CHEMISTRY: Less Strain, More Force

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Science  29 Aug 2008:
Vol. 321, Issue 5893, pp. 1135a
DOI: 10.1126/science.321.5893.1135a

Many studies have probed the force required to pull apart double-stranded DNA. Given the interest in using pore structures to sequence nucleic acids, Ashcroft et al. have now measured the force needed to separate hairpins in a self-attracted single strand of DNA as it is pulled through such a pore, in this case a β-cyclodextrin ring. The ring was attached to an atomic force microscope tip and threaded onto a surface-immobilized polyethylene glycol molecule, to which a single strand of DNA that could form a hairpin was then linked at the free end. The force needed to pull the β-cyclodextrin ring through the hairpin was about 40 times greater than that typically needed to pull double-stranded DNA apart directly. The authors note that the transition state for destabilizing the hairpin occurs over a much smaller distance, and so more force must be applied. — PDS

Small 4, 10.1002/smll.200800233 (2008).

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