Joined: 16 Mar 2004
|Posted: Mon Mar 31, 2008 3:12 pm Post subject: Nanoslit puts DNA in perfect position
|Planar fluidic nanoslits are making it easier for molecular biologists to spot the association and dissociation of proteins on fluorescently labelled DNA. The simple system could even help researchers visualize induced tertiary structures such as loops, which push conventional optical or magnetic stretching methods to the limit.
The apparatus requires no externally applied forces or fields and has been developed jointly by researchers from the Technical University of Dresden and the Institute for Integrative Nanosciences (IFW), both in Germany.
To unravel the molecules, scientists place a drop of solution containing DNA at one end of the nanoslit array. Capillary action then draws the liquid into channels measuring 2–10 μm wide and 100 nm deep. After 1 minute, a drop of buffer solution is added at the other end of the slit to equalize the pressure in the device and stop the flow.
In slits of 100 nm depth or less, DNA molecules spontaneously adopt an extended state adjacent to the slit wall. "The physics to stretch a DNA molecule is built into the structure of the device," Madhavi Krishnan from the university's biophysics group said. "Fabrication of the slits is trivial and the unit is easy to mass produce."
Devices are made by first patterning a silicon substrate using laser lithography and then forming a parallel array of 100 nm deep slits by either reactive ion etching in CHF3 plasma or wet etching in HF. Cover glass was bonded to the workpiece to seal the channels from above.
"We used two different fabrication methods to investigate whether the etch chemistry modified the stretching of DNA," said Krishnan. "However, we found the stretching effect to be the same in both cases."
Source: http://nanotechweb.org/articles/news/6/6/20/1 ( James Tyrrell )
Story posted: 27th June 2007