Polypeptide compositions of proteins derived from α₂-PI–incorporated cross-linked fibrin. Fibrinogen (90 μg) was clotted with thrombin and factor XIII for 30 minutes in the presence of CaCl₂ and α₂-PI. The clots were solubilized and subjected to PAGE in two lanes under reducing conditions followed by blotting onto PVDF-membranes as described in Materials and Methods. The protein bands were stained with CBB. Major bands 1-9 in the patient's sample were separetely subjected to amino-terminal sequence analysis.