Editing Bohr effect (section)

=== Allosteric interactions ===
[[File:Hemoglobin t-r state ani.gif|thumb|278x278px|Haemoglobin changes conformation from a high-affinity R state (oxygenated) to a low-affinity T state (deoxygenated) to improve oxygen uptake and delivery.]]The Bohr effect hinges around allosteric interactions between the [[heme]]s of the haemoglobin [[Tetrameric protein|tetramer]], a mechanism first proposed by [[Max Perutz]] in 1970.<ref>{{Cite book|title=Science is Not a Quiet Life|last=Perutz|first=Max|publisher=World Scientific|isbn=9789814498517|date=1998-01-15}}</ref> Haemoglobin exists in two conformations: a high-affinity R state and a low-affinity T state. When oxygen concentration levels are high, as in the lungs, the R state is favored, enabling the maximum amount of oxygen to be bound to the hemes. In the capillaries, where oxygen concentration levels are lower, the T state is favored, in order to facilitate the delivery of oxygen to the tissues. The Bohr effect is dependent on this allostery, as increases in CO<sub>2</sub> and H<sup>+</sup> help stabilize the T state and ensure greater oxygen delivery to muscles during periods of elevated cellular respiration. This is evidenced by the fact that [[myoglobin]], a [[monomer]] with no allostery, does not exhibit the Bohr effect.<ref name="Voet" /> Haemoglobin mutants with weaker allostery may exhibit a reduced Bohr effect. For example, in Hiroshima variant [[haemoglobinopathy]], allostery in haemoglobin is reduced, and the Bohr effect is diminished. As a result, during periods of exercise, the mutant haemoglobin has a higher affinity for oxygen and tissue may suffer minor [[Hypoxia (medical)|oxygen starvation]].<ref>{{cite journal | last=Olson | first=JS |author2=Gibson QH|author3=Nagel RL|author4=Hamilton HB| title=The ligand-binding properties of hemoglobin Hiroshima ( 2 2 146asp )| journal=The Journal of Biological Chemistry | volume=247 | issue=23 | pages=7485–93 | date=December 1972 | doi=10.1016/S0021-9258(19)44551-1 | pmid=4636319| doi-access=free }}</ref>