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《Analytical letters》2012,45(14):1185-1189
Abstract A specific and non-destructive test for basic esters of benzilic and α-glycolic acids in water is described. The compounds are collected on a glass fiber filter as water insoluble complexes with sodium tetraphenylboron. The filter is dried and sprayed with a 2-diphenylacetyl-l, 3-indandione-l-imine derivative. A positive test is the visual observation of fluorescence. 相似文献
367.
《Analytical letters》2012,45(10):1581-1594
Abstract 9-Bromomethylacridine (9-Br · Ma) gave blue fluorescent 9-acridinylmethyl (9-AM) esters by the reaction with carboxylic acids. The reactions were performed simply by mixing the 9-Br · Ma, tetraethylammonium carbonate (TEA C) and carboxylic acids in N,N-dimethylformamide at room temperature. The 9-AM derivatives of fifteen kinds of fatty acids were separated and detected with high performance liquid chromatography. By this method, fatty acids could be determined at levels down to either pmol order by fluorometry or 10 pmol order by UV method. After saponification, those in triacylglycerols were also determined. When four kinds of fatty acids were added to a butter, their recoveries were 92–101%. The coefficient of variation of myristate as a representative was 2.5% (42.8 pmol, n=6). 相似文献
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Comparison of the 1H and 13 C NMR spectra of a series of substituted 5‐benzylidene‐N,N′‐dimethylbarbituric acids (1) revealed chemical‐shift variations of different centers that correlated with the theoretical electrophilicities or with the substituent electrophilic constant σω , in an example of the usefulness of these DFT‐based indices. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Swagata Chakraborty Susmitha A. L. Ramakrishna V. Hosur 《Magnetic resonance in chemistry : MRC》2012,50(9):587-591
Direct detection of 13C nucleus can be used as a valuable alternative where 1H detection poses a challenge due to relaxation effects, chemical exchange and poor chemical shift dispersion. In this context, we have designed a suite of 2D 13Cα‐detected hNCA experiments that provide sequential correlations of 13Cα with 15N on one hand and efficient spectroscopic labeling of certain groups of residues, namely, Gly, Ala, Ser and Thr, on the other. These residues act as checkpoints in the sequential walk, which in turn offer new possibilities of backbone assignment of small proteins from a set of 2D experiments, thereby providing great economy in terms of spectrometer time. The direct identification of peptide segments around Gly, Ala, Ser and Thr residues along a protein chain will be highly valuable for deriving important information on sites of ligand binding, phosphorylation, inhibitor/substrate binding, understanding protein folding pathways, comprehending local conformational dynamics etc. without having to obtain complete sequence‐specific assignments, which can be time consuming and at times formidable, especially in large proteins. We have illustratively demonstrated the multifaceted applications of these variants of 2D experiments on ubiquitin and M‐crystallin. We foresee that these 2D hNCA experiments will provide economic and efficient strategies for studying the structure and function of proteins. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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