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Stable trapping of single molecules in solution:

 

Recent experiments on electrostatically trapped single pigment-protein complex in solution have revealed the role of slow conformational motion on ultrafast energy transfer. In single molecule manipulation, a micron sized spherical plastic bead is tethered to the (macro)molecule and this bead is trapped so that the forces exerted on the bead can be measured and the process be observed in bright-field video microscopy. The challenge for directly trapping a single (macro)molecule or a dielectric nanoparticle is due to erractic Brownian motion as well as low polarizability. It was speculated that using femtosecond laser excitation smaller particles may be trapped more efficiently.

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By harnessing optical nonlinearity, can we directly trap individual single macromolecules in solution without attaching them to a bead?