13CO exchange process between the hemoglobin irons observed with 13C NMR

13C NMR signals of 13CO free and bound to hemoglobin (Hb13CO) were investigated at 9.4 T. Existence of 13CO exchange between α and β hemoglobin irons was proven by 13C NMR temperature line splitting and by the shift of the 13CO NMR signal, after mixing α13CO with deliganded β or β13CO with deliganded α. 13C NMR bandwidth of 13CO bound to hemoglobin was investigated for various HbCO ligandation levels: from low (16%) to full 13CO association, the kinetics of the 13CO exchange decreases. A model using the exchange kinetics can generate the sigmoidal shape of the hemoglobin ligandation curve.