Deep hypothermia protects the brain from ischemic injury, which is why it's employed for major cardiovascular procedures that necessitate cardiopulmonary bypass and a period of circulatory arrest. With an experiment [9] conducted to moderate hypothermia, small ubiquitin-like modifier (SUMO1-3) conjugation was significantly activated in the brain. The effects of hypothermia on SUMO conjugation were evaluated in this experiment[9] using Western blot and immunohistochemistry in animals that were either normothermic (37 °C) or deep to moderate (18 °C, 24 °C, 30 °C) hypothermic cardiopulmonary bypass. In these cells, even 30 °C hypothermia was enough to significantly boost SUMO2/3-conjugated protein levels and nucleus accumulation. Deep hypothermia caused the SUMO-conjugating enzyme Ubc9 to translocate to the nucleus, implying that the increase in nuclear levels of SUMO2/3-conjugated proteins seen in hypothermic animals' brains is an active process. Deep hypothermia caused only a small increase in the amounts of SUMO2/3-conjugated proteins in primary neuronal cells. This shows that neurons in vivo have a greater capacity to activate this endogenous possibly neuroprotective mechanism when exposed to hypothermia than neurons in vitro. Identifying proteins that are SUMO2/3 conjugated during hypothermia could aid in the development of new preventive and therapeutic therapies to make neurons more resistant to a transient blood supply interruption.