Search!

Updated: April 5, 2005
Figure 22.1 Response mechanisms of membrane potential–sensitive probes. Fast-response probes undergo electric field–driven changes of intramolecular charge distribution that produce corresponding changes in the spectral profile or intensity of their fluorescence (represented by color changes in the illustration). Slow-response probes are lipophilic anions (in this illustration) or cations that are translocated across membranes by an electrophoretic mechanism. Fluorescence changes associated with transmembrane redistribution (represented by color changes in the illustration) result from sensitivity of the probe to intracellular and extracellular environments. Thus, potentiometric response speeds directly reflect the time constants of the underlying processes — fast intramolecular redistribution of electrons versus relatively slow transmembrane movement of entire molecules.
Image