will explain in the following, this approach does not prevent us from taking into account the possibility of conformational changes. We now describe the details of the model with the approximations we make to reduce the complexity of the problem, bearing in mind that our aim is to show that the competitive adsorption can be understood in terms of a general mechanism, regardless the specific details of the real interactions in the system.

We consider the three most abundant proteins in human blood: Albumin (Alb), Immunoglobulin-$\gamma$ (IgG) and Fibrinogen (Fib), for which competitive adsorption on hydrophobic surfaces has been observed [@Bale1988; @Lassen1997]. The model assumes an implicit solvent and includes through effective potentials the specific energetic and entropic effects of the water hydrating the proteins and the surface [@fbi2011], as well as those effects due to the charge distribution on the protein surface or the counter ions in the solution [@Gallo2011]. This method has been validated in many specific cases (e.g., see [@Lund2008; @Ravichandran2000]) and follows a general approach that has led to the well established DLVO theory (e.g., see [@Oberholzer1997; @Ruggiero1999; @Bellion2008]).

Alb is a globular protein, with an almost spherical shape and an isoelectric point (IEP) at approximately 