IBM today announced an ambitious effort to build a nanoscale DNA sequencer. In following video IBM Researchers Stas Polonsky and Gustavo A Stolovitzky explain how project could improve throughput and bring cost as low as $100 to $1,000.Basically idea is to pass single stranded DNA molecules through the nanometer-sized tunnels or nanopores available on DNA transistor cheap. On the DNA cheap these nonopores are is created using an electron beam from a tunneling electron microscope. Under the influence of electric field, which attracts the negatively charged DNA strand, single stranded DNA molecules floating above the microchip are pulled through the nanopore. Inside the pore the sensor detects the individual nucleotides based on their electrical properties and due to overlapping electrical properties of these four nucleotides control over the passing speed is critical because for the better the accuracy more time is needed to measure each nucleotide. So key is the optimization of the process which controls the rate at which a DNA strand pass through the nanopore. For this IBM researchers have formulated a cyclic getting mechanism which will facilitate slow moving of DNA strands through the nanopore at a rate of one nucleotide per cycle a rate at which will give about 1 millisecond time to detect single DNA nucleotide which is reasonably good. Here is the schematics of the DNA transistor operation for the control of the translocation of a DNA through a nanopore followed by another video describing how it works.
A membrane containing the nanopore, funtionalized with metal contacts (orange) separated by dielectric materials (lime), divides a reservoir into a top part containing an ionic solution with a high concentration of single stranded DNA, and a bottom part, where the DNA will be translocated to. The DNA on the top reservoir is induced to go to the bottom reservoir by the action of a biasing voltage. In the absence of anything else, the DNA would translocate through the pore at a speed of several million bases per second. To control the passage of DNA through the nano-hole, voltages of appropriate polarity (not shown) are applied to the metal contacts inside the pore, which create an internal electric field that trap the DNA. By alternating the trapping voltages applied to the metal contacts, the DNA can be made ratchet from the top to the bottom reservoirs in a controlled way. (Image ©2009,IBM)
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