Comparing the effect of the patient’s IgG on the incorporation of dansylcadaverine into N,N-dimethylcasein by rA₂′ in the presence and absence of Ca²⁺. Reactions were performed at 37°C in a total volume of 125 μL with no IgG (○,•), 25 μg normal IgG (▿, ▾) or patient IgG (□,▪; isolated on a Protein A column from serum drawn 9/12/91), 50 mmol/L Tris-HCl, pH 7.5, 2 mg/mL N,N-dimethylcasein, 0.5 mmol/L dansylcadaverine, and 0.25 μg rA₂′, in the absence (open symbols) or presence of 1 mmol/L CaCl₂(closed symbols). Fluorescence was measured as in Fig 3.