An approach to the identification of unknown signals in selenium speciation analysis of yeast by reversed-phase chromatography with ICP-MS detection is described. The analytical strategy was based on: (i), heart-cutting of a Secontaining fraction in the reversed-phase chromatographic eluate followed by its lyophilization; (ii), pneumaticallyassisted electrospray (ESI) MS and ESI tandem MS of the lyophilizate; and (iii) confirmation of the fragmentation pattern obtained using the sulfur analogue of the seleno compound that was expected to have been identified. The approach developed allowed the identification of Seadenosylhomocysteine as the major selenium species in an extract of a selenized yeast sample.

No abstract

An MS-based method, combining reversed-phase capillary liquid chromatography (capillary LC) with quadrupole time-of-flight tandem mass spectrometry (nano-ESI Q-TOF MS/MS), was developed with the aim of identifying a set of peptides that can function as markers for peanut allergens. Emphasis was given to the identification of the three major peanut allergens Ara h 1, Ara h 2, and Ara h 3, because these proteins are considered to represent >30% of the total protein content of peanut and are directly relevant for the allergenic potential of this food. The analytical data obtained were used to perform databank searching in combination with de novo sequencing and led to the identification of a multitude of sequence tags for all three peanut allergens. Food processing such as roasting of peanuts is known to affect the stability of proteins and was shown to influence the detection of allergen sequence tags. The analysis of raw and roasted peanuts allowed the identification of five peanut-specific sequence tags that can function as markers of the specific allergenic proteins. For Ara h 1, two peptide markers were proposed, namely, VLEENAGGEQEER (m/z 786.88, charge 2+) and DLAFPGSGEQVEK (m/z 688.85, charge 2+), whereas for Ara h 2 only one peptide, RQQWELQGDR (m/z 439.23, charge 3+), was found to satisfy the required conditions. For Ara h 3, the two specific peptides, SPDIYNPQAGSLK (m/z 695.35, charge 2+) and SQSENFEYVAFK (m/z 724.84, charge 2+), were selected. Other peptides have been proposed as indicative for food processing.

The metabo-ring initiative brought together five nuclear magnetic resonance instruments (NMR) and 11 different mass spectrometers with the objective of assessing the reliability of untargeted metabolomics approaches in obtaining comparable metabolomics profiles. This was estimated by measuring the proportion of common spectral information extracted from the different LCMS and NMR platforms. Biological samples obtained from 2 different conditions were analysed by the partners using their own in-house protocols. Test #1 examined urine samples from adult volunteers either spiked or not spiked with 32 metabolite standards. Test #2 involved a low biological contrast situation comparing the plasma of rats fed a diet either supplemented or not with vitamin D. The spectral information from each instrument was assembled into separate statistical blocks. Correlations between blocks (e.g., instruments) were examined (RV coefficients) along with the structure of the common spectral information (common components and specific weights analysis). In addition, in Test #1, an outlier individual was blindly introduced, and its identification by the various platforms was evaluated. Despite large differences in the number of spectral features produced after post-processing and the heterogeneity of the analytical conditions and the data treatment, the spectral information both within (NMR and LCMS) and across methods (NMR vs. LCMS) was highly convergent (from 64 to 91 % on average). No effect of the LCMS instrumentation (TOF, QTOF, LTQ-Orbitrap) was noted. The outlier individual was best detected and characterised by LCMS instruments. In conclusion, untargeted metabolomics analyses report consistent information within and across instruments of various technologies, even without prior standardisation.Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-014-0740-0) contains supplementary material, which is available to authorized users.

No abstract