Jonas Hannestad oral presentation (OB2-Mon1-2-3)
Characterization of supported lipid bilayers with nanometer resolution using Time-of-Flight Secondary Ion Mass Spectrometry.
Research Institutes of Sweden, Brinellgatan 4, 501 15 Borås, Sweden
The plasma membrane that surrounds living cells fulfills a wide range of functionalities that are of fundamental importance for its very existence. Not only does it serve as a barrier against the surrounding environment upholding the integrity of the cell. It also serves as a host for a plethora of different proteins such as aquaporins, ion channels and receptors. Attaining knowledge of the constitutional and functional complexity of the plasma membrane is an important goal in for the biological sciences and is vital for the understanding of many diseases and the development of new drugs. One step towards that goal is an accurate characterization of the lipid composition of the cell membrane, since the properties of its individual constituent will greatly affect the functioning of the overall membrane.
Historically, cell-based studies have provided great insight into cell membrane functions. A limitation to this approach is the complexity of the cell which makes detailed understanding difficult to obtain. An alternative strategy is to use supported lipid bilayers, which provide means to control sample characteristics and experimental conditions.
Here, we present a method to characterize the molecular composition of supported lipid bilayers on the nanometer scale using Time-of-Flight Secondary Ion Spectrometry (ToF-SIMS). ToF-SIMS is a powerful technique for analyzing the components of lipid surfaces capable of distinguishing between a wide range of lipid species with high specificity. However, its limited spatial resolution prevents a detailed understanding of how lipid compassion affects membrane properties such as lipid distribution and clustering. We overcome this limitation by measuring the dimer of two different lipids, formed from the same primary ion impacts. Since the formation of dimers is confined to separate impact spots, the resulting signals reflect the local molecular environment within the imaged area. This allows us to characterize parameters such as lipid mixing at length scales down to single nanometers.
Our results show that content distribution in lipid-covered surfaces is dictated, not only by the relative occurrence of different lipid species, but also by the physical and chemical properties of said lipids. The results provide a platform for characterizing biological membranes with high complexity and constitute a step towards understanding how chemical properties of individual lipid molecules can influence global lipid membrane properties.