Resistance to diffusion
This figure is a potential response to Reviewer’s 1 question about the difference between pore discovery and transmembrane resistances and Reviewer’s 2 question about membrane vs. well resistance.
a. Resistances for an ultrathin membrane with large pores. The pore discovery resistance is larger than the transmembrane (steric/frictional) resistance for small molecule sizes. The total resistance is the addition of pore discovery and transmembrane resistances, and will eventually overlay with the increasing transmembrane resistance for large molecule sizes.
b. Resistances for an ultrathin membrane with smaller pores. The pore discovery and transmembrane resistances are more comparable for small molecules, though the addition of the two is significantly larger than the transmembrane resistance alone.
c. Resistances for a thick membrane with large pores. The transmembrane resistance is much larger than the pore discovery resistance for all molecules sizes and overlays with the total resistance.
d. Comparison of the fluid well resistance and the total membrane resistance for thick and ultrathin membranes. The fluid well resistance is greater than the membrane resistance in both thick and thin membranes for small molecules. However, the resistance in thick membranes increases faster than ultrathin membranes and becomes larger than the well resistance long before the physical pore cutoff (60 nm). The resistance for ultrathin membranes increases closer to the physical pore cutoff.