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101.
The parallel synthesis of chiral bidentate ligands and their subsequent use in situ for a catalytic process is described. The ligands thus prepared gave comparable results to those obtained when the ligands were synthesized and purified by conventional means. This includes oxazolines and other compounds of similar complexity, meaning that for the first time these valuable compounds have been brought into the field of combinatorial catalysis. 相似文献
102.
The enzymatic activation of 3,4-dehydrolysine and subsequent formation of the 12-membered syringolin macrolactam were investigated. The timing of the desaturation was elucidated through the analysis of the initial adenylation domain of SylD. The SylD-TTE didomain was characterized and demonstrated to be the catalyst for formation of 12-membered macrocycles. When the SylD thioesterase domain was reacted with a family of acyclic CoA both natural and unnatural macrocycles were generated. 相似文献
103.
We introduce the WeightedGrammar constraint and propose propagation algorithms based on the CYK parser and the Earley parser. We show that the traces of these algorithms can be encoded as a weighted negation normal form (WNNF), a generalization of NNF that allows nodes to carry weights. Based on this connection, we prove the correctness and complexity of these algorithms. Specifically, these algorithms enforce domain consistency on the WeightedGrammar constraint in time O(n 3). Further, we propose that the WNNF constraint can be decomposed into a set of primitive arithmetic constraint without hindering propagation. 相似文献
104.
105.
The tumor microenvironment, or stroma, is chemically and morphologically modified during carcinoma progression. The predominant cell type in the stroma, the fibroblast, maintains collagen properties in normal tissue and often transformed during tumor progression. Biochemical changes within fibroblasts upon initial cancer activation, however, are relatively poorly defined. Here, we hypothesized that Fourier transform infrared (FT-IR) spectroscopic imaging could potentially be employed to examine these early transformations. Further, we employ attenuated total reflectance (ATR) microscopy to characterize subcellular spectra and their changes upon transformation. We characterized fibroblast transitions upon stimulation with both a molecular agent and a carcinoma-mimicking cellular co-culture system. Changes were predominantly observed in the 1080 cm(-1) and 1224 cm(-1) peak absorbance, commonly associated with nucleic acids, as well as in the band at 2930 cm(-1) associated with the C-H stretching of proteins in the cytoplasmic compartment. In conclusion, biochemical changes in cancer-associated fibroblasts that express α-SMA are dominated by the cytoplasm, rather than the nucleus. This ensures that spectral changes are not associated with proliferation or cell cycle processes of the cells and the cells are undergoing a true phenotypic change denoted by protein modifications in the cell body. 相似文献
106.
Hamilton SM Hopkins WS Harding DJ Walsh TR Haertelt M Kerpal C Gruene P Meijer G Fielicke A Mackenzie SR 《The journal of physical chemistry. A》2011,115(12):2489-2497
Far- and mid-infrared multiple photon dissociation spectroscopy has been employed to study both the structure and surface reactivity of isolated cationic rhodium clusters with surface-adsorbed nitrous oxide, Rh(n)N(2)O(+) (n = 4-8). Comparison of experimental spectra recorded using the argon atom tagging method with those calculated using density functional theory (DFT) reveals that the nitrous oxide is molecularly bound on the rhodium cluster via the terminal N-atom. Binding is thought to occur exclusively on atop sites with the rhodium clusters adopting close-packed structures. In related, but conceptually different experiments, infrared pumping of the vibrational modes corresponding with the normal modes of the adsorbed N(2)O has been observed to result in the decomposition of the N(2)O moiety and the production of oxide clusters. This cluster surface chemistry is observed for all cluster sizes studied except for n = 5. Plausible N(2)O decomposition mechanisms are given based on DFT calculations using exchange-correlation functionals. Similar experiments pumping the Rh-O stretch in Rh(n)ON(2)O(+) complexes, on which the same chemistry is observed, confirm the thermal nature of this reaction. 相似文献
107.
A number of nickel based materials are investigated as potential oxygen evolution catalysts under conditions close to those met in modern, high current density alkaline water electrolysers. Microelectrodes are used to avoid distortion of voltammetric data by IR drop even at the high current densities employed in such water electrolysers. High surface area nickel metal oxides prepared by cathodic deposition and mixed oxides prepared by thermal methods are considered. A mixed Ni/Fe oxide is the preferred electrocatalyst. The influence of hydroxide ion concentration and temperature on the voltammetry is defined. Preliminary stability tests in a zero gap cell with an OH(-) conducting membrane show no significant increase in overpotential during 10 days operation in 4 M NaOH electrolyte at a current density of 1 A cm(-2) at 333 K. 相似文献
108.
The reaction of Z,Z‐2,3,4,5‐tetrahalo‐2,4‐dien‐1,6‐dibromides ( 3 , R1 ‐ R4 = Cl, Br) with primary amines in the presence of potassium carbonate leads to both the dihydroazepines 4 and secondary enamines 5 . The formation of enamine is suppressed with toluene sulfonamide as nitrogen source. (2Z,4Z)‐2,3,4,5‐Tetrabromo‐hexa‐2,4‐diene‐1,6‐diol (2, R1 ‐ R4 = Br) is atropisomeric in solution. 相似文献
109.
Measurements of the mean cell volume and mean cell aspect ratio are reported for suspensions of the polymorphic yeast Kluyveromyces marxianus var. marxianus NRRLy2415 and for cakes of the same microorganism recovered after crossflow microfiltration with a tubular ceramic membrane at fixed trans-membrane pressure and crossflow velocity. The mean cell volume and the mean cell aspect ratio in the cake were determined using image analysis. The mean cell volume was found to be consistently smaller in the cake than in the suspension while tentative evidence was found that the mean cell aspect ratio was also smaller in the cake. Enhanced deposition of less elongated cells is likely to be a consequence of preferential deposition of small cells because, for the microorganism used in this study, the mean cell aspect ratio in a suspension increases with increasing mean cell volume. Close analysis of the data reveals that the mean cell aspect ratio is greater in the cake than would be expected based on the mean cell volume in the suspension, suggesting that the deposition of more elongated cells is favoured over less elongated cells of the same volume. 相似文献
110.
S. E. Boganov M. P. Egorov V. I. Faustov I. V. Krylov O. M. Nefedov R. Becerra R. Walsh 《Russian Chemical Bulletin》2005,54(3):483-511
The results of time resolved gas phase studies of labile germylenes (GeH2 and GeMe2) and dimethylstannylene (SnMe2) reactions reported to date are considered together with data of quantum-chemical investigations of the potential energy surfaces of these systems. Reaction mechanisms are discussed. A comparison of reactivity in the series of carbene analogs, ER2 (E = Si, Ge, Sn, R = H, Me), is made.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 477–505, March, 2005. 相似文献