Fluorescence Mossbauer spectroscopy

Mosshauer effect The resonance fluorescence by y-radiation of an atomic nucleus, returning from an excited state to the ground state. The resonance energy is characteristic of the chemical environment of the nucleus and Mossbauer spectroscopy may be used to yield information about this chemical environment. Used particularly in the study of Fe. Sn and Sb compounds. 

The spectroscopic techniques that have been most frequently used to investigate biomolecular dynamics are those that are commonly available in laboratories, such as nuclear magnetic resonance (NMR), fluorescence, and Mossbauer spectroscopy. In a later chapter the use of NMR, a powerful probe of local motions in macromolecules, is described. Here we examine scattering of X-ray and neutron radiation. Neutrons and X-rays share the property of being found in expensive sources not commonly available in the laboratory. Neutrons are produced by a nuclear reactor or spallation source. X-ray experiments are routinely performed using intense synclirotron radiation, although in favorable cases laboratory sources may also be used. 

KEYWORDS Mossbauer spectroscopy, MIMOSI la, Mars Exploration Rover, ln-situ resource utilization, X-ray fluorescence spectroscopy... 

Apart from fluorescence, several other methods may be used to obtain time-resolved information. In the case of proteins containing an iron atom, Mossbauer spectroscopy allows the determination, in the iron binding site, of not only root-mean-square shifts of atoms but also the times over which such shifts occur. Detailed investigations of myoglobin have yielded relaxation times on the order of 10 8 Proton NMR spectroscopy can be used to... 

Ti ossbauer spectroscopy is the term now used to describe a new ana-lytical technique which has developed using y-ray nuclear resonance fluorescence or the Mossbauer effect. For most of the time since Rudolf Mossbauer s discovery in 1958 it was the physicist who utilized this new tool. Starting approximately in 1962 some chemists realized the potential of this new technique. Since then they have applied Mossbauer spectroscopy to the study of chemical bonding, crystal structure, electron density, ionic states, and magnetic properties as well as other properties. It is now considered a complimentary tool to other accepted spectroscopic techniques such as NMR, NQR, and ESR. 

At the time this suggested that the activation of aconitase required reduction of the Fe-S cluster, rather than the addition of iron. This would relegate iron to the role of an efficient reductant of the Fe-S cluster. Also, while reduction of the cluster by sodium dithionite was immediate, development of full enzyme activity required minutes (41,42). This suggested that perhaps cluster reduction triggered a conformational change which led to activation. Fluorescence studies on the reduction and activation process of aconitase by Ramsay (43,44) supported this idea. Again Mossbauer spectroscopy provided the key to understand the fate of the added iron (39). 

Many methods are used for pigment identification. Among those x-ray diffraction, x-ray fluorescence, optical emission spectroscopy, and microscopy are frequently in demand (8,10,1121,59,83,91-93). The use of Mossbauer spectroscopy for pigment studies has received a great deal of attention in the past few years. The development of this field has been quite rapid and promising (59,94r 103). 

Mossbauer spectroscopy is the study of recoilless resonant fluorescence " Sn Mossbauer spectroscopy has been found to be a most usefifl method for studying the bonding and stereochemistry of tin compounds in the solid state. The two most important parameters are the isomer shift (5, mm s ) and the quadrupole sphtting (A q, nuns ), although the recoil-free fractions and temperature coefficients can also supply useful structural indications. 

Noninvasive surface spectroscopies can be applied in the presence of liquid water most of them involve the input and detection of photons. The best known examples are nuclear magnetic resonance, electron spin resonance, Raman, Fourier transform infrared, UV-visible fluorescence, X-ray absorption, and Mossbauer spectroscopies, although Brown (28) enumerated many others that are available to detect adsorbed ions. These methods, some of which are listed in Table II along with citations of illustrative applications, can be used both noninvasively and in conjunction with in situ probes. 

On-line Instrumentation Applicable to the Coal Preparation Industry. Although numerous measurement concepts have been considered for on-line analysis in the coal preparation industry and several of these are being evaluated in the laboratory, e.g. Mossbauer spectroscopy ( ), x-ray diffraction, and x-ray fluorescence, this section will discuss only those systems that have undergone or are scheduled for field testing and are advertised as available. These include elemental analyzer systems, a moisture monitor, and a coal-rock-water slurry meter. 

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. 

XRF X-ray fluorescence SPH spectrophotometry AA atomic absorption iCP inductiveiy coupied piasma spectroscopy Coi coiorimetry MS Mossbauer spectroscopy PD Parkinson s disease. 

Studies of the corrosion mechanisms occurring in laboratory tests are often conducted in order to ensure that real-world conditions are being simulated, and to increase confidence in the test results [3/]. Visual and microscopic examination is used to characterize the mode of attack, and a variety of analytical methods, including X-ray difftaction and fluorescence and Raman, infrared, and Mossbauer spectroscopies are employed to identify corrosion products. 

The photons emitted by the de-excitation of nuclear levels that are populated in the course of radioactive decays can be resonantly scattered. Nuclear resonance fluorescence experiments can give information on the velocity distribution of recoil atoms and the chemical modifications following transmutations and on the slowing-down process of hot atoms. This technique can be applied in gaseous, liquid, and solid systems, giving an advantage over Mossbauer spectroscopy. Nuclear resonance fluorescence has been reviewed, with particular reference to the following systems ... 

Chemical shifts also exist in X-ray photoelectron (106), X-ray fluorescence (21), and Mossbauer (123) spectroscopy. The common theme in all these phenomena is that inner electronic or nuclear energy levels are measurably affected by chemical changes in the valence electron distribution. 

Protein rate processes are strongly affected by hydration. The dry protein shows greatly reduced internal motions, measured by Moss-liauer spectroscopy, neutron scattering, fluorescence spectroscopy, and other methods. Surface motions, monitored by spin probes or spin or Mossbauer labels, are similarly frozen in the dry protein. The following paragraphs comment on the appearance of motion characteristic of the hydrated protein and on the coupling between protein and solvent motions. 

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