Probing DNA with micro- and nanocapillaries and optical tweezers

Abstract

We combine for the first time optical tweezer experiments with the resistive pulsetechnique based on capillaries. Quartz glass capillaries are pulled into a conicalshape with tip diameters as small as 27 nm. Here, we discuss the translocation ofλ-phage DNA which is driven by an electrophoretic force through the nanocapillary.The resulting change in ionic current indicates the folding state of singleλ-phage DNA molecules. Our flow cell design allows for the straightforward incorporation ofoptical tweezers. We show that a DNA molecule attached to an optically trapped colloid ispulled into a capillary by electrophoretic forces. The detected electrophoretic force is ingood agreement with measurements in solid-state nanopores.