排序方式: 共有100条查询结果,搜索用时 359 毫秒
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Paula Bracco Hein J. Wijma Bastian Nicolai Jhon Alexander Rodriguez Buitrago Thomas Klünemann Agustina Vila Patrick Schrepfer Wulf Blankenfeldt Dick B. Janssen Prof. Dr. Anett Schallmey 《Chembiochem : a European journal of chemical biology》2021,22(6):1099-1110
CYP154C5 from Nocardia farcinica is a P450 monooxygenase able to hydroxylate a range of steroids with high regio- and stereoselectivity at the 16α-position. Using protein engineering and substrate modifications based on the crystal structure of CYP154C5, an altered regioselectivity of the enzyme in steroid hydroxylation had been achieved. Thus, conversion of progesterone by mutant CYP154C5 F92A resulted in formation of the corresponding 21-hydroxylated product 11-deoxycorticosterone in addition to 16α-hydroxylation. Using MD simulation, this altered regioselectivity appeared to result from an alternative binding mode of the steroid in the active site of mutant F92A. MD simulation further suggested that the entrance of water to the active site caused higher uncoupling in this mutant. Moreover, exclusive 15α-hydroxylation was observed for wild-type CYP154C5 in the conversion of 5α-androstan-3-one, lacking an oxy-functional group at C17. Overall, our data give valuable insight into the structure–function relationship of this cytochrome P450 monooxygenase for steroid hydroxylation. 相似文献
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C. Magro A. Tressaud L. Lozano N. Hudáková C. Cardinaud G. Turban 《Journal of Materials Science》1994,29(16):4225-4231
The radiofrequency plasma technique involving mixtures of CF4+O2 gases has been applied to the surface treatment of high Tc superconducting oxides (YBa2Cu3O7–). Investigation of the various experimental parameters of the process has shown that the improvement of the critical current density, J
c, mainly depends on the inlet precursor composition CF4+%O2, on the total pressure and on the reaction time. The presence of fluorine in the bulk of the ceramics has been observed from electron microprobe analysis, together with an increase of the Cu3+ content. The plasma-enhanced fluorination (PEF) treatment improves the superconducting properties of the materials: both values of the resistivity in the normal state and of the superconducting transition width are reduced and the critical transition temperature is improved by about 1 K. 相似文献
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We investigate a quantum-correction method for Monte Carlo device simulation. The method consists of reproducing quantum mechanical
density-gradient simulation by classical drift-diffusion simulation with modified effective oxide thickness and work function
and using these modifications subsequently in Monte Carlo simulation. This approach is found to be highly accurate and can
be used fully automatically in a technology computer-aided design (TCAD) workbench project. As an example, the methodology
is applied to the Monte Carlo simulation of the on-current scaling in p- and n-type MOSFETs corresponding to a 65 nm node technology. In particular, it turns out that considering only the total threshold
voltage shift still involves a significant difference to a Monte Carlo simulation based on the combined correction of oxide
thickness and work function. Ultimately, this quantum correction permits to consider surface scattering as a combination of
specular and diffusive scattering where the conservation of energy and parallel wave vector in the specular part takes stress-induced
band structure modifications and hence the corresponding surface mobility changes on a physical basis into account. 相似文献
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Akram El Hasni Stefan Pfirrmann Anett Kolander Erwin Yacoub-George Martin König Christof Landesberger Anja Voigt Gabi Grützner Uwe Schnakenberg 《Microfluidics and nanofluidics》2017,21(3):41
We present a new epoxy-based negative-tone dry film photoresist (DFR) for fabricating multilayer microfluidic devices using a lamination process combined with a standard photolithography technology. As proof-of-concept, a complex 3D-hydrodynamic focusing device was produced via a six-layer lamination process of 33 µm-thick DFR layers. The bonding strength of the new DFR was tested on silicon, glass, and titanium substrates, respectively. A maximum bonding strength of 37 MPa was obtained for the dry film photoresist laminated on glass. No leakage was found, and burst tests proved excellent robustness and sealing reliability of the microchannels. 相似文献
