Electron Micrographs of Cross-Sections of Protein Monolayers

Abstract

ELECTRON micrographs of cross-sections of protein monolayers have been obtained in the following way. A monolayer of protein, a commercial sample of egg albumen, was spread at the surface of water contained in a small Langmuir type trough. This layer was then compressed and crumpled by advancing a barrier coated with paraffin wax towards a second retaining barrier. When the two barriers were about a centimetre apart, the crumpled film became visible at the interface and was lifted from the water as a frail thread by means of a wire yoke. Portions of this thread were prepared for cross-sectioning by dehydrating in an alcohol series and embedding in an epoxide resin¹. It was found advantageous to ‘stain’ the specimen first by treating it for a short time in a buffered osmium tetroxide solution. The thread, darkened and hardened by this treatment, was easier to handle and to see by eye in the block and also in the electron microscope. Very thin sections were cut from the block at right angles to the length of the thread by the standard procedure for electron microscopy² and examined in a Siemens ‘Elmiskop I’ microscope.