Editing Bohr effect (section)

=== T-state stabilization ===
When hemoglobin is in its T state, the [[N-terminal]] amino groups of the α-subunits and the [[C-terminal]] [[histidine]] of the β-subunits are protonated, giving them a positive charge and allowing these residues to participate in [[Ionic bonding|ionic interactions]] with carboxyl groups on nearby residues. These interactions help hold the haemoglobin in the T state. Decreases in pH (increases in acidity) stabilize this state even more, since a decrease in pH makes these residues even more likely to be protonated, strengthening the ionic interactions. In the R state, the ionic pairings are absent, meaning that the R state's stability increases when the pH increases, as these residues are less likely to stay protonated in a more basic environment. The Bohr effect works by simultaneously destabilizing the high-affinity R state and stabilizing the low-affinity T state, which leads to an overall decrease in oxygen affinity.<ref name="Voet" /> This can be visualized on an [[Oxygen–hemoglobin dissociation curve|oxygen-haemoglobin dissociation curve]] by shifting the whole curve to the right.

Carbon dioxide can also react directly with the N-terminal amino groups to form [[carbamates]], according to the following reaction:
: <chem>R-NH2 + CO2 <=> R-NH-COO^- + H+</chem>
CO<sub>2</sub> forms carbamates more frequently with the T state, which helps to stabilize this conformation. The process also creates protons, meaning that the formation of carbamates also contributes to the strengthening of ionic interactions, further stabilizing the T state.<ref name="Voet" />