Lateral diffusion coefficients in membranes measured by resonance energy transfer and a new algorithm for diffusion...

Area of Science:

• Membrane biophysics
• Physical chemistry
• Spectroscopy

Background:

• Lateral diffusion is crucial for membrane function.
• Measuring slow diffusion (below 10(-8) cm(2)/s) is challenging.
• Resonance energy transfer (RET) is a powerful tool for studying molecular interactions and dynamics.

Purpose of the Study:

• To develop and validate a novel method for measuring slow lateral diffusion in lipid membranes.
• To utilize long-lifetime rhenium (Re) metal-ligand complex lipids as donors for enhanced RET measurements.
• To establish a new numerical algorithm for analyzing RET data in two-dimensional systems.

Main Methods:

• Utilized a rhenium (Re) metal-ligand complex lipid as a long-lifetime donor (decay time ~3 µs).
• Employed a new numerical algorithm based on the relaxation method in Laplace space to solve the 2D diffusion equation for RET.
• Analyzed frequency-domain data from rhenium donors and Texas red-lipid acceptors in lipid membranes (DMPG and DOPC).

Main Results:

• Successfully measured lateral diffusion coefficients as low as 4.4 x 10(-9) cm(2)/s.
• Demonstrated the ability to recover diffusion coefficients and acceptor concentrations independently.
• Obtained diffusion coefficients ranging from 4.4 x 10(-9) cm(2)/s in DMPG at 10°C to 1.7 x 10(-7) cm(2)/s in DOPC at 35°C.

Conclusions:

• The developed method enables direct measurement of slow lateral diffusion coefficients in membranes.
• Long-lifetime rhenium donors combined with the new algorithm significantly enhance the sensitivity and accuracy of RET-based diffusion measurements.
• This approach opens new avenues for studying membrane dynamics and molecular organization.