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Sorption coefficients for pyrene on dissolved humic substances and on poly(acrylic acid) esters as well-defined model polymers were determined using solid-phase microextraction (SPME) and the fluorescence quenching technique (FQT). The results of both analytical methods were compared and theoretically evaluated, which led to the conclusion that the sorption coefficients measured by SPME and FQT are inevitably different: SPME measures activity-based and FQT concentration-based sorption coefficients. The environmental relevance of the two types of sorption coefficients is discussed. FQT is inappropriate to measure sorption coefficients for pyrene with the synthetic sorbents. Inspection of the vibrational structure of the fluorescence spectra of those solutions indicates a highly hydrophobic microenvironment of pyrene. This can be explained by an intra- or intermolecular agglomeration of hydrophobic moieties forming a favorable host for hydrophobic solutes. 相似文献
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M Lászlóffy N Keszei T Kákosy G Soós A Hudák M Náray 《Canadian Metallurgical Quarterly》1998,139(16):963-965
Authors describe the case-history of a 17 year old male who accidentally ingested a fishing weight that was retained in the stomach and caused a serious lead poisoning. It is worth mentioning that beside the wellknown symptoms and signs of lead intoxication also the liver was seriously affected. The histologically verified toxic lesion of the liver presumably can be attributed to the large quantities of lead absorbed within a short period. This also explains the appearance of symptoms and signs indicating to encephalopathy beside the young age of the patient. The foreign body could not be removed by means of gastroscopy, therefore a gastrotomy was carried out followed by chelating treatment with i.v. CaNa2EDTA that resulted in complete clinical and laboratory recovery. The case history draws the attention to the importance of the quick removal of the retained lead containing objects out of the gastrointestinal tract. 相似文献
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Doris Pospiech Andreas Korwitz Kathrin Eckstein Hartmut Komber Dieter Jehnichen Marcus Suckow Albena Lederer Kerstin Arnhold Michael Göbel Martina Bremer Anton Hoffmann Steffen Fischer Anett Werner Thomas Walther Harald Brünig Brigitte Voit 《应用聚合物科学杂志》2019,136(46):48257
Thermotropic liquid crystalline polyesters with varied chemical structure are synthesized by melt transesterification polycondensation. They are employed as matrix for blends with lignin materials to obtain melt-spinnable precursors for carbon fibers. The lignin samples are carefully purified by fractionation, enzymatic removal of reducing sugars, and subsequent modification of the terminal OH groups. Effective melt blending is achieved with liquid-crystalline aromatic–aliphatic polyesters having melting ranges that match the softening temperature of the lignin fractions, which is necessary to prevent thermal decomposition of the lignin. Polyester/lignin blends are partially compatibilized, phase-separated materials. The polyester/lignin materials are melt-spun successfully. The fiber properties depend on the lignin purification process. X-ray scattering reveals that orientation in lignin-containing fibers is maintained. First experiments show that the fibers can be converted successfully to carbon fibers by thermal annealing procedures. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48257. 相似文献
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Chiamaka Obianyor Gary Newnam Bryce E. Clifton Prof. Martha A. Grover Prof. Nicholas V. Hud 《Chembiochem : a European journal of chemical biology》2020,21(23):3359-3370
Chemical ligation is an important tool for the generation of synthetic DNA structures, which are used for a wide range of applications. Surprisingly, reported chemical ligation yields can range from 30 to 95 % for the same chemical activating agent and comparable DNA structures. We report a systematic study of DNA ligation by using a well-defined bimolecular test system and a water-soluble carbodiimide (EDC) as a phosphate-activating agent. Our results emphasize the interplay between template-substrate complex stability and the rates of the chemical steps of ligation, with 3′ phosphate substrates providing yields near 100 % after 24 hours for particularly favorable reaction conditions. Ligation rates are also shown to be sensitive to the identity of the base pairs flanking a nick site, with as much as threefold variation. Finally, the observation that DNA substrates are modified by EDC at rates that can be comparable with ligation rates emphasizes the importance of considering side reactions when designing protocols to maximize ligation yields. 相似文献