Lecithin electron microscope studies

Combined film balance and electron microscope studies reveal some remarkable properties of lecithin monolayers. A microporosity of the film, which is observed at low surface pressures and persists into the intermediate and high pressure regions, might, if present in membrane structures, be related to the penetration of proteins and other materials into cell membranes. Films of related materials and their mixtures warrant detailed study. 

The textures in homeotropic lamellar phases of lecithin are studied in lecithin-water phases by polarizing microscopy and in dried phases by electron microscopy. In the former, we observe the La phase (the chains are liquid, the polar heads disordered)—the texture displays classical FriedeVs oily streaks, which we interpret as clusters of parallel dislocations whose core is split in two disclinations of opposite sign, with a transversal instability of the confocal domain type. In the latter case, the nature of the lamellar phase is less understood. However, the elementary defects (negative staining) are quenched from the La phase they are dislocations or Grandjean terraces, where the same transversal instability can occur. We also observed dislocations with an extended core these defects seem typical of the phase in the electron microscope. 

In this paper we describe two types of observations on egg-yolk lecithin. We present the results of our study of homeotropically oriented samples of La phases by polarizing optical microscopy. This study provides evidence, amid apparently nonsimilar aspects, of the existence of an elementary typical object which we have interpreted as a dislocation. We also studied thin samples of stained lecithin in the high vacuum of the electron microscope. In addition to the defects that are typical of this type of sample, we observed the same elementary object as in La lecithin. 

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