Direct Observation of Transitions between Surface-Dominated and Bulk Diffusion Regimes in Nanochannels

Protein diffusion through charged nanopores with different radii at low ionic strength

“…Biesheuvel and co-workers 20 have analysed thoroughly protein adsorption and partition equilibrium in charged nanopores. Renaud and co-workers 29 have provided experimental and theoretical evidences for the transport transition between the surface-dominated and bulk diffusion regimes of Fig. 4 in the case of planar nanochannels with controlled geometry (see, e.g., Fig.…”

“…More detailed microscopic models for the two-region pore and the electrostatic equations can be used at the price of increasing complexity. 20,29,30 In particular, Zydney and co-workers [30][31][32] have also identified the (protein charge)-(pore charge) interaction in the exponentials of eqn (3) as a crucial term in more rigorous models of protein ultrafiltration. Biesheuvel and co-workers 20 have analysed thoroughly protein adsorption and partition equilibrium in charged nanopores.…”

“…4. Assuming a continuous radial variation of the pore properties 29,30,33 would be more realistic for quantitative estimations but it is difficult in our case because of the limited microscopic information on the protein-pore surface interaction. Note also that eqn (3) is a crude estimation for the protein surface transport that oversimplifies the pore electrostatics and considers only the effect of the protein net charge.…”

Molecular Dynamics and Monte Carlo simulations resolve apparent diffusion rate differences for proteins confined in nanochannels

“…If the molecule is in the bulk, the travel distance is determined from a Gaussian distribution with mean equal to the bulk step size, assuming that the molecule is initially centered i the travel direction is defined such that the molecule would impinge on a nanochannel wall the bulk travel distance is truncated at the point of intersection. The channel height available for bulk mole account for the Debye screening length: [28] …”

“…[27] In the second set of experiments, WGA molecules were observed by fluorescence correlation spectroscopy (FCS) in a nanochannel formed by two parallel borosilicate glass plates separated by 50 nm. [28] The FCS observation volume is well approximated by a right circular cylinder with radius 420 nm. It was found that, depending on the concentration, net charge of the proteins, and the ionic strength of the solution, diffusion was dominated by steric exclusion, the reversible surface adsorption of the biomolecules, or the exclusion-enrichment effect.…”