title: Competition for space between a protein and lipid monolayers.
abstract: Competitive adsorption is a general problem both in polymer and in biological systems. The equilibrium composition at a surface in contact either with polymer solutions or biological fluids depends on the competition between all the surface active material present in the medium. Such competition is particularly important in cell membranes where membrane proteins generated on ribosomes have to incorporate in the cell. Here we use fluovideo microscopy to study the competition for adsorption at the air/water interface between the enzyme glucose oxidase (GOx) and fluid monolayers of pentadecanoic acid (PDA). Although water soluble, GOx has a strong affinity for the air/water interface. We show that under certain conditions it inserts in the monolayer and causes a contraction of the Langmuir film and the formation of condensed domains. When exposed to a heterogeneous surface it is inserted in the less dense regions. Its crystallization leads to the deformation of the condensed domains followed by the destruction of their initial shape. By compressing the layer the protein is not removed from the interface where it eventually forms three-dimensional structures.
authors.affiliation: Institut Curie, Labo PSI, 11 rue Pierre et Marie Curie, 75231 Paris, France. fragneto@ill.eu
authors.forename: Giovanna
authors.initials: G
authors.lastname: Fragneto
authors.forename: Stéphane
authors.initials: S
authors.lastname: Alexandre
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Valleton
authors.forename: Francis
authors.initials: F
authors.lastname: Rondelez
mesh_terms: D000327:Adsorption; D001234:Aspergillus niger / Q000201:enzymology; D005227:Fatty Acids / Q000378:metabolism*; D005949:Glucose Oxidase / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D019814:Myristic Acid / Q000378:metabolism*; D011312:Pressure; D013696:Temperature; D014966:Xanthenes / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D014966:Xanthenes; D019814:Myristic Acid; C034657:Texas red; C117025:pentadecanoic acid; D005949:Glucose Oxidase