Cell Meter™ Fluorimetric Cellular Voltage Assay Kit

Almost all plasma membranes have an electrical potential across them, with the inside usually negative with respect to the outside. Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential. This change in the electric field can be quickly affected by either adjacent or more distant ion channels in the membrane. Those ion channels can then open or close as a result of the potential change, reproducing the signal. Cell Meter™ Fluorimetric Cellular Voltage Assay Kit uses a FRET pair (VSB 405 and VSR 555) to monitor changes in cellular membrane potentials. The lipophilic VSB 405 is primarily located on the outer layer of lipid membranes while the localization of VSR 555 is sensitive to cellular membrane potential. At rest state, the inner layer of has a relatively negative potential, making VSR 555 predominantly located in close proximity to the outer layer of cell membranes, thus close to the blue fluorescent VSB405, resulting in efficient fluorescence transfer from blue (VSB 405) to red (VSR 555). When the cell is depolarized, VSR 555 translocates to the inner layer of the cell membrane, thus separating the FRET pair and disrupting FRET. The ratio of blue/red fluorescence is proportional to the cell voltage. This assay can used for screening compounds that modulate ion channels.