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Phys. Rev. Lett. 99, 018302 (2007) [4 pages]

Direct Measurements of Base Stacking Interactions in DNA by Single-Molecule Atomic-Force Spectroscopy

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Changhong Ke1,*, Michael Humeniuk1,*, Hanna S-Gracz2, and Piotr E. Marszalek1,†
1Department of Mechanical Engineering and Materials Science, Center for Biologically Inspired Materials and Material Systems, Duke University, Durham, North Carolina, USA
2Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, USA

Received 22 January 2007; published 5 July 2007

We investigate the elasticity of two types of single-stranded synthetic DNA homopolydeoxynucletides, poly(dA) and poly(dT), by AFM-based single-molecule force spectroscopy. We find that poly(dT) exhibits the expected entropic elasticity behavior, while poly(dA) unexpectedly displays two overstretching transitions in the force-extension relationship. We suggest that these transitions, which occur at ∼23  pN and ∼113  pN, directly capture, for the first time, the mechanical signature of base-stacking interactions among adenines in DNA, in the absence of base pairing.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.99.018302
DOI:
10.1103/PhysRevLett.99.018302
PACS:
82.39.Pj, 87.15.La

*These two authors contributed equally to this work.

†Corresponding author: pemar@duke.edu

Phone: 919-660-5381

 
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