Electroosmotic flow through an α -hemolysin nanopore

Nanopores are emerging as powerful tools for biosensing at a single molecule level, and their characterization under different working conditions is crucial for applications. In this perspective, we studied the ionic and electroosmotic flows across an alpha-hemolysin nanopore using an extensive set of molecular dynamics simulations. Results show that the alteration in the solution pH has a dramatic effect on both electroosmotic flow and nanopore selectivity. Upon lowering the pH, the internal pore surface becomes globally more positively charged and, consequently, the transport of positive ions is hindered leading to a strong unbalance of positive and negative ionic fluxes. This unbalance gives rise to an intense electroosmotic flow that in certain regimes can overwhelm the ionic flux. Finally, we compared our data with continuum prediction for ideal electroosmotic flows, showing that, although the alpha-hemolysin case is quite far from the ideality, the continuum theory is able to capture the magnitude of the electroosmotic mechanism.