Electrostatic potential distribution of a soft spherical particle with a charged core and pH-dependent charge density

In this paper we provide numerical results for the electrostatic potential profile of a soft charged particle with a charged core and pH-dependent charge density. The present study serves as a useful platform for better quantification of the electrostatic potential profile of the MS2 bacteriophage virus. In this context, this work improves the analysis of a similar recent study [Phan et al., J. Chem. Phys. 139 (2013) 244908] in two aspects. First, as compared to the previous study, we provide numerical rather than analytical results for the electrostatic potential profile. This is important because the analytical treatment forbids the investigation of cases with intermediate to large charge density, relative to the bulk charge density of the electrolyte, of the viral surface. Second, the consideration of pH-dependent charge density in the electrostatic potential profile is a more credible representation of the electrostatics of the virus, which is known to demonstrate pH-dependent variation in the electrophoretic mobility. In fact, we establish that the various predictions on the electrostatic potential profile made in the previous study are substantially modified when the effect of pH is considered, and the result must now be described in terms of the difference pH-pKa, where Ka refers to the ionization constant of the acid that produces the PEL ions.