Physics (Internal)

Controlling Complex Molecules with Light

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: To study a single molecule, one would like to hold the molecule still, without perturbing its internal dynamics. I will present a machine that achieves this goal. The Anti-Brownian Electrokinetic trap (ABEL trap), tracks the Brownian motion of a single molecule using fluorescence microscopy, and applies electrical kicks to the molecule that are timed to induce an electrokinetic drift that cancels the Brownian motion. The ABEL trap can immobilize single biomolecules for extended observation and has been used to study the dynamics of individual DNA molecules and protein chaperonins. I will give examples of new things that can be learned from trapped molecules.

In a second example, I will discuss using light to control an internal degree of freedom: molecular chirality. Electromagnetic fields may be engineered to excite molecules of a single handedness in a mixture containing equal numbers of left- and right-handed molecules. This observation provides a new route to using light to impart a chiral bias to a photochemical reaction.