Fig. 6. Dimerization analysis of mutation 519-526. 2x10⁸ cells of cell line 519-526 were permeabilized with 500 µl 20 mM HEPES, 0.15 M NaCl, pH 7.6 containing 1% (v/v) Nonidet P40. Insoluble material was removed by centrifugation (16 000 g for 15 minutes), and the supernatant was loaded onto a Sephacryl S-200 column. Fractions were TCA-precipitated and analysed by SDS-PAGE. Western blot with anti-VSG 117 (A) or anti-VSG 221 (B) antibodies. As determined by running standards (see Materials and Methods), dimerized VSG should peak in fraction 19. The lower bands on the gel correspond to VSG degradation products, which are exaggerated in this long exposure.