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

Autori
Vuletić, Tomislav ; Dolanski Babić, Sanja ; Grgičin, Danijel ; Aumiler, Damir ; Raedler, Joachim ; Livolant, Francoise ; Tomić, Silvia

Izvornik
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics (1539-3755) 83 (2011), 4; 041803-1

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Manning condensation ; rodlike polyelectrolyte ; DNA ; FCS ; conductometry

Sažetak
We quantified the Manning free (uncondensed) counterions fraction $\theta$ for dilute aqueous solutions of rod-like polyions - 150bp DNA fragments, in presence of very low concentration of monovalent salt $c_{; ; \mathrm{; ; salt}; ; }; ; <0.05$mM. Conductivity measurements of these solutions for DNA basepair concentration range $0.015\leq c \leq 8$~mM were complemented by fluorescence correlation spectroscopy (FCS) measurements of the DNA polyion diffusion coefficient $D_p(c)$. We observed a crossover in the normalized conductivity $\sigma(c)/c$ which nearly halved across $c=0.05-1$ mM range, while $D_p(c)$ remained rather constant, as we established by FCS. Analyzing these data we extracted $\theta(c)=0.30 - 0.45$, and taking the Manning asymmetry field effect on polyelectrolyte conductivity into account we got $\theta(c)=0.40-0.60$. We relate the $\theta(c)$ variation to gradual DNA denaturation occuring, in the very low salt environment, with the decrease in DNA concentration itself. The extremes of the experimental $\theta(c)$ range occur towards the highest, above 1 mM and the lowest, below 0.05 mM, DNA concentrations, and correspond to the theoretical $\theta$ values for dsDNA and ssDNA, respectively. Therefore, we confirmed Manning condensation and conductivity models to be valuable in description of dilute solutions of rod-like polyions.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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