Vv. Khramtsov et al., NMR spin trapping: Detection of free radical reactions with a new fluorinated DMPO analog, FREE RAD B, 30(10), 2001, pp. 1099-1107
Electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spin tra
pping were used for detection of free radical reactions utilizing a new flu
orinated analog of DMPO, 4-hydroxy-5,5-dimethyl-2-trifluoromethylpyrroline-
1-oxide (FDMPO). The parent FDMPO spin trap exhibits a single F-19-NMR reso
nance at -66.0 ppm. The signal to noise ratio improved 10.4-fold compared t
o P-31-NMR sensitivity of the phosphorus-containing spin trap, DEPMPO. The
spin adducts of FDMPO with (OH)-O-., (CH3)-C-., and (CH2OH)-C-. were charac
terized. Competitive spin trapping of FDMPO with DMPO showed that both have
similar rates of addition of (OH)-O-. and C-centered radicals. The corresp
onding paramagnetic spin adducts of FDMPO were extremely stable to degradat
ion. In the presence of ascorbate, reaction products from C-centered radica
ls resulted in the appearance of two additional F-19-NMR signals at -78.6 a
nd -80 ppm for FDMPO/(CH3)-C-. and at -74.6 and -76.75 ppm for FDMPO/(CH2OH
)-C-.. In each case, these peaks were assigned to the two stereoisomers of
their respective, reduced hydroxylamines. The identification of the hydroxy
lamines for FDMPO/(CH3)-C-. was confirmed by EPR and F-19-NMR spectra of in
dependently synthesized samples. In summary, spin adducts of FDMPO were hig
hly stable for ESR. For NMR spin trapping, FDMPO showed improved signal to
noise and similar spin trapping efficiency compared to DEPMPO. (C) 2001 Els
evier Science Inc.