Simultaneous Multipass Resistive-Pulse Sensing and Fluorescence Imaging of Liposomes.

Simultaneous multipass resistive-pulse sensing and fluorescence imaging have been used to correlate the size and fluorescence intensity of individual lipid liposomes composed of polar lipid extracts labeled with membrane-bound 3,3-dioctadecyloxacarbocyanine (DiO) fluorescent molecules. Here, a nanopipet serves as a waveguide to direct excitation light to the resistive-pulse sensing zone at the end of the nanopipet tip. Individual DiO-labeled liposomes (>50 nm radius) were multipassed back and forth through the orifices of glass nanopipets' 110-150 nm radius via potential switching to obtain subnanometer sizing precision, while recording the fluorescence intensity of the membrane-bound DiO molecules.

Monitoring the escape of DNA from a nanopore using an alternating current signal.

We present the use of an alternating current (AC) signal as a means to monitor the conductance of an alpha-hemolysin (alphaHL) pore as a DNA hairpin with a polydeoxyadenosine tail is driven into and released from the pore. Specifically, a 12 base pair DNA hairpin attached to a 50-nucleotide poly-A tail (HP-A(50)) is threaded into an alphaHL channel using a DC driving voltage. Once the HP-A(50) molecule is trapped within the alphaHL channel, the DC driving voltage is turned off and the conductance of the channel is monitored using an AC voltage.