Nucleic Acids Research Advance Access originally published online on January 18, 2008
Nucleic Acids Research 2008 36(5):1443-1449; doi:10.1093/nar/gkm1146
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2008, Vol. 36, No. 5 1443-1449
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Structural Biology |
Interaction of cationic surfactants with DNA: a single-molecule study
1Rowland Institute at Harvard, Harvard University, 100 Edwin H Land Blvd., Cambridge MA 02142, USA, 2Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College Dublin, College Green, Dublin 2, Ireland, 3HSG-IMIT—Institute for Micromachining and Information Technology, Wilhelm-Schickard-Strasse 10, 78052 Villingen-Schwenningen, Germany and 4Department of Chemistry, University of Basel, St. Johanns–Ring 19, CH-4056 Basel, Switzerland
*To whom correspondence should be addressed. Tel: + 353 1 896 4502; Fax: + 353 1 896 3037; Email: wilfried.grange{at}tcd.ie Correspondence may also be addressed to Martin Hegner. Tel: + 353 1 896 2285; Fax: + 353 1 896 3037; Email: martin.hegner{at}tcd.ie
Received October 22, 2007. Revised December 3, 2007. Accepted December 10, 2007.
The interaction of cationic surfactants with single dsDNA molecules has been studied using force-measuring optical tweezers. For hydrophobic chains of length 12 and greater, pulling experiments show characteristic features (e.g. hysteresis between the pulling and relaxation curves, force-plateau along the force curves), typical of a condensed phase (compaction of a long DNA into a micron-sized particle). Depending on the length of the hydrophobic chain of the surfactant, we observe different mechanical behaviours of the complex (DNA-surfactants), which provide evidence for different binding modes. Taken together, our measurements suggest that short-chain surfactants, which do not induce any condensation, could lie down on the DNA surface and directly interact with the DNA grooves through hydrophobic–hydrophobic interactions. In contrast, long-chain surfactants could have their aliphatic tails pointing away from the DNA surface, which could promote inter-molecular interactions between hydrophobic chains and subsequently favour DNA condensation.
Former address: Sudhir Husale, Wilfried Grange, Marc Karle and Martin Hegner, NCCR Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.