Specific activity (SA) time-course over 2 hours in an untransfused patient with HbE/β thalassemia (IVS 1-130). The incubation temperatures are 37°C (A) and 41°C (B). Synthesis is linear at 37°C, suggesting that there is no significant hemoglobin instability. At 41°C, the curve flattens after 1 hour, consistent with hemoglobin instability. (□) γ; (•) β^E; (○) .