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We have performed single-molecule studies of GFP-LacI repressor proteins bound to bacteriophage lambda DNA containing a 256 tandem lac operator insertion confined in nanochannels. An integrated photon molecular counting method was developed to determine the number of proteins bound to DNA. By using this method, we determined the saturated mean occupancy of(More)
A nanopore-based device provides single-molecule detection and analytical capabilities that are achieved by electrophoretically driving molecules in solution through a nano-scale pore. The nanopore provides a highly confined space within which single nucleic acid polymers can be analyzed at high throughput by one of a variety of means, and the perfect(More)
We present a continuous-flow microfluidic device that enables cell by cell separation of cells selectively tagged with magnetic nanoparticles. The cells flow over an array of microfabricated magnetic stripes, which create a series of high magnetic field gradients that trap the magnetically labeled cells and alter their flow direction. The process was(More)
The successful design of nanofluidic devices for the manipulation of biopolymers requires an understanding of how the predictions of soft condensed matter physics scale with device dimensions. Here we present measurements of DNA extended in nanochannels and show that below a critical width roughly twice the persistence length there is a crossover in the(More)
We show that genomic-length DNA molecules imaged in nano-channels have an extension along the channel that scales linearly with the contour length of the polymer, in agreement with the scaling arguments developed by de Gennes for self-avoiding confined polymers. This fundamental relationship allows us to measure directly the contour length of single DNA(More)
– We consider the diffusive motion of a localized knot along a linear polymer chain. In particular, we derive the mean diffusion time of the knot before it escapes from the chain once it gets close to one of the chain ends. Self-reptation of the entire chain between either end and the knot position, during which the knot is provided with free volume, leads(More)
Separation of blood cells by native susceptibility and by the selective attachment of magnetic beads has recently been demonstrated on microfluidic devices. We discuss the basic principles of how forces are generated via the magnetic susceptibility of an object and how microfluidics can be combined with micron-scale magnetic field gradients to greatly(More)
We show that genomic-length DNA molecules imaged in nanochannels have an extension along the channel that scales linearly with the contour length of the polymer, in agreement with the scaling arguments developed by de Gennes for self-avoiding confined polymers. This fundamental relationship allows us to measure directly the contour length of single DNA(More)
Shelterin protein TRF2 modulates telomere structures by promoting dsDNA compaction and T-loop formation. Advancement of our understanding of the mechanism underlying TRF2-mediated DNA compaction requires additional information regarding DNA paths in TRF2-DNA complexes. To uncover the location of DNA inside protein-DNA complexes, we recently developed the(More)
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