Anti-ARGS western blot of ELISA-captured material. Aggrecan fragments captured by the anti-keratan sulfate (KS)-coated plates were extracted after a completed ELISA and analyzed by western blot. Seventy-four wells of captured ARGS standards (STD) and 152 wells of SF from 152 patients were used. The samples were chondroitinase, keratanase, and keratanase II digested, separated on a SDS-PAGE gel, transferred to a polyvinylidene difluoride (PVDF) membrane and probed with the ARGS antibody OA-1. For comparison, the STD (0.5 μg sulfated glycosaminoglycan (sGAG)/well) and an SF D1 sample pooled from 40 osteoarthritis (OA) patients (0.75 μg sGAG/well) were used as controls. The size (kDa) and position of the molecular weight markers are indicated.