Letter abstract
Nature Physics 3, 641 - 644 (2007)
Published online: 5 August 2007 | doi:10.1038/nphys697
Subject Category: Biological physics
Charge inversion accompanies DNA condensation by multivalent ions
K. Besteman, K. Van Eijk & S. G. Lemay
The condensation of stiff, highly charged DNA molecules into compact structures by condensing agents ranging from multivalent ions1 to small cationic proteins2, 3 is of major biological and therapeutic importance4, 5, yet the underlying microscopic mechanism remains poorly understood1, 6, 7, 8, 9. It has been proposed7, 10 that DNA condensation is a purely electrostatic phenomenon driven by the existence of a strongly correlated liquid (SCL) of counterions at the DNA surface. The same theoretical argument predicts that multivalent counterions overcompensate the DNA charge when present at high concentration11, in turn destabilizing the condensates12. Here, we demonstrate the occurrence of DNA charge inversion by multivalent ions through measurements of the electrophoretic mobility of condensed DNA. By observing the multivalent-ion-induced condensation of a single DNA molecule using magnetic tweezers, we further show that charge inversion influences condensation by modulating the barrier for condensate nucleation in a manner consistent with the SCL mechanism.
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
Correspondence to: S. G. Lemay e-mail: s.g.lemay@tudelft.nl
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