Nonadditivity in Many-Body Interactions between Membrane-Deforming Spheres Increases Disorder

Area of Science:

• Biophysics
• Soft Matter Physics
• Cell Biology

Background:

• Membrane-induced interactions are critical for organizing proteins within cell membranes.
• Previous studies indicated nonadditive interactions between 2-3 membrane-deforming objects, suggesting complex many-body effects.
• Experimental evidence for these many-body effects in membrane interactions remained scarce.

Purpose of the Study:

• To experimentally investigate and quantify many-body effects in membrane-mediated interactions.
• To understand how multiple membrane-deforming objects arrange and interact on a membrane.
• To explore the implications of these interactions for cellular organization.

Main Methods:

• Developed an experimental setup using colloidal spheres confined between a deflated giant unilamellar vesicle and a planar substrate.
• Measured interaction forces between colloidal particles causing membrane deformation.
• Employed numerical energy minimization to analyze particle arrangements and attraction mechanisms.

Main Results:

• Observed attractive forces between two particles (max 0.2 pN) and a preference for triangular over linear arrangements for three particles.
• Identified reduced membrane-deformation energy as the source of attraction.
• Found a preference for hexagonally close-packed clusters with increasing particle numbers, up to 36.
• Noted decreased particle order and increased diffusivity with a higher number of particles.

Conclusions:

• Demonstrated that nonadditive membrane-mediated interactions significantly influence particle arrangement and behavior.
• Showcased the formation of spherical aggregates with liquid-like order from these interactions.
• Highlighted the potential relevance of these findings for understanding cellular processes and organization.