Mossbauer analysis

Resonance Raman studies of the recombinant proteins showed vibrational bands at the 200-430 cm region characteristic of iron-sulfur clusters (124). Most interestingly, on Fe and O isotope sensitive band was detected at 801 cm which could be attributed to either a Fe(IV)=0 species or a monobridged Fe-O-Fe structure. This observation, together with Mossbauer analysis, which indicated a mixed N, 0, and S ligand environment for cluster 2, suggests a Fe-O-Fe or Fe=0 unit as part of the structure for cluster 2. 

Ovchinnikov, V.V. Mossbauer Analysis of the Atomic and Magnetic Structure of Alloys. Cambridge International Science, Cambridge (2004)... 

Typically, many researchers assume that the active site in heat-treated macrocycles is similar in nature to the original macrocycle, thus the mechanism is thought to be the same. Bouwkamp-Wijnoltz recently presented evidence to back up this assumption.49 With in situ Mossbauer analysis, the researchers showed similar changes occur in the oxidation state of Fe while applying a voltage to a traditional macrocycle cathode and a heat-treated (up to 700 °C) macrocycle cathode. However, by the authors own admission, more evidence is needed to link this redox cycle to the active site. Additionally, in samples treated at higher temperatures the redox cycle was no longer observed. 

Sprenkel-Segel and Hanna (28) during their Mossbauer analysis of meteorites also determined the shifts (relative to Fe) and splittings of olivine (13 to 26% Fe) and an orthopyroxene (15-26% Fe). Their values are summarized in Table VII. 

Experimental Conditions and the Results of the Mossbauer Analysis of Specimens Partially Reacted in SO (1 5 x 6.0 mm pellets)... 

Weaver, C.E., Wampler, J.M. and Pecuil, T.C., 1967. Mossbauer analysis of iron in clay minerals. Science, 156 504-508. 

Other recent reports of the use of Mossbauer in the characterization of iron-containing zeolites involve the study of coordination complexes synthesized in zeolites. One such study carried out by Lunsford and coworkers (12) involved the study of tris(2,2 bipyridine) iron(II) complexes In zeolite Y. These materials were reacted with chlorine gas in order to oxidize the iron. Another study done by Banerjee (13) involved the Mossbauer analysis of lron(II)phenanthrollne complexes sorbed on zeolite 3A. These are most of the Mossbauer studies of iron-containing zeolites that we have found, although some earlier work has not been Included since reviews (14) are available. 

Fig. 10. Mdssbauer spectra of reduced (left panels) and oxidized (right panels) PS-I core complex at 80 K (top panels) and 4.2 K (bottom panels), The lower spectrum in each of the left panels was corrected for the unreduced component. The table at top right lists the experimentally determined isomer-shift (IS) and quadrupole-splitting (QS) parameters for oxidized and reduced core complexes at 77 K lower table lists isomer-shift values reported in the literature for other [4Fe 4S] and [2Fe 2S] clusters. Data source Petrouleas, Brand, Parrett and Golbeck (1989) A Mossbauer analysis of the low-potential iron-sulfur center in photosystem I Spectroscopic evidence that Fx is a [4Fe-4S] cluster. Biochemistry 28 8982.

As-isolated wild-type LipA contained 6.9 0.5 mol of iron and 6.4 0.9 mol of sulfide per mol of protein, and possessed a UV—vis spectrum that resembled those previously reported. Mossbauer spectroscopy showed that the sample contained almost exclusively [4Fe-4S] clusters with at most 5% of the total iron in the form of [2Fe-2S] clusters, indicating that there were 1.7 0.2 [4Fe-4S] clusters per as-isolated wild-type LipA polypeptide. When the as-isolated protein was reconstituted in the presence of additional Fe and sulfide and then characterized, it was found to contain 13.8 0.6 mol of iron and 13.1 0.2 mol of sulfide per mol of polypeptide. However, Mossbauer analysis of the reconstituted protein showed it to contain significant amounts of adventitiously bound iron in addition to [4Fe-4S] clusters (67 6%), indicating that only... 

Kallai and Rozenson (1980) by Mossbauer analysis in Fe-containing muscovite and by Guggenheim et al. (1987) in the thermal analysis of muscovite and by MacKenzie et al. 

Spectroscopic studies were performed on Ni- and Co-substituted Rds and Dx [50] while Fe replacement was done for Mossbauer analysis [35]. The Dx derivatives containing Zn and " Cd in the protein s metal site have been analy2ed by 2D-NMR spectroscopy and the solution structures have been determined [38, 39]. NMR studies were also done with the Zn, Cd and " Hg derivatives for Rd [9, 22, 51, 52]. The Ni-containing derivative is of particular interest, as Ni-substituted Rd and Dx were shown to mimic the reactivity pattern of Ni-containing hydro-genases with respect to hydrogen production, deuterium-proton and inhibition by carbon monoxide [53]. However, there is no three-dimensional structure yet available for either the Rd or the Dx Ni-substituted proteins. 

This is also in agreement with a microstructural characterization [7] which has shown that the Ru-Sn/C catalysts are made mainly of metallic Ru particles and ionic tin. No Sn particles have been found. The absence of Sn° has been confirmed by a Mossbauer analysis carried out on samples which have not been exposed to air. 

Patterns and physicochemical entities. In general, the fingerprint method operates with patterns ( fingerprints ) characteristic of different phases, compounds, crystallographic sites etc., which will be referred to as physicochemical entities for brevity. The correspondence between individual patterns and such entities is determined by the nature of interactions serving as a basis for the analytical method. In the case of Mossbauer analysis, the basic interactions are the hyperfine interactions. 

MOSSBAUER ANALYSIS OF YAG DOPED WITH DILUTE IRON... 

Figure 2.43 shows an example of routine Mossbauer analysis of finely dispersed particles formed in the cooling system of a power plant. The particles were collected from the coolant with a special filter and analyzed with standard... 

Compare the value of NMR and Mossbauer analysis for ceramic materials. 

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