![]() ![]() A typical isotope tracer experiment can result in multiple chromatograms, each containing mass spectrometric (MS) information on dozens of analytes, each of which can yield mass isotopomer patterns of multiple fragments. As parallel processing of samples and automated instrumental analyses have become common, accurate processing of labeling data can limit the throughput of flux analysis or profiling. The example of metabolomics is instructive where sample preparation, spectrometric analysis and data processing are now routinely integrated. ![]() This involves automating and integrating different steps of the analytical process. ![]() In other “omic” technologies higher throughput rates have evolved through the development of more efficient workflows. To avoid systematic errors in the determined fluxes, the labeling levels detected have to be corrected for these biases. the McLafferty rearrangement and (iv) dilution by the original biomass of the biological sample prior to the feeding of isotope labeled tracers. The extent of this depends on the chemical nature of the metabolites, the mass spectrometric technique employed, and the sample composition, e.g. The determination of the amount of label taken up is complicated by several factors: (i) naturally occurring stable isotopes (NOIs) of almost all elements found in metabolites, including 13C: 1.1%, 2H 0.0115%, 17O 0.038%, 18O 0.2% 15N 0.366%, and 34S: 4.2%, (ii) additional elements with stable isotopes introduced by derivatization such as 29Si or 30Si, natural abundance 4.7% and 3.1%, respectively (iii) proton gain or loss during mass spectrometric analysis. However, MFA is characterized by certain technical and conceptual challenges, for example the exact quantification of the stable isotopes introduced to the system under investigation. Taken together the model and the metabolite labeling information facilitate the calculation of in vivo fluxes not accessible by direct techniques. To achieve this, MFA combines a stoichiometric model, as the mathematical representation of the metabolic network, and measurement data from isotope labeling experiments. MFA allows the determination of in vivo fluxes in a given metabolic network.
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