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Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
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Sensing cholesterol-induced rigidity in model membranes with time-resolved fluorescence spectroscopy and microscopy
Bidisha Biswas1, Dhari Shah1, Sarah J Cox-Vázquez1
1Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA. ricvazqu@iu.edu.
Journal of Materials Chemistry. B
|June 20, 2024
Summary
Cholesterol restricts membrane fluidity, increasing the fluorescence lifetime of DI-8-ANEPPS dye. This shift from liquid-disorder to liquid-order membrane phases is primarily due to restricted movement, not altered dipole potentials.
Area of Science:
- Biophysics
- Membrane Biology
- Spectroscopy
Background:
- Membrane fluidity is crucial for cellular function.
- Cholesterol significantly influences membrane properties.
- Twisted intramolecular charge transfer (TICT) dyes offer insights into membrane dynamics.
Purpose of the Study:
- To characterize the effect of cholesterol on membrane fluidity using a TICT dye.
- To investigate the photophysical changes of DI-8-ANEPPS with varying cholesterol concentrations.
- To elucidate the mechanisms underlying cholesterol's impact on membrane organization.
Main Methods:
- Utilized time-correlated single photon counting (TCSPC) and fluorescence lifetime imaging microscopy (FLIM).
- Employed liposomes with varying cholesterol levels (0-50%) and a fixed POPC:POPG ratio.
- Performed fluorescence anisotropy and zeta-potential measurements.
Main Results:
- Increased cholesterol levels (0-50%) extended DI-8-ANEPPS fluorescence lifetime by 55% (2.36 ns to 3.65 ns).
- Observed reduced Stokes shifts and higher quantum yield, indicating a shift from TICT to localized excitation (LE).
- Fluorescence anisotropy indicated a transition from liquid-disorder (Lα) to liquid-order (LO) membrane phases.
Conclusions:
- Cholesterol's primary impact on DI-8-ANEPPS photophysics is through restricting molecular movement, not altering local dipole strength.
- Time-resolved spectroscopy with TICT dyes is valuable for studying membrane lipid-protein-sterol interactions.
- Findings provide insights into membrane fluidity, organization, and function.
