Spectroscopy electron spin echo

Extensive analysis of the EPR and redox behavior of this unusual copper protein led to the hypothesis that the protein might contain a Cu(A) site similar to that in cytochrome oxidase (Riester et ai, 1989) and that the unusual seven-line EPR is due to the Cu(A)-type site. An alternative interpretation of this EPR is based on electron spin-echo spectroscopy as well, and that is that the seven-line EPR is due to a half-met Cu—Cu pair and to unusual type I sites (Jin et ai, 1989). Three sets of spin-echo peaks can be attributed to nitrogens on imidazole ligands to a CuA-type site and to another imidazole on the half-met site. The electron spin-echo spectra of cytochrome oxidase are similar, although there is not enough copper in cytochrome oxidase for a half-met site. Conceivably, the property of delocalization of the paramagnetic electron could be effected by the proposed bridging between Cub and heme as (nomenclature summarized by Capaldi, 1990), which are proposed to be 3-4 A apart. 

Di Benedetto, F., Costagliola, P., Benvenuti, M. et al. (2006) Arsenic incorporation in natural calcite lattice evidence from electron spin echo spectroscopy. Earth and Planetary Science Letters, 246(3-4), 458-65. 

Mims, W. B., Peisach, J. Electron Spin Echo Spectroscopy and the Study of Metalloproteins in Biological Magnetic Resonance, Vol. 3, (eds.) Berliner, L. J., Reuben, J., pp 213-263, New York, Plenum Press, 1981... 

N. Narayana and, L. Kevan, Characterization of Silver Species Locations and Environments in A, X, and Y Zeolites by Electron Spin Echo Spectroscopy. J. Chem. Phys., 1982, 76, 3999 1005. 

Karthein, R., Motschi, H., Schweiger, A., Ibric, S., Sulzberger, B., and Stumm, W. (1991). Interactions of chromium(ni) complexes with hydrous 5-AI2O3 rearrangements in the coordination sphere studied by electron spin resonance and electron spin-echo spectroscopies. Inorg. Chem. 30, 1606-1611. 

Ros M and Groenen EJJ (1989) The triplet state of dodeca-pentaenal Electron spin echo spectroscopy of a polyenal. Chem Phys Lett 154 29-33... 

Through electron spin echo spectroscopy, a splitting of the low-field lines was observed, arising from the interaction of copper(II) with the remote N atoms of the coordinated imidazoles. This splitting, which disappears at low pH, was attributed to the presence of a divalent metal linked by an imidazolate bridge (247). 

Two methods are useful to measure slow motion spin label spectra saturation transfer (ST-EPR) and two-dimensional electron spin echo spectroscopy (2D ESE). In the ST-EPR experiment, " a cw spectrometer is operated at high microwave power, and this causes partial saturation of the nitroxide spectrum. As the field is scanned, molecular motion carries this saturation to nearby regions of the spectrum, yielding spectra that are very sensitive to the rotational correlation time. One of the great advantages of ST-EPR is that little instrumentation is required beyond the conventional cw EPR instrument. Most any laboratory equipped to perform EPR can also perform ST-EPR. 

Electron spin echo spectroscopy (ESE) monitors the spontaneous generation of microwave energy as a function of the timing of a specific excitation scheme, i.e. two or more short resonant microwave pulses. This is illustrated in Fig. 7. In a typical two-pulse excitation, the initial n/2 pulse places the spin system in a coherent state. Subsequently, the spin packets, each characterized by their own Larmor precession frequency m, start to dephase. A second rx-pulse at time r effectively reverses the time evolution of the spin packet magnetizations, i.e. the spin packets start to rephase, and an emission of microwave energy (the primary echo) occurs at time 2r. The echo ampHtude, as a fvmction of r, constitutes the ESE spectrum and relaxation processes lead to an irreversible loss of phase correlation. The characteristic time for the ampHtude decay is called the phase memory time T. This decay is often accompanied by a modulation of the echo amplitude, which is due to weak electron-nuclear hyperfine interactions. The analysis of the modulation frequencies and ampHtudes forms the basis of the electron spin echo envelope modulation spectroscopy (ESEEM). 

The basic principle involved in electron spin echo spectroscopy is the formation of an echo. The simplest spin echo experiment uses two microwave pulses to form an echo, which is also... 

Electron Spin Echo Spectroscopy and the Study of Metalloproteins... 

One example is a study of the molecular dynamics of an elongated nitroxide in frozen toluene matrices by two-dimensional electron spin echo spectroscopy (ESE) carried out by Poluektov and Doubinski at 95 GHz. The spectra were... 

ESE Abbreviation for the time-domain electron spin resonance technique of electron spin-echo spectroscopy. 

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