1nq7
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(New page: 200px<br /> <applet load="1nq7" size="450" color="white" frame="true" align="right" spinBox="true" caption="1nq7, resolution 1.50Å" /> '''Characterization of...)
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Revision as of 16:17, 12 November 2007
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Characterization of ligands for the orphan nuclear receptor RORbeta
Overview
A new method was developed for the analysis of pesticide residues in, tobacco. The objective was to significantly increase the number of samples, that can be processed by the laboratory and to enable the extension of the, current coverage to additional pesticides. A new analytical approach was, therefore defined based on two main axes, the automation of the sample, preparation and the selectivity of the analyte detection using tandem mass, spectrometry. This latter aspect reduces the stringency of the, requirements placed on the clean-up of the extracts and on the, chromatographic resolution when less selective detectors are used. The, extraction of the analytes from the matrix is performed using the, pressurized liquid extraction technique. Tobacco samples are extracted at, elevated temperature and pressure (100 C and 100 atm; 1 atm = 101,325 Pa), using acetone as an extraction solvent. The resulting extract is then, concentrated using a Vortex evaporator. Three different solid-phase, extraction (SPE) procedures, adjusted to the chemical properties of the, different active ingredients to be measured, are applied to the, concentrated extract, thus leading to three extract fractions. The first, fraction contains such main classes of active ingredients as, organohalogenated and 2,6-dinitroaniline compounds while the second one, collects the organophosphorus and acylalanines residues; these two, fractions are analyzed by capillary gas chromatography coupled to tandem, mass spectrometry using negative chemical ionization and electron impact, ionization in the positive mode, respectively. The third extract fraction, gathers the N-methylcarbamates residues which are analyzed by HPLC with, post-column derivatization and fluorescence detection. The different, sample preparation stages from extraction to SPE clean-up have been, automated through the use of recent analytical technologies. In, combination with the analysis by tandem mass spectrometry, this provided a, potential for a high sample throughput.
About this Structure
1NQ7 is a Protein complex structure of sequences from Rattus norvegicus with ARL as ligand. Full crystallographic information is available from OCA.
Reference
Analysis of multiple pesticide residues in tobacco using pressurized liquid extraction, automated solid-phase extraction clean-up and gas chromatography-tandem mass spectrometry., Haib J, Hofer I, Renaud JM, J Chromatogr A. 2003 Dec 12;1020(2):173-87. PMID:14661742
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