Stochastic Detection of Terrorist Agents and Biomolecules in a Biological Channel - Nanopores: Sensing and Fundamental Biological Interactions - page 328

Fig. 13.11 Interaction of dsDNA with WT and M113R- HL pores. (a) Current blockades

observed after the addition of dsDNA (1.0 m M) to the cis side of a WT pore at pH 7.6. The
very long current blockades most likely do not correspond to DNA translocation events (see the
text). The occluded pore was reopened by ramping the potential to negative and then positive
potentials ( vertical arrows ). (b) Selection of shorter current blockades caused by the interaction
of dsDNA with WT nanopores at pH 7.6. (c) Current blockades observed after the addition of
dsDNA (1.0 m M) to M113R pores at pH 7.6. The relatively long current blockades (but shorter
than the very long events seen with WT- a HL) suggest that M113R promotes the unzipping of
duplexes. ssDNA then traverses the pore (see the text). (d) Fractional residual current vs. dwell
time of the current blockades for the interaction of dsDNA with M113R nanopores at pH 7.6.
(e) dsDNA-induced blockades through M113R pores at pH 11.7. The very short current
blockades represent direct translocation of ssDNA after denaturation of the dsDNA (2.0

a

M)
at the alkaline pH of the solution. (f) Fractional residual current vs. dwell time of the current
blockades for the interaction of (dissociated) dsDNA with M113R nanopores at pH 11.7. The
buffer was 10 mM Tris-HCl, 10 mM CAPS, 15 mM K phosphate, 1.0 M KCl, 100

m

M EDTA,
pH 7.6. The pH in panels (e) and (f) was adjusted to 11.7 by adding small aliquots of 1.0 M
KOH directly to the cis and trans chambers with a pore in the bilayer. Figure reprinted with
permission from [ 21 ]. Copyright 2009 American Chemical Society

m