Mobile Mossbauer spectroscopy

Mobile Mossbauer Spectroscopy with MIMOS in Space and on Earth... 

On the other hand, the spectroscopic techniques probe individual ionic species which build up the ionic aggregates. These techniques permit the investigation of the immediate chemical environments, the mobility of cations and water-ions Interactions. Metal nuclear magnetic resonance and Mossbauer spectroscopy are sensitive probes of counter cations and provide valuable information on the cations and their environment. Infrared spectroscopy is complementary to the above methods and addresses itself to the bound SO3" anions or water and the interaction of water molecules with the various species with which it is in contact. A common conclusion that is reached in the above mentioned studies is that four or five water molecules are needed to complete the hydration process. Reducing the level of moisture content (which surrounds the ionic species) below four water molecules per unit SOj site enhances the Coulombic interaction between the ionic species. This eventually leads to the formation of ion pairs in the dry membranes. These ion pairs do not necessarily disperse homogeneously in the fluorocarbon matrix but tend to form aggregates, phase separated from the matrix materials as demonstrated in the scattering studies. 

In summary, results of Mossbauer spectroscopy studies indicate that the primary interaction with oxygen leads to a strong enrichment of tin in the surface layer in the bimetallic particles and tin, both in the surface layer and in the bulk of the nanocluster, is oxidized to Sn. " In the presence of CO + O2 mixture two forms of Sn oxide have been found, i.e., (i) a more stable one, Sn +(ox) with isomer shift around zero, and (ii) a mobile one, Sn " (sf) with IS = 0.79-0.94 mm s During the room temperature CO oxidation no separation of the oxidized Sn forms was observed, as both the Sn (ox) and Sn (sf) components were easily reconverted in hydrogen at room temperature to PtSn(a) and PtSn(b) phases. During the CO + O2 reaction, the surface of the nanoparticle containing of both mono and bimetallic metallic sites are probably covered mostly by Sn " species, while providing simultaneous access to CO on the surface of the formed PtSn (1 1) or Pt phases. In this way indirect experimental proof for the formation of metal ion - metal nanocluster ensemble sites has been obtained. 

Evidence for mobility within proteins comes from a variety of physical methods single crystal X-ray or neutron diffraction, electron microscopy, and spectroscopic techniques such as NMR, fluorescence depolarization, Mossbauer spectroscopy and H-exchange studies. Theoretical approaches such as potential-energy minimization and molecular-dynamics calculations may also be used to study flexibility. An illustration of the frequency range of the various thermal motions detected in proteins is given in Table 1. 

Shiloh H, lancu TC, Bauminger E, Link G, Pinson A, Hershko C (1992) Defer-oxamine-induced iron mobilization and redistribution of myocardial iron in cultured rat heart cells studies of the chelatable iron pool by electron microscopy and Mossbauer spectroscopy. J Lab Clin Med 119 429-437 Singh S, Hider RC (1988) Colorimetric detection of the hydroxyl radical comparison of the hydroxyl-radical-generating ability of various iron complexes. Anal Biochem 171 47-54... 

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