Mossbauer spectra of reduced

Mossbauer spectra of the reduced proteins in the above study are not consistent with subsequent data for these proteins (153,164,165). It is now believed (personal communications, W. H. Orme-Johnson and Graham Palmer) that 1, the samples in these experiments were impure, and 2. the buffers used in these experiments were not strong enough to maintain a buffer pH level during the dithionite reductions. Therefore, the Mossbauer spectra of reduced spinach ferredoxin in the above experiment resulted from a mixture of oxodized protein iron and iron from denatured protein material. 

Fig. 14. Mossbauer spectra of reduced plant-type ferredoxins in zero magnetic field at low temperature. Abbreviations AZl = Azotobacter Fe-S Protein I, 4.2 °K Put. = Putidaredoxin, 4.2 °K Clos. = Clostridial Paramagnetic Protein, 4.2 °K Ad. = Adrenodoxin, 4.2 °K Parsley = Parsley Ferredoxin, 4.6 °K. Velocity scale is relative to source in platinum matrix...

The Mossbauer spectra of reduced nontronite samples show the presence of both Fe2 and Fe3 and may give semi-quantitative results as stated above As the extent of reduction increases, the area associated with Fe2 increases at the expense of that associated with Fe3 (Figures 13 and 14) Using two Fe3 doublets to fit the spectra of unaltered SWa-1, Lear (34) postulated that the reduction of Fe3 to Fe2 occurs predominately at one of the two Fe3 sites Interpretations of Mossbauer spectra is always speculative, however, because results from the computer-fitting used to analyze the data may represent only one of many possible solutions, and unavoidably reflect operator bias ... 

Fig. 9.a Mossbauer spectrum of reduced reconstituted D. gigas ferredoxin II taken at 4.2 K in a field of 600 G applied parallel to the observed 7-radiation b Mossbauer spectra of reduced D. gigas ferredoxin I (subtraction of 25 % of a spectrum of a three-iron center run in the same conditions was made). Spectrum obtained in natural abundance Fe56. Experimental conditions as for spectrum (a). 

Fig. 13.4 Mossbauer spectra of reduced red cells at 4 K in (a) zero magnetic field, (b) a field of 7-5 kG perpendicular to the direction of observation, (c) a field of 30 kG. [Ref. 10, Fig. 5]...

Figure 31. Zero-field Mossbauer spectra of reduced Z)g Fd II (a) (137) and cluster 55 (b, c) at 4.2 K (4, B) and 260 K (c). The doublets of Fd II subsite 4 (Fe ) and delocalized pair subsites 2 and 3 (Fe ) are marked by brackets. The solid line in spectrum b is a least-squares fit to four sites of equal intensity. The doublet of low-spin Fe is drawn separately above spectrum b. The solid line in spectrum c is a least-squares fit to two doublets with a 1 3 intensity ratio. (Reproduced with permission from Ref. 217.)...

Quasi in situ Fe Mossbauer spectra of reduced Ir-Fe/Si02 catalyst upon exposure to different atmospheres at 80 C for 1h. 

The Mossbauer spectra of reduced laterite samples at 800 W, with two times the stoichiometric carbon addition and 11.75g sample mass at 120 (a), 240 (b), 360 (c), and 480 (d) s. (Reproduced from Ref. 19 with permission of Elsevier.)... 

Bimetallic Au/Pd nanoparticles were prepared by ultrasound irradiation of a mixture solution of NaAuCl4-H20/PdCl2 2NaCl-3H20 by which the Au and Pd ions were reduced to the metallic state. The Mossbauer spectra of AuPd-SDS particles, with SDS (sodium dodecyl sulfate) representing the surfactant of the system, consist of two components, one for the pure Au core and the other for the alloy layer at the interface of Au core and Pd shell [435]. 

Mossbauer spectra of calcined samples (Table 1). The Fe3+(3) and Fe3+(4) components are probably located in tetrahedral (framework) positions. The charge distribution around the Fe3+(3) is asymmetric (large QS), thus here the charge compensation is probably provided by Fl+, i.e. indicating the existence of Bronsted sites. The charge symmetry around Fe3+(4) is more symmetric, thus the counterion is probably Na+ or Fe(OFl)+. Fe2+ ions are probably located outside of the framework (due to their larger ionic radius). Thus, in the hydrogen a small part of Fe3+ is reduced to Fe2+, and is probable removed to extra-framework sites. 

Figure 5.12 In situ Mossbauer spectra of a reduced Felr/Si02 catalyst at a reaction temperature of 525 K and during CO hydrogenation when the catalyst is in its steady state (methanol-producing state). The bottom spectrum represents the difference between the two upper spectra it is characteristic of an iron carbide in superparamagnetic state (courtesy of Hyung Woo, adapted from [8]).

Figure 6. Mossbauer spectra of the reduced uteroferrin phosphate complex at 55K (a) and 4.2K (b) and the oxidized uteroferrin-phosphate complex at 4.2K (c). (Reproduced with permission from ref. 90. Copyright 1986 American Society for Biological Chemists.)...

Figure 3. MOssbauer spectra of the reduced Rieske protein Thermus Thermophilus. (A) Spectrum taken at 230 K. The brackets indicate the doublets of the trapped-valence Fe2+ and Fe3+ sites. (B) 4.2 K spectrum of the same sample. The solid line is a spectral simulation based on an S = 1/2 spin Hamiltonian. S = 1/2 is the system spin resulting from coupling S = Sa + Sb according to H = JSa-Sb for J > 0 Sa = 5/2 and Sb = 2.

Figure 4. Mossbauer spectra of the reduced Fe3S4 cluster (S = 2) of Fd II recorded at 4.2 K in zero field (A) and at 1.3 K in parallel applied field of 1.0 Tesla (B). The solid lines in (B) are theoretical curves for the delocalized pair (I) and the Fe3+ site (II). The sum is drawn through the data. Parameters, fitting procedures and additional spectra are given in ref (11).

Fig. 18. Mossbauer spectra of Cr-Fc304 catalyst after room temperature exposure to air and COz/CO treatment at 703 K. (a) Spectrum in air at 296 K after sample has been stored in air. (b) Sample from (a) reduced in a C02/CO = 4 mixture at 703 K for 10 hr. Spectrum obtained in reaction mixture at 703 K. (c) After cooling (b) to 483 K. (d) After cooling (c) to 296 K. (e) Spectrum of a 0.001-in. Fe NBS standard foil at 296 K. Zero velocity is with respect to a 7Co in copper source. Reproduced from Tops0e and Boudart (96) with permission.

Bearden and Moss (12) and Moss et al. (152) presented the Mossbauer spectra of spinach ferredoxin in its oxidized and reduced states. These spectra showed the two iron atoms in the oxidized protein in identical electronic environments. Upon protein reduction, one of the iron atoms exhibited a spectrum characteristic of a high-spin ferrous ion. The... 

The Mossbauer spectra of the reduced proteins at 4.2 °K are shown in Fig. 11 for 3.4 kilogauss applied field and in Fig. 12 for 46 kilogauss applied field. Since the spectra are so similar, we shall speak exclusively in terms of the spinach ferredoxin data. Fig. 13 is low-temperature... 

Figure 13 Mossbauer spectra of (a) unaltered, (b) slightly reduced (Fe2+ 88 13% of total Fe), and (c) moderately reduced (Pe2 34% of total Fe) ferruginous smectite (sample SWa-1 from the Source Clay Minerals Repository of The Clay Minerals Society) at 120 K. (Adapted from Ref. 34.)...

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