ESEEM spectroscopy

Figure Bl.15.12. ESEEM spectroscopy. (A) Top energy level diagram and the corresponding stick spectrum for the two allowed (a) and two forbidden (f) transitions. Bottom time behaviour of the magnetization of an allowed (a) spin packet and a forbidden (f) spin packet during a two-pulse ESE sequence (see figure Bl.15.11 (A)). (B) The HYSCORE pulse sequence.

Hyperfine Coupling Values of the Nitrogen Ligands of Rieske and Rieske-Type Clusters Determined by ENDOR and ESEEM Spectroscopy... 

Y. Deligiannakis, M. Louloudi and N. Hadjiliadis, Electron spin echo envelope modulation (ESEEM) spectroscopy as a tool to investigate the coordination environment of metal centers, Coord. Chem. Rev., 2000, 204, 1. 

Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy... 

Catalases catalyze the conversion of hydrogen peroxide to dioxygen and water. Two families of catalases are known, one having a heme cofactor and the second a structurally distinct family, found in thermophilic and lactic acid bacteria. The manganese enzymes contain a binuclear active site and the functional form of the enzyme cycles between the (Mn )2 and the (Mn )2 oxidation states. When isolated, the enzyme is in a mixture of oxidation states including the Mn /Mn superoxidized state and this form of the enzyme has been extensively studied using XAS, UV-visible, EPR, and ESEEM spectroscopies. Multifrequency EPR and microwave polarization studies of the (Mn )2 catalytically active enzyme from L. plantarum have also been reported. ... 

In the absence of suitable crystals for an X-ray structural study, combinations of FTIR, RR, XAS, EPR, ENDOR, XANES, and ESEEM spectroscopies were used to characterize the manganese site in the OEC. Vibrational spectroscopy, particularly low-frequency FT infrared and... 

PLP radical was proved by application of [2-2H]lysine and [2-13C]lysine instead of lysine 24 to the reaction mixture [38]. In the first experiment the EPR signal was narrowed in the second it was broadened. The involvement of PLP in the reaction was proven by ESEEM spectroscopy. By incubation of the aminomutase with lysine, SAM, and [4 -2H]PLP a prominent doublet centered at the Lamour frequency for 2H was recognized [39], in accordance with the structure of an external aldi-mine. These findings establish a new role for PLP in enzyme reactions - PLP facilitates the radical isomerization. 

Recently, the spin density (p) localized on the cyano nitrogens, ethylene carbons, and cyano carbons in. i(mnt)2 1 were determined by Hoffman and co-workers (381) using a combination of ENDOR and ESEEM spectroscopies. These studies were important, in that they were able to quantify the extent of spin delocalization onto the olefinic carbon atoms. The [Ni(mnt)2]1 study was complimented by 19F ENDOR studies on [ X i (tfd) 211 which, when interpreted in the context of the [Ni(tds)2]1 data (389), allowed a detailed account of the ji spin delocalization partitioned on each atomic center of [Ni(mnt)2J1 and [Ni(tds)2 1 (381). The experimental and calculated spin densities for the... 

Peisach, J.. (1995) ESEEM spectroscopy - probing active site structures of metalloproteins, Bioradicals Detected by ESR Spectroscopy 203-215. 

Wamcke, K., Brooks, H. B., Lee, H.-L, McCracken, J. L., Davidson, V. L., and Babcock, G. T., 1995, Stmcture of the dithionite-generated tryptophan tryptophylquinone cofactor radical in methylamine dehydrogenase revealed by ENDOR and ESEEM spectroscopies, J. Am. Chem. Soc. 117 10063nl0075. 

ESEEM spectroscopy is a time-domain (i.e. pulsed) analog of EPR see Electron Spin Echo Envelope Modulation Spectroscopy). In principle, ESEEM contains the same information as is found in EPR and ENDOR, although in practice ESEEM is much more sensitive to weakly coupled nuclei that are not easily detected by ENDOR. On the other hand, strongly coupled nuclei can be undetectable by ESEEM, thus the combination of both techniques is often useful. 

Electron Paramagnetic Resonance (EPR) Spectroscopy, Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy Electron-Nuclear Double Resonance (ENDOR) Spectroscopy Nuclear Magnetic Resonance (NMR) Spectroscopy of Inorganic/Organometallic Molecules. 

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