Rapid-scan EPR of immobilized nitroxides

Yu, Zhelin; Quine, Richard W.; Rinard, George A.; Tseitlin, Mark; Elajaili, Hanan; Kathirvelu, Velavan; Clouston, Laura J.; Boratyński, Przemysław J.; Rajca, Andrzej; Mchaourab, Hassane S.

doi:10.1016/j.jmr.2014.08.008

Cited by 21 publications

(28 citation statements)

References 26 publications

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“…3). The strongly temperature-dependent values of T 1 for spin-labeled T4L in this temperature interval at Q-band (Table 1) are similar to those reported for 2 in 1:1 water/glycerol at X-band (Table S1) (30). The~T À2.7 temperature dependence of T 1 is consistent with domination of the relaxation by a local mode, which is frequency independent (29).…”

Section: Spin-labeled T4l Relaxation and Deer 80-160 Ksupporting

confidence: 81%

Room-Temperature Distance Measurements of Immobilized Spin-Labeled Protein by DEER/PELDOR

Meyer

Swanson

Clouston

et al. 2015

Biophysical Journal

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100

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Nitroxide spin labels are used for double electron-electron resonance (DEER) measurements of distances between sites in biomolecules. Rotation of gem-dimethyls in commonly used nitroxides causes spin echo dephasing times (Tm) to be too short to perform DEER measurements at temperatures between ∼80 and 295 K, even in immobilized samples. A spirocyclohexyl spin label has been prepared that has longer Tm between 80 and 295 K in immobilized samples than conventional labels. Two of the spirocyclohexyl labels were attached to sites on T4 lysozyme introduced by site-directed spin labeling. Interspin distances up to ∼4 nm were measured by DEER at temperatures up to 160 K in water/glycerol glasses. In a glassy trehalose matrix the Tm for the doubly labeled T4 lysozyme was long enough to measure an interspin distance of 3.2 nm at 295 K, which could not be measured for the same protein labeled with the conventional 1-oxyl-2,2,5,5-tetramethyl-3-pyrroline-3-(methyl)methanethio-sulfonate label.

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Section: Spin-labeled T4l Relaxation and Deer 80-160 Ksupporting

confidence: 81%

Room-Temperature Distance Measurements of Immobilized Spin-Labeled Protein by DEER/PELDOR

Meyer

Swanson

Clouston

et al. 2015

Biophysical Journal

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100

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“…Multiharmonic reconstruction may be especially important in obtaining accurate projections for EPR imaging because overmodulation can be used to improve the S/N without losing resolution in the projection and the resulting image. The coil driver and Litz wire coils developed for rapid scan EPR [4,5] produce wider scans with a uniform field over a longer sample than is possible with the standard commercial modulation fields. The modulation field uniformity permits the extension of the previously described multiharmonic method to samples with lengths of about 5 mm, which is close to optimal for the B 1 distribution in the Bruker dielectric resonator that was used for the experiments.…”

Section: Discussionmentioning

confidence: 99%

“…In the initial reports the samples were very small because the magnetic field uniformity that could be obtained with commercial modulation coils was adequate for multiharmonic spectroscopy only over a small region of space and with limited modulation amplitudes [2,3]. The larger scan coils that have been developed for rapid scan EPR improve the magnetic field homogeneity over larger samples [4] relative to what can be achieved with conventional modulation coils. In addition, the rapid scan coil driver can generate larger modulation amplitudes [5] than conventional modulation coil drivers.…”

Section: Introductionmentioning

confidence: 99%

Multiharmonic electron paramagnetic resonance for extended samples with both narrow and broad lines

Tseytlin

Eaton

2015

Journal of Magnetic Resonance

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Multiharmonic electron paramagnetic resonance spectroscopy was demonstrated for two samples with both narrow and broad lines: (i) α,γ-Bisdiphenylene-β-phenylallyl (BDPA) with ΔBpp of 0.85 G plus ultramarine blue with ΔBpp of 17 G, and (ii) a nitroxide radical immobilized in sucrose octaacetate. Modulation amplitudes up to 17 G at 41 kHz were generated with a rapid scan coil driver and Litz wire coils that provide uniform magnetic field sweeps over samples with heights of 5 mm. Data were acquired with a 2-D experiment in the Xepr software through the transient signal path of a Bruker E500T and digitized in quadrature with a Bruker SpecJet II. Signals at the modulation frequency and its harmonics were calculated by digital phase-sensitive detection. The number of harmonics with signal intensity greater than noise increases as the ratio of the modulation amplitude to the narrowest peak increases. Spectra reconstructed by the multiharmonic method from data obtained with modulation amplitudes up to five times the peak-to-peak linewidths of the narrowest features have linewidths that are broadened by up to only about 10% relative to linewidths in spectra obtained at low modulation amplitudes. The signal-to-noise improves with increasing modulation amplitude up to the point where the modulation amplitude is slightly larger than the linewidth of the narrowest features. If this high a modulation amplitude had been used in conventional methodology the linewidth of the narrowest features would have been severely broadened. The multiharmonic reconstruction methodology means that the selection of the modulation amplitude that can be used without spectral distortion is no longer tightly tied to the linewidth of the narrowest line.

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“…The method has provided substantially improved signal-to-noise (S/N) relative to CW EPR for a wide range of samples including paramagnetic defects in solids (20) , the radiationinduced defects in teeth (21) , defects in gamma irradiated solids (22) and immobilized organic radicals (23) . These papers demonstrate the improvement in S/N that can be achieved by rapid scan for samples with a wide range of relaxation times.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Continuous Wave and Rapid Scan X-band Electron Paramagnetic Resonance of Irradiated Clipped Fingernails

Elajaili

McPeak

Romanyukha³

et al. 2016

Radiat Prot Dosimetry

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X-band rapid scan electron paramagnetic resonance (EPR) measures the free radicals in irradiated clipped fingernails with higher signal-to-noise (S/N) and lower standard deviation of the signal amplitude for replicate measurements than does conventional continuous wave (CW) EPR in the same measurement time. For a clipped fingernail sample irradiated to 10 Gy and data acquisition time of 30 s with B 1 = 8.5 μT, the S/N for rapid scan is >2000 for the absorption spectrum and 1200 for the corresponding first derivative. The standard deviation for replicate measurements of signal amplitude is~1%. For CW spectra, the S/N depends on the modulation amplitude. The CW signal has a first derivative peak-to-peak linewidth of 0.95 mT. For 30 s of CW acquisition time, the S/N was 30 for a conservative modulation amplitude of 0.2 mT and B 1 of 2.3 μT or 90 for a modulation amplitude of 0.4 mT and B 1 of 3.2 μT, which resulted in standard deviations of replicate measurements of 5% or 2%, respectively.

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Rapid-scan EPR of immobilized nitroxides

Cited by 21 publications

References 26 publications

Room-Temperature Distance Measurements of Immobilized Spin-Labeled Protein by DEER/PELDOR

Room-Temperature Distance Measurements of Immobilized Spin-Labeled Protein by DEER/PELDOR

Multiharmonic electron paramagnetic resonance for extended samples with both narrow and broad lines

Comparison of Continuous Wave and Rapid Scan X-band Electron Paramagnetic Resonance of Irradiated Clipped Fingernails

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