Figure 1

(Color online) (a) Stiff chain under an external force $f$ with the imposed boundary angle $\gamma$. (b) Illustration of a part of the kinked chain with the half-kink angle $\gamma ={\theta }_k/2$. (c) Illustration of cisplatin binding on DNA.Reuse & Permissions

Figure 2

Symmetric and skew-symmetric configurations. The origin is chosen to be the middle point between two neighboring kinks. At the boundary of subchain, $s=\pm S$, the angle $\gamma$ is imposed at kink.Reuse & Permissions

Figure 3

(Color online) Force-extension data and their fits for DNA incubated in 3.3 mM cisplatin solution (a) with 20 mM salt, (b) with 60 mM salt, and (c) with 180 mM salt. The symbols represent experimental data and the lines are fits with an effective persistence length $\Gamma$. ${\Gamma }^K=9\text{nm}$ for the large-force regime and ${\Gamma }^R=12.5\text{nm}$ for the small-force regime in (a) and ${\Gamma }^K=20\text{nm}$ $\left({\Gamma }^R=25\text{nm}\right)$ for the large-force (small-force) regime in (b). The inset of each panel shows the force-extension curves in semilogarithmic scale. The force extension of the natural DNA with 10 mM salt is also shown in both panels (rightmost curve) fitted with ${\Gamma }^0=51\text{nm}$.Reuse & Permissions

Figure 4

(Color online) The effective persistence lengths ${\Gamma }^{K,R}/l_p$ vs the degree of cisplatin binding. The dot-dashed line is from the random-flight model suitable for the low-tension regime and the dashed line is from the aligned-kink model for the high-tension regime. From each force-extension measurement, we extract the effective $l_p$ by fitting the curves with Eq. (20). By comparing the experimental values with the two theoretical expressions of the effective $l_p$ (i.e., ${\Gamma }^R,{\Gamma }^K$), we obtained a pair of $p$ values. We also show error bars in the estimate of $p$. The size of error bar indicates the standard deviation of $p$ values from different measurements. Symbols represent the experimental data under various conditions. The maximum concentration for a random sequence is expected to be around $p=1/8=0.125$, limited by inherent G-G pairs. We used $l_p/a=150$ for fitting.Reuse & Permissions