binding of cationic surfactants to DNA. compressibility and volume effects

Kudryashov E., Morrissey S., Gorelov A., Buckin V., Dawson K

Biophysical Journal, 72, pp. 362 (1997)

We have studied complex formation between different cationic surfactants and short fragments of DNA using combination of the dynamic light scattering, ultrasound velocity, and density measurements combined with surfactant selective electrode method. From the binding isotherm of the surfactant with DNA, measured by the potentiometric technique with a cationic surfactant-selective electrode, we obtained the dependence of the apparent molar volume and compressibility of DNA on the amount of surfactant bound. In addition, we obtained the volume and compressibility effects of micelle formation in solutions of surfactants alone. The compressibility of the DNA surfactant solutions increases significantly with the binding ratio, whereas, the volume shows a negligible change. Analogous volume and compressibility changes were observed in the micelle formation of free surfactants. The results were interpreted in terms of micelle like structure of the surfactant around DNA.

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