Donnan membrane equilibrium,sedimentation equilibrium,and coil expansion of DNA in salt solutions |
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Authors: | Dirk Stigter |
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Institution: | (1) Department of Pharmaceutical Chemistry, University of California, 94143 San Francisco, CA |
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Abstract: | This is a review of applications of the McMillan-Mayer-Hill virial theory and the ionic double-layer theory to dilute colloidal
solutions, in particular, solutions of DNA. Interactions of highly charged colloidal rods are developed in terms of the second
virial coefficients between two rods, and between one rod and one small co-ion. The relevant cluster integrals are evaluated
with interaction potentials based on the Poisson-Boltzmann equation. The treatment is extended to the intrachain repulsion
responsible for the statistical swelling of coiled DNA (excluded volume effect). The theory is compared with three sets of
experimental data: The salt distribution in Donnan membrane equilibria of DNA-salt solutions, sedimentation equilibria of
short DNA fragments at different ionic strengths, and the intrinsic viscosity of T7 DNA in NaCl solutions. In all cases the
theory agrees well with the experiments. The agreement is not convincing for the sedimentation equilibrium at low ionic strength,
because here the experimental DNA concentration is too high for the truncated dilute solution expansion of the DNA-salt repulsion. |
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Keywords: | McMillan-Mayer theory ionic double layer Donnan membrane equilibrium osmotic pressure salt distribution second virial coefficient rodlike colloids negative salt adsorption excluded volume coil expansion sedimentation equilibrium T7 DNA |
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