Improved Sensitivity for Imaging Spin Trapped Hydroxyl Radical at 250 MHz

• Published in: Chemphyschem 2015-02, Vol.16 (3), p.528-531
• Main Authors: Biller, Joshua R., Tseitlin, Mark, Mitchell, Deborah G., Yu, Zhelin, Buchanan, Laura A., Elajaili, Hanan, Rosen, Gerald M., Kao, Joseph P. Y., Eaton, Sandra S., Eaton, Gareth R.
• Format: Article
• Language: English
• Subjects: Cyclic N-Oxides - chemistry; Electron Spin Resonance Spectroscopy; EPR imaging; Hydroxyl Radical - chemistry; hydroxyl radicals; image reconstruction; rapid-scan EPR; Spin Trapping
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201402835

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. 1) Spin‐trapped adducts of BMPO have lifetimes that are long enough to make imaging by EPR at 250 MHz feasible. 2) The signal‐to‐noise ratio of rapid‐scan EPR is substantially higher than for conventional continuous‐wave EPR. 3) 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 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. Three′s a charm: Reactive oxygen species can be detected by spin trapping. Previously high detection limits at the low frequencies required for in vivo EPR imaging are dramatically reduced by combining three enabling technologies: the spin‐trap BMPO, rapid‐scan EPR and a new image reconstruction algorithm, and demonstrated by a 2D spectral spatial image of 5 μM BMPO–OH.