Solid-state nanopores for single molecule biophysics

Nanopores are single nanometer-sized holes in thin insulating
membranes, which present a new tool for the detection and analysis of
individual biopolymers such as DNA. Applying a voltage bias, negatively
charged DNA molecules are pulled through the pore by the electric
field. When a molecule enters the channel, it displaces its own volume
of solution and hence it alters the pore ionic conductance. By
recording the ionic current it is possible to detect the passage of
individual molecules.

We are currently using solid-state nanopores in combination with
optical tweezers to study real-time dynamics of DNA and protein-DNA
interactions. DNA translocation is stalled at a specific site and its
position is controlled with nanometer accuracy. The capture of DNA
inside the pore is detected as changes in both the ionic conductance
and the force on the molecule. These measurements also allow us to gain
insight into the microscopic structure of the ionic atmosphere
surrounding DNA polymers.