Coupling between Inclusions and Membranes at the Nanoscale

TL;DR

This paper investigates the elastic coupling between membrane inclusions and lipid bilayers, measuring the slope at the inclusion boundary using combined experimental and modeling approaches, revealing unexpectedly steep slopes.

Contribution

It introduces a novel measurement of the slope at the inclusion boundary, combining small-angle x-ray scattering with elastic modeling, and compares results across different membrane systems.

Findings

The slope at the inclusion boundary is surprisingly steep.

The measurement method is validated across different membrane types.

Results align with recent simulations and conductivity data.

Abstract

The activity of cell membrane inclusions (such as ion channels) is influenced by the host lipid membrane, to which they are elastically coupled. This coupling concerns the hydrophobic thickness of the bilayer (imposed by the length of the channel, as per the hydrophobic matching principle) but also its slope at the boundary of the inclusion. However, this parameter has never been measured so far. We combine small-angle x-ray scattering data and a complete elastic model to measure the slope for the model gramicidin channel and show that it is surprisingly steep, in two membrane systems with very different elastic properties. This conclusion is confirmed and generalized by the comparison with recent results in the simulation literature and with conductivity measurements.