Pushing the Complexity of Model Bilayers: Novel Prospects for Membrane Biophysics

Abstract

As an interface between different biological compartments, membranes guarantee an efficient exchangeof matter, energy and/or signals. For this purpose, such an interface has to be designed as a verydynamic system, yet with a non-random distribution of its components, lipids and proteins. A delicatebalance of lipid and protein interactions is the basis of tightly regulated mechanisms to concentrate moleculesat the site of interest at a specific time and, thereby, exclude unwanted components. In order toelucidate this highly intricate architecture, the top-down approach—by looking at the intact cell—isbest complemented by a bottom-up strategy, by building the whole complexity starting from a minimalnumber of components. Within this framework, model membranes are key systems to isolate the biologicalmachinery and identify its function. In this paper, we review research on biomimetic membranes for opticalmicrospectroscopy. In particular, we focus on giant unilamellar vesicles (GUVs), and their applicationto studies on domain assembly and on membrane curvature and deformations. In order to build complexity,efforts must be made towards mimicking cellular compositions, by using GUVs with native lipid compositions,to reconstitute (complexes of) membrane proteins and to include components of an artificial cytoskeletonunderneath the bilayer. Novel exciting avenues lie ahead in the arena of membrane biophysics, many of whichare strongly coupled to the promising developments of optical technologies.