Trypsin digestion time course of α18-21, α18-21¹⁸⁵⁷, and α18-21^1857-Δ46. Recombinant α spectrin samples were digested with trypsin at an enzyme-to-substrate ratio of 1:100 at 0°C in PBS buffer. Protein samples (4 μg/lane) were analyzed on a 12% Tris-Tricine gel and stained with Coomassie Brilliant Blue. Lanes 1 through 5, α18-21 after 0, 15, 30, 60, and 90 minutes of treatment with trypsin, respectively; lanes 6 through 10, α18-21¹⁸⁵⁷ after 0, 15, 30, 60, and 90 minutes of treatment with trypsin, respectively; lanes 11 through 15, α18-21^1857-Δ46 after 0, 15, 30, 60, and 90 minutes of treatment with trypsin, respectively.