Electroosmotic Flow and Pressure Influences DNA Configuration in Nanopores

Nanopores have a promising ability of DNA sequencing. One disadvantage with sequencing using solid-state nanopores is that the molecules translocate through the pore far too quickly for detection of each nucleotide. Nanopore research has pushed for the discovery of new techniques to slow down translocating molecules, such as: changing the electrolyte solution, modifying the nanopore surface, and modulating fluid flow. An example of fluid flow modulation is incorporating a trans-pore pressure bias, which has been shown to ‘slow-down’ translocating molecules in high salt conditions¹. Here, we use low salt conditions (i.e. electro-osmotic flow, EOF, dominated) to translocate Lambda phage DNA (λ-DNA) through glass nanopores. When a negative voltage is applied, λ-DNA translocates the pore, resulting in current enhancing (conductive) spikes. Under EOF dominated conditions, pressure affects not only the λ-DNA dwell time, but also the configuration. We describe how λ-DNA configurations can fluctuate depending on pore size, voltage applied, and method of translocation (i.e. EOF or electrophoretically). This work reveals the optimal environment slowing down linearly translocating DNA in preparation for using solid-state nanopores to sequence DNA.
1.Zhang, Hengbin et al. (2013) Small.