Molecular organization in phospholipid monolayer domains by electron diffraction

Abstract

In the LC/LE phase of phospholipid monolayers at the air/water interface, solid and fluid domains may be visualized by epi-fluorescence microscopy. Supposedly, solid domains are distinguished by the absence of fluorescence due to the preferential partitioning of most fluorescent dyes to the surrounding fluid phase lipids. The size, shape and stability of these domains are governed by molecular dipole-dipole interaction and inter-phase line tension. While x-ray and neutron diffractions offer some global average molecular packing information on a large sampling area of monolayers, selected area electron diffraction may provide local structural information within and along individual domains.Dipalmitoyl-monomethyl-phosphatidylethanolamine [DP(Me)PE] and dipalmitoyldimethyl-phosphatidylethanolamine [DP(Me)PE] monolayers were spread on an environmentally controlled Langmuir trough. The monolayers were adjusted to the LE/LC phase by a servo-motor-driven Teflon bar moving along the surface of the trough.