Quantification of Randomly-methylated-beta-cyclodextrin effect on liposome: an ESR study

Area of Science:

• Biochemistry
• Membrane Biophysics
• Physical Chemistry

Background:

• Cell membranes are dynamic structures whose fluidity is crucial for function.
• Cholesterol modulates membrane properties, influencing microviscosity and phase transitions.
• Cyclodextrins are known for their ability to interact with and modify lipid bilayers.

Purpose of the Study:

• To investigate the effect of Randomly-methylated-beta-cyclodextrin (Rameb) on dimyristoyl-l-alpha phosphatidylcholine (DMPC) bilayer microviscosity.
• To quantify the cholesterol extraction capability of Rameb from DMPC bilayers.
• To understand how cholesterol influences membrane domains and fluidity using spin labels.

Main Methods:

• Electron Spin Resonance (ESR) spectroscopy was employed to probe membrane microviscosity.
• 16-doxyl stearic acid (16-DSA) spin label was used to investigate different membrane domains.
• Liposomes composed of DMPC and varying concentrations of cholesterol were prepared.

Main Results:

• Rameb demonstrated a clear ability to extract cholesterol from DMPC bilayers, quantified over a range of Rameb concentrations.
• The microviscosity of the DMPC bilayer was significantly affected by Rameb-mediated cholesterol extraction.
• Cholesterol was found to suppress the abrupt increase in membrane fluidity at the lipid phase transition temperature (23.9°C) in DMPC liposomes.

Conclusions:

• Rameb is an effective agent for cholesterol extraction from lipid bilayers, altering membrane properties.
• The study provides novel insights into the quantitative aspects of Rameb-cholesterol interactions within membranes.
• Understanding these interactions is vital for applications in drug delivery and membrane biophysics.