- high-resolution terminology - matching measurements at high-resolution
Oxygen flux
Description
Oxygen flux, J, is a specific quantity. Oxygen flux is oxygen flow, I [mol·s-1 per system], divided by system size. Flux may be volume-specific (flow per volume [pmol·s-1·ml-1]), mass-specific (flow per mass [pmol·s-1·mg-1]), or marker-specific (e.g. flow per mtDNA). Oxygen flux (e.g. per body mass, or per cell mass) is distinguished from oxygen flow (per subject, or per million cells).
Abbreviation: JO2
Reference: Gnaiger 2014 MitoPathways, Gnaiger 1993 PAC, Renner_2003_Biochim_Biophys_Acta
MitoPedia methods:
Respirometry
Labels:
HRR: Theory
Oxygen flux in open O2k-Chamber
MitoPedia O2k and high-resolution respirometry:
O2k-Open Support
In an open chamber of the O2k the liquid phase in the chamber (aqueous medium) is in equilibrium with the atmosphere. All oxygen consumed by the polarographic oxygen sensor (POS) is immediately replaced from the atmosphere. The oxygen signal therefore has to be constant and the (negative) time derivative of the oxygen signal, called "O2 slope uncorr." in DatLab, has to be zero. The background corrected oxygen flux is meaningless for the open chamber situation. This is because the background correction at air saturation subtracts the consumption of oxygen by the sensor from the negative slope, when diffusion into and out of the chamber is zero at air saturation. Therefore, the background-corrected oxygen flux in the open chamber at air saturation is shown as a negative value. To avoid this apparent artefact, the "O2 slope uncorr." is selected to be shown while the chamber is open. Only Graph Layouts that display "O2 slope uncorr." are suitable for assessing the stability of the oxygen signal when the chamber is open. Such Layouts are:
- 01 Calibration Exp Gr3-Temp
- 02 Background Experiment
- 04 Flux per Volume uncorrected
- Z Trouble Shooting
The observation of a zero flux with an open chamber is an important performance parameter. It indicates that thermal stability and equilibrium of oxygen between the gas and aqueous phases have been reached. Therefore no experiment should be started before a zero "O2 slope uncorr." has been reached with an open chamber. The suggested criterion for signal stability is a "O2 slope uncorr." between -1 pmol/(s ml) and + 1 pmol/(s ml).
Problem
- The "O2 slope uncorr." does not reach the interval +/- 1 pmol/(s ml) even after a prolonged time (1 to 2 hours).
Solutions
- The oxygen level in the gas phase may not correspond to air. Move the stopper upwards to exchange the gas phase and insert it partially using the Stopper-Spacer as a guide.
- The "O2 slope uncorr." is always calculated from the calibrated O2 signal. Check the POS calibration.
- Observe the Raw signal and check if it is in the expected range
- If the raw signal is unstable, and thereby creating an apparent O2 flux, follow the instructions for Locating a problem.
See also
