Fig. 6.

Length dependences of change in coulombic free energy ($\Delta G_{\mathrm{u}}^{\text{coul}}∕\mathit{RT}$) and salt ion association ($\Delta n_{\mathrm{u}}^{\text{coul}}$) in duplex melting transition. The per charge free energy $G_{\mathrm{u}}^{\text{coul}}∕\mathit{RT}$ (panel A) and salt ion association $n_{\mathrm{u}}^{\text{coul}}$ (panel B) both at 0.15 M concentration of 1 : 1 salt from all-atom calculations plotted as function of the number of bases (ss DNA oligomer) of base pairs (ds DNA oligomer). The change in free energy $\Delta G_{\mathrm{u}}^{\text{coul}}∕\mathit{RT}$ and in salt ion association $\Delta n_{\mathrm{u}}^{\text{coul}}$ calculated per charge of ds oligomer $[\Delta G_{\mathrm{u}}^{\text{coul}}∕\mathit{RT}=(G_{\text{ss}1}^{\text{coul}}∕\mathit{RT}+G_{\text{ss}2}^{\text{coul}}∕\mathit{RT}-G_{\text{ds}}^{\text{coul}}∕\mathit{RT})∕\mid Z_{\mathrm{D},\text{ds}}\mid ,\Delta n_{\mathrm{u}}^{\text{coul}}=(n_{\text{ss}1}^{\text{coul}}+n_{\text{ss}2}^{\text{coul}}-n_{\text{ds}}^{\text{coul}})∕\mid Z_{\mathrm{D},\text{ds}}\mid ]$ are plotted as function of the number of base pair.