^(13)C Magnetic Resonance Studies of Hemoglobin Carbamylation

^(13)C magnetic resonance techniques have been used to study the reaction of ^(13)C-enriched cyanate with human adult and sickle cell hemoglobin. The carbamyl resonances from carbamylated hemoglobin are assigned on the basis of chemical evidence and comparisons with model amino acid and peptide derivatives. Carbamylation of the α-amino groups of the N-terminal valine residues shows considerable pH dependence in the range 6.7-8.2 while carbamylation of the e-amino groups of the lysine residues is relatively pH independent. Spin-lattice relaxation time and nuclear Overhauser effect measurements for carbamyl carbons are reported.