Interaction of cationic surfactants with DNA: a single-molecule study.
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.
Husale
Sudhir
S
Rowland Institute at Harvard, Harvard University, 100 Edwin H Land Blvd., Cambridge MA 02142, USA.
Grange
Wilfried
W
Karle
Marc
M
Bürgi
Stephan
S
Hegner
Martin
M
D002412:Cations / Q000737:chemistry; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D008956:Models, Chemical; D052898:Optical Tweezers; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
D002412:Cations; D002593:Cetrimonium Compounds; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; C013912:decyltrimethylammonium; C042006:octyltrimethylammonium; D004247:DNA; D000077286:Cetrimonium