Preparation of nicked β2GPI and AS4.5. AS4.5 was prepared from Glu-plasminogen by plasmin digestion followed by purification using lysine-Sepharose column and Sephadex G-75 column. Purified AS4.5 was treated with PNGase F or Endo H to determine whether AS4.5 undergoes glycosylation. Glu-plasminogen, purified product (AS4.5), AS4.5 treated with PNGase F, and AS4.5 treated with Endo H were subjected to sodium dodecyl sulfate-PAGE under reduced conditions.