Protein diffusion in charged nanotubes: "On-Off" behavior of molecular transport

The effect of low ionic strength (I=0.01 M) on the selectivity of separation of two proteins, bovine serum albumin (BSA) and bovine hemoglobin (BHb) in surface modified, nanoporous membranes was examined. Low ionic strength gave a large double layer thickness on both protein molecule and the nanopore surface to cause significant electrostatic interactions of BSA and BHb with the nanopore surface for sufficiently small nanopores. In comparison to the diffusion of uncharged proteins at their PI, above and below the pI electrostatic interactions drastically reduced the protein transport in the nanopore.