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. 2014 Oct:247:67-71.
doi: 10.1016/j.jmr.2014.08.008. Epub 2014 Aug 30.

Rapid-scan EPR of immobilized nitroxides

Zhelin Yu  1 , Richard W Quine  2 , George A Rinard  2 , Mark Tseitlin  1 , Hanan Elajaili  1 , Velavan Kathirvelu  1 , Laura J Clouston  3 , Przemysław J Boratyński  3 , Andrzej Rajca  3 , Richard Stein  4 , Hassane Mchaourab  4 , Sandra S Eaton  1 , Gareth R Eaton  5
Affiliations

Rapid-scan EPR of immobilized nitroxides

Zhelin Yu et al. J Magn Reson. 2014 Oct.

Abstract

X-band electron paramagnetic resonance spectra of immobilized nitroxides were obtained by rapid scan at 293 K. Scan widths were 155 G with 13.4 kHz scan frequency for (14)N-perdeuterated tempone and for T4 lysozyme doubly spin labeled with an iodoacetamide spirocyclohexyl nitroxide and 100 G with 20.9 kHz scan frequency for (15)N-perdeuterated tempone. These wide scans were made possible by modifications to our rapid-scan driver, scan coils made of Litz wire, and the placement of highly conducting aluminum plates on the poles of a Bruker 10″ magnet to reduce resistive losses in the magnet pole faces. For the same data acquisition time, the signal-to-noise for the rapid-scan absorption spectra was about an order of magnitude higher than for continuous wave first-derivative spectra recorded with modulation amplitudes that do not broaden the lineshapes.

Keywords: Immobilized nitroxide; Litz wire coils; Rapid scan EPR; Sucrose octaacetate glass; Trehalose glass.

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Figures

Figure 1
Figure 1
Power saturation curves at the peak of the absorption (rapid scan) or first derivative (CW) spectra of 0.15 mM 14N-PDT in sucrose octaacetate at 293 K. The scan widths were 155 G and rapid-scan frequencies were 7.7 or 13.4 kHz. The amplitude of the CW spectra is scaled to match that obtained for the rapid scans at low B1.
Figure 2
Figure 2
CW and rapid-scan spectra of 0.15 mM 14N-PDT in sucrose octaacetate at 293 K obtained with 10 s acquisition time. (A) Absorption spectrum obtained by rapid scan with the parameters listed in Table 2, (B) first derivative spectrum obtained from (A) by numerical differentiation, and (C) field-modulated CW spectrum obtained with 100 kHz and 0.63 G modulation amplitude, which is 20% of ΔBpp = 3.2 G.
Figure 3
Figure 3
CW and rapid-scan spectra of 0.018 mM 15N-PDT in sucrose octaacetate at 293 K. (A) Absorption spectrum obtained by rapid scan with the parameters listed in Table 2, (B) first derivative obtained from (A) by numerical differentiation, and (C) field-modulated CW spectrum obtained with 100 kHz modulation frequency and 0.9 G modulation amplitude, which is 20% of ΔBpp = 7.23 G. The data acquisition times were 10 s for (A) and 5 min for (C).
Figure 4
Figure 4
CW and rapid-scan spectra at 293 K of spin label 2 attached to T4 lysozyme obtained with 10 s acquisition times. (A) Absorption spectrum obtained by rapid-scan with the parameters listed in Table 2, (B) first derivative obtained from (A) by numerical differentiation, (C) field-modulated CW spectrum obtained with 100 kHz modulation frequency and 1.8 G modulation amplitude which is 20% of ΔBpp = 1.06 G
See this image and copyright information in PMC

References

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