Using 3-D dense packing models to predict surface tension change due to protein adsorption.

Protein adsorption modeling primarily focuses on the role of the complexities and differences in the role of the protein constituents. However, experimental evidence suggests that adsorption of human blood-borne protein molecules of widely varying size and purpose is more similar than different. A model, which treats proteins as hard, non-interacting spheres, explains the observed regularity of human blood borne protein adsorption as a result of the dominant role of the solvent in the adsorption process. Here we independently evaluate the efficacy of this model, and adjust the model to a dependence on molecular volume as opposed to molecular weight. In addition, we explore the role of adsorption-induced conformation or orientation changes, and demonstrate that volume invariant changes are well represented by this model and changes that include changes in the molecular volume are not. By focusing on molecular volume, the model can be applied to non-spherical molecules such as fibrinogen and accurately captures differences between BSA, multi-layer, and HSA, monolayer, adsorption. These findings confirm the importance of the solvent in protein adsorption, elucidate the importance of molecular volume on surface tension change, and suggest that this model is generally applicable.