Detection of SDS-stable serpin-proteinase complexes by SDS-PAGE analysis. Tracks contain Nec-fl, proteinase, or a mixture of serpin and proteinase at Molar ratios of 1:1 or 4:1. Tested proteinases are human neutrophil cathepsin G (CATG), human neutrophil elastase (HNE), bovine pancreatic α-chymotrypsin (Chym), porcine pancreatic elastase (PPE), human thrombin (Throm) and bovine pancreatic trypsin (Tryp). “≪” indicates SDS-stable serpin-proteinase complex band.