Polymers partitioning into highly confined spaces can be studied using single nanometer-scale pores formed by protein ion channels. The ionic conductance of a channel depends on the state of occupancy of the pore by polymer and serves as a measure of polymer partitioning. Specifically, the movement of neutral polymer into the pore causes a reduction of the channel's conductance. The mean conductance is used to determine the polymer partition coefficient and the conductance fluctuations report the rates at which polymer exchanges between the bulk and the pore. Three theoretical approaches to describe the steric interaction of polymer and a single pore (hard spheres, random flight model, and scaling theory) fail to describe the partitioning of poly (ethylene glycol) into two structurally and chemically different ion channels (staphylococcus aureus α-hemolysin and alamethicin). In particular, these theories cannot account for the sharp molecular weight dependence of the partition coefficient.
Citation: Structure and Dynamics of Confined Polymers (NATO Science Partnership Sub-Series)
Publisher Info: Springer, New York, NY
Pub Type: Books
alamethecin, alpha-hemolysin, diffusion, ion channel, noise analysis, partition coefficient, PEG, poly(ethylene glycol), water-soluble polymers