Hyperfine-shifted proton resonances chemical shifts

The effective distances obtained by Nordenskiold et al. (40) are compared with the internuclear distances in Table I. Clearly, the point dipole approximation is reasonable for the hydrogen nuclei in these complexes, while substantial deviations are observed for the oxygen nuclei. The findings of these early quantum chemical studies were confirmed by Sahoo and Das (41-43). Wilkens et al. have reported DFT calculations using Eq. (16) for a 104 atom model for high-spin Fe(III) rubredoxin (44). Large discrepancies between the effective distances and the input distances for the calculations were found for the hyperfine-shifted nitrogen-15 resonances, as well as for proton and carbon-13 nuclei in cysteines bound to the iron center. 

Fig. 46. 250-MHz ferric hyperfine-shifted proton resonances of the abnormal p chains of 15% Hb M Milwaukee (p67Val — Glu, a2p2) as a function of oxygenation in 0.1 M Bis—Tris in D20 at pH 6.6 and 30°C. The proton chemical shifts are referenced to HDO. The range of the fractional saturation (y) was based on P50 = 5 torr or P5 = 10 torr. [Adapted from Fung et al. (1977)].

Zhang et have studied the heme environment and ligand binding properties of two large membrane proteins (quinol oxidases) containing multiple paramagnetic metal centers. Perturbations of hyperfine-shifted proton resonances were used to probe the chemical changes induced by oxidation-reduction reactions and cyanide addition. 

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