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A long-lifetime Ru(II) metal-ligand complex as a membrane probe
X Q Guo1, F N Castellano, L Li
1Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore 21201, USA.
Biophysical Chemistry
|May 20, 1998
Summary
A ruthenium complex ([Ru(bpy)2(dppz)]2+) acts as a sensitive photoluminescence probe for lipid membrane dynamics. Its luminescence changes with temperature and cholesterol content, revealing insights into membrane composition and dynamics.
Area of Science:
- Biophysical Chemistry
- Materials Science
- Membrane Biophysics
Background:
- Investigating lipid dynamics is crucial for understanding membrane function.
- Developing sensitive probes is essential for detailed biophysical studies.
- [Ru(bpy)2(dppz)]2+ is a luminescent metal-ligand complex with potential as a probe.
Purpose of the Study:
- To utilize [Ru(bpy)2(dppz)]2+ as a photoluminescence probe for submicrosecond lipid dynamics.
- To investigate the influence of temperature and cholesterol on lipid bilayer behavior.
- To explore the probe's sensitivity to membrane composition and dynamics.
Main Methods:
- Employing [Ru(bpy)2(dppz)]2+ as a photoluminescence probe in a dipalmitoyl-L-alpha-phosphotidylglycerol (DPPG) model bilayer system.
- Measuring emission intensity and frequency-domain emission intensity decays as a function of temperature (2-57°C).
- Comparing oxygen and iodide quenching to assess probe location heterogeneity.
Main Results:
- Luminescence of [Ru(bpy)2(dppz)]2+ is quenched in buffer but activated within DPPG vesicles.
- Emission intensity increases with temperature towards the lipid phase transition, an effect abolished by high cholesterol concentrations.
- Two lifetime components were observed, with the short lifetime disappearing above the phase transition temperature.
- Probe location was found to be heterogeneous below and homogeneous above the phase transition temperature.
Conclusions:
- [Ru(bpy)2(dppz)]2+ is a sensitive photoluminescence probe for lipid dynamics and membrane composition.
- The probe's sensitivity to temperature and cholesterol highlights its utility in studying membrane phase transitions.
- [Ru(bpy)2(dppz)]2+ enables microsecond-timescale measurements of lipid vesicle rotational correlation times due to its long lifetime and polarized emission.