Voltage dependent dye

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A voltage-dependent dye (also potentiometric dye , voltage-sensitive dye ) is a dye that changes its color when a voltage is applied .


Voltage-dependent dyes are used, among other things, in electrophysiology and neurobiology in order to be able to microscopically follow changes in membrane potential such as action potentials , e.g. B. in neurons and myocytes . This shows the origin, the direction and the speed of propagation of the action potential. The change in color is evident in the event of a voltage change through a change in the extinction coefficient or through a shift in the maximum in the absorption spectrum or, in the case of fluorescent dyes, through a shift in the maximum in the emission spectrum . The exact mechanism of the change in color or increase in color of the various types of dye is still unknown. In the case of voltage-dependent merocyanine dyes, there is no shift in wavelength, but only an increase in fluorescence. Therefore, various mechanisms have been discussed, e.g. B. the dislocation of the dye between the membrane and the aqueous environment, a change in the dielectricity of the surrounding biomembrane or dimerizations and their dissociation. In contrast, there is a shift in the spectral maxima with ANEP dyes.

The color change can be followed by a decrease in the extinction coefficient at the original wavelength or by an increase in the extinction coefficient at the wavelength of the changed color. Since voltage-dependent dyes are less precise in determining the change in voltage compared to electrodes , they are mostly used where electrodes cannot be inserted, e.g. B. in mitochondria . Alternatively, voltage-dependent reporter proteins are used, e.g. B. VSFP or PROPS.

Compared to electrodes, many neurons can be observed in parallel, including the direction and speed of the potentials. The process is partially reversible; after observation, the cells can be rinsed with culture medium to remove the dye. The reproducibility , the signal-to-noise ratio and the sensitivity are comparatively lower. The diffusion through connective tissue is less than through other tissues. Colorants can have undesirable pharmacological effects, e.g. B. an increase in photosensitivity . Serum components in the culture medium can reduce the fluorescence, which is why it is usually stained in an isotonic buffer.


Slow-response probes change their distribution coefficient after a change in voltage and are only then stored in the cell membrane, e.g. B. some cationic cyanines (e.g. Merocyanin 540), rhodamines , and ionic oxonols (e.g. DiBAC 4 ).

Fast-response probes (in German, fast-reacting probes') are generally amphiphilic dyes having aliphatic side chains in the cell membrane store and a hydrophilic radical with the fluorophore z. B. ANNINE-6, ANNINE-6plus. Voltage dependent dyes are often aminonaphthylethenylpyridine dyes, e.g. B. di-4-ANEPPS (1- (3-sulfonatopropyl) -4- [β- [2- (di-n-butylamino) -6-naphthyl] vinyl] pyridinium betaine), di-8-ANEPPS and RH237.


The voltage-dependent dye merocyanine 540 was first published in 1976 by Guy Salama and Martin Morad. The ANEP dyes were described by Leslie Loew's group from 1985 onwards.


  • Leslie M. Loew: Potentiometric dyes: Imaging electrical activity of cell membranes. In: Pure Appl. Chem. (1996), Vol. 68, No. 7, pp. 1405-1409.

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