Europhys. Lett.
Volume 69, Number 3, February 2005
Page(s) 461 - 467
Section Interdisciplinary physics and related areas of science and technology
Published online 05 January 2005
Europhys. Lett., 69 (3), pp. 461-467 (2005)
DOI: 10.1209/epl/i2004-10367-2

DNA bundle formation induced by cationic surfactants

D. McLoughlin1, M. Delsanti2, C. Tribet3 and D. Langevin4

1  Strategic Technology Group, ICI, Wilton Centre Redcar TS10 4RF, UK (Current address.)
2  Service de Chimie Moléculaire, CEA-Saclay - France
3  Laboratoire de Physico-Chimie Macromoléculaire, ESPCI - Paris, France
4  Laboratoire de Physique des Solides, Université Paris-Sud - Orsay, France

received 16 September 2004; accepted in final form 26 November 2004
published online 5 January 2005

We have evidenced bundle formation in DNA solutions, induced by the addition of a monovalent cationic surfactant to a solution of short DNA rods. The bundles are rod-like, with a large axial ratio ( $\sim 10$). Their formation is very likely controlled not only by electrostatic interactions, but also by hydrophobic interactions between surfactant chains, once bound to the DNA. The bundles have diameters and lengths both remarkably well defined and possess internal organisation. The value of the diameter is close to that predicted by a model in which interactions are mediated by condensed counterions; the length might be limited by steric hindrance due to bundle overlapping or by intrinsic chain flexibility.

82.39.Pj - Nucleic acids, DNA and RNA bases.
82.70.Uv - Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions).

© EDP Sciences 2005