Compaction and Decompaction of DNA in the Presence of Catanionic Amphiphile Mixtures

The dissociation of DNA−cationic surfactant complexes with the addition of a negative amphiphile was studied by fluorescence microscopy (FM). The unfolding of DNA molecules previously compacted with cationic surfactant was shown to be dependent on the anionic surfactant chain length; lower amounts of a longer-chain surfactant were needed to release DNA into solution. However, we observed no dependence on the hydrophobicity of the compacting agent. The structures of the aggregates formed by the two surfactants, after the interaction with DNA, were imaged by cryogenic transmission electron microscopy (cryo-TEM). We found that it is possible to predict the structure of the aggregates the surfactants will form, such as vesicle phases, from the behavior of mixed surfactant systems, which brings new insight to this subject and several interesting opportunities for applications.