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Issue 31, 2017
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Accurate nanoscale flexibility measurement of DNA and DNA–protein complexes by atomic force microscopy in liquid

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Abstract

The elasticity of double-stranded DNA (dsDNA), as described by its persistence length, is critical for many biological processes, including genomic regulation. A persistence length value can be obtained using atomic force microscopy (AFM) imaging. However, most AFM studies have been done by depositing the sample on a surface using adhesive ligands and fitting the contour to a two-dimensional (2D) wormlike chain (WLC) model. This often results in a persistence length measurement that is different from the value determined using bulk and single molecule methods. We describe a method for obtaining accurate three-dimensional (3D) persistence length measurements for DNA and DNA–protein complexes by using a previously developed liquid AFM imaging method and then applying the 3D WLC model. To demonstrate the method, we image in both air and liquid several different dsDNA constructs and DNA–protein complexes that both increase (HIV-1 Vpr) and decrease (yeast HMO1) dsDNA persistence length. Fitting the liquid AFM-imaging contour to the 3D WLC model results in a value in agreement with measurements obtained in optical tweezers experiments. Because AFM also allows characterization of local DNA properties, the ability to correctly measure global flexibility will strongly increase the impact of measurements that use AFM imaging.

Graphical abstract: Accurate nanoscale flexibility measurement of DNA and DNA–protein complexes by atomic force microscopy in liquid

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Publication details

The article was received on 13 Jun 2017, accepted on 19 Jul 2017 and first published on 01 Aug 2017


Article type: Paper
DOI: 10.1039/C7NR04231K
Citation: Nanoscale, 2017,9, 11327-11337
  • Open access: Creative Commons BY-NC license
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    Accurate nanoscale flexibility measurement of DNA and DNA–protein complexes by atomic force microscopy in liquid

    D. Murugesapillai, S. Bouaziz, L. J. Maher, N. E. Israeloff, C. E. Cameron and M. C. Williams, Nanoscale, 2017, 9, 11327
    DOI: 10.1039/C7NR04231K

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