Coupling of Leaflet Structure in Asymmetric Lipid Vesicles Lipid asymmetry is a hallmark of biological membranes [1]. In particular, prototypical mammalian plasma membranes are known to be composed of an outer leaflet enriched in cholinephospholipids, while the majority of the aminophospholipids are confined to the inner leaflet [2]. A relatively new model system for biological membranes are asymmetric large unilamellar lipid vesicles (aLUVs), which are produced via cyclodextrin-mediated lipid exchange [3]. These systems were shown to be stable over several days [4] and have already been investigated by elastic scattering techniques (small-angle neutron and X-ray scattering; SANS/SAXS), providing insight into structural properties of the individual leaflets [5]. One of the enduring questions concerning plasma membrane architecture and lipid asymmetry is the possibility of bilayer leaflets being coupled to each other, which may influence a number of physiological processes that require communication between interior and exterior of the cell [6]. However, in the physiologically relevant fluid phase no evidence of structural coupling has yet been reported. In this work, we explore the role of hydrocarbon chain interdigitation as a potential trigger for transleaflet coupling. We use combinations of dipalmitoylphosphatidylcholine DPPC) in the inner leaflet and mixed lipids with varying chain length mismatch in the outer leaflet, in particular C16:0/C18:1 PC (POPC), C18:0/C18:1 PC (SOPC), C18:0/C14:0 (SMPC), C14:0/C18:0 (MSPC) and C16:0/C14:0 PC (PMPC). |