Aviv 69978, Tel Aviv, Israel
- ' Service de Physique Theorique, CE-Saclay, 91191 Gif sur Yvette, Cedex, France'
author:
- 'Roland R. Netz[@address] and David Andelman'
- 'H. Orland[@address2]'
title:  Protein adsorption on lipid monolayers at their coexistence region 
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Introduction
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Monolayers of amphiphilic molecules spread on liquid surfaces have traditionally been studied as models for biological membranes[@Gaines; @Bloom]. Such insoluble and monomolecular films made of suitable phospholipids or fatty acids are stable over a wide range of surface pressures and temperatures due to the strong reduction of the water surface tension and are called [*Langmuir monolayers*]{}[@Mohwald]. In typical experiments, the amphiphiles are solubilized in a volatile solvent and placed on the air-water interface. As the solvent evaporates, the amphiphiles spontaneously spread and form a monolayer. When the insoluble film is then compressed (while keeping the temperature fixed), the lateral pressure can be measured as a function of the area per amphiphilic molecule in analogy to bulk isotherms.

Using film balance techniques[@Gaines; @Bloom; @Mohwald; @Albrecht1; @Albrecht2], the following general picture emerged. When the extremely expanded film is compressed, it produces the liquid expanded phase (LE), which, at low enough temperatures, transforms upon further compression into the liquid condensed phase 