Abstract
Model membranes offer a simplified representation of biomembranes, allowing for controlled structural and functional studies without the inherent complexity of biological systems. Due to the confined space and strong interactions with the support, supported lipid bilayers (SLBs) exhibit markedly distinct properties compared to those of their free-standing counterparts. However, the nano- and microscale origins of these differences, structural effects, and the related biophysical consequences remain incompletely understood. Using a combination of spectroscopy and micromanipulation techniques, we reveal that lipids in SLBs are strongly attached to the support. These SLBs are intrinsically stretched and under tension, causing membrane rupture, and form stable ∼2 nm aqueous pores that allow the permeation of small hydrophilic molecules. Despite strong adhesion, SLBs can undergo localized shape changes associated with membrane fusion, and membrane nanotubes can be extruded under optical forces. The findings underscore the very distinct properties of model membranes, and we anticipate that they will have important consequences in the fields of drug-delivery systems and membrane biophysics.