Invitrogen™ Tetramethylrhodamine, Methyl Ester, Perchlorate (TMRM)

If you use our FluoVolt Membrane Potential Kit (Cat. No. F10488), the kit provides a background suppressor to reduce this problem. For other indicators, consider the use of BackDrop Background Suppressor (Cat no. R37603, B10511, and B10512).

Molecules that change their structure in response to the surrounding electric field can function as fast-response probes for the detection of transient (millisecond) potential changes. Slow-response dyes function by entering depolarized cells and binding to proteins or membranes. Increased depolarization results in additional dye influx and an increase in fluorescence, while hyperpolarization is indicated by a decrease in fluorescence. Fast-response probes are commonly used to image electrical activity from intact heart tissues or measure membrane potential changes in response to pharmacological stimuli. Slow-responding probes are often used to explore mitochondrial function and cell viability.

A membrane potential indicator selection guide can be found here (https://www.thermofisher.com/us/en/home/life-science/cell-analysis/cell-viability-and-regulation/ion-indicators/membrane-potential-indicators.html).

Regardless of which dye you use - tetramethylrhodamine, methyl ester (TMRM), JC-1 or MitoTracker - untreated cells will fluoresce. It's just that cells with reduced mitochondrial membrane potential will fluoresce less. It is the degree of change which is important. JC-1 dye not only changes intensity, but has a ratiometric spectral change in excitation and emission. It is very important to have an untreated control as well as a positive control treated with a mitochondrial membrane potential destabilizer, such as CCCP or FCCP. Most mitochondrial stains are only for use with live cells, as the signal will not be retained to the same degree with fixation.