Enhanced Facilitated Diffusion of Membrane-Associating Proteinsunder Symmetric Confinement

The facilitated surface diffusion of transiently adsorbing molecules in a planarconfined microenvironment (i.e., slit-like confinement) is highly relevant to biologicalphenomena, such as extracellular signaling, as well as numerous biotechnology systems. Here,we studied the surface diffusion of individual proteins confined between two symmetric lipidbilayer membranes, under a continuum of confinement heights, using single-moleculetracking and convex lens-induced confinement as well as hybrid, kinetic Monte Carlosimulations of a generalized continuous time random walk process. Surface diffusion wasobserved to vary non-monotonically with confinement height, exhibiting a maximum at aheight of similar to 750 nm, where diffusion was nearly 40% greater than that for a semi-infinite system. This demonstrated that planarconfinement can, in fact, increase surface diffusion, qualitatively validating previous theoretical predictions. Simulations reproducedthe experimental results and suggested that confinement enhancement of surface diffusion for symmetric systems is limited to caseswhere the adsorbate exhibits weak surface sticking.

Automated summary

This study investigates the surface diffusion of proteins confined between two symmetric lipid bilayer membranes in a planar constrained microenvironment. The results show that the surface diffusion varies non-monotonically with confinement height, reaching a maximum at around 750 nm. Simulations validate the experimental findings and suggest that confinement enhancement of surface diffusion is limited to cases where the adsorbate exhibits weak surface sticking.