Destabilization of HbA or HbS with increasing temperature.

Ellipticity at 220 nm was measured using UVCD every 5 minutes at 37, 50, or 55°C and the ΔEllipticity at 220 nm was recorded as the hemoglobin unfolded over time. The ΔEllipticity for HbA and HbS was similar when recording at 37°C and 55°C. At 50°C, the difference between HbS and HbA was statistically significant, but only after 10 minutes. At 5 minutes, thermal destabilization of HbS or HbA at 37°C, 50°C and 55°C was similar, as measured using ΔEllipticity. The 5 minute time point was chosen to evaluate the sensitivity of αB crystallin to HbA or HbS under thermal stress, prior to measurable unfolding.