Difference between revisions of "Q-redox state"

Revision as of 17:47, 9 February 2021

high-resolution terminology - matching measurements at high-resolution

Q-redox state

Description

The Q redox state reflects the redox status of the Q-junction in the mitochondrial or chloroplast electron transfer system (ETS). Ubiquinones, also known as coenzyme Q, and plastoquinones are essential mobile components of the mitochondria and chloroplasts that transfer electrons between the respiratory or photosynthetic complexes of the ETS. The Q redox state is dependent on the relative activities of the ETS enzymes that reduce and oxidize the quinones. Therefore, deficiencies in the mitochondrial ETS, originating from e.g. the malfunction of respiratory enzymes (complexes), can be detected by measuring the changes of the Q redox state with respect to respiratory activity.

Abbreviation: Q_r/Q_t

Calculation of the Q redox fractions

The Q redox state is expressed as the fraction of reduced Q (Q_r) in each steady state of a SUIT protocol. In order to calculate the reduced Q fraction, the raw Q signal (Uraw) is calibrated against the fully oxidized Q signal (U_ox) and the fully reduced Q signal (U_red). U_ox is measured in the presence of CoQ2 and isolated mitochondria. The CI inhibitor rotenone might have to be added to inhibit respiration of endogenous substrates. U_red is determined under anoxia after the sample consumed the accessible O₂ in the O2k-chamber. Q_r is calculated as a proportion of the fully reduced Q. The sum of the oxidized and reduced fractions of Q equals 1, Q_r+Q_ox = 1. In this formalism the intermediate redox state of semiquinone is not taken into account.

$Q fraction.png$

The Q-Module is part of the NextGen-O2k project

The Q-Module allows for monitoring of the redox state of electron transfer-reactive coenzyme Q at the Q-junction using the specific Q-Stoppers with the integrated three-electrode system and the modified electronics of the NextGen-O2k. Cyclic voltammetry is used for quality control and for defining the polarization voltage applied during Q-redox measurements.

Reference:

Komlódi T, Cardoso LHD, Doerrier C, Moore AL, Rich PR, Gnaiger E (2021) Coupling and pathway control of coenzyme Q redox state and respiration in isolated mitochondria. Bioenerg Commun 2021.3. https://doi.org/10.26124/bec:2021-0003

Communicated by Komlodi T, Cardoso LHD 2020-07-28

Bioblast links: Q - >>>>>>> - Click on [Expand] or [Collapse] - >>>>>>>

Coenzyme Q

» Coenzyme Q

» Quinone, Ubiquinone Q; oxidized

» Quinol, Ubiquinol QH₂; reduced

» Semiquinone

» Coenzyme Q2

» Q-redox state

» Q-pools

Mitochondrial pathways, respiratory Complexes, and Q

» Q-cycle

» Q-junction

» Convergent electron flow

» NS-pathway

» FNS

» FNSGp

» N-pathway

» Reverse electron flow from CII to CI

» CI

» Rotenone

» Amytal

» Piericidin

» S-pathway

» CII

» Malonate

» F-pathway

» CETF, Electron-transferring flavoprotein complex

» Gp-pathway

» CGpDH, Glycerophosphate dehydrogenase complex

» CIII

» Myxothiazol

» Choline dehydrogenase

» Dihydro-orotate dehydrogenase

NextGen-O2k and Q-Module

» NextGen-O2k

» Q-Module

» Q-Sensor

» Cyclic voltammetry

» Three-electrode system

General

» Categories of SUIT protocols

» Electron transfer pathway

» Electron-transfer-pathway state

» F-junction

» N-junction

@@ Line 5: / Line 5: @@
-== Calculation of the Q redox fractions (''in preparation'') ==
+== Calculation of the Q redox fractions ==
-The Q redox state is expressed as the fraction of reduced Q (Q<sub>r</sub>) in each steady state of a SUIT protocol.  In order to calculate the reduced Q fraction, the raw Q signal (Uraw) is calibrated against the fully oxidized Q signal (''U''<sub>ox</sub>) and the fully reduced Q signal (''U''<sub>red</sub>). ''U''<sub>ox</sub> is measured in the presence of CoQ2 and isolated mitochondria. The CI inhibitor rotenone might have to be added to inhibit respiration of endogenous substrates. ''U''<sub>red</sub> is determined under anoxia after the sample consumed the accessible O<sub>2</sub> in the O2k-chamber. ''Q''<sub>r</sub> is calculated as a proportion of the fully reduced Q (Table 1). The sum of the oxidized and reduced fractions of Q equals 1, ''Q''<sub>r</sub>+''Q''<sub>ox</sub> = 1. In this formalism the intermediate redox state of semiquinone is not taken into account.
+The Q redox state is expressed as the fraction of reduced Q (Q<sub>r</sub>) in each steady state of a SUIT protocol.  In order to calculate the reduced Q fraction, the raw Q signal (Uraw) is calibrated against the fully oxidized Q signal (''U''<sub>ox</sub>) and the fully reduced Q signal (''U''<sub>red</sub>). ''U''<sub>ox</sub> is measured in the presence of CoQ2 and isolated mitochondria. The CI inhibitor rotenone might have to be added to inhibit respiration of endogenous substrates. ''U''<sub>red</sub> is determined under anoxia after the sample consumed the accessible O<sub>2</sub> in the O2k-chamber. ''Q''<sub>r</sub> is calculated as a proportion of the fully reduced Q. The sum of the oxidized and reduced fractions of Q equals 1, ''Q''<sub>r</sub>+''Q''<sub>ox</sub> = 1. In this formalism the intermediate redox state of semiquinone is not taken into account.
+:::[[File:Q fraction.png| 900 px]]
 == The [[Q-Module]] is part of the [[NextGen-O2k]] project==
 {{Template:Q-Module}}