Figure 1.

(A) Three layers of the TB region around an RNA. The nondehydrated (ND) layer for the ND ions, the outer-shell dehydrated (OSD) layer for the OSD ions, and the inner-shell dehydrated (ISD) layer for the ISD ions are shown as the outermost, the middle, and the innermost layers. (B) The volume exclusion energy between a particle and an Mg²⁺ ion. $u_{\text{LJ}}^{\text{N}}$, $u_{\text{LJ}}^{\text{O}}$, and $u_{\text{LJ}}^{\text{I}}$ are the “12-6” LJ potentials between the particle and an ND Mg²⁺ ion, an OSD Mg²⁺ ion, and an ISD Mg²⁺ ion, respectively. u_vol is calculated by the Boltzmann average for the three LJ potentials. Inset: the outer and inner layers around the magnesium ion represent the outer and inner hydration shells, respectively. The dark and light blue balls are the fully dehydrated Mg²⁺ and the other particle. (C) The dehydration energies of the inner and the outer shells as a function of the number of the removed water molecules. Inset: the blue and red regions show the volumes of the outer and inner shells occupied by the other particles. To see this figure in color, go online.