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排序方式: 共有272条查询结果,搜索用时 15 毫秒
1.
Böcking T Kilian KA Hanley T Ilyas S Gaus K Gal M Gooding JJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10522-10529
Surface modification with oligo(ethylene oxide) functionalized monolayers terminated with reactive headgroups constitutes a powerful strategy to provide specific coupling of biomolecules with simultaneous protection from nonspecific adsorption on surfaces for the preparation of biorecognition interfaces. To date, oligo(ethylene oxide) functionalized monolayer-forming molecules which can be activated for attachment of biomolecules but which can selectively form monolayers onto hydrogen terminated silicon have yet to be developed. Here, self-assembled monolayers (SAMs) containing tetra(ethylene oxide) moieties protected with tert-butyl dimethylsilyl groups were formed by thermal hydrosilylation of alkenes with single-crystal Si(111)-H. The protection group was used to avoid side reactions with the hydride terminated silicon surface. Monolayer formation was carried out using solutions of the alkene in the high-boiling-point solvent 1,3,5-triethylbenzene. The protecting group was removed under very mild acidic conditions to yield a free hydroxyl functionality, a convenient surface moiety for coupling of biological entities via carbamate bond formation. The chemical composition and structure of the monolayers before and after deprotection were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry. To demonstrate the utility of this surface for covalent modification, two reagents were compared and contrasted for their ability to activate the surface hydroxyl groups for coupling of free amines, carbonyl diimidazole (CDI), and disuccinimidyl carbonate (DSC). Analysis of XP spectra before and after activation by CDI or DSC, and after subsequent reaction with glycine, provided quantitative information on the extent of activation and overall coupling efficiencies. CDI activated surfaces gave poor coupling yields under various conditions, whereas DSC mediated activation followed by aminolysis at neutral pH was found to be an efficient method for the immobilization of amines on tetra(ethylene oxide) modified surfaces. 相似文献
2.
S. T. Howard J. P. Huke I. W. Parsons S. J. Till 《International journal of quantum chemistry》1991,39(1):71-91
The usefulness of the MS -Xα method for calculating molecular transition properties is investigated in a study of NO2. Two-dimensional potential surfaces are obtained in C2v symmetry for the X?2A1/Ã2B2 system. Potential curves that approximately follow the asymmetric stretch coordinate are also presented: On investigation, no symmetry-broken solutions were found. At all nuclear geometries investigated, the muffin-tin sphere radii were chosen by an energy-minimization technique. The inclusion of corrections to the muffin-tin form of the Xα total energy is shown to be essential, if the computed surfaces are to be qualitatively correct. The transition dipole moment connecting the two states is evaluated as a function of nuclear coordinates, using the transition-state approximation. Finally, the radiative decay of a single vibronic level in NO2 is modeled and the relevance to experiment is discussed. 相似文献
3.
Till Opatz 《Tetrahedron》2004,60(39):8613-8626
Carbohydrates are useful polyfunctional scaffold molecules which allow the selective attachment of a number of different side chains. The combinatorial solid phase synthesis of diverse amino acid or peptide conjugates of a polyfunctional glucose scaffold based on a set of selectively removable and orthogonally stable protecting groups is described. The resulting carbohydrate-peptide hybrids constitute potential turn mimetics. 相似文献
4.
Till?R?hrich Bassam?Abu Thaher Nico?Manicone Hans-Hartwig?OttoEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(8):979-999
Summary. (RS)-2-tert-Butyldimethylsilyl-1,2-thiazetidine-3-acetic acid 1,1-dioxide prepared from (RS)-S-benzyl--homocysteine was condensed via DCC/NHS with various L-amino acid esters or dipeptide esters yielding N-silylated -sultam peptides. A -sultam active ester was isolated as an intermediate. Desilylation with TBAF in THF yielded stable N-unsubstituted products, and deprotection of the benzyl esters was achieved by catalytic hydrogenation. (S)-S-Benzyl--homocysteine was obtained by fractional crystallization of the brucine salt of the racemate and transformed into benzyl (S)-1,2-thiazetidine-3-acetate, which was on the other hand synthesized by an enantiospecific route from -benzyl Boc-L-aspartate. Some -sultam peptides were prepared from the (S)-enantiomer, and finally some -sultam peptides containing D-Ala units were obtained. 相似文献
5.
