the monolayer of an already adsorbed homogenous protein monolayer. The aggregation of this new heterogenous protein mixture causes the "turning" of the double-protein complex which exposes the initially adsorbed protein to the solution. In the third step, the protein that was initially adsorbed can now diffuse out into the solution and the new protein takes over. This 3 part "transient complex mechanism" is further explained and verified through AFM imaging by Hirsh et al. pH Cycling Jung et al. also describe a molecular mechanism for fibrinogen displacement involving pH cycling. Here the αC domains of fibrinogen change charge after pH cycling which results in conformational changes to the protein that leads to stronger interactions with the protein and the biomaterial. Mathematical Models The simplest mathematical model to explain the Vroman Effect is the Langmuir model using the Langmuir isotherm. More complex models include the Fruendlich isotherm and other modifications to the Langmuir model. This model explains the kinetics between reversible adsorption and desorption, assuming the adsorbate behaves as an ideal gas at isothermal conditions. See also Protein adsorption Langmuir adsorption model References Surface science Blood