Heparin affinity chromatography of β₂GPI from acid-treated and UK-activated plasma. Both normal and plasminogen-depleted human plasmas were treated with acid and activated with UK as described in Materials and Methods. After the treatment with perchloric acid, sample was applied to a column of HiTrap Heparin and eluted with a linear gradient of NaCl. (1), normal plasma; (2), plasminogen-depleted plasma.