PROTEIN ADSORPTION INTO CHARGED CONFINING PORES

The confinement of proteins on porous materials is essential for several applications since protein stability and biological activity are enhanced. In the case of charged confining surfaces, like silica, the protein charge distribution is one of the main factors for this applicability since it determines their orientation regarding the surface and the exposure of active sites. In this study the adsorption properties of Lysozyme and Cytochrome C into a negatively charged silica pore are investigated using a coarse-grained model and constant–pH Monte Carlo simulations. The effects of pH and ionic strength on the protein orientation and spatial distribution of its residues regarding the pore surface are evaluated. We observe an orientational transition of the adsorbed Lysozyme when the solution pH gets closer to its isoelectric point, unlike the Cytochrome C behavior, which keeps the same region in contact with the pore surface for the whole pH range in which the protein is adsorbed. These findings are related to changes in the protein charge distribution caused by the adsorption due to the pK a shift of some key residues that stabilizes the adsorption in the observed protein orientation.