Fig. 1.

Effective (Eq. 5) Mg²⁺–P potential (red) constructed by combining the short-ranged part of the PMF (gray dashed line) with the long-ranged Debye–Hückel potential (blue dashed line). Calculations of the PMF were performed at 1.0 mM magnesium monophosphate and 25 ^○C using the RISM theory (for details see SI Appendix). The first minimum represents the inner-shell interaction, where Mg²⁺ interacts directly with the phosphate groups. The second minimum at $r\approx 5$ Å represents the outer-shell interaction, where Mg²⁺ retains its first hydration shell.