Glycan reducing end dual isotopic labeling (GREDIL) for mass spectrometry-based quantitative N-glycomics

GREDIL for quantitative N-glycomics largely improves the stability of N-glycan 18O-labeling and greatly decreases the interference of isotopic cluster overlap.

Features-Based Deisotoping Method for Tandem Mass Spectra

For high-resolution tandem mass spectra, the determination of monoisotopic masses of fragment ions plays a key role in the subsequent peptide and protein identification. In this paper, we present a new algorithm for deisotoping the bottom-up spectra. Isotopic-cluster graphs are constructed to describe the relationship between all possible isotopic clusters. Based on the relationship in isotopic-cluster graphs, each possible isotopic cluster is assessed with a score function, which is built by combining nonintensity and intensity features of fragment ions. The non-intensity features are used to prevent fragment ions with low intensity from being removed. Dynamic programming is adopted to find the highest score path with the most reliable isotopic clusters. The experimental results have shown that the average Mascot scores and F-scores of identified peptides from spectra processed by our deisotoping method are greater than those by YADA and MS-Deconv software.

Production and use of mycotoxins uniformly enriched with stable isotopes for their dosage in biological samples

Due to their low concentrations in biological matrices, mycotoxin analyses often encounter detection and quantification problems, especially for toxicokinetic studies. We have developed a strategy to produce in a single process, several fungi secondary metabolites uniformly enriched with 13C, 15N stable isotopes in their 'natural' composition. This includes: (1) a plant culture in the presence of 10%, 50% or 100% 13CO2 as the only source of carbon, and in the presence or not of 10% 15N-enriched nitrogen salts – as expected wheat or maize uniformlyincorporate enriched isotopes into their bioproducts; (2) a subsequent solid culture of different filamentous fungi on plant biomass led to the production of a 'natural' mixture of isotopes-enriched mycotoxins – these compounds exhibit a characteristic isotopic cluster, which can be easily detected by mass spectrometry. As an example, we achieved 10% uniformly 13C-enriched zearalenone, deoxynivalenol and mycophenolic acid by growing Fusarium graminearum or Penicillium brevicompactum on 10% 13C enriched wheat seeds and 3 to 10% 13C, 15N uniformly enriched fumonisins from Fusarium verticillioides cultures on maize seeds or straw. These compounds were used for metabolism and transport studies in mammals either in vitro or in vivo and analysed by MS and MSn spectra of the isotopic cluster but also by 13C, 15N NMR. Moreover, such isotopic pattern enrichment can be used for quantitative evaluations of mycotoxins transport across mammalian biological membranes, alone or in their 'natural' conditions in the presence of other fungi secondary metabolites. Finally, we used such enriched compounds with high reliabilityin order to study zearalenone metabolism but these enriched compounds would also be used as internal standards to quantify zearalenone or fumonisins in contaminated food samples.