Lipid lateral diffusion measurements in model membranes

Area of Science:

• Biophysics
• Physical Chemistry
• Materials Science

Background:

• Understanding lipid lateral diffusion is crucial for membrane dynamics.
• Electron Spin Resonance (ESR) spectroscopy is a powerful tool for studying molecular motion in lipid bilayers.
• Spin-labeling techniques allow for probing specific molecular environments within membranes.

Purpose of the Study:

• To investigate the rate of lipid lateral diffusion in dimyristoyl phosphatidylcholine (DMPC) vesicles.
• To develop and apply a computer simulation method for analyzing ESR spectra.
• To determine lipid lateral diffusion coefficients and probe-probe collision frequencies.

Main Methods:

• Computer simulation of electron spin resonance (ESR) spectra.
• Utilizing spin-labeled dimyristoyl phosphatidylcholine (DMPC) vesicles.
• Employing an optimization method to fit experimental spectra to modified Bloch-equation calculations.

Main Results:

• The method successfully determined spin exchange contributions to spectral line broadening.
• Both static dipolar interaction and dynamic spin exchange significantly contribute to line broadening above the phase transition.
• The lipid lateral diffusion coefficient in DMPC bilayers at 36°C was measured as (2.3 ± 0.2) x 10⁻¹¹ m²/s.

Conclusions:

• The developed ESR spectral analysis method is sensitive to spin exchange and provides accurate diffusion coefficients.
• This approach enhances the understanding of molecular dynamics and interactions within lipid bilayers.
• The quantified diffusion coefficient offers valuable data for biophysical and materials science applications.