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Bjørn Grung

Publications and source records attributed to Bjørn Grung.

3 recordsLinked to original sources

High-throughput data analysis for detecting and identifying differences between samples in GC/MS-based metabolomic analyses.

In metabolomics, the objective is to identify differences in metabolite profiles between samples. A widely used tool in metabolomics investigations is gas chromatography-mass spectrometry (GC/MS). More than 400 compounds can be detected in a single analysis, if overlapping GC/MS peaks are deconvoluted. However, the deconvolution process is time-consuming and difficult to automate, and additional processing is needed in order to compare samples. Therefore, there is a need to improve and automate the data processing strategy for data generated in GC/MS-based metabolomics; if not, the processing step will be a major bottleneck for high-throughput analyses. Here we describe a new semiautomated strategy using a hierarchical multivariate curve resolution approach that processes all samples simultaneously. The presented strategy generates (after appropriate treatment, e.g., multivariate analysis) tables of all the detected metabolites that differ in relative concentrations between samples. The processing of 70 samples took similar time to that of the GC/TOFMS analyses of the samples. The strategy has been validated using two different sets of samples: a complex mixture of standard compounds and Arabidopsis samples.

Arabidopsis↗

Assigning environmental variables to observed biological changes.

A method for assigning environmental variables to observed biological changes in benthic communities is proposed. The approach requires biological and environmental sampling at the same sites. Additionally, a biological gradient or trend such as a change in observed species or a significant change in their relative abundances is necessary in order to connect the biological observations to the environmental measurements. Whether there is a statistical significant correspondence between the environmental measurements and the biological changes is tested after quantifying the biological changes by using the community disturbance index (CDI). Finally, the environmental variables that are most strongly associated with the biological changes are identified, and it is proposed that these are strong candidates as the pollutants responsible for the biological changes observed. However, this cannot be confirmed using the monitored data only. The approach is tested on data collected in monitoring surveys at the Ekofisk oil field in the North Sea. The results indicate the method is feasible for assigning environmental variables to observed biological changes.

Ecosystem↗

Toxicological evaluation of complex mixtures by pattern recognition: correlating chemical fingerprints to mutagenicity.

We describe the use of pattern recognition and multivariate regression in the assessment of complex mixtures by correlating chemical fingerprints to the mutagenicity of the mixtures. Mixtures were 20 organic extracts of exhaust particles, each containing 102-170 individual compounds such as polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs, oxy-PAHs, and saturated hydrocarbons. Mixtures were characterized by full-scan GC-MS (gas chromatography-mass spectrometry). Data were resolved into peaks and spectra for individual compounds by an automated curve resolution procedure. Resolved chromatograms were integrated, resulting in a predictor matrix that was used as input to a principal component analysis to evaluate similarities between mixtures (i.e., classification). Furthermore, partial least-squares projections to latent structures were used to correlate the GC-MS data to mutagenicity, as measured in the Ames Salmonella assay (i.e., calibration). The best model (high r2 and Q2) identifies the variables that co-vary with the observed mutagenicity. These variables may subsequently be identified in more detail. Furthermore, the regression model can be used to predict mutagenicity from GC-MS chromatograms of other organic extracts. We emphasize that both chemical fingerprints as well as detailed data on composition can be used in pattern recognition.

Animals↗