13C NMR signals of 13CO free and bound to hemoglobin (Hb 13CO) 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 α 13CO with deliganded β or β 13CO 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.
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