Interview for Faculty Position

Single-molecule biophysics in nanofluidic devices

Serge Lemay

Kavli Institute of Nanoscience
Delft University of Technology

Modern lithography techniques allow fabricating structures with dimensions approaching the size of large biomolecules, creating fundamentally new opportunities for molecular biophysics experiments.

In the first part of the talk, I will present measurements of the force exerted by an electric field on a single DNA molecule threading through a solid-state nanopore. The experiment employs optical tweezers to arrest the translocation of a single DNA strand inside the pore and determine the force. These experiments elegantly demonstrate that the forces in electrophoresis cannot be understood solely in terms of electrostatics, and that solvent-mediated hydrodynamic interactions between the DNA, its counterions, and the environment play a central role.

In the second part of the talk, I will report on our progress in the development of a new single-molecule technique based on electrochemical detection in nanofluidic channels. We can at present detect the electrical signal from as few as ~70 electrochemically-active molecules. This electrical signal undergoes characteristic fluctuations, and we show that these quantitatively reflect the independent Browian motion of the molecules. Further downscaling of this device is expected to lead to the electrochemical detection of the individual biocatalytic events from a single enzyme.