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Direct force measurements on DNA in a solid-state nanopore

Nature Physics volume 2, pages 473477 (2006) | Download Citation

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Abstract

Among the variety of roles for nanopores in biology, an important one is enabling polymer transport, for example in gene transfer between bacteria1 and transport of RNA through the nuclear membrane2. Recently, this has inspired the use of protein3,4,5 and solid-state6,7,8,9,10 nanopores as single-molecule sensors for the detection and structural analysis of DNA and RNA by voltage-driven translocation. The magnitude of the force involved is of fundamental importance in understanding and exploiting this translocation mechanism, yet so far it has remained unknown. Here, we demonstrate the first measurements of the force on a single DNA molecule in a solid-state nanopore by combining optical tweezers11 with ionic-current detection. The opposing force exerted by the optical tweezers can be used to slow down and even arrest the translocation of the DNA molecules. We obtain a value of 0.24±0.02 pN mV−1 for the force on a single DNA molecule, independent of salt concentration from 0.02 to 1 M KCl. This force corresponds to an effective charge of 0.50±0.05 electrons per base pair equivalent to a 75% reduction of the bare DNA charge.

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Acknowledgements

We thank M.-Y. Wu and H. Zandbergen for help in fabrication of the nanopores, B. Quinn, D. Stein, D. Lubensky, and R. Seidel for useful discussions, P. Veenhuizen and S. Hage for preparing the DNA constructs, and K. Klein for taking the data with the untethered DNA. J. van der Does is acknowledged for help in designing and building the flow cell and mechanical parts of the tweezers setup. We thank NWO and FOM for financial support.

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  1. Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands

    • Ulrich F. Keyser
    • , Bernard N. Koeleman
    • , Stijn van Dorp
    • , Diego Krapf
    • , Ralph M. M. Smeets
    • , Serge G. Lemay
    • , Nynke H. Dekker
    •  & Cees Dekker

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The authors declare no competing financial interests.

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Correspondence to Nynke H. Dekker or Cees Dekker.

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https://doi.org/10.1038/nphys344

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