Protein adsorption kinetics model applicability

Fig. 13. Most of the kinetic models which might be applicable to protein adsorption (see Refs.70 73)) k is rate constant, subscript a and d are adsorption and desorption respectively, 1 and 2 are adsorption states — usually native and denatured...

The adsorption kinetics of a surfactant to a freshly formed surface as well as the viscoelastic behaviour of surface layers have strong impact on foam formation, emulsification, detergency, painting, and other practical applications. The key factor that controls the adsorption kinetics is the diffusion transport of surfactant molecules from the bulk to the surface [184] whereas relaxation or repulsive interactions contribute particularly in the case of adsorption of proteins, ionic surfactants and surfactant mixtures [185-188], At liquid/liquid interface the adsorption kinetics is affected by surfactant transfer across the interface if the surfactant, such as dodecyl dimethyl phosphine oxide [189], is comparably soluble in both liquids. In addition, two-dimensional aggregation in an adsorption layer can happen when the molecular interaction between the adsorbed molecules is sufficiently large. This particular behaviour is intrinsic for synergistic mixtures, such as SDS and dodecanol (cf the theoretical treatment of this system in Chapters 2 and 3). The huge variety of models developed to describe the adsorption kinetics of surfactants and their mixtures, of relaxation processes induced by various types of perturbations, and a number of representative experimental examples is the subject of Chapter 4. 

The main advantage of the simulations is that they provide the exact solution of the model system. The main disadvantage is that they are very demanding computationally and therefore in order to make systematic studies a compromise must be reached between the molecular detail in the model system and the number of studies that can be carried out. Furthermore, in some applications, for example protein adsorption on tethered polymer layers, the time scale for the process may be too long to be able to be simulated even with a simple model. However, combined effective potentials obtained from other theoretical approaches with, for example, BD simulations may lead to studies of the kinetic prop>erties of protein adsorption in tethered protein layers. As computational capabilities increase we may be able to reach more complex and detailed systems by the use of straightforward simulations. 

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