Iberius
The Iberius cell spectroscopy system measures
- Oxygen consumption at constant oxygen tension
- Membrane potential, pH gradient and proton motive force in millivolts
- Oxidation state and redox potential of mitochondrial NADH, ubiquinone and cytochrome c
- Turnover numbers of the bc1
complex, cytochrome c and cytochrome oxidase
- Oxidation state of bH, bL
and
c1
of the
bc1
complex, cytochrome c and heme a of cytochrome oxidase
- Functionality of complex I and cytochrome oxidase
Label-free from living cells in suspension, isolated mitochondria and isolated mitochondrial membranes.
It brings together several new technologies into a system that gives unprecedented insight into the function of the mitochondrial electron transport chain. Once conventional high-throughput respirometry has detected a functional change, the Iberius can pinpoint and explain that change.
The Iberius is available as a turn-key system for measuring mitochondrial bioenergetics in living mammalian cells and as a research system which has more flexibility. Contact us for a demonstration and to learn more.

An Iberius system installed at Cancer Research UK, Scotland Institute
Control over Oxygen
The oxygen tension in the stirred cell suspension is precision controlled by exchange of oxygen across an oxygen-permeable membrane using a computerized gas blended to mix oxygen nitrogen and carbon dioxide. allowing finger-tip control of the oxygen tension. The oxygen tension can be held at any value from anoxia to hyperoxia with continuous measurement of oxygen consumption.
Precision Spectroscopy
The hemes of the electron transport chain dominate the optical absorption spectrum of a cell suspension but the concentration of hemes is so low that the signal is smaller than that from an exoplanet crossing its star. The Iberius uses precision spectroscopy and multiwavelength spectral fitting to measure changes in the oxidation state of all the hemes of the electron transport chain in living cells and isolated mitochondria.
Absolute Quantitation
The Iberius uses absorption spectroscopy to measure changes in heme oxidation state from baseline in units of nanomolar. We use anoxic conditions to fully reduce the hemes and mitochondrial inhibitors to fully oxidize the hemes allowing the content of the hemes, and hence the respiratory complex, to be calculated and the oxidation state (percent oxidized) and redox potential to be calculated.
Mitochondrial Membrane Potential and pH Gradient
Mitochondrial membrane potential is estimated in cells using membrane permeable fluorescent cations such as TMRM, TMRE and JC1 that accumulate in the mitochondrial matrix exponentially depending on the membrane potential. These compounds suffer from a number of confounding factors
- Sensitive to the plasma membrane potential
- non-specific binding
- mitochondrial matrix swelling and cristae remodelling
- self-quenching and aggregation
- The fluorescence signal depends on the matrix volume which may not be constant.
The signal is rarely quantitated in millivolts.
The b-hemes of the bc1
complex straddle the membrane and are an intrinsic sensor of the membrane potential. The Iberius measures the oxidation state of the hemes and calculates the membrane potential, in millivolts, from their equilibrium. The Iberius can also measure the pH gradient, in millivolts, from the equilibrium of the
bc1
complex.
Functionality of Complex I
The functionality of a reversible, near-equilibrium enzyme, such as complex I, is a metric of how well the enzyme functions.
At equilibrium (ΔG=0), the net flux through complex I is zero. The flux increases linearly with ΔG as complex I is driven away from equilibrium and then saturates far from equilbrium. The functionality is the slope of the force (ΔG)-flux relationship. If complex I is operating with high functionality then the complex needs to be displaced from equilibrium by a small mount to achieve high electron transfer and proton pumping. A post translational modification, such as a signalling phosphorylation, would be expected to change the functionality.