(515b) From Domain Size Distributions to Probing Lipid-Protein Interactions in Lung Surfactant Mixtures
The shape and size of a single domain in monolayers at coexistence has been shown to be a result of a balance of forces. Domain shape analysis of fluorescence images of a single or multi-component lipid monolayer can provide detailed information about the minimum energy radius, R0, the electric dipole density difference, m, and the line tension between domains. Alterations in the domain size distribution of lipid monolayers in the presence of protein molecules may be used to analyze lipid-protein interactions in these systems. In this talk, we will present interactions between negatively charged lung surfactant monolayers and positively charged surfactant protein SP-B which together play an important role in the mechanism of breathing. By analyzing the domain size distribution we find that while the entropy of mixing plays a likely role in domain size distributions, addition of SP-B molecules reduces R0 as well as increases m. Our results therefore prove that SP-B alters the electrostatic interactions between domains by interacting with the negatively charged lipid monolayers.