Fibronectin preparation. Human whole plasma was passed through gelatin-Sepharose column three times, and fibronectin eluted from the column as described in Materials and Methods. SDS-PAGE of adult human plasma (A), purified plasma fibronectin (10 μg, B), and fibronectin-depleted adult human plasma (C) is shown. The gel was then stained with Coomassie blue. Note the missing fibronectin doublet in lane C and that no other protein bands are missing.