Envelope Modulation in Spin-Echo Experiments

Mims, W. B.

doi:10.1103/physrevb.5.2409

Cited by 549 publications

(412 citation statements)

References 9 publications

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“…The cavity used for the ESEEM experiments was a folded stripline, which could accommodate frozen samples in conventional 3 mm internal diameter quartz EPR tubes [17,18]. ESEEM data were collected at 1.8 K using the stimulated echo technique (90°-r-90°-T-90°) with values of r chosen to suppress modulations arising from weakly coupled protons [19]. Spectra were obtained by Fourier transformation using a modified version of the dead time reconstruction method of Mims [20].…”

Section: Methods Of Pulsed Epr Spectroscopymentioning

confidence: 99%

A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase

et al. 1988

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The nickel centre of hydrogenase from Desulfovibrio gigas was studied by electron spin echo envelope modulation (ESEEM) spectroscopy in the oxidized, unready (Ni‐A) and H2‐reduced active (Ni‐C) states, both in H2O and 2H2O solution. Fourier transforms of the 3‐pulse ESEEM, taken at 8.7 GHz, for Ni‐A and Ni‐C in H2O contained similar peaks with narrow linewidths at frequencies of 0.4, 1.2 and 1.6 MHz, and a broader peak centred at 4.5 MHz. At 11.6 GHz, the low frequency components showed small field‐dependent shifts, while the high frequency component was shifted to 5.1 MHz. These results are consistent with the presence of 14N, possibly from imidazole, coupled to the nickel centre. In 2H2O, Ni‐A was shown to be inaccessible for exchange with solvent deuterons. In contrast, Ni‐C was accessible to solvent exchange, with a deuterium population being in close proximity to the metal ion. Thus, the nickel environment of the active protein is different from that in the oxidized or unready state. On illumination of Ni‐C, although EPR changes are seen, 14N coupling remains, and for the 2H2O sample, deuterium coupling is also retained.

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Section: Methods Of Pulsed Epr Spectroscopymentioning

confidence: 99%

A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase

et al. 1988

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“…The hyperfine terms, A iso and A dip , are all divided by the ␥( 1 H)/␥( 2 H) = 6.5 ratio for these simulations, and electric quadrupolar parameters of e 2 qQ = 0.22 MHz and = 0.1 are used for simulations for this nuclear spin I = 1 nucleus. The simulations are carried out via a matrix diagonalization program previously described (Britt et al 1989) based on the density matrix calculations described by Mims (1972). Figure 4a,b shows the data for fixed A dip and varied A iso values.…”

Section: (C) Eseem and Ese-endor Spectral Trendsmentioning

confidence: 99%

Simulations of the ¹ H electron spin echo–electron nuclear double resonance and ² H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S ₂ –state photosystem II manganese cluster

Aznar

Britt

2002

Phil. Trans. R. Soc. Lond. B

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The pulsed EPR methods of electron spin echo envelope modulation (ESEEM) and electron spin echoelectron nuclear double resonance (ESE-ENDOR) are used to investigate the proximity of exchangeable hydrogens around the paramagnetic S 2 -state Mn cluster of the photosystem II oxygen-evolving complex. Although ESEEM and ESE-ENDOR are both pulsed electron paramagnetic resonance techniques, the specific mechanisms by which nuclear spin transitions are observed are quite different. We are able to generate good simulations of both 1 H ESE-ENDOR and 2 H ESEEM signatures of exchangeable hydrogens at the S 2 -state cluster. The convergence of simulation parameters for both methods provides a high degree of confidence in the simulations. Several exchangeable protons-deuterons with strong dipolar couplings are observed. In the simulations, two of the close (Ϸ2.5 Å ) hydrogen nuclei exhibit strong isotropic couplings and are therefore most probably associated with direct substrate ligation to paramagnetic Mn. Another two of the close (Ϸ2.7 Å ) hydrogen nuclei show no isotropic couplings and are therefore most probably not contained in Mn ligands. We suggest that these proximal hydrogens may be associated with a Ca 2ϩ -bound substrate, as indicated in recent mechanistic proposals for O 2 formation.

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“…In parallel, theory was developed for analyzing linewidths and lineshapes in CW EPR spectra in terms of molecular dynamics [8][9][10]. At about the same time a few select groups in the Soviet Union and the USA worked on pulse experiments, using spin echo phenomena to measure electron spin relaxation [11], to detect hyperfine couplings by electron spin echo envelope modulation (ESEEM) techniques [12], to acquire ENDOR spectra in a broader temperature range than with CW methods [13], and to measure distances between electron spins [14]. These developments were pursued by physicists, were heavily focused on methodology, and were hardly recognized by mainstream chemists even by the end of the 1980s when the groundwork was all done.…”

Section: Prefacementioning

confidence: 99%

EPR Spectroscopy

2012

Topics in Current Chemistry

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Envelope Modulation in Spin-Echo Experiments

Cited by 549 publications

References 9 publications

A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase

A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase

Simulations of the ¹ H electron spin echo–electron nuclear double resonance and ² H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S ₂ –state photosystem II manganese cluster

EPR Spectroscopy

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Envelope Modulation in Spin-Echo Experiments

Cited by 549 publications

References 9 publications

A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase

A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase

Simulations of the 1 H electron spin echo–electron nuclear double resonance and 2 H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S 2 –state photosystem II manganese cluster

EPR Spectroscopy

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Simulations of the ¹ H electron spin echo–electron nuclear double resonance and ² H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S ₂ –state photosystem II manganese cluster