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Abstract
This article explores the role of some geometrical factors on the electrophoretically
driven translocations of macromolecules through nanopores. In the case of asymmetric
pores, we show how the entry requirements and the direction of translocation can modify
the information content of the blocked ionic current as well as the transduction of
the electrophoretic drive into a mechanical force. To address these effects we studied
the translocation of single-stranded DNA through an asymmetric alpha-hemolysin pore.
Depending on the direction of the translocation, we measure the capacity of the pore
to discriminate between both DNA orientations. By unzipping DNA hairpins from both
sides of the pores we show that the presence of single strand or double strand in
the pore can be discriminated based on ionic current levels. We also show that the
transduction of the electrophoretic drive into a denaturing mechanical force depends
on the local geometry of the pore entrance. Eventually we discuss the application
of this work to the measurement of energy barriers for DNA unzipping as well as for
protein binding and unfolding.