PMF of Ca ²⁺ /Na ⁺ in TRPV1 and TRPV6. (A) PMF of Ca²⁺/Na⁺ in TRPV1. The center-of-mass deviation (COM Δz) measures the z distance between the ion and the COM of the protein. The blue solid line indicates the PMF for Na⁺ while the orange solid line is for Ca²⁺. The shades indicate the standard deviation estimated from bootstrap calculations. (B) Similar to A but for TRPV6. (C) PMF of Ca²⁺ in TRPV6 with an additional ion bound at the S1 binding site. The blue solid line indicates the PMF for Ca²⁺ with a Na⁺ bound at S1, while the orange solid line indicates the PMF for Ca²⁺ with a Ca²⁺ bound at S1. The shades indicate the standard deviation estimated from bootstrap calculations.