Improved Sensitivity for Imaging Spin Trapped Hydroxyl Radical at 250 MHz

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Hydroxyl radical, Image reconstruction, Rapid-scan EPR, Spin-trapping

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College of Natual Science and Mathematics, Chemistry and Biochemistry


Radicals, including hydroxyl, superoxide, and nitric oxide, play key signaling roles in vivo. Reaction of these free radicals with a spin trap affords more stable paramagnetic nitroxides, but concentrations in vivo still are so low that detection by electron paramagnetic resonance (EPR) is challenging. Three innovative enabling technologies have been combined to substantially improve sensitivity for imaging spin-trapped radicals at 250 MHz. (i) Spin trapped adducts of BMPO have lifetimes that are long enough to make imaging by EPR at 250 MHz feasible. (ii) The signal-to-noise of rapid scan EPR is substantially higher than for conventional continuous wave EPR. (iii) An improved algorithm permits image reconstruction with a spectral dimension that encompasses the full 50 G spectrum of the BMPO-OH spin-adduct without requiring the very wide sweeps that would be needed for filtered backprojection. A 2D spectral-spatial image is shown for a phantom containing ca. 5 μM BMPO-OH.

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