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Origin of the electrophoretic force on DNA in solid-state nanopores

2009; Nature Portfolio; Volume: 5; Issue: 5 Linguagem: Inglês

10.1038/nphys1230

1745-2481

Stijn van Dorp, Ulrich F. Keyser, Nynke H. Dekker, Cees Dekker, Serge G. Lemay,

Microfluidic and Capillary Electrophoresis Applications

When a single strand of DNA is threaded through a nanopore, a direct test of the effect of pore size indicates that a hydrodynamic model for the process should include the coupled Poisson–Boltzmann and Stokes equations. Despite gel electrophoresis being one of the main workhorses of molecular biology, the physics of polyelectrolyte electrophoresis in a strongly confined environment remains poorly understood. Theory indicates that forces in electrophoresis result from interplay between ionic screening and hydrodynamics1,2, but these ideas could so far be addressed only indirectly by experiments based on macroscopic porous gels. Here, we provide a first direct experimental test by measuring the electrophoretic force on a single DNA molecule threading through a solid-state nanopore3 as a function of pore size. The stall force gradually decreases on increasing the nanopore diameter from 6 to 90 nm, inconsistent with expectations from simple electrostatics and strikingly demonstrating the influence of the hydrodynamic environment. We model this process by applying the coupled Poisson–Boltzmann and Stokes equations in the nanopore geometry4,5 and find good agreement with the experimental results.