Article Dans Une Revue Physical Review E : Statistical, Nonlinear, and Soft Matter Physics [2001-2015] Année : 2011

Manning free counterion fraction for a rodlike polyion: Aqueous solutions of short DNA fragments in presence of very low added salt

T. Vuletić
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S. Dolanski Babić
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D. Grgičin
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D. Aumiler
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J. Rädler
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S. Tomić
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Résumé

We quantified the Manning free (uncondensed) counterions fraction θ for dilute aqueous solutions of rodlike polyions: 150 bp DNA fragments, in the presence of a very low concentration of monovalent salt csalt<0.05 mM. Conductivity measurements of these solutions for DNA base pair concentration range 0.015≤c≤8 mM were complemented by fluorescence correlation spectroscopy (FCS) measurements of the DNA polyion diffusion coefficient Dp(c). We observed a crossover in the normalized conductivity σ(c)/c that nearly halved across the c=0.05-1 mM range, while Dp(c) remained rather constant, as we established by FCS. Analyzing these data we extracted θ(c)=0.30-0.45, and taking the Manning asymmetry field effect on polyelectrolyte conductivity into account we got θ(c)=0.40-0.60. We relate the θ(c) variation to gradual DNA denaturation occurring, in the very low salt environment, with the decrease in DNA concentration itself. The extremes of the experimental θ(c) range occur toward the highest, above 1 mM, and the lowest, below 0.05 mM, DNA concentrations and correspond to the theoretical θ values for dsDNA and ssDNA, respectively. Therefore, we confirmed Manning condensation and conductivity models to be valuable in description of dilute solutions of rodlike polyions.

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Dates et versions

hal-04883258 , version 1 (13-01-2025)

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T. Vuletić, S. Dolanski Babić, D. Grgičin, D. Aumiler, J. Rädler, et al.. Manning free counterion fraction for a rodlike polyion: Aqueous solutions of short DNA fragments in presence of very low added salt. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics [2001-2015], 2011, 83 (4), ⟨10.1103/PhysRevE.83.041803⟩. ⟨hal-04883258⟩
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