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

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