The
effect of an electrolyte cation on the unzipping of furan-containing
double-stranded DNA in an α-hemolysin (αHL) nanopore is
described. The current through an open αHL channel increases
in proportion to the ion mobility. However, the ionic current measured
during residence of a DNA duplex inside of the protein pore shows
a more complex dependence on the choice of cation, indicating that
the current measured during DNA residence in the pore is modulated
by the specific interactions of the cations with the DNA and/or αHL.
The residence time (stability) of the DNA duplex inside of the pore
prior to unzipping is also highly dependent on the cation, in striking
contrast to the small variation in duplex stability (as measured by
the melting temperature) in bulk electrolyte solution. A missing base
in DNA can be detected in the latch region of αHL with optimal
current resolution in RbCl, while optimal time resolution is possible
in LiCl
