No abstract

No abstract

No abstract

No abstract

Metabolic changes of Daphnia magna pools due different abiotic factors linked to global climate change (salinity, temperature and hypoxia) were investigated using untargeted GC-MS and advanced chemometric strategies using a three factors two-level full factorial experimental design (DoE). Effects of these three factors and identity of the metabolites whose concentrations changed because of them were investigated. The simultaneous analysis of GC-MS data sets using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) allowed the resolution of the elution and mass spectra profiles of a large number of D. magna metabolites. Changes in peak areas of these metabolites were then analyzed by Principal Component Analysis (PCA), by ANOVA-Simultaneous Component Analysis (ASCA) and by Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA), and the combined effects of the three investigated stressors were assessed. Results confirmed the strong influence of increasing environmental salinity levels on the D. magna metabolome. This impact was specially highlighted by changes on the cellular content of carbohydrates, fatty acids, organic acids and amino acid molecules. In contrast, these effects were less significant for the other two factors (temperature and hypoxia) at the moderate stressing experimental conditions investigated in this work when they were not combined with salinity.

No abstract

The performances of gas chromatography with mass spectrometry and of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry are examined through the comparison of Daphnia magna metabolic profiles. Gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with mass spectrometry were used to compare the concentration changes of metabolites under saline conditions. In this regard, a chemometric strategy based on wavelet compression and multivariate curve resolution-alternating least squares is used to compare the performances of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry for the untargeted metabolic profiling of Daphnia magna in control and salinity-exposed samples. Examination of the results confirmed the outperformance of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry over gas chromatography with mass spectrometry for the detection of metabolites in D. magna samples. The peak areas of multivariate curve resolution-alternating least squares resolved elution profiles in every sample analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry were arranged in a new data matrix that was then modeled by partial least squares discriminant analysis. The control and salt-exposed daphnids samples were discriminated and the most relevant metabolites were estimated using variable importance in projection and selectivity ratio values. Salinity de-regulated 18 metabolites from metabolic pathways involved in protein translation, transmembrane cell transport, carbon metabolism, secondary metabolism, glycolysis, and osmoregulation.

No abstract