Translocation of synthetic polyelectrolytes through protein and synthetic nanopores
The complexity of biological processes manifests itself in many ways, with the most notable being the high level of dynamical control they possess. For the full potential of biological mimicry to be unlocked, it is essential for the scientific community to partake in an exhaustive search to understand the governing dynamics behind these biological processes. In this vein, this work investigates the bulk conductivity behavior of sodium polystyrene sulfonate (NaPSS) as a function of polymer (Cp) and salt (Cs) concentrations. This was carried out in an attempt to understand the individual contributions from each of the conducting species of a polyelectrolyte solution (chain, counter-ions, and/or salt) to the bulk conductivity in its most simple aqueous environment. The translocation behavior of NaPSS through α-hemolysin protein pores was also investigated. We demonstrate how single molecules of NaPSS, varying over two orders of magnitude in the degree of polymerization, can be pulled in aqueous media by an externally applied electric field through the α-hemolysin channel embedded in a lipid bilayer. We propose a two-barrier free energy landscape for polyelectrolyte translocation through α-hemolysin protein pores. Based on the proposed energy landscape, a detailed mechanism behind the array of interactions between a charged polymer and the α-hemolysin protein pore is described. Although the experimental setup and the measurement protocol are identical to the original investigation involving DNA, this work demonstrates that synthetic polymer translocation displays many significant distinguishing features when compared to the behavior of DNA or RNA. We have also investigated the sculpting of synthetic nanopores for translocation of bottle-brush polyelectrolytes towards understanding the transport behavior of more complex chain architectures. The use of synthetic nanopores allows for the custom tailoring of pore diameter, allowing for the translocation properties for a variety of chain architectures to be studied.