Catch, Hold, and Release: Manipulating Single DNA Molecules in Solution

Abstract

The ability to manipulate matter on submicron length scales has revolutionized biophysical research and fueled important scientific and technological advances in past decades. For example, larger dielectric particles can be trapped free in solution by steep electromagnetic field gradients produced by a strongly focused laser beam (optical tweezers).Pushing the limits to the nanometer level, however, has proven challenging. The only known method for trapping fluorescent nanoparticles such as single molecules uses a time-varying DC field in a feedback loop to counteract Brownian motion. This trap, however, can only operate when the particle can be located through fluorescence detection, which is problematic in the case of single molecules where intermittent fluorescence emission is often observed, and requires a complex hardware and software setup.In this contribution, we will discuss a novel and elegant approach for the trapping and manipulation of single molecules and other particles over extended periods of time: the electrostatic corral. The proposed trapping scheme has distinct characteristics which set it apart from other trapping techniques, such as a trapping efficiency that scales favorably with particle size (down to the single molecule level), a stable potential well that does not require any imaging for particle trapping, and multi-particle trapping capabilities. The feasibility of the corral trap approach will be demonstrated with experiments on micro- and nanoscale particles, with particular emphasis on the trapping of single-stranded DNA molecules.