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101.
Dr. Josef Houser Dr. Stanislav Kozmon Dr. Deepti Mishra Zuzana Hammerová Prof. Michaela Wimmerová Prof. Jaroslav Koča 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(47):10769-10780
The molecular recognition of carbohydrates by proteins plays a key role in many biological processes including immune response, pathogen entry into a cell, and cell–cell adhesion (e.g., in cancer metastasis). Carbohydrates interact with proteins mainly through hydrogen bonding, metal-ion-mediated interaction, and non-polar dispersion interactions. The role of dispersion-driven CH–π interactions (stacking) in protein–carbohydrate recognition has been underestimated for a long time considering the polar interactions to be the main forces for saccharide interactions. However, over the last few years it turns out that non-polar interactions are equally important. In this study, we analyzed the CH–π interactions employing bioinformatics (data mining, structural analysis), several experimental (isothermal titration calorimetry (ITC), X-ray crystallography), and computational techniques. The Protein Data Bank (PDB) has been used as a source of structural data. The PDB contains over 12 000 protein complexes with carbohydrates. Stacking interactions are very frequently present in such complexes (about 39 % of identified structures). The calculations and the ITC measurement results suggest that the CH–π stacking contribution to the overall binding energy ranges from 4 up to 8 kcal mol−1. All the results show that the stacking CH–π interactions in protein–carbohydrate complexes can be considered to be a driving force of the binding in such complexes. 相似文献
102.
Michaela Fecková Ioannis Konstantinos Kalis Dr. Thierry Roisnel Dr. Pascal le Poul Prof. Oldřich Pytela Dr. Milan Klikar Prof. Françoise Robin-le Guen Prof. Filip Bureš Prof. Mihalis Fakis Dr. Sylvain Achelle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):1145-1159
Six pyrimidine-based push–pull systems substituted at positions C2 and C4/6 with phenylacridan and styryl moieties, employing methoxy or N,N-diphenylamino donors, have been designed and synthesized through cross-coupling and Knoevenagel reactions. X-ray analysis confirmed that the molecular structure featured the acridan moiety arranged perpendicularly to the residual π system. Photophysical studies revealed significant differences between the methoxy and N,N-diphenylamino chromophores. Solvatochromic studies revealed that the methoxy derivatives showed dual emission in polar solvents. Time-resolved spectroscopy revealed that the higher energy band involved very fast (<80 ps) fluorescence, whereas the lower energy one included long components (≈30 ns) due to long-lived intramolecular charge-transfer fluorescence. In contrast to N,N-diphenylamino chromophores, the methoxy derivatives also showed aggregation-induced emission in mixtures of THF/water, as well as dual emission in thin films, covering almost the whole visible spectrum with corresponding chromaticity coordinates not far from that of pure white light. These properties render the methoxy derivatives as very promising organic materials for white organic light-emitting diodes. 相似文献
103.
Internal Peptide Late‐Stage Diversification: Peptide‐Isosteric Triazoles for Primary and Secondary C(sp3)−H Activation
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Michaela Bauer Wei Wang Dr. Mélanie M. Lorion Chuan Dong Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2018,57(1):203-207
Secondary C(sp3)?H arylations were accomplished by palladium catalysis with triazoles as peptide bond isosteres. The unique power of this approach is highlighted by the possibility of achieving secondary C(sp3)?H functionalizations on terminal peptides as well as the unprecedented positional‐selective C(sp3)?H functionalization of internal peptide positions, setting the stage for modular peptide late‐stage diversification. 相似文献
104.
Michaela?Bleile Hans-Hartwig?OttoEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(10):1799-1809
Summary. 5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloadditions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They
were transformed into the hydroxy derivatives by treatment with H2SO4, selectively reduced to the ether by H2/Pd–C, and in the imide moiety by L-Selectride?. From the analogous BOC protected indole derivative the parent α,β-unsaturated ketones were obtained, which were transformed into hydroxyimino compounds,
and which could be deprotected by heating to the melting point. Deprotection of the tosyl derivatives was not successful.
The imide part of the molecule was hydrolyzed using methanolic NaOH. The stereochemistry of all products was elucidated mainly
by spectroscopic methods, and compared with results of calculations. 相似文献
105.
Helmut Schmidhammer Karin Mayer-Valkanover Michaela Walla-Kugler 《Helvetica chimica acta》1990,73(7):1986-1990
Starting from 5-methyl-oxycodone ( 6 ), 5-methylnaloxone ( 4 ), and 5-methylnaltrexone ( 5 ) have been prepared in several steps. Both 4 and 5 behaved as partial agonists in the AcOH writhing agonism and antagonism test in mice. 相似文献
106.
107.
108.
In this paper existence and regularity results for a class of degenerate nonlinear parabolic equations are proved. Indeed,
the diffusion operator may degenerate as the solution diverges and may depend on space and time variables in a non–regular
way, too. Some estimates on the behaviour of the solutions for t → +∞ are also given. 相似文献
109.
A new method for the oxidation of ergoline alcohols to aldehydes was found (TFFA-DMSO, −78 °C, then DIPEA). Structural features of ergolines required for successful C7-C8 double bond introduction via Polonovski-Potier reaction of respective 6-N-oxides were defined and experimentally confirmed: (i) the presence of electron-withdrawing group at C-8; (ii) trans-diaxial orientation of N6-O and C7-H bonds (both requirements are fulfilled for dihydrolyserg-17-al and its 2,4-dinitrophenyl hydrazone prepared in this work). 相似文献
110.
Christopher A. Lukey Michaela Tymichova Hugh R. Brown 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1282-1286
A novel route to styrene/p‐aminostyrene copolymers is described that involves the introduction of amino functionality into the structure of pure monodisperse polystyrene. The simple two‐step synthesis involves the introduction of a bromo group into the aromatic ring by electrophilic substitution and then a palladium‐catalyzed reaction with LiN(SiMe3)2 followed by an acid and base treatment to release the free amine. All reactions are carried out at room temperature. This approach avoids the difficulties often associated with the preparation of copolymers from incompatible monomers. The technique also gives a product with a precisely known molecular weight and polydispersity, important parameters governing many physical properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1282–1286, 2007 相似文献