SE AUC analysis for the GluA2 and GluA3 ATDs. A wide range of K_d values is illustrated by representative data for GluA3 (A) and two replicate experiments for EndoH-digested GluA2S with high (B) and low (C) K_ds. In each panel, the top section shows the raw data and best-fit distribution (red line) and calculated monomer (magenta) and dimer (blue) species; the bottom section shows the radial distribution of residuals from three different rotor speeds recorded from the same cell. Traces shown are at initial loading concentrations of 4.8 (A), 7.4 (B), and 5.8 µM (C), respectively, after establishing an equilibrium concentration gradient at 16,000 (A) and 18,000 rpm (B and C), all taken from the global analysis of data from multiple cells at a range of different loading concentrations, recorded using multiple signals. In B and C, only a subset of the SE profile is shown to highlight the low concentration region close to the meniscus, which provides information on dimer dissociation.