Manning free counterions fraction for a rod-like polyion - short DNA fragments in very low salt - Condensed Matter > Soft Condensed MatterReportar como inadecuado




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Abstract: We quantified the Manning free uncondensed counterions fraction $\theta$for dilute solutions of rod-like polyions - 150bp DNA fragments, in very lowsalt $<0.05$mM. Conductivity measurements of aqueous DNA solutions in theconcentration range $0.015\leq c \leq 8$~mM bp were complemented byfluorescence correlation spectroscopy FCS measurements of the DNA polyiondiffusion coefficient $D pc$. We observed a crossover in the normalizedconductivity $\sigmac-c$ which nearly halved across $c=0.05-1$ mM range,while $D pc$ remained rather constant, as we established by FCS. Analyzingthese data we extracted $\thetac=0.30 - 0.45$, and taking the Manningasymmetry field effect on polyelectrolyte conductivity into account we got$\thetac=0.40-0.60$. We relate the $\thetac$ variation to gradual DNAdenaturation occuring, in the very low salt environment, with the decrease inDNA concentration itself. The extremes of the experimental $\thetac$ rangeoccur towards the highest, above 1 mM and the lowest, below 0.05 mM, DNAconcentrations, and correspond to the theoretical $\theta$ values for dsDNA andssDNA, respectively. Therefore, we confirmed Manning condensation andconductivity models to be valuable in description of dilute solutions ofrod-like polyions.



Autor: Tomislav Vuletic, Sanja Dolanski Babic, Danijel Grgicin, Damir Aumiler, Joachim Raedler, Francoise Livolant, Silvia Tomic

Fuente: https://arxiv.org/







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