EDC cross-linking of A2 with A1/A3-C1-C2 or A1³³⁶/A3-C1-C2. Reactions (40 μL) containing A1/A3-C1-C2 (200 nmol/L) (lanes 1 through 4) or A1³³⁶/A3-C1-C2 (200 nmol/L) (lanes 5 through 8) were incubated with the following: no additions (lanes 1 and 5), 100 nmol/L A2 (lanes 2 and 6), 200 nmol/L A2 (lanes 3 and 7), or 400 nmol/L A2 (lanes 4 and 8) for 30 minutes at room temperature. EDC (200 μmol/L) was added and incubation was continued for 1 hour. After addition of SDS sample buffer, reactions were subjected to electrophoresis on 6% to 15% gels, transferred to PVDF, and immunoblotted with 58.12 (A) or R8B12 (B).