Figure 2.

(A) Aldolase antibody 40F12 (75 μM binding sites) with 4 eq. of 2,4-pentanedione presented the typical absorption maximum of the enaminone at 318 nm (shown in orange) whereas inactive antibodies did not (shown in blue). (B) Rate of enaminone formation as a function of pH. Enaminone formation between antibody 40F12 and 2,4-pentanedione was followed spectrophotometrically at 318 nm at 22°C. The incubation mixtures contained 15 μM antibody binding sites and 50 μM 2,4-pentanedione in citrate-phosphate buffer in the pH range from 5.0 to 8.6. The reaction rates were calculated with the use of the experimentally determined extinction coefficient ɛ₃₁₈ = 17.4 mM⁻¹⋅cm⁻¹.