The Use of Optical Probes to Monitor the Formation of pH Gradients and Membrane Potential in Tonoplast Membrane Vesicles
Concomittant with an increasing interest in the role of ion gradients in energizing and regulating a variety of cellular functions, methods have been developed to monitor these gradients in cells, organelles, and membrane vesicles. Of particular interest are gradients of H+ (ΔpH) which, in association with electric potential gradients (ΔΨ), are of central importance in cellular bioenergetics. Because of this central importance of H+ and electric potential gradients a variety of methods have been developed to specifically monitor the formation and magnitude of ΔpH and Δψ in membrane structures too small to be impaled with microelectrodes. Most methods rely on the use of chemical “probes” which distribute across membranes in response to ΔpH or Δψ and whose distribution can be quantified and correlated with the magnitude of the gradient.
KeywordsMembrane Vesicle Fluorescence Quenching Optical Probe Diffusion Potential Electric Potential Gradient
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