Purified α and β dimerization site peptides. A 10% Laemmli SDS gel stained with Coomassie Brilliant Blue is shown. The GST fusion proteins (2 μg/lane) are as follows: lanes 1 through 3, α18-21, α18-21¹⁸⁵⁷, and α18-21^1857-Δ46, respectively. Recombinant peptides after protease cleavage, rechromatography on glutathione-Sepharose, and preparative HPLC gel filtration are as follows: lanes 4 through 7, α18-21, α18-21¹⁸⁵⁷, α18-21^1857-Δ46, and β1-4⁺.