DiSBAC₂(3) (Bis-(1,3-Diethylthiobarbituric Acid)Trimethine Oxonol)

The slow-response potential-sensitive probe, DiSBAC₂(3) can enter depolarized cells where it binds to intracellular proteins or membrane and exhibits enhanced fluorescence and a red spectral shift. Increased depolarization results in additional influx of the anionic dye and an increase in fluorescence. Conversely, hyperpolarization is indicated by a decrease in fluorescence. Potential-dependent fluorescence changes generated by this bis-oxonol are typically ∼1% per mV. Also, this probe has an excitation maxima of 530 nm and emission maxima of 560 nm. DiBAC dyes are excluded from mitochondria because of their overall negative charge, making them superior to carbocyanines for measuring plasma membrane potentials.