Interaction of DNA with Catioic Micelles: Effects of Micelle Surface Charge Density, Michelle Shape, and Ionic Strength on Complexation and DNA Collapse

摘要

Complexation between DNA and cationiclnonionic micelles of dodecyldimethylamine oxide (DMDAO) at various ionic strengths (1) was studied by monitoring turbidity or dynamic light scattering as a function of pH at various ionic strengths (1). Complexation takes place at a critical degree of micelle protonation (/3c) and is therefore primarily controlled by the ratio of cationic:nonionic surfactant, not by the ratio of surfactant:DNA. /3c corresponds to a critical micelle surface charge density (ac), which increases nearly linearly withI. The dependence of /3conI displays a discontinuity when the DMDAO micelle shape changes from spherical to rodlike. The proximity of the complexation boundary to the coil/coil-globule coexistence boundary reported from fluorescence microscopyl indicates that the DNA -micelle complexation observed by scattering also corresponds to micelle-induced collapse of DNA.