The 1H‐NMR spectra of deoxymyoglobin and reduced cytochrome P450 are analyzed by NOE spectroscopy. Progress has been made in the assignment of the hyperfine‐shifted signals of deoxymyoglobin. The ...nuclear longitudinal‐relaxation‐time values indicate short electron‐relaxation times whereas Curie relaxation contributes significantly to the signals linewidths. For reduced cytochrome P450 the linewidths are larger due to the Curie‐relaxation contribution in a large protein. Therefore, the spectral information is poor. The electron‐relaxation rates are discussed in terms of possible electronic structure.
Since the orbital insertion of the Rosetta spacecraft, comet 67P/Churyumov-Gerasimenko (67P/C-G) has been mapped by OSIRIS camera and VIRTIS spectro-imager, producing a huge quantity of images and ...spectra of the comet's nucleus. The aim of this work is to search for the presence of H\(_2\)O on the nucleus which, in general, appears very dark and rich in dehydrated organic material. After selecting images of the bright spots which could be good candidates to search for H\(_2\)O ice, taken at high resolution by OSIRIS, we check for spectral cubes of the selected coordinates to identify these spots observed by VIRTIS. The selected OSIRIS images were processed with the OSIRIS standard pipeline and corrected for the illumination conditions for each pixel using the Lommel-Seeliger disk law. The spots with higher I/F were selected and then analysed spectrophotometrically and compared with the surrounding area. We selected 13 spots as good targets to be analysed by VIRTIS to search for the 2 micron absorption band of water ice in the VIRTIS spectral cubes. Out of the 13 selected bright spots, eight of them present positive H\(_2\)O ice detection on the VIRTIS data. A spectral analysis was performed and the approximate temperature of each spot was computed. The H\(_2\)O ice content was confirmed by modeling the spectra with mixing (areal and intimate) of H\(_2\)O ice and dark terrain, using Hapke's radiative transfer modeling. We also present a detailed analysis of the detected spots.
The 600-MHz super(1H-NMR NOESY spectra on Co(II))d7-reconstituted metallothionein (Co sub(7)MT), exhibiting hyperfine signals in the range 350 ppm to -50 ppm, with nuclear relaxation times of the ...order of a few milliseconds, have been measured and several interproton connectivities have been detected. The hyperfine-shifted signals belong to the cysteine-ligand protons of the Co sub(4)S sub(11) cluster of Co- sub(7)MT. Together with results from one-dimensional NOE experiments, the two-dimensional experiments allowed us to proceed with the pairwise assignment of the isotropically shifted signals of the C beta H sub(2) groups of the metal-coordinated cysteines. With the aid of computer-graphics inspection of the four-metal-cluster domain, based on the NMR solution structure of Cd sub(7)MT, it is possible to propose sequence-specific assignments of a few hyperfine-shifted super(1)H-NMR signals. In particular, a tentative assignment is given for the six signals whose shifts exhibit an antiCurie temperature dependence.
super(1)H one-dimensional and two-dimensional NMR spectra have been recorded for the oxidized and reduced forms of the high-potential iron-sulfur protein (HiPIP) from Rhodopseudomonas globiformis) ...which has the highest known reduction potential. The spectrum of the oxidized protein is similar to that of Chromatium vinosum and Rhodocyclus gelatinosus HiPIP but different from that of the HiPIP II from Ectothiorhodospira halophila . Surprisingly, site-specific assignment has shown that in the oxidized protein the distribution of oxidation numbers within the cluster is very similar to that found for E. halophila HiPIP II and different from that of the other two proteins. The spectrum of the reduced species is very similar to that of all other HiPIPs known to date, indicating very similar electronic and geometric structures for the reduced forms. These findings are discussed in terms of cluster structure in HiPIPs and of redox potentials.
1H one‐dimensional and two‐dimensional NMR spectra have been recorded for the oxidized and reduced forms of the high‐potential iron‐sulfur protein (HiPIP) from Rhodopseudomonas globiformis which has ...the highest known reduction potential. The spectrum of the oxidized protein is similar to that of Chromatium vinosum and Rhodocyclus gelatinosus HiPIP but different from that of the HiPIP II from Ectothiorhodospira halophila. Surprisingly, site‐specific assignment has shown that in the oxidized protein the distribution of oxidation numbers within the cluster is very similar to that found for E. halophila HiPIP II and different from that of the other two proteins. The spectrum of the reduced species is very similar to that of all other HiPIPs known to date, indicating very similar electronic and geometric structures for the reduced forms. These findings are discussed in terms of cluster structure in HiPIPs and of redox potentials.
super(1)H two dimensional nuclear Overhauser effect spectroscopy (NOESY) and two-dimensional correlated spectroscopy (COSY) spectra of cytochrome c' from Chromatium vinosum) have been obtained. The ...protein is of medium size, essentially high spin (S = 5/2) although some quantum mechanical spin admixing with S = 3/2 may be present.
Proteases in preparations of carboxypeptidase A progressively inactivate solutions of the apoenzyme but not the metal-containing enzyme. Free amino acids generated by proteolysis interfere with ...spectral studies after reconstituting the apoenzyme with cobalt. Purification by affinity chromatography eliminates this effect. Affinity-purified apoenzyme is susceptible to digestion with chymotrypsin but the metalloenzyme is not.
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