The binding of n-butyl isocyanide to human hemoglobin

The binding of n-butyl isocyanide to hemoglobin has been investigated by ¹⁹F-nuclear magnetic resonance spectroscopy. The ¹⁹F-nmr spectrum of hemoglobin trifluoroacetonylated at cysteine β93 exhibits chemical shift changes on binding of ligands to the β chains. Comparison of these changes to the fractional change in the visible spectrum, shows that in the presence of diphosphoglyceric acid initial ligands bind preferentially to α chains. In the absence of DPG, ligation of β chains increases linearly with overall fractional ligation, indicating that binding to α and β chains is random under these conditions.