Incompatibility of mixing of proteins in adsorbed binary protein films at the air-water interface.
Competitive adsorption of proteins from several binary protein solutions to the air-water interface has been studied. With a few exceptions, the equilibrium composition of the saturated monolayer of mixed protein films at various bulk concentration ratios did not follow a Langmuir-type competitive adsorption model. The deviation from ideal behavior results from incompatibility of mixing of proteins in the film at the air-water interface. This immiscibility alters the ratio of the binding affinity of the proteins in a protein 1/protein 2/water ternary film compared to that in a protein 1/water and protein 2/water binary film. A method to determine the extent of incompatibility between two proteins in a mixed protein film has been developed. It is shown that the incompatibility index derived for 19 protein 1/water and protein 2/water systems studied show a linear relationship with the absolute difference between Flory-Huggins protein-solvent interaction parameters, that is, /chi(1s) - chi(2)/, of the constituent proteins. On the basis of the evidence, it is theorized that, because of incompatibility, proteins in a mixed protein film at interfaces may undergo two-dimensional phase separation.
Razumovsky
L
L
Department of Food Science, University of Wisconsin-Madison, Madison, WI 53706, USA.
Damodaran
S
S
D000327:Adsorption; D000388:Air; D018441:Biofilms; D008962:Models, Theoretical; D011506:Proteins / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D014867:Water
D011506:Proteins; D012996:Solutions; D014867:Water