Monomolecular Films and Membrane Structure

The liquid condensed and liquid expanded physical states in an insoluble monomolecular film at the air-water interface and the gel and liquid crystelline states in fully hydrated bilayers are discussed and compared. It is postulated that, under reasonable restraints, the monolayer may be regarded as an adequate model membrane system. The interfacial behavior of a number of fatty acid spin-label and fluorescent probes are then outlined both for pure and mixed monomolecular films. As in bilayers and membranes these probes exhibit perturbation and immiscibility phenomena which should be taken into account when investigating membrane structure. While the perturbations of any individual probe may be small, they appear to be significant where bilayer profiles are concerned.