Detailed scaling analysis of low-force polyelectrolyte elasticity
| Autor: | Noah Ribeck, Dustin B. McIntosh, Omar A. Saleh |
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| Rok vydání: | 2009 |
| Předmět: | |
| Zdroj: | Physical Review E. 80 |
| ISSN: | 1550-2376 1539-3755 |
| DOI: | 10.1103/physreve.80.041803 |
| Popis: | Single-molecule force-extension data are typically compared to ideal models of polymer behavior that ignore the effects of self-avoidance. Here, we demonstrate a link between single-molecule data and the scaling pictures of a real polymer. We measure a low-force elasticity regime where the extension $L$ of chemically denatured single-stranded DNA grows as a power law with force $f$: $L\ensuremath{\sim}{f}^{\ensuremath{\gamma}}$, with $\ensuremath{\gamma}\ensuremath{\approx}0.60--0.69$. This compares favorably with the ``tensile-blob'' model of a self-avoiding polymer, which predicts $\ensuremath{\gamma}=2/3$. We show that the transition out of the low-force regime is highly salt dependent, and use the tensile-blob model to relate this effect to the salt dependence of the polymer's Kuhn length and excluded-volume parameter. We find that, contrary to the well-known Odijk-Skolnick-Fixman theory, the Kuhn length of single-stranded DNA is linearly proportional to the Debye length of the solution. Finally, we show that the low-force elasticity becomes linear $(\ensuremath{\gamma}=1)$ at $\ensuremath{\approx}3\text{ }\text{M}$ salt, and interpret this as a $\ensuremath{\Theta}$ point of the polymer. At this point, the force-extension data is best described by the wormlike chain model, from which we estimate the bare (nonelectrostatic) persistence length of the polymer to be $\ensuremath{\approx}0.6\text{ }\text{nm}$. |
| Databáze: | OpenAIRE |
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