Proteolytic breakdown products lead to artificially high Kd estimates for EndoH-digested GluA2 ATD dimer assembly. (A) Silver-stained gel for the same preparation before SE (Pre) and for material recovered after the SE experiment (Post), showing degradation products at 11, 13, and 26 kD. (B) Subset of theoretical SE signal profiles simulated for conditions mimicking the experiment shown in Fig. 6, assuming a hypothetical Kd of 10 nM, superimposed with signals from 11-, 13-, and 26-kD fragments, each at 2% of the total loading concentration and with signals from 2% of binding-incompetent monomer. The corresponding global fit to the simulated data is shown as solid lines, leading to an apparent Kd of 130 nM. The residuals are shown in the bottom panel, with the same radials scale. The root-mean-square deviation is 0.0011 OD.
