Calorimetric and dynamic light-scattering investigation of cationic surfactant--DNA complexes |
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Authors: | Marchetti S Onori G Cametti C |
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Institution: | Dipartimento di Fisica, Universita' di Firenze, Via G. Sansone, I-50019 Sesto Fiorentino, Firenze, Italy. |
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Abstract: | By means of combined calorimetric and dynamic light-scattering measurements, we have investigated the conformational behavior of DNA chains after thermal melting in the presence of a cationic surfactant at different concentrations, up to a surfactant-to-phosphate group molar ratio close to unity. Both the specific heat capacity, C(ex)(p) and the hydrodynamic radius R of the DNA chains provide support for the existence of two structural arrangements with different thermal stabilities, coexisting in the bulk solution. Although a component remains an elongated unfolded DNA chain originated in the thermal denaturation, the second component, consisting of DNA-surfactant complexes, assumes a compact structure with an average size of about 80 nm, whose thermal denaturation occurs at temperatures higher than 100 degrees C. |
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