Beyond the Helix Pitch: Direct Visualization of Native DNA in Aqueous Solution
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- 作者：Shinichiro Ido ; Kenjiro Kimura ; Noriaki Oyabu ; Kei Kobayashi ; Masaru Tsukada ; Kazumi Matsushige ; Hirofumi Yamada
- 刊名：ACS Nano
- 出版年：2013
- 出版时间：February 26, 2013
- 年：2013
- 卷：7
- 期：2
- 页码：1817-1822
- 全文大小：413K
- 年卷期：v.7,no.2(February 26, 2013)
- ISSN：1936-086X
文摘
The DNA double helix was first elucidated by J.D. Watson and F.H.C. Crick over a half century ago. However, no one could actually 鈥渟ee鈥?the well-known structure ever. Among all real-space observation methods, only atomic force microscopy (AFM) enables us to visualize the biologically active structure of natural DNA in water. However, conventional AFM measurements often caused the structural deformation of DNA because of the strong interaction forces acting on DNA. Moreover, large contact area between the AFM probe and DNA hindered us from imaging sub-molecular-scale features smaller than helical periodicity of DNA. Here, we show the direct observation of native plasmid DNA in water using an ultra-low-noise AFM with the highly sensitive force detection method (frequency modulation AFM: FM-AFM). Our micrographs of DNA vividly exhibited not only overall structure of the B-form double helix in water but also local structures which deviate from the crystallographic structures of DNA without any damage. Moreover, the interaction force area in the FM-AFM was small enough to clearly discern individual functional groups within DNA. The technique was also applied to explore the synthesized DNA nanostructures toward the current nanobiotechnology. This work will be essential for considering the structure鈥揻unction relationship of biomolecular systems in vivo and for in situ analysis of DNA-based nanodevices.