Vesicle adhesion in the electrostatic strong-coupling regime studied by time-resolved small-angle X-ray scattering

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Lipid vesicle adhesion is crucial for biological processes.
• Electrostatic interactions, particularly with divalent ions, significantly influence membrane behavior.
• Understanding ion-mediated vesicle interactions is key to deciphering cellular functions.

Purpose of the Study:

• To investigate lipid vesicle adhesion in the electrostatic strong-coupling regime induced by divalent ions.
• To explore the influence of surface charge density and ion type on vesicle adhesion and bilayer structure.
• To examine the dynamic nature of adhesion and subsequent structural transformations.

Main Methods:

• Time-resolved small-angle X-ray scattering (SAXS) was employed to study vesicle adhesion.
• Stopped-flow rapid mixing technique was combined with SAXS for dynamic measurements.
• Vesicles composed of varying DOPC:DOPS mixtures were analyzed with different divalent ions (Ca2+, Sr2+, Zn2+).

Main Results:

• Adhesion and interbilayer distances (dw) were measured for different lipid compositions and ions.
• Results showed good agreement with strong coupling theory, including ion-correlation-based like-charge attraction.
• Highly charged bilayers exhibited transient adhesion, followed by transformation into multilamellar vesicle phases.

Conclusions:

• Divalent ions effectively induce lipid vesicle adhesion via strong electrostatic coupling.
• The observed adhesion and subsequent transformations are consistent with theoretical predictions.
• Microfluidic environments show promise for future advanced SAXS studies of vesicle dynamics.