L. Till 《Journal of Thermal Analysis and Calorimetry》1971,3(2):177-180
Decomposition temperatures of barium peroxide in equilibrium with the oxygen pressure in the gas phase have been determined by thermogravimetric measurements at temperatures from 670 to 843. Enthalpies and entropies of the reaction BaO2= =BaO+0.5O2 and of the formation of BaO2 have been calculated.
Zusammenfassung Zersetzungstemperaturen von mit dem Sauerstoffdruck in der Gasphase in Gleichgewicht stehendem Bariumperoxyd wurden thermogravimetrisch im Temperaturbereich von 670 bis zu 843 ermittelt. Enthalpie- und Entropiewerte der Reaktion BaO2= =BaO+0.5 O2 und der Bildung von BaO2 wurden errechnet.
Résumé On a déterminé les températures de décomposition du peroxyde de baryum en équilibre avec la pression d'oxygène de la phase gazeuse, par mesures thermogravimétriques entre 670 et 843. On a calculé les enthalpies et les entropies correspondant à la réaction BaO2=BaO+0.5 O2 et à la formation de BaO2.
, , , 670 843. BaO2= + +0.5 O2 BaO2.相似文献
6.
Eckhard Flter Till Wettlaufer Valentina Conty Maria Scharfe 《Molecules (Basel, Switzerland)》2021,26(6)
Oleogels or, more precisely, non-triglyceride structured lipid phases have been researched excessively in the last decade. Yet, no comprehensive knowledge base has emerged, allowing technology elevation from the laboratory bench into the industrial food application. That is partly due to insufficient characterization of the structuring systems studied. Examining a single composition decided upon by arbitrary methods does not stimulate progress in the research and technology area. A framework that gives much better guidance to product applications can easily be derived. For example, the incremental structure contribution concept is advocated as a parameter to compare the potency of structuring systems. These can straightforwardly be determined by combining solubility data and structural measurements in the recommended manner. The current method to determine the oil-binding capacity suffers from reproducibility and relevance. A newly developed method is suggested to overcome these shortcomings. The recommended new characterization of oleogels should contribute to a more comprehensive knowledge base necessary for product innovations. 相似文献
7.
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9.
Matthias Krumb Dr. Maximilian Jäger Alice Voss Loreen Immig Dr. Karin Peters Danuta Kowalczyk Prof. Dr. Albrecht Bufe Prof. Dr. Till Opatz Prof. Dr. Otto Holst Prof. Dr. Christian Vogel Dr. Marcus Peters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):928-933
Arabinogalactan, a microheterogeneous polysaccharide occurring in plants, is known for its allergy-protective activity, which could potentially be used for preventive allergy treatment. New treatment options are highly desirable, especially in a preventive manner, due to the constant rise of atopic diseases worldwide. The structural origin of the allergy-protective activity of arabinogalactan is, however, still unclear and isolation of the polysaccharide is not feasible for pharmaceutical applications due to a variation of the activity of the natural product and contaminations with endotoxins. Therefore, a pentasaccharide partial structure was selected for total synthesis and subsequently coupled to a carrier protein to form a neoglycoconjugate. The allergy-protective activity of arabinogalactan could be reproduced with the partial structure in subsequent in vivo experiments. This is the first example of a successful simplification of arabinogalactan with a single partial structure while retaining its allergy-preventive potential. 相似文献
10.
Nicola Otto Prof. Dr. Till Opatz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13064-13077
Owing to their various modes of reactivity, α‐aminonitriles represent versatile building blocks for the construction of a wide range of nitrogen heterocycles. The present Concept article focuses on synthetic methodologies using their bifunctional nature which is the basis of their reactivity as α‐amino carbanions and as iminium ions. Reactions exclusively taking place on either the amine or on the nitrile moiety will not be considered. 相似文献