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11.
Städler B Falconnet D Pfeiffer I Höök F Vörös J 《Langmuir : the ACS journal of surfaces and colloids》2004,20(26):11348-11354
We present a novel concept for the creation of lipid vesicle microarrays based on a patterning approach termed Molecular Assembly Patterning by Lift-off (MAPL). A homogeneous MAPL-based single-stranded DNA microarray was converted into a vesicle array by the use of vesicles tagged with complementary DNAs, permitting sequence-specific coupling of vesicles to predefined surface regions through complementary DNA hybridization. In the multistep process utilized to fulfill this achievement, active spots consisting of PLL-g-PEGbiotin with a resistant PLL-g-PEG background, as provided by the MAPL process, was converted into a DNA array by addition of complexes of biotin-terminated DNA and NeutrAvidin. This was then followed by addition of POPC vesicles tagged with complementary cholesterol-terminated DNA, thus providing specific coupling of vesicles to the surface through complementary DNA hybridization. Quartz crystal microbalance with dissipation (QCM-D) and optical waveguide lightmode spectroscopy monitoring were used to optimize the multistep surface modification process. It was found that the amount of adsorbed biotinDNA-NeutrAvidin complexes decreases with increasing molar ratio of biotinDNA to NeutrAvidin and decreasing ionic strength of the buffer solution. Modeling of the QCM-D data showed that the shape of the immobilized vesicles depends on the amount of available anchoring groups between the vesicles and the surface. Fluorescent microscopy images confirmed the possibility to create well-defined patterns of DNA-tagged, fluorescently labeled vesicles in the micrometer range. 相似文献
12.
Hubert Paulus Susanne Kornely Janos Giber Karl -Heinz Müller 《Mikrochimica acta》1997,125(1-4):223-227
Depth profiles of Ga2O3/a-SiO2/Al2O3- substrate, Ga2O3/a-Si3N4/Al2O3- substrate, and Ga2O3/Al2O3 substrate thin layers were determined by the SNMS/HFM method. Al diffusion from the Al2O3 substrate was investigated after 50, and in some cases after 600 hours of heat treatment time at different temperatures (600 °C,850 °C,950 °C,1050 °C and 1150 °C). The diffusion coefficient of Al at 850 °C was found to be D
Al=8.7 * 10–18 cm2/s in amorphous SiO2; D
Al=1.5*10–17 cm2/s in amorphous Si3N4 and D
Al=5.5* 10–16 cm2/s in Ga2O3 at 600 °C, respectively. The possible diffusion mechanism is explained in terms of the metal-oxygen bond-strengths. Although the studied materials have high resistivity at room temperature, the applied SNMS/HFM method has proven to be an efficient surface analytical tool even in these cases.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
13.
Zhen G Eggli V Vörös J Zammaretti P Textor M Glockshuber R Kuennemann E 《Langmuir : the ACS journal of surfaces and colloids》2004,20(24):10464-10473
Understanding the conformation, orientation, and specific activity of proteins bound to surfaces is crucial for the development and optimization of highly specific and sensitive biosensors. In this study, the very efficient enzyme beta-lactamase is used as a model protein. The wild-type form was genetically engineered by site-directed mutagenesis to introduce single cysteine residues on the surface of the enzyme. The cysteine thiol group is subsequently biotinylated with a dithiothreitol (DTT)-cleavable biotinylation reagent. beta-Lactamase is then immobilized site-specifically via the biotin group on neutral avidin-covered surfaces with the aim to control the orientation of the enzyme molecule at the surface and study its effect on enzymatic activity using Nitrocefin as the substrate. The DTT-cleavable spacer allows the release of the specifically bound enzyme from the surface. Immobilization of the enzyme is performed on a monolayer of the polycationic, biotinylated polymer PLL-g-PEG/PEG-biotin assembled on niobium oxide (Nb2O5) surfaces via neutral avidin as the docking site. Two different assembly protocols, the sequential adsorption of avidin and biotinylated beta-lactamase and the immobilization of preformed complexes of beta-lactamase and avidin, are compared in terms of immobilization efficiency. In situ optical waveguide lightmode spectroscopy and colorimetric analysis of enzymatic activity were used to distinguish between specific and unspecific enzyme adsorption, to sense quantitatively the amount of immobilized enzyme, and to determine Michaelis-Menten kinetics. All tested enzyme variants turned out to be active upon immobilization at the polymeric surface. However, the efficiency of immobilized enzymes relative to the soluble enzymes was reduced about sevenfold, mainly because of impaired substrate (Nitrocefin) diffusion or restricted accessibility of the active site. No significant effect of different enzyme orientations could be detected, probably because the enzymes were attached to the surface through long, flexible PEG chain linkers. 相似文献
14.
15.
Zusammenfassung Penicilliumsäure wurde aus einem einer Tropfsteinhöhle entstammendenPénicillium-Thomii-Stamm in kristalliner Form isoliert. Die Tautomerie des Wirkstoffes wurde durch UV-spektroskopische Messungen eingehend untersucht und diskutiert.
Summary Penieillic acid was isolated in crystalline form from aPenicillium-Thomii- strain coming from a dripstone cave. The tautomerism of the active material was thoroughly studied by UV spectroscopic measurements and discussed.
Résumé On a isolé l'acide pénioillique sous forme cristalline à partir d'une souche dePénicillium-Thornii provenant d'une grotte de stalactites.On a étudié d'une manière approfondie et discuté la tautomérie du constituant actif par des mesures en spectroscopie ultraviolette.相似文献
16.
Laurent Jeannin Janos Sapi Elka Vassileva Pierre Renard Jean-Yves Laronze 《合成通讯》2013,43(9):1711-1719
Three methods have been proposed for the preparation of functionalized 1-oxo-1,2,3,4-tetrahydro-β-carboline-3 carboxylates (3) from which the “acylazide formation-Curtius rearrangement-acid catalyzed ring closure” sequence starling from hemi-ester hemi-acids (8) seemed to be quite general. 相似文献
17.
Janos Karátson 《Central European Journal of Mathematics》2012,10(1):231-249
This paper is devoted to the numerical solution of nonlinear elliptic partial differential equations. Such problems describe
various phenomena in science. An approach that exploits Hilbert space theory in the numerical study of elliptic PDEs is the
idea of preconditioning operators. In this survey paper we briefly summarize the main lines of this theory with various applications. 相似文献
18.
19.
József Békési Gábor Galambos Michael N. Jung Marcus Oswald Gerhard Reinelt 《Mathematical Methods of Operations Research》2014,80(1):47-81
The coupled task problem is to schedule jobs on a single machine where each job consists of two subtasks and where the second subtask has to be started after a given time interval with respect to the first one. The problem has several applications and is NP-hard. In this paper we present a branch-and-bound algorithm for this problem and compare its performance with four integer programming models. 相似文献
20.
Emmanuel Dardennes Stéphane Gérard Christian Petermann Janos Sapi 《Tetrahedron: Asymmetry》2010,21(2):208-215
The trimolecular condensation of indole, Meldrum’s acid and chiral, sugar-derived aldehydes took place in good yield and high diastereoselectivity. The absolute configuration of the α-carbon of the chiral aldehydes ensured a predictable diastereocontrol of the newly created stereogenic centre except for (3aR,5S,6S,6aR)-6-benzyloxy-2,2-dimethyl-tetrahydrofuro[3,2-d][1,3]dioxole-5-carbaldehyde 3i. In this case, the opposite stereochemistry may be explained by a less congested conformer of the Knoevenagel-adduct intermediate. 相似文献