Open AccessCyanine Dye as Monitor of Membrane Potentials in Escherichia coli Cells and Membrane Vesicles
Author(s) -
LETELLIER Lucienne,
SHECHTER Emanuel
Publication year - 1979
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1979.tb04259.x
Subject(s) - valinomycin , vesicle , chemistry , cyanine , membrane potential , quenching (fluorescence) , membrane , fluorescence , iodide , biophysics , escherichia coli , electrochemical gradient , analytical chemistry (journal) , photochemistry , chromatography , biochemistry , inorganic chemistry , biology , physics , quantum mechanics , gene
The fluorescence response of a positively charged cyanine dye: 3,3′‐dimethylindodicarbocyanine iodide can be specifically related to the generation in Escherichia coli cells and E. coli membrane vesicles of an electrical membrane potential induced either by substrate oxidation or by an artificially imposed potassium diffusion gradient. The energy‐dependent quenching of the dye fluorescence correlates well with the known effect on ΔΨ of: oxidation of various energy sources, external pH and solute accumulation. Thus, in the vesicles, the fluorescence quenching of the dye increases from succinate to d ‐lactate, to ascorbate/phenazine methosulfate and parallels the increasing ability of these electron donors to generate a ΔΨ. In the vesicles, ΔΨ is only weakly dependent on external pH, whereas in the cells, ΔΨ increases with increasing external pH. Lactose accumulation in the vesicles results in the partial utilization of ΔΨ A calibration of the dye fluorescence in terms of ΔΨ has been determined using valinomycin‐induced potassium diffusion potential.