Competitive hybrid spectrin-ankyrin binding assays. Hybrid spectrins, formed from control (C_α and C_β) and proband (P_α and P_β) spectrin monomers, were bound to spectrin-depleted inside-out vesicles (IOV) in the presence of a constant amount of¹²⁵I-labeled control spectrin dimer. The amount of bound control spectrin was plotted versus the amount of hybrid spectrin competitor added. All binding data are shown as the mean of duplicates that had ranges less than + or −8.5%. Proband α spectrin reduced the ankyrin binding of hybrid spectrins.