- high-resolution terminology - matching measurements at high-resolution
Respiratory acceptor control ratio
Description
The respiratory acceptor control ratio (RCR) is defined as State 3/State 4 [1]. If State 3 is measured at saturating [ADP], RCR is the inverse of the OXPHOS control ratio, L/P (when State 3 is equivalent to the OXPHOS state, P). RCR is directly but non-linearly related to the phosphorylation control factor, βP/P = 1-L/P. Whereas βP/P has boundaries from 0.0 to 1.0, RCR ranges from 1.0 to infinity, which needs to be considered when performing statistical analyses. In intact cells, RCR has been used for the ratio State 3u/State 4o, i.e. for the inverse L/E ratio [2,3]. Then for conceptual and statistical reasons, RCR should be replaced by the biochemical coupling efficiency, jE-L= 1-L/E [4].
Abbreviation: RCR
Reference: Chance 1955 JBC-III, Gnaiger 2014 MitoPathways
MitoPedia methods:
Respirometry
MitoPedia topics: "Respiratory control ratio" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property.
Respiratory control ratio"Respiratory control ratio" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property.
Compare
- OXPHOS coupling efficiency
- Discussion: OXPHOS versus ETS capacity.
- More details: Β»Biochemical coupling efficiency
Problem: The RCR is low in isolated mitochondria
At a high mitochondrial concentration (0.5 mg protein/ml), ADP is exhausted very rapidly if added at a concentration typically used for State 3 measurements (200-300 Β΅M), which may stimulate flux below the ADP-saturated state of OXPHOS capacity. The slope increases sharply and returns to State 4 (LEAK), even before the plot of flux shows the true maximum, resulting in a low apparent RCR.
Tests and solutions
- Reduce the data recording interval (standard is 2 seconds) to the minimum of 0.2 s (setting in the Oxygraph Control window; see MiPNet12.06 O2k-Start). As the data recording interval is reduced, the flux appears more noisy, but represents transitions more accurately and reduces the apparent time-delay. At high flux per volume, the increased noise level presents no problem. Flux then shows a period of constant OXPHOS capacity rather than a sharp peak.
- Reduce the mitochondrial concentration, thus prolonging the duration of ADP-saturated respiration (OXPHOS capacity) over 120 seconds. If flux reaches a constant maximum value, then analysis is possible without application of signal deconvolution (standard plot of flux in DatLab).
- Otherwise, export the data into DatLab 2, and apply a time correction (signal deconvolution), as described by Gnaiger 2001 Respir Physiol.
- See also βNotes on Time resolutionβ.
References
- Chance B, Williams GR (1955) Respiratory enzymes in oxidative phosphorylation: III. The steady state. J Biol Chem 217: 409-427.
- HΓΌtter E, Renner K, Pfister G, StΓΆckl P, Jansen-DΓΌrr P, Gnaiger E (2004) Senescence-associated changes in respiration and oxidative phosphorylation in primary human fibroblasts. Biochem J 380: 919-928.
- Gnaiger E (2009) Capacity of oxidative phosphorylation in human skeletal muscle. New perspectives of mitochondrial physiology. Int J Biochem Cell Biol 41: 1837β1845.
- Gnaiger E (2014) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 4th ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck