do surfactants form micelles on the surface of DNA?

V. Buckin, E. Kudryashov, S. Morrissey, T Kapustina, and K Dawson.

Progress in Colloid and Polymer Science, 110, pp. 214-219 (1998)

The complex formation between the cationic surfactant, dodecyltrimethylammonium bromide (C12TAB), and short fragments of Calf Thymus DNA, 220 base pairs, has been studied by using a combination of highprecision ultrasonic velocity and density measurements. The compressibility and the volume effects of the binding of C12TAB with DNA are 139 cm3 mol-1 Gpa-1 and 9.0 cm3 mol-1, respectively. In addition to that we obtained the compressibility effect in the micelle formation for three surfactant molecules C12TAB, C14TAB and C16TAB. These effects are 127.5, 148.9 and 169.2 cm3 mol-1, Gpa-1 for C12TAB, C14TAB and C16TAB, respectively. The high value of the compressibility effect in the binding of the C12TAB surfactant to DNA cannot be explained by hydration changes only and indicates the formation of a structure with a highly compressible core. This conclusion, and the close values of the compressibility effect in the formation of the C12TAB micelles in solution, and in the binding of C12TAB to DNA, demonstrates the formation of micelle-like aggregates of C12TAB molecules on the DNA surface.

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