A close look at domain formation in DPPC monolayers

Insoluble monolayers of dipalmitoylphosphatidylcholine (DPPC) exhibit a phase transition resulting in the formation of domains with interesting shapes. We studied the features of DPPC domain shapes throughout the coexistence region. We find that the basic domain shape is an asymmetric "bean" with a flattened lobe and a distinct cavity. The cavity is a locus for growth, in the form of either a terminal nub or a projection which grows to form a new lobe. Multilobed domains thus grow from beans via a specific process; however, these are not stable and transform over time back to beans. We also find that atypical compression schemes can be used to generate domain shapes that stray markedly from the norm, such as multilobed complexes or toruses.