Mild an severe responses at different temperatures. At T = 40°C and T = 41°C the cell is under a mild stress and the activity is on the rise. For T = 42°C the stress is transitioning from mild to severe whereas at T = 44°C it is extremely severe.
Cates et al. BMC Biophysics 2011 4:16 doi:10.1186/2046-1682-4-16