Nonequilibrium collective dynamics in photoexcited lipid multilayers by time resolved diffuse x-ray scattering

Area of Science:

• Biophysics
• Materials Science
• Soft Matter Physics

Background:

• Phospholipid multibilayers are fundamental components of cell membranes.
• Understanding lipid bilayer dynamics is crucial for cell biology and drug delivery.
• Nonequilibrium processes can significantly alter membrane properties.

Purpose of the Study:

• To investigate nonequilibrium shape fluctuations in lipid bilayers under laser excitation.
• To analyze the temporal evolution of lipid bilayer undulations after optical excitation.
• To characterize the underlying physical mechanisms driving these changes.

Main Methods:

• Utilizing fluorescence-labeled phospholipid multibilayers (DOPC and Texas red).
• Employing pulsed laser excitation to drive systems out of equilibrium.
• Recording temporal evolution of undulations via time-resolved X-ray diffraction.

Main Results:

• Moderate peak laser intensities induce significant changes in undulation modes within a specific wavelength band.
• Observed phenomena evolve on nanosecond to microsecond timescales post-excitation.
• The changes are consistent with a modulation instability in the lipid multilamellar stack.

Conclusions:

• Pulsed laser excitation is an effective method to study nonequilibrium dynamics in lipid bilayers.
• Modulation instability plays a key role in the observed rapid shape fluctuations.
• This research provides insights into the dynamic behavior of lipid membranes under external stimuli.