The structural characterisation of self-assembled films of dimyristoyl phosphatidylcholine: a neutron reflectivity and Brewster angle microscopy study

Abstract

Self-assembled films of dimyristoylphosphatidylcholine (DMPC) were formed at the air/water interface and examined by neutron reflectivity and Brewster angle microscopy to characterise their structure. The films were formed from anhydrous powder and transported to the air/water interface via a bridge from a remote reservoir. The Brewster angle microscopy results revealed that discoidal structures were associated with the film at higher surface pressures and that the population of these increased with compression. A mechanism for their formation and their subsequent role in film behaviour is suggested. A number of films were examined where the powder form of DMPC was spread directly at the air/water interface of the Langmuir trough without the bridge (in-situ films). This resulted in more heterogeneous films characterised by strings of three-dimensional structures which appeared to be multilamellar liposomes. Reflectivity studies revealed a Bragg peak representing long range order and a repeat distance of 61 Å consistent with stacks of hydrated bilayers in the liposomes.