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

Self-assembled films of dimyristoylphosphatidylcholine (DMPC) were formed a t the air/water interface and examined by neutron reflectivity and Brewster angle microscopy to characterise their structure. The films were formed fr om anhydrous powder and transported to the air/water interface via a bridge from a remote reservoir. The Brewster angle microscopy results revealed th at discoidal structures were associated with the film at higher surface pre ssures and that the population of these increased with compression. A mecha nism for their formation and their subsequent role in film behaviour is sug gested. A number of films were examined where the powder form of DMPC was s pread directly at the air/water interface of the Langmuir trough without th e bridge (in-situ films). This resulted in more heterogeneous films charact erised by strings of three-dimensional structures which appeared to be mult ilamellar liposomes. Reflectivity studies revealed a Bragg peak representin g long range order and a repeat distance of 61 Angstrom consistent with sta cks of hydrated bilayers in the liposomes. (C) 2000 Elsevier Science B.V. A ll rights reserved.