Electrostatic Attraction between DNA and a Cationic Surfactant Aggregate. The Screening Effect of Salt
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- 作者：Cecí ; lia Leal ; Elham Moniri ; Luis Pegado ; Hå ; kan Wennerströ ; m
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：May 31, 2007
- 年：2007
- 卷：111
- 期：21
- 页码：5999 - 6005
- 全文大小：178K
- 年卷期：v.111,no.21(May 31, 2007)
- ISSN：1520-5207
文摘
Anionic DNA and cationic surfactants form charge neutral complexes that contain finite amounts of water.There is a strong electrostatic attraction between the oppositely charged species, and the finite swelling iscaused by an opposing repulsive force. Adding NaCl to the complexes provides an opportunity to modulatethe strength of the electrostatic attraction. The thermodynamics of the isothermal swelling process has beenexperimentally characterized using a calorimetric technique monitoring both the free energy and the enthalpy.The experimental results are quantitatively analyzed in calculations using the Poisson-Boltzmann equationto describe the electrostatic effects. The main findings are as follows: (i) Addition of salt results in an increasedswelling at a given water activity. (ii) The effect of the salt can be quantitatively modeled on the basis of thePoisson-Boltzmann equation with a dielectric description of the water. (iii) There exists a short-range repulsiveforce between DNA double helices and surfactant aggregates. (iv) Solid NaCl dissolves in the complex atwater activities in the range 0.5-0.6 rather than at 0.74 as in a saturated aqueous solution. (v) The heat ofsolution of NaCl in the complexes is around +1.6 ± 0.5 kJ/mol, surprisingly close to the values found for thedissolution into bulk aqueous solutions.