Flux control ratio

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Bioblasts - Richard Altmann and MiPArt by Odra Noel
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Flux control ratio


Flux control ratios (FCR), are ratios of oxygen flux in different respiratory control states, normalized for maximum flux in a common reference state, to obtain theoretical lower and upper limits of 0.0 and 1.0 (0% and 100%).

For a given protocol or set of respiratory protocols, flux control ratios provide a fingerprint of coupling and substrate control independent of (i) mt-content in cells or tissues, (ii) purification in preparations of isolated mitochondria, and (iii) assay conditions for determination of tissue mass or mt-markers external to a respiratory protocol (CS, protein, stereology, etc.). FCR obtained from a single respirometric incubation with sequential titrations (sequential protocol; SUIT protocol) provide an internal normalization, expressing respiratory control independent of mitochondrial content and thus independent of a marker for mitochondrial amount. FCR obtained from separate (parallel) protocols depend on equal distribution of subsamples obtained from a homogenous mt-preparation or determination of a common mitochondrial marker.

Abbreviation: FCR

Reference: Gnaiger 2014 MitoPathways, Gnaiger 2009 Int J Biochem Cell Biol, Pesta 2012 Methods Mol Biol, MiPNet19.18E O2 flux analysis - DatLab 6

MitoPedia concepts: Respiratory control ratio, SUIT concept 

MitoPedia methods: Respirometry 

MitoPedia O2k and high-resolution respirometry: DatLab 

Unknown sample concentration and normalization per unit sample [x]

  • Used in new Excel Template for DatLab 7.4
If the sample concentration is not yet known, the box ‘Known sample concentration’ can be unchecked, and the concentration will be considered by default as 1, with units [x·mL-1]. In this way, flux values can be normalized and FCRs can be obtained even if the sample concentration is unknown. Extensive_quantity

Flux control factor: normalization of mitochondrial respiration

» More details: Flux control factor


The entire plot of oxygen flux can be transformed to a FCR. Click on 'Flux/Slope' in the pull-down menu. - MiPNet19.18E O2 flux analysis - DatLab 6.