LONG-RANGE TILT ORIENTATIONAL ORDER IN PHOSPHOLIPID MONOLAYERS - A COMPARISON OF THE ORDER IN THE CONDENSED PHASES OF DIMYRISTOYLPHOSPHATIDYLETHANOLAMINE AND DIPALMITOYLPHOSPHATIDYLCHOLINE

The morphology of the condensed phase domains is very different in monolayers of dimyristoylphosphatidylethanolamine (DMPE) and dipalmitoylphosphatidylcholine (DPPC). In DMPE monolayers, only the inner structure indicates the chirality, whereas in DPPC domains the chirality is also reflected by the outer shape. Nevertheless, there are some common features. The condensed phase domains of both lipids reflect the chirality of the molecules. The condensed phases of both monolayers exhibit long range orientational order. As well as lines at which the molecular orientation jumps, continuous changes in the molecular orientation are also observed, indicating a low elastic energy caused by these changes in orientation. The domains of both phospholipids fuse independent of the molecular orientation in the contacting domain parts. The big head group of the DPPC molecule effects not only the phase behaviour and the collapse, but also the domain shape.