Predicting the Electrophoretic Mobility of Charged Particles in an Aqueous Medium

Electrophoresis of charged particles
has important applications
in biochemical separation processes. The mobility of these particles
depends on the surrounding electric double layer (EDL), which is impacted
by solvent restructuring because of hydration interactions. Nevertheless,
most theoretical estimates ignore such interactions during computation
of the electrophoretic mobility. Here, we employ a complementary blend
of mean-field analysis and molecular dynamics simulations performed
for a peptide–G-quadruplex complex to assess how hydration
interactions alter the mobility of a charged particle in an aqueous
medium. These interactions are seen to stabilize the EDL, resulting
in more significant localized counterion concentrations while strengthening
the ensuing electrokinetic flow. The ordering of ions near the particle
surface is obtained only upon including hydration interaction, revealing
that the hydration water molecules act as a glue for forming a stable
EDL, a key finding of this work. Conversely, the observed microstructure
of ions near the charged surface as obtained from our theory establishes
a bridge link between the micro and continuum model. The presence
of larger counter ions enhances the drag on the particle, thus restricting
its mobility. The mobility also becomes dependent on size, which may
be useful for isolating a wide array of biomolecules. The impact of
hydration interactions intensifies with increases in particle size,
surface charge density, and bulk ion concentration.