Hyperfine-shifted resonances

NMR spectra have been reported for the Rieske-type ferredoxins from Xanthobacter strain Py2 (88) and of toluene 4-monooxygenase from Pseudomonas mendocina (T4MOC) (88a) as well as for the water-soluble Rieske fragment from the bci complex of Paracoccus deni-trificans (ISFpd) (89). The spectra of these proteins are similar, which is consistent with the close structural relationship between the three proteins. In the reduced (paramagnetic) state, all three proteins show several hyperfine-shifted resonances between +83 and -16 ppm at 400 MHz or between 110 and +25 ppm at 300 MHz (Table X). 

In the spectrum of ferricytochrome c (Fig. 19) the resonances between —0.5 and —9 ppm correspond to ca. 650 protons of the polypeptide chain. Essentially all the proton resonances of heme c and the axial ligands were found to be shifted by hyperfine interactions with the unpaired electron (Kowalsky (62) Wuthrich (110)), and some ring current-shifted resonances were also outside of the spectral region from DSS to —10 ppm. From a temperature study similar to that shown for MbCN (Figs. 15 and 16) the temperature dependent hyperfine-shifted resonances in Fig. 20 were identified (110). A tentative assignement of some of these lines... 

Fig. 20. Dependence on temperature of the resolved hyperfine-shifted resonances of ferricytochrome c. The numbers on the right give the relative intensities of the lines...

Kurland et al. (64) observed hyperfine-shifted resonances of ferrimyoglobin between —20 and —90 ppm. Comparison with the spectra of the iron(III)-complexes with protoporphyrin IX, deuteroporphyrin IX, and mesoporphyrin IX seems to indicate that four of the low field resonances correspond to the four ring methyl groups. Additional lines at high fields from DSS were observed in ferrimyoglobin (116), and in high spin porphyrin-iron(III) complexes (Caughey et al. (19)). The observation... 

The basic features of the Mb111 (Ns) spectrum are similar to those of cyanoferrimyoglobin (Fig. 14). Only one set of hyperfine-shifted resonances is observed, but the hyperfine shifts are larger and the lines broader than in MbmCN. Furthermore the temperature dependences of the resonances positions show drastic deviations from Curie s law (Eq. 4). Similar data were also obtained for azidoporphyrin-iron(III) complexes in pyridine solution 116). 

Figures 49 and 50 show the 600-MHz H NMR spectra of cross-linked mixed-valency asymmetric hybrid Hbs with one cyanomet chain per Hb tetramer. Figures 49A and 50A give the proton resonances of (a+CNP)A(aP)cXL and (aP+CN)A(a(3)cXL in D20 from +7 to +20 ppm from HDO. These hyperfine-shifted resonances arise from the protons in the heme groups and/or the protons of the amino acid residues in the immediate surroundings of the heme group. They are shifted from their usual diamagnetic positions by hyperfine interactions between the unpaired electrons from the low-spin ferric and high-spin ferrous heme iron atoms and the nearby protons. As discussed earlier, they are very sensitive to the environment of the heme pocket. The signals from the subunits with high-spin ferrous heme iron are much broader than those from cyanomet (low-spin...

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