Nanomechanics of Double Stranded DNA Structures
Friday, October 8, 2010 - 11:45am
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Elasticity is a key property of DNA. Throughout the cell cycle, DNA is subjected to mechanical loadings that deform its original structure. Beyond the biological significance of DNA elasticity, in DNA nanotechnology, a solid understanding of DNA reaction to force is necessary to create functional nanostructures. We, for the first time, characterize the elastic profile of different canonical DNA double helical structures, specifically the A and Z helices, by stretching with atomic force microscope (AFM) based single-molecule force spectroscopy. A-DNA is a wider, shorter helix, compared to the standard B form, whereas Z-DNA is extended and narrower. We expect these structural variations to manifest in varied elastic profiles. When stretched, we find that the force spectra of A-DNA exhibit a short initial length before the characteristic overstretching force plateau, compared to the final fully stretched length. Conversely, Z-DNA force spectra show a relatively long initial length, before overstretching. Also, interestingly, neither the force spectra of A nor Z-DNA exhibit a pronounced second high force “melting” plateau like B-DNA. These results help link the structure and mechanical properties of DNA, and will help us better understand fundamental cellular DNA processing, while also providing materials properties for future DNA nanomachines.