Supported double bilayers: an experimental model to probe biomembrane properties (MSc Niek de Lange)

The structure and topological stability of membranes is crucial for living cells and plays a key role in numerous vital cellular processes. To achieve its diverse and complex behaviour, the cell membrane is composed of a complex variety of biomolecules, notably lipids and proteins. However, small variations in the lipid architecture can already have large and potentially catastrophic effects on the properties and stability of the membrane. Understanding complex and dynamic cellular processes, such as endocytosis and exocytosis is, whilst urgently needed, difficult and progress is therefore slow.


Schematic illustration of the formation of supported double bilayers: a and b) formation of the proximal layer by adsorption of vesicles containing biotinylated lipids (biotin on a flexible spacer). The formation of the second bilayer: c) streptavidin has four binding sites for biotin and a sufficient number is added so that approximately half the binding sites remain free. d) Subsequently, new biotinylated vesicles are added, which will bind to the streptavidin layer. e) After rupture of the vesicles the double bilayer configuration is formed.

Progress in theoretical modelling (our group has performed molecularly detailed self-consistent field (SCF) calculations on lipid bilayer membranes) in combination with advanced and cutting-edge techniques have enabled us to perform more advanced experiments on lipid bilayers. This makes it possible to determine on how lipids and other membrane constituents organise the delicate force balances in bilayers that are responsible for the structure and structural (in)stability.

The aim of this PhD project is to develop an experimental membrane platform to determine mechanical properties and topological integrity of lipid membranes of increasing complexity. The experimental platform comprises of a supported double lipid membrane in a flow cell, mounted in a set-up including a TIRF microscope and an AFM dedicated to force measurements. The influence of various perturbing stimuli, such as edge-active agents, antimicrobial peptides and nanoparticles, on these membrane properties will be investigated. Edge-active agents and antimicrobial peptides induce the formation of pores in specific membranes and insight in this phenomenon is urgently needed, in particular in view of the search for new antibiotics.