Alkaline treatment of the cross-linked A1-A2 dimer. Cross-linked factor VIIIa (750 nmol/L) was incubated in the presence of 0.75 mol/L ammonium hydroxide, pH 11, for 15 minutes. Sample buffer was added and reactions (25 μL) were subjected to electrophoresis on 6% to 15% gels, transferred to PVDF, and immunoblotted with the anti-A1 subunit antibody, 58.12. Lane 1, factor VIIIa; lane 2, cross-linked factor VIIIa; and lane 3, cross-linked factor VIIIa plus 0.75 mol/L NH₄OH.