排序方式: 共有126条查询结果,搜索用时 15 毫秒
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Wuyts S De Temmerman K De Vos D Jacobs P 《Chemical communications (Cambridge, England)》2003,(15):1928-1929
Acid zeolites like H-Beta are efficient heterogeneous catalysts for racemization of benzylic alcohols in water; by combination of the racemization with an enzymatic kinetic resolution in a two-phase system, enantiomerically pure esters were obtained in high yield via a dynamic kinetic resolution. 相似文献
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Bultinck P Augustynen S Hilbers HW Moret EE Tollenaere JP 《Journal of computational chemistry》2002,23(7):746-754
The program Generate, aimed at generating 3-D structures for peptides and peptidomimetics, is presented. The algorithm is based on a build-up procedure, using a library of conformations of amino acid residues. This library is built from conformational analysis of amino acids placed in a di- or tripeptide environment to mimic the surroundings of the amino acid in a true peptide, considering different positions of the residue in the peptide chain (peptidyl fragment, NH(+)(3)-terminus or COO(-)-terminus). Cis-trans isomerism in the amide bonds is taken into account by construction of rotamer libraries for different isomers. Water solvation is included through the GB/SA model. New amino acid residues can easily be added to the libraries, making it possible to generate conformations of peptidomimetics. 相似文献
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Dr. Stijn F. M. van Dongen Dr. Johannes A. A. W. Elemans Prof. Dr. Alan E. Rowan Prof. Dr. Roeland J. M. Nolte 《Angewandte Chemie (International ed. in English)》2014,53(43):11420-11428
Nature’s enzymes are an ongoing source of inspiration for scientists. The complex processes behind their selectivity and efficiency is slowly being unraveled, and these findings have spawned many biomimetic catalysts. However, nearly all focus on the conversion of small molecular substrates. Nature itself is replete with inventive catalytic systems which modify, replicate, or decompose entire polymers, often in a processive fashion. Such processivity can, for example, enhance the rate of catalysis by clamping to the polymer substrate, which imparts a large effective molarity. Reviewed herein are the various strategies for processivity in nature’s arsenal and their properties. An overview of what has been achieved by chemists aiming to mimic one of nature’s greatest tricks is also included. 相似文献
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Squeezing,Then Stacking: From Breathing Pores to Three‐Dimensional Ionic Self‐Assembly under Electrochemical Control 下载免费PDF全文
Kang Cui Dr. Kunal S. Mali Dr. Oleksandr Ivasenko Dongqing Wu Dr. Xinliang Feng Dr. Michael Walter Prof. Klaus Müllen Prof. Steven De Feyter Dr. Stijn F. L. Mertens 《Angewandte Chemie (International ed. in English)》2014,53(47):12951-12954
We demonstrate the spontaneous and reversible transition between the two‐ and three‐dimensional self‐assembly of a supramolecular system at the solid–liquid interface under electrochemical conditions, using in situ scanning tunneling microscopy. By tuning the interfacial potential, we can selectively organize our target molecules in an open porous pattern, fill these pores to form an auto‐host–guest structure, or stack the building blocks in a stratified bilayer. Using a simple electrostatic model, we rationalize which charge density is required to enable bilayer formation, and conversely, which molecular size/charge ratio is necessary in the design of new building blocks. Our results may lead to a new class of electrochemically controlled dynamic host–guest systems, artificial receptors, and smart materials. 相似文献
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Probing Functional Heteromeric Chemokine Protein–Protein Interactions through Conformation‐Assisted Oxime Ligation 下载免费PDF全文
Stijn M. Agten Dr. Rory R. Koenen Dr. Hans Ippel Veit Eckardt Dr. Philipp von Hundelshausen Prof. Dr. Kevin H. Mayo Prof. Dr. Tilman M. Hackeng 《Angewandte Chemie (International ed. in English)》2016,55(48):14963-14966
Protein–protein interactions (PPIs) govern most processes in living cells. Current drug development strategies are aimed at disrupting or stabilizing PPIs, which require a thorough understanding of PPI mechanisms. Examples of such PPIs are heteromeric chemokine interactions that are potentially involved in pathological disorders such as cancer, atherosclerosis, and HIV. It remains unclear whether this functional modulation is mediated by heterodimer formation or by the additive effects of mixed chemokines on their respective receptors. To address this issue, we report the synthesis of a covalent RANTES‐PF4 heterodimer (termed OPRAH) by total chemical synthesis and oxime ligation, with an acceleration of the final ligation step driven by PPIs between RANTES and PF4. Compared to mixed separate chemokines, OPRAH exhibited increased biological activity, thus providing evidence that physical formation of the heterodimer indeed mediates enhanced function. 相似文献
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Marchand E Atemnkeng MA Vanermen S Plaizier-Vercammen J 《Biomedical chromatography : BMC》2008,22(5):454-459
Owing to the development of parasite resistance to standard antimalarial treatments like chloroquine and sulfadoxine-pyrimethamine, the demand for Artemisia annua, a key ingredient for new and highly effective antimalarial drugs, is huge. Therefore selective and precise methods to determine the content of artemisinin in dry plant material and in raw impure extracts are needed. In this work a method is described for the clear separation and extraction of artemisinin from other plant components in the Artemisia annua L. plant by thin-layer chromatography (TLC). To obtain optimal extraction and recovery efficiency, several parameters were evaluated, including choice of extraction solvent, TLC plate type and sensitivity between UV and visible light. Method validation was performed on both the dry plant material and non-purified plant extracts. Toluene presented the highest extraction efficiency compared with petroleum ether, hexane and methanol. Reversed-phase plates showed more concentrated spots than normal-phase plates, while the sensitivity of the analysis in UV was comparable to that in visible light but less precise. The impure plant extracts were analyzed by both TLC and HPLC-UV at 215 nm and both methods met the requirements for linearity, selectivity, precision and accuracy. Hence, the proposed TLC method can easily be used for both qualitative and quantitative control of the raw plant extract in areas where advanced methods are scarce. 相似文献
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A new, efficient, sensitive, and reliable color test for the visual detection of resin-bound primary and secondary amines is described. The reaction between amines and 1-methyl-2-(4'-nitrophenyl)-imidazo[1,2- a]pyrimidinium perchlorate (DESC) provides the "on-bead generated" colored stable intermediate azadiene. The developed protocols allow detection of resin-bound primary amines in the presence of secondary amines. The test can also be used for the detection of resin bound thiols. 相似文献