ELDOR detected NMR

H. Mino and T. Ono, Applications of pulsed ELDOR-detected NMR measurements to studies of photosystem II Magnetic characterization of Yd tyrosine radical and Mn2+ bound to the high-affinity site, Appl. Magn. Reson., 2003, 23, 571. 

ESEEM experiments on Yp.398,399 Mino and Ono400,401 used a new technique, ELDOR-detected NMR, to measure the hyperfine structure of Yp in PS II. Except for slightly higher linewidths the spectrum was found to correspond with the one from pulse ENDOR. 

Rapatskiy L, Cox N, Ames W, et al. Detection of the water binding sites of the oxygen-evolving complex of photosystem II using W-band 170 ELDOR-detected NMR spectroscopy. J Am Chem Soc 2011 Epub date August 31, 2012. 

Figure 1. Scheme of the pulse EPR sequences mentioned in this chapter, (a) Two-pulse ESEEM. (b) Three-pulse ESEEM. (c) Four-pulse ESEEM. When times fi and ti are stepped under the constraint of ti= ti= T, combination-peak experiment is performed. Two-dimensional HYSCORE spectroscopy is done using the same sequence, whereby t and are stepped independently. The second and third nil pulse are replaced by high-tuming-angle (HTA) pulses in a matched HYSCORE experiment, (d) SMART-HYSCORE. The first and third pulses are HTA pulses, (e) Davies ENDOR. (f) Mims ENDOR. (g) ELDOR-detected NMR. 

A large variety of hyperfine spectroscopy methods exist that allow the detection of hyperfine and nuclear quadrupole interactions electron spin-echo envelope modulation (ESEEM), ENDOR, and ELDOR-detected NMR (electron-electron doubleresonance detected nuclear magnetic resonance) [13]. Although there are cases in which ESEEM and ENDOR perform equally well, ESEEM-like methods tend to be... 

In some cases, it may be beneficial to use ELDOR-detected NMR [20] instead of ENDOR to obtain the larger nuclear transitions. This technique bears similarities with the above-mentioned ENDOR techniques, but instead of using an RF pulse, a microwave pulse with variable microwave frequency is used to affect the electron populations. The nuclear transition frequencies follow from monitoring the polarization changes as a function of the difference between the two microwave frequencies. 

HYSCORE and SMART HYSCORE (see Fig. 4 manuseript in preparation). The pseudonuclear effect to the g value can nicely be observed in the double-quantum cross-peaks and used beneficially to determine flic sign of the hyperfine values (Fig. 4). Furthermore, die use of ELDOR (electron double resonance) detected NMR techniques [57] at W-band largely facilitates the analysis of high-spin iron(III) heme proteins [94]. 

There are a variety of techniques for the determination of the various parameters of the spin-Hamiltonian. Often applied are Electron Paramagnetic or Spin Resonance (EPR, ESR), Electron Nuclear Double Resonance (ENDOR), Electron Electron Double Resonance (ELDOR), Nuclear Magnetic Resonance (NMR), occassionally utilizing effects of Chemically Induced Dynamic Nuclear Polarization (CIDNP), Optical Detection of Magnetic Resonance (ODMR), Atomic Beam Spectroscopy and Optical Spectroscopy. The extraction of the magnetic parameters from the spectra obtained by application of these and related techniques follows procedures which may in detail depend on the technique, the state of the sample (gaseous, liquid, unordered solid, ordered solid) and on spectral resolution. For particulars, the reader is referred to the general references (D). 

---