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ABSTRACT: A theory is presented which quantitatively accounts for the cooperative adsorption of cationic surfactants to anionic polyelectrolytes. For high salt concentration we find that the critical adsorption concentration (CAC) is a bilinear function of the polyion monomer and salt concentrations, with the coefficients dependent only on the type of surfactant used. The results presented in the paper might be useful for designing more efficient gene delivery systems.
09/2007;
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Paulo S. Kuhn
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ABSTRACT: A theory is presented which quantitatively accounts for the cooperative adsorption of cationic surfactants to anionic polyelectrolytes. For high salt concentration, we find that the critical adsorption concentration (CAC) is a bilinear function of the polyion monomer and salt concentrations, with the coefficients dependent only on the type of surfactant used. The results presented in the paper might be useful for designing more efficient gene delivery systems.
09/2007;
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ABSTRACT: We present a model for describing flexible polyelectrolytes in a good solvent a nd in the presence of monovalent salt . The molecule composed by $N$ monomers is characterized by the end to end distanc e $R_e=b (Z-1)^\gamma$ and the number of associated counterions $n$. At high tem peratures the polyelectrolyte behaves as a neutral polymer ($\gamma=0.588$). Dec reasing the temperature, the macromolecule changes from this extended configurat ion($\gamma=0.588$) to a stretched form ($\gamma\approx 1$). At even lower temp eratures, above the Manning condensation threshold, the polyelectrolyte collapse s ($\gamma\approx 0.3$). Our results show good agreement with simulations.
07/2004;
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ABSTRACT: We study complex formation between the DNA and cationic amphiphilic molecules. As the amphiphile is added to the solution containing DNA, a cooperative binding of surfactants to the DNA molecules is found. This binding transition occurs at a specific density of amphiphile, which is strongly dependent on the concentration of the salt and on the hydrophobicity of the surfactant molecules. We find that for amphiphiles which are sufficiently hydrophobic, a charge neutralization, or even charge inversion of the complex is possible. This is of particular importance in applications to gene therapy, for which the functional delivery of specific base sequence into living cells remains an outstanding problem. The charge inversion could, in principle, allow the DNA–surfactant complexes to approach the negatively charged cell membranes permitting the transfection to take place.
Physica A: Statistical Mechanics and its Applications. 09/1999;
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ABSTRACT: We investigate the properties of rigid polyelectrolyte solutions in the presence of monovalent salt. The free energy within the Debye−Hückel-Bjerrum (DHBj) theory (Fisher, M. E.; Levin, Y. Phys. Rev. Lett. 1993, 71, 3826) is constructed. It is found that at thermodynamic equilibrium the polyelectrolyte solution consists of clusters composed of one polyion and various counterions. The distribution of the cluster densities is determined by finding the minimum of the Helmholtz free energy. The osmotic pressure and the average charge of the cluster are found and their dependence on Manning parameter ξ is elucidated. A good agreement with the experimental results is obtained.
10/1998;
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ABSTRACT: We investigate the properties of rigid polyelectrolyte solutions in presence of monovalent salt. The free energy within the Debye-H\"uckel-Bjerrum (DHBj) theory [M. E. Fisher and Y. Levin, {\it Phys. Rev. Lett.} 71, 3826 (1993)] is constructed. It is found that at thermodynamic equilibrium the polyelectrolyte solution consists of clusters composed of one polyion and various counterions. The distribution of the cluster densities is determined by finding the minimum of the Helmholtz free energy. The osmotic pressure and the average charge of the cluster are found and their dependence on Manning parameter $\xi$ is elucidated. A good agreement with the experimental results is obtained. Comment: 11 pages, Revtex (using twocolumn style), 15 figures and postscript file. Submitted to Macromomelecules
03/1998;
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ABSTRACT: The interaction between polyelectrolyte and ionic surfactant is of great importance in different areas of chemistry and biology. In this Letter we present a theory of polyelectrolyte–ionic-surfactant solutions. The new theory successfully explains the cooperative transition observed experimentally, in which the condensed counterions are replaced by ionic surfactants. The transition is found to occur at surfactant densities much lower than those for a similar transition in non-ionic polymer–surfactant solutions. Possible application of DNA surfactant complex formation to polynucleotide delivery systems is also mentioned.
Chemical Physics Letters.
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ABSTRACT: We investigate the thermodynamic properties of a polyelectrolyte solution in the presence of multivalent salts. The polyions are modeled as rigid cylinders with the charge distributed uniformly along the major axis. The solution, besides the polyions, contain monovalent and divalent counterions as well as monovalent coions. The strong electrostatic attraction existing between the polyions and the counterions results in formation of clusters consisting of one polyion and a number of associated monovalent and divalent counterions. The theory presented in the paper allows us to explicitly construct the Helmholtz free energy of a polyelectrolyte solution. The characteristic cluster size, as well as any other thermodynamic property can then be determined by an appropriate operation on the free energy.
Physica A: Statistical Mechanics and its Applications.
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ABSTRACT: A model of polar fluid is studied theoretically. The interaction potential, in addition to dipole–dipole term, possesses a dispersion contribution of the van der Waals–London form. It is found that when the dispersion force is comparable to dipole–dipole interaction, the fluid separates into coexisting liquid and gas phases. The calculated critical parameters are in excellent agreement with Monte Carlo simulations. When the strength of dispersion attraction is below critical, no phase separation is found.
Physica A: Statistical Mechanics and its Applications.
