Isolation of C3. a) Gel filtration of goat C3 on Superose 6. b) SDS-PAGE of the final step gel filtration on Superose 6. Lane 1: Molecular weight standard, lane 2 and 3: fractions of the gel filtration (14, 15). Fractions were concentrated with Strataclean beads. Gel was stained with Coomassie blue.