Quadrupole splitting temperature dependence of high and low affinity deoxyhemoglobin encapsulated in wet silica gel

Abstract

Hemoglobin (Hb) is still one of the most studied proteins due to its physiological function and because of its allosteric properties. It is actually well known that hemoglobin has at least two quaternary structures, one when the protein is fully oxygenated (R structure) and the other one when it is fully deoxygenated (T structure). In the last years, the encapsulation of hemoglobin in wet silica gel, preventing a change in the quaternary structure, gave the opportunity to show the existence of two T states: high affinity (HA) and low affinity (LA). Hb T state, in presence (LA) and in absence (HA) of allosteric effectors when it is encapsulated in wet silica gel, binds oxygen in non-cooperative way. Small differences between the quadrupole splitting values of HA and LA samples can be pointed out at low temperature regime. However, at present, these are too small differences to deduce that HA and LA Hbdeoxy states are different within the iron surrounding.