Autoradiogram of ¹²⁵I-PF4 after incubation with KKO or RTO. Molecular mass markers are to the left of each panel correspond to 55, 71, 117, and 268 kDa. Lanes 1 and 4 show PF4 complexes with KKO (1) or RTO (4) that were subsequently cross-linked with bis-sulfosuccinimidyl suberate. Lanes 2 and 5 show PF4 cross-linked with bis-sulfosuccinimidyl suberate, and lanes 3 and 6 show PF4 alone (uncross-linked). Higher molecular mass PF4 complexes in the presence of the KKO comprise ∼ 60% of the total PF4 tetramers versus ∼ 2% with RTO. Data are representative of 3 such experiments.