Talk:Q-redox state

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Talk:Q-redox state


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: Qr/Qt

Calculation of the Q redox ratios

To analyze the Q redox state, SUIT protocols are designed with one step in which the Q is fully reduced and one in which it is fully oxidized. The values obtained will be used to calculate the Q redox ratios.

First, the signal is corrected for the fully oxidized Q state (Qox), which can be measured, e.g. in the presence of isolated mitochondria or permeabilized cells and CoQ2. (To fully oxidize the Q-pool rotenone can be added which inhibits respiration of endogenous substrates. However, it cannot be applied when NADH- or F-linked O2 flux is measured). Qox is then subtracted from the raw Q signal for every step before the calculation of the ratios:

Qr = Qraw-Qox

Then, the Q redox ratio is calculated between the given Q-signal in the presence of different substrates/inhibitors/uncouplers (Qr) and the fully reduced Q state (Qt, also corrected for Qox), which can be detected under anoxia for isolated mitochondria:


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

In the NextGen-O2k project we are working on developing the Q-Module for the new series of our O2k-Respirometer, the NextGen-O2k. The Q-Module allows us to simultaneously monitor the O2 flux and Q redox state of the Q-junction using the specific Q-Stoppers with the integrated three-electrode system and with the modified electronics in the O2k housing.

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

MitoPedia: NextGen-O2k

» NextGen-O2k«
Hydrogen peroxideH2O2
Hydrogen peroxide
Hydrogen peroxide, H2O2 or dihydrogen dioxide, is one of several reactive oxygen intermediates generally referred to as reactive oxygen species (ROS). It is formed in various enzyme-catalyzed reactions (e.g., superoxide dismutase) with the potential to damage cellular molecules and structures. H2O2 is dismutated by catalase to water and oxygen. H2O2 is produced as a signaling molecule in aerobic metabolism and passes membranes more easily compared to other ROS.
Light-enhanced dark respirationLEDRLight-enhanced dark respiration LEDR is a sharp (negative) maximum of dark respiration in plants in response to illumination, measured immediately after switching off the light. LEDR is supported by respiratory substrates produced during photosynthesis and closely reflects light-enhanced photorespiration (Xue et al 1996). Based on this assumption, the the total photosynthetic oxygen flux TP is calculated as the sum of the measured net photosynthetic oxygen flux NP plus the absolute value of LEDR.
Mitochondrial membrane potentialmtMP, Δψ [V]The mitochondrial membrane potential, mtMP, is the electric part of the protonmotive force, ΔpH+.

Δψ = ΔpH+ - ΔµH+ / F

mtMP or Δψ is the potential difference across the inner mitochondrial (mt) membrane, expressed in the electric unit of volt [V]. Electric force of the mitochondrial membrane potential is the electric energy change per ‘motive’ electron or per electron moved across the transmembrane potential difference, with the number of ‘motive’ electrons expressed in the unit coulomb [C].
NextGen-O2k InstrumentNextGen-O2k Instrument
NextGen-O2k Technical developments
Oxygen kineticsOxygen kinetics describes the dependence of respiration of isolated mitochondria or cells on oxygen partial pressure. Frequently, a strictly hyperbolic kinetics is observed, with two parameters, the oxygen pressure at half-maximum flux, p50, and maximum flux, Jmax. The p50 is in the range of 0.2 to 0.8 kPa for cytochrome c oxidase, isolated mitochondria and small cells, strongly dependent on Jmax and coupling state.
PB-ModulePB-ModuleThe PB-Module has been developed for conducting measurements of PhotoBiology, including photosynthesis. It consists of the PB-Sensor and electronic components which are an integral part of the NextGen-O2k. Measurements are recorded and evaluated with the DatLab 8 software.
PB-SensorThe PB-Sensor has been designed as a part of the PB-Module to provide with an external source of light, in the range of the blue (451 nm) or red (634 nm) wavelengths. This enables experiments for evaluating the production/consumption of O2 in the presence of light. The PB-Sensor consists on one LED and one photodiode mounted on the sensor tip behind a plastic cover. The LED emits with blue or red light on the sample and its intensity can be regulated from 0 to 5000 µEinsteins*m-2*s-1. The photodiode provides real-time measurement of the light intensity allowing for continuous adjustment to the desired value, which can also help compensate for the temperature rise due to the operation of the LED.
PhotoBiologyPBPhotoBiology is the science of the effect of light on biological processes. This includes photosynthesis, photochemistry, photophysics, photomorphogenesis, vision, bioluminescence, circadian rhythms and photodynamic therapy. Phototoxicity results from non-ionizing radiation (i.e. ultraviolet, visible and infrared radiation). Non-ionizing radiation is any type of electromagnetic radiation that does not carry enough energy per quantum (photon energy below 10 eV) to completely remove an electron from an atom or molecule. When photons interact with molecules, the molecules can absorb the photon energy and become excited, reacting with surrounding molecules and stimulating "photochemical" and "photophysical" changes. Respiration may be affected by light during photosynthesis or in dark respiration, with the transient response of light-enhanced dark respiration.
Q-ModuleQ-ModuleThe Q-Module, developed both for measuring the Q redox state and for cyclic voltammetry measurements, is an integral part of the NextGen-O2k and consists of the Q-Sensor, integrated electronic components in the O2k, and the DatLab software.
Q-SensorThe Q-Sensor has been designed as a part of the Q-Module for measurements with cyclic voltammetry and voltammetry, allowing for analysis of the Q redox state. The Q-Stopper with the reference electrode is called Q-Sensor, which is plugged in the NextGen-O2k. A three-electrode system is used to detect the Q redox state. Two of the three electrodes (glassy carbon and platinum electrode) are built into the Q-Stopper, while the reference electrode is removable (Reference-Electrode\2.4 mm).
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Mitochondrial NADH and respiration

» Nicotinamide adenine dinucleotide
» NADH electron transfer-pathway state
» N-junction
» Complex I
» Rotenone
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» Piericidin

Mitochondrial NADH production

» Tricarboxylic acid cycle
» Fatty acid oxidation


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Phosphorylation pathway

» Phosphorylation pathway
» ATP synthase
» Adenine nucleotide translocase
» Phosphate carrier

Phosphorylation pathway substrates

» Inorganic phosphate

Phosphorylation pathway inhibitors

» Oligomycin
» Carboxyatractyloside
» Atractyloside
» Bongkrekik acid

Coupling control

» Oxidative phosphorylation
» OXPHOS capacity
» P-L control efficiency
» ROUTINE respiration
» R-L control efficiency

Respiratory complexes and coupling

» Complex I
» Complex III
» Complex IV
» Proton pump
» Electron-transfer-pathway state

ATP production measurement

» Magnesium Green


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PhotoBiology: photosynthesis

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Plant physiology: respiration

» Photorespiration
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NextGen-O2k and PB-Module

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