solution in THF), Karstedt's catalyst (Pt2[(VinSiMe2)2O]3) and platinum on the charcoal (5%). Reactions were carried out at various temperatures with different ratios of initial compounds. It was shown, that not all active ≡Si? H groups take part in the hydrosilylation reaction. Some kinetic parameters of reactions were studied. The synthesized oligomers were characterized by FTIR, 1H, 13C, H,H‐COSY, and C,H‐correlation NMR spectroscopy. Calculations using the quantum‐chemical semi empirical AM1 method for modeling reactions between methyldimethoxysilane [Me(MeO)2SiH] and 4‐vinyl‐1‐cyclohexene were performed to evaluate possible reaction paths. Synthesized oligomers were characterized by gel‐permeation chromatography, differential scanning calorimetric, thermogravimetric, and wide‐angle X‐ray analyses. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
50.
Tamara V. Basova Nadezhda M. Kurochkina Aslan Yu. Tsivadze Asim K. Ray 《Journal of Electronic Materials》2010,39(2):145-148
Hybrid inorganic/organic nanocomposites were produced by the exposure of spun films of octa-(benzo-15-crown-5)-substituted
phthalocyanine of Cd(II) to an environment of hydrogen sulfide gas. The formation of cadmium sulfide (CdS) quantum dots in
the metal free phthalocyanine matrix was identified in the phthalocyanine matrix from atomic force microscopy images. The
mean size of CdS quantum dots was estimated to be 2–3 nm, from optical absorption and Raman spectra for the nanocomposites. 相似文献