Afterwards several figures of merit have been evaluated. Bearing in mind that triazines are one of the most frequently used group of herbicides in agriculture and atrazine and simazine are included in the list of priority substances in Annex II of Directive 2008/105/EC, in this work, these analytes have been analysed in three natural waters. Prior to determination
by gas chromatography with mass spectrometry detection (GC/MS) a step with solid LY2606368 phase extraction (SPE) has been carried out. The calibration set is made up of 40 standards 33 are external standards prepared in acetone and seven matrix matched prepared in deionised water subjected to the SPE procedure. Moreover, each kind of water, stream, well, and river, is analysed both unspiked and spiked. For the triazine determination, the second order PARAFAC advantage allows the use of samples prepared in acetone together with those prepared in deionised water subjected to SPE. The decision limit, CC alpha, and the capability of detection, CC beta, are calculated according to ISO 11843-2, assessing the false positive and false negative.
The m/z ratios chosen fulfils the SANCO identification GW4869 Apoptosis inhibitor criteria and also the spectrum obtained in the PARAFAC decomposition, which is common in all samples for each triazine. However, when the same experimental data are used to carry out a univariate calibration with the abundance of the base peak of each triazines, a lot of samples lie outside the permitted tolerances depending on the reference experimental spectra used, despite the fact that all of them have a triazine content above Caspase cleavage the detection limit. Also, the PARAFAC calibration allows us to detect the test samples which are not similar to the calibration samples and in this way their mistaken quantification is avoided. (C) 2012 Elsevier B.V. All rights reserved.”
“Dihydrouridine synthase (Dus) is
responsible for catalyzing dihydrouridine formation in RNA by the reduction of uridine. To elucidate its RNA-recognition mechanism, Dus from Thermus thermophilus (TthDus) and its complex with tRNA were crystallized. Diffraction data sets were collected from crystals of native and selenomethionine-substituted TthDus to resolutions of 1.70 and 2.30 angstrom, respectively. These crystals belonged to space group P1. Preliminary X- ray crystallographic analysis showed that two molecules of TthDus were contained in an asymmetric unit. In addition, diffraction data were collected to 3.51 angstrom resolution from a crystal of selenomethionine-substituted TthDus in complex with tRNA, which belonged to space group P4(1)2(1)2. Preliminary structural analysis showed that the asymmetric unit contained two TthDus-tRNA complexes.