Metabolomics pp 177-197 | Cite as

Determination of Metabolic Flux Ratios From 13C-Experiments and Gas Chromatography-Mass Spectrometry Data

Protocol and Principles
  • Annik Nanchen
  • Tobias Fuhrer
  • Uwe Sauer
Part of the Methods in Molecular Biology™ book series (MIMB, volume 358)


Network topology is a necessary fundament to understand function and properties of microbial reaction networks. A valuable method for experimental elucidation of metabolic network topology is metabolic flux ratio analysis, which quantifies the relative contribution of two or more converging pathways to a given metabolite. It is based on 13C-labeling experiments, gas chromatography-mass spectrometry analysis, and probabilistic equations that relate mass distributions in proteinogenic amino acids to pathway activity. Here, we describe the protocol for sample generation and illustrate the principles underlying the calculation of metabolic flux ratios with three examples. These principles are also implemented in the publicly available software FiatFlux, which directly calculates flux ratios from the mass spectra of amino acids.


Metabolic Flux Analysis Correction Matrix Input Substrate Proteinogenic Amino Acid Natural Isotope Abundance 
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Copyright information

© Humana Press Inc. 2007

Authors and Affiliations

  • Annik Nanchen
    • 1
  • Tobias Fuhrer
    • 1
  • Uwe Sauer
    • 1
  1. 1.Institute for Molecular Systems BiologyETH ZürichZürichSwitzerland

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