Nanopore-Based DNA Sequencing and DNA Motion Control - Nanopores: Sensing and Fundamental Biological Interactions - page 261

Fig. 11.5 A single alpha-HL channel is shown in cross section embedded in a lipid bilayer. Image
adapted from [ 12 ]

Fig. 11.6 Supporting apparatus for horizontal bilayer experiments. Image adapted from [ 13 ]

To figure out the reason for this counter intuitive effect, the authors of [ 13 ]
examined blockades caused by RNA of composition A(30)C(70)Gp [ 12 ]. As shown
in Fig. 11.9 , there are two levels of ionic current blockages: always 95-85%,
indicating that the 3 0 poly (C) end of A(30)C(70)Gp always entered the pore first.
The explanation is that poly (C) traverses through the

-hemolysin channel as a
helix, while helical segments along a poly (A) strand have to be unwound and
extended to permit translocation through the channel, which is also the reason
of this opposite effect that the current blockage of poly (A) is smaller than that of
poly (C) (Fig. 11.10 ).

a