Spectroscopic characterization magnetic circular dichroism

The magnetic and electronic properties of the D. gigas Fdll [3Fe-4S] center were revealed by different and complementary spectroscopic techniques EPR 89), Mossbauer 90, 91), resonance Raman (RR) 92), magnetic circular dichroism MCD) 93), EXAFS 94), saturation magnetization (95), electrochemistry 96), and NMR (97, 98). The [4Fe-4S] center is also well characterized and surprising information has been obtained in relation to cluster interconversions and noncysteinyl coordination, as illustrated for D. gigas Fdl and D. africanus Fdlll, as well as the possibility of generating unusual reduced states. 

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

Sensitive immunoassays specific for PAH-DNA adducts allow the detection of one adduct per 10 nucleotides. Fluorimetry has also been used as an alternative detection method to immunoassays. In another method, isomeric tetrols of PAH are liberated by acid hydrolysis of the DNA-PAH adducts and analyzed by LC with fluorescence detection. Structural studies and detailed characterization of PAH metabolites and their conjugates has been performed by trapping the corresponding fractions at the exit of the LC system. As an example, the total characterization of the in t /tro-formed benzo(a)pyrenetetra-hydrodiol-epoxide-guanosine adduct has been achieved by a combination of nuclear magnetic resonance, circular dichroism, and mass spectroscopic techniques. 

Structural information on proteins can be obtained with X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy however, due to various limitations intrinsic to these high-resolution structmal methods, only alternate spectroscopic techniques (especially fluorescence, circular dichroism (CD), Raman, and infrared spectroscopic techniques) can be employed for conformational characterization of proteins as well as stabilization and denaturation of enzymes. 

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