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Phys Rev Lett. 2011 Aug 19;107(8):088102. Epub 2011 Aug 19.

Direct determination of the base-pair force constant of DNA from the acoustic phonon dispersion of the double helix.

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Reactor Institute Delft, Delft University of Technology, Mekelweg 15, 2629JB, Delft, The Netherlands.


Quantifying the molecular elasticity of DNA is fundamental to our understanding of its biological functions. Recently different groups, through experiments on tailored DNA samples and numerical models, have reported a range of stretching force constants (0.3 to 3 N/m). However, the most direct, microscopic measurement of DNA stiffness is obtained from the dispersion of its vibrations. A new neutron scattering spectrometer and aligned, wet spun samples have enabled such measurements, which provide the first data of collective excitations of DNA and yield a force constant of 83 N/m. Structural and dynamic order persists unchanged to within 15 K of the melting point of the sample, precluding the formation of bubbles. These findings are supported by large scale phonon and molecular dynamics calculations, which reconcile hard and soft force constants.

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