Figure 2.

Me²⁺-binding selectivities of PIP2 isomers. (A) The binding of Ca²⁺ to three PIP2 isomers without Mg²⁺. Mean ± SE, n = 3. (B) Similar Ca²⁺ binding curve at 1 mM Mg²⁺. (C) Surface pressure drop induced by 1 mM Ca²⁺ under different Mg²⁺ concentrations. Data were fit by the Langmuir adsorption model (Eq. 2) to find (D) the apparent K_D for Ca²⁺ and Mg²⁺, and (E) the selective ratio in binding to PIP2s. The color coding is consistent through (A) to (E), while the white bar in last two panels represents L-α-PI(4,5)P2.