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Partial Structures (partial + structure)
Selected AbstractsConsistent Bioactive Conformation of the Neu5Ac,(2,3)Gal Epitope Upon Lectin BindingCHEMBIOCHEM, Issue 18 2008Anirban Bhunia Dr. Get to NOE MAG: Partial structures of GQ1b,, the natural ligand of the myelin-associated glycoprotein (MAG), have been synthesized and subjected to NOE experiments to determine their bioactive conformations. The experiments show that the flexible ,(2,3)-glycosidic linkage between N -acetylneuraminic acid and galactose present in all ligands adopts a "sialyl Lewisx -type" binding mode. This information is valuable for the future design of conformationally preorganized MAG inhibitors. [source] Nucleophilic Carbenes and Pseudo-Cross-Conjugated Mesomeric Betaines of Indazole Starting from Analogues of the Alkaloid-Betaine NigellicineEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2005Andreas Schmidt Abstract The alkaloid Nigellicine possesses the indazolium-3-carboxylate ring system as electronically relevant partial structure which represents a member of the class of pseudo-cross-conjugated mesomeric betaines. Indazolium-3-carboxylate, prepared starting from indazole-3-carboxylic acid by an esterification,methylation,saponification sequence, can be converted into the isoconjugated phenyl- and 4-(nitrophenyl)amidates and the thiocarboxylate as additional examples of pseudo-cross-conjugated systems. In accordance with results of ab initio calculations decarboxylation of indazolium-3-carboxylate with formation of the nucleophilic carbene indazol-3-ylidene begins at approximately 40 °C as evidenced by temperature-dependent NMR spectroscopy. The carbene can be trapped with protons as indazolium salts, and carbon dioxide which reconstitutes the pseudo-cross-conjugated mesomeric betaine. According to the calculations, the carbene adopts a singlet ground state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] A parallel program using SHELXD for quick heavy-atom partial structural solution on high-performance computersJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2007Zheng-Qing Fu A parallel algorithm has been designed for SHELXD to solve the heavy-atom partial structures of protein crystals quickly. Based on this algorithm, a program has been developed to run on high-performance multiple-CPU Linux PCs, workstations or clusters. Tests on the 32-CPU Linux cluster at SER-CAT, APS, Argonne National Laboratory, show that the parallelization dramatically speeds up the process by a factor of roughly the number of CPUs applied, leading to reliable and instant heavy-atom sites solution, which provides the practical opportunity to employ heavy-atom search as an alternative tool for anomalous scattering data quality evaluation during single/multiple-wavelength anomalous diffraction (SAD/MAD) data collection at synchrotron beamlines. [source] Electrospray ionization mass spectrometric studies of nucleophilic carbenes derived from pyrazolium and indazolium carboxylatesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2005Andreas Schmidt Pyrazolium-3-carboxylate and indazolium-3-carboxylate, which belong to the class of pseudo-cross-conjugated mesomeric betaines and which represent the electronically relevant partial structures of the betaine alkaloid Nigellicin, were examined by electrospray ionization mass spectrometry. These compounds decarboxylate to pyrazol-3-ylidene and indazol-3-ylidene. The formation of adducts of these new nucleophilic carbenes under the measurement conditions was examined. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||