Interaction of cationic surfactants with DNA: a single-molecule study |
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Authors: | Husale Sudhir Grange Wilfried Karle Marc Bürgi Stephan Hegner Martin |
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Institution: | Sudhir Husale, Wilfried Grange, Marc Karle, Stephan Bürgi, and Martin Hegner |
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Abstract: | 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. |
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