Scanning electron micrograph of a cross section of the finished device. An array of densely spaced nanopillars constitutes the entropically unfavorable region. The pillar spacing was 135 nm and their width approximately 80 nm. Copyright © Cornell
Fluorescing DNA molecules show the separation of two different lengths of DNA. In the first image, DNA molecules pulled by a weak electric field gather at the edge of a sieve made of tiny pillars. After a stronger field pulse of two seconds, the shorter molecules were fully inserted, while the longer molecules remained partially in the open, entropically favorable region. When the field was removed, the longer molecules extracted themselves from the pillar region, as shown at right. Copyright © Cornell University
Cornell University researchers have demonstrated a novel method of separating DNA molecules by length. The technique might eventually be used to create chips or other microscopic devices to automate and speed up gene sequencing and DNA fingerprinting.
The method, which uses a previously discovered entropic recoil force, has better resolution -- that is, better ability to distinguish different lengths -- than others tried so far, the researchers say. They separated DNA strands of two different lengths, using their own nanofabricated device, and demonstrated that modifications would make it possible to separate strands of many different lengths.
A description of the experiment is scheduled to be published in the Oct. 1, 2002, issue of the journal Analytical Chemistry by graduate student Mario Cabodi, postdoctoral researcher Stephen Turner and Harold Craighead, the C.W. Lake Jr. Professor of Productivity.
Bill Steele | Cornell News
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