Biomaterial Database

Optical probes of membrane potential. 1976

A Waggoner

There are two basically different mechanisms for the fluorescence and absorption changes of merocyanine, cyanine and oxonol dyes. The permeant dyes (cyanine and oxonol dyes, with delocalized charges) work by a potential-dependent accumulation mechanism. These dyes show large (up to 80%) fluorescence and absorption changes with suspensions of cells, and the changes are complete in seconds. The impermeant dyes (merocyanine dyes, with localized charges) and the permeant dyes also show optical changes that take place in fractions of milliseconds. The rapid optical changes are relatively small (less than or equal to 5 X 10(-3)) but can often be easily detected in experiments with single cells. The rapid, nonaccumulative, optical changes result from membrane-localized dye movements. Cyanine dye-absorption changes occur because of a potential-dependent partition of dye between the membrane and the adjacent aqueous region at the high dye-concentration side of the membrane. Dimers and larger aggregates are formed in the aqueous region during the change. Merocyanine dyes may also work by the same mechanism. DiS-C3-(5) is presently the best dye for measuring membrane potentials of cells, organelles, and vesicles in suspension, but several other cyanines work nearly as well (P.J. Sims, A.S. Waggoner, C.-H. Wang, J.F. Hoffman, Biochemistry 13:3315, 1974). For each system, the ratio of dye to membrane must be varied until the optimum fluorescence change is found. A separate calibration curve must be obtained for each system. For measuring fluorescence and/or absorption changes in single cells, merocyanine 540 and diBA-C4-(5) work well but produce some photodynamic damage with high intensity illumination. A rhodanine merocyanine (WW-375) gives very large absorption changes and does not damage tissue during strong illumination. As the mechanisms of the optical changes are worked out, it should be possible to design and synthesize more sensitive, less toxic dyes that are easier to calibrate. And, as the mechanisms of the optical changes are worked out, these dyes may be useful for studying the structure and dynamics of excitable membranes.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D002468	Cell Physiological Phenomena	Cellular processes, properties, and characteristics.	Cell Physiological Processes,Cell Physiology,Cell Physiological Phenomenon,Cell Physiological Process,Physiology, Cell,Phenomena, Cell Physiological,Phenomenon, Cell Physiological,Physiological Process, Cell,Physiological Processes, Cell,Process, Cell Physiological,Processes, Cell Physiological
D005456	Fluorescent Dyes	Chemicals that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.	Flourescent Agent,Fluorescent Dye,Fluorescent Probe,Fluorescent Probes,Fluorochrome,Fluorochromes,Fluorogenic Substrates,Fluorescence Agents,Fluorescent Agents,Fluorogenic Substrate,Agents, Fluorescence,Agents, Fluorescent,Dyes, Fluorescent,Probes, Fluorescent,Substrates, Fluorogenic
D000817	Anilino Naphthalenesulfonates	A class of organic compounds which contain an anilino (phenylamino) group linked to a salt or ester of naphthalenesulfonic acid. They are frequently used as fluorescent dyes and sulfhydryl reagents.	Naphthalenesulfonates, Anilino
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013050	Spectrometry, Fluorescence	Measurement of the intensity and quality of fluorescence.	Fluorescence Spectrophotometry,Fluorescence Spectroscopy,Spectrofluorometry,Fluorescence Spectrometry,Spectrophotometry, Fluorescence,Spectroscopy, Fluorescence
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships