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Biophysical characterization of styryl dye-membrane interactions
1Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, USA.
Biophysical Journal
|July 8, 2009
Summary
Styryl dyes (FM dyes) are used to study synaptic vesicle recycling. This study reveals their membrane dissociation occurs on millisecond timescales, faster than previously thought, aiding interpretation of neuronal function.
Area of Science:
- Neuroscience
- Biophysics
- Chemical Biology
Background:
- Styryl dyes, also known as FM dyes, are vital fluorescent probes for studying synaptic vesicle recycling in neurons.
- Previous research has lacked direct comparisons of FM dye properties and their membrane interaction kinetics.
Purpose of the Study:
- To compare fluorescence intensities of FM dyes bound to membranes.
- To measure time-resolved dye-membrane binding and unbinding reactions.
- To characterize the kinetics of a new lipophilic dye, SGC5.
Main Methods:
- Comparative fluorescence intensity measurements of FM dyes and SGC5.
- Stopped-flow kinetics to determine dye-membrane binding and unbinding rates.
- Analysis of factors influencing dissociation, including temperature, pH, and cholesterol.
Main Results:
- Fluorescence intensity correlated with lipophilic tail length: SGC5 > FM1-84 > FM1-43 > SynaptoGreen C3 > FM2-10/FM4-64/FM5-95.
- Dye hydrophobicity dictates affinity and dissociation rates.
- All tested dyes dissociated from membranes on millisecond timescales, significantly faster than overall presynaptic destaining.
Conclusions:
- Dye dissociation from neuronal membranes is rapid (milliseconds).
- This rapid dissociation is faster than previously appreciated and impacts the interpretation of synaptic vesicle recycling studies.
- Departitioning kinetics are temperature-dependent but independent of pH and cholesterol.
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