Nanoscale structure of lipid domain boundaries

Analysis of membrane domain segregation and phase separation is important for the understanding of cell membrane structure and function. In this paper, we report an atomic force microscopy approach using both derivatised tip functionalities and force–volume imaging for the analysis of membrane phase separation. Simultaneous topology and mapping of interaction forces of binary component phospholipid bilayer membranes were performed. Measurements enabled the lateral mapping of bilayer lipid composition at a resolution of 10–20 nm, providing insights into dynamic membrane structure and behaviour. Very sharp boundaries between the two domains are observed in addition to domain boundaries that are quite diffuse with both lipids intermixing. Additionally, some nanoscale domains of one lipid within the domain of the second lipid are observed. The sharp boundaries of the large domains are observed in regions close to these nanodomains.