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

Abstract

The diffusion of two similar molecular weight proteins, bovine serum albumin (BSA) and bovine haemoglobin (BHb), through nanoporous charged membranes with a wide range of pore radii is studied at low ionic strength. The effects of the solution pH and the membrane pore diameter on the pore permeability allow quantifying the electrostatic interaction between the charged pore and the protein.Because of the large screening Debye length, both surface and bulk diffusion occur simultaneously. By increasing the pore diameter, the permeability tends to the bulk self-diffusion coefficient for each protein.By decreasing the pore diameter, the charges on the pore surface electrostatically hinder the transport even at the isoelectric point of the protein. Surprisingly, even at pore sizes 100 times larger than the protein, the electrostatic hindrance still plays a major role in the transport. The experimental data are qualitatively explained using a two-region model for the membrane pore and approximated equations for the pH dependence of the protein and pore charges. The experimental and theoretical results should be useful for designing protein separation processes based on nanoporous charged membranes.

Fabrication of Nanoporous Alumina Ultrafiltration Membrane with Tunable Pore Size Using Block Copolymer Templates

“…This Debye length is significant for pore sizes of ~ 20 nm and proteins diameters of ~ 6 nm. [21,54,55] The flux and the separation selectivity were compared between three membranes: a) the hierarchical AlOx/AAO membrane developed in this study (AlOx membrane templated by the 141 nm thick BCP film treated with 3 cycles of Al2O3 SIS and transferred onto a commercially available AAO membrane with 100 nm pores), b)…”

“…These flux values are in good agreement with other protein separation results using membranes with the same characteristic pore size. [52,55] The selectivity of separation, calculated from the flux ratio between two proteins, was 1.1 ± 0.1 (Figure 7c). Although at pH = 4.7 BSA has neutral charge while BHb and the AlOx membrane are positively charged (Al2O3 isoelectric point is 9), the difference in the charge states has little effect on the separation selectivity since the effective pore size (with the EDL) is considerably larger than the hydrated protein diameters.…”

Standalone interferometry-based calibration of convex lens-induced confinement microscopy with nanoscale accuracy

“…However, there have been a number of experiments where the CLiC geometry alone provided a suitable environment for studying the dynamics of large molecules as a function of confinement. 24,25,44 An extension of these types of experiments to smaller gap thickness will enable the study of molecular behavior at varying degrees of confinement that are relevant to a wide range of applications, including protein separation methods, 28,29 polyelectrolyte adsorption at biointerfaces, 45 and single-molecule sensors. 46…”

“…While gap heights on the order of a hundred nanometers or higher are relevant to many industrial and biological applications, there are situations where smaller gap heights are critically important. Many separations techniques, including protein separation using ultrafiltration, 28,29 as well as recent analytical methods such as electrochemical correlation spectroscopy 30 occur within environments that have confined dimensions on the order of tens of nanometers. Within the evolving field of nanofluidics, there remain unique challenges as well as opportunities associated with strongly confined molecular transport (confined dimensions between 1-100 nm).…”

A novel technique for detoxification of phenol from wastewater: Nanoparticle Assisted Nano Filtration (NANF)

“…1. The details of the reactor is given elsewhere [19]. The effective permeation area of the NF membrane was 1.77 cm 2 , and the volumes of both compartments were 35.0 mL.…”