Oxygen flux

high-resolution terminology - matching measurements at high-resolution

Oxygen flux

Description

Oxygen flux, J_O2, is a specific quantity. Oxygen flux is oxygen flow, I_O2 [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: J_O2

Reference: Gnaiger 2014 MitoPathways, Gnaiger 1993 PAC, Renner_2003_Biochim_Biophys_Acta

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MitoPedia methods: Respirometry

MitoPedia O2k and high-resolution respirometry: DatLab

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HRR: Theory

MitoPedia O2k and high-resolution respirometry: O2k-Open Support

Instability of the oxygen signal in the open O2k-Chamber

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.