Figure 1

(a) Platination of DNA under external force $f$. (b) The part of kinked DNA with a half-kink angle $\gamma =20°$. (c) Schematic illustration of the kink caused by a cisplatin binding.Reuse & Permissions

Figure 2

Bimodal fit for the force-extension data of platinated DNAs. (a) Symbols indicate the force-extension curve of cisplatin-bound DNA. The molecule was incubated with $3.3\mathrm{m}M$ cisplatin in $[\mathrm{NaCl}]=20\mathrm{m}M$. The effective $l_p$’s were deduced from the two regimes: ${\Gamma }^K=9\mathrm{nm}$ ($p=0.076$) and ${\Gamma }^R=12.5\mathrm{nm}$ ($p=0.087$) for high and low tensions. The inset shows the same data in semilog scale. The force-extension of bare DNA (fitted with ${\Gamma }^0=51\mathrm{nm}$) is also shown for comparison. (b) The effective persistence lengths versus the degree of cisplatin binding. The upper (dot-dashed) line is from the random flight model suitable for the low-tension regime and the lower (dashed) line from the aligned kink model for the high-tension regime. Symbols represent the experimental data under various conditions (batch I: ⋄, ×, +, *, □ for $[\mathrm{NaCl}]=20$, 40, 60, 90, and $180\mathrm{m}M$, respectively, and the concentration of cisplatin is $3.3\mathrm{m}M$ for all the data; batch II: ○, △ for $[\mathrm{NaCl}]=10$ and $30\mathrm{m}M$, respectively [16]). The $p$ values for each experimental data set were obtained by reading them from the theoretical curves relating $p$ to ${\Gamma }^{R,K}$. Ideally, identical symbols should be positioned vertically as $p$ should be the same for both. The discrepancy indicates the precision of determining cisplatin occupancy with this method. The theoretical maximum of $p$ ($=1/8$) is marked as a double dotted line. At the high kink density, kinks remain correlated even at 5 pN and, consequently, the accuracy of ${\Gamma }_K$ is compromised there.Reuse & Permissions