For surfactant solutions this can be expressed by the adsorp-A thermodynamic treatment of protein adsorption layers is pretion principle of Braun- . It states that sented and an equation of state of the interfacial layer is derived. when the adsorbed molecule may occupy different parts of Only by assuming different models for the activity coefficients in the interface, then for small values of P a maximum surface the interfacial layer different are models derived considering ideal area v is occupied, whereas minimum v is achieved at large and nonideal entropy and enthalpy of mixing. As special cases, P. Obviously this agrees with the well-known fact that the well-known equations from other authors are obtained which are adsorption layer thickness increases with increasing protein frequently used for the description of surfactant and polymer adconcentration. Thermodynamic approaches cannot take into sorption. Concerning the configuration of adsorbed protein moleconsideration the adsorption layer thickness, while in statisticules, i.e., number of protein segments adsorbed, the composition of the adsorption layer is caused by a self-regulation process which cal and scaling theories it is a necessary prerequisite. On the is mainly influenced by the chain flexibility and determines the other hand, nonideal behavior of mixing in the interfacial surface pressure. Only four basic parameters describe the adsorplayer allows further possibilities for the present model.
tion equilibrium of the protein. A sufficiently good agreement be-
The present paper gives a thermodynamic treatment of tween literature data and the model is obtained, although best-fit protein adsorption layers, i.e., deriving an equation of state procedures do not exist so far and the isotherm parameters were of the interfacial layer, the adsorption isotherm, and the isoadjusted only manually.