JBC, Vol. 250, Issue 16, 6403-6407, Aug, 1975
Studies of individual carbon sites of hemoglobins in solution by natural abundance carbon 13 nuclear magnetic resonance spectroscopy
E. Oldfield and A. Allerhand
Proton-decoupled natural abundance 13C NMR spectra of carbon monoxide
hemoglobins were recorded at 15.18 MHz by the Fourier transform method,
under conditions of spectrometer sensitivity sufficient for detection of
individual carbon resonances. The aromatic region of each spectrum contains
broad bands of methine carbon resonances, and some relatively narrow peaks
arising from nonprotonated carbons. Resonances of heme carbons were
detected in spectra of carbon monoxide hemoglobins, but not in spectra of
ferrihemoglobin (as a result of paramagnetic effects). Spectra of carbon
monoxide hemoglobins from various species yielded only a few well resolved
individual carbon resonances, most notably those of Cgamma of tryptophan
residues. A comparison of the spectra of human adult, human fetal, chicken
AII, and bovine fetal hemoglobins yielded specific assignments for all
resonances of Cgamma of tryptophan residues. In the cases of human fetal,
chicken AII, and bovine fetal hemoglobins, each tryptophan yielded a
completely resolved individual carbon resonance. The chemical shift
difference between the resonances of Cgamma of Trp-130beta and Cgamma of
Trp-37beta is about 6 ppm. The chemical shift difference between Trp
A12[14]alpha and Trp A12[15]beta is 1 ppm or less. A comparison of the
chemical shifts of analogous tryptophan residues of the four carbon
monoxide hemoglobins suggests very similar conformations in solution.