The use of 5,5-dimethylpyrroline-N-oxide ( DMPO ) as a veralso efficiently trapped, such as alkoxyl (5), alkylperoxyl satile spin trap was first published in this journal ( E. G. Janzen (6), hydroxyalkyl (7), alkyl (8), thiyl (9), and aryl (10). and J. I.-P. Liu, J. Magn. Reson. 9, 510 -512 ( 1973 ) . In this The rate constants for spin trapping are high (10) but the paper, the general use of an improved DMPO-type spin trap, lifetimes for DMPO spin adducts are sometimes low, denamely 5-methyl-5-phenylpyrroline-N-oxide ( MPPO ) , is propending on the structure of the group that was the radical. posed. MPPO is more stable than DMPO and has an excellent Also in biological systems, DMPO seems to almost exclushelf life. Commonly known artifacts of DMPO are not present sively concentrate in polar regions since this nitrone is very in MPPO. The EPR spectra of MPPO spin adducts have the water soluble and the partition coefficient for lipid phases same patterns as DMPO spin adducts which users have become is very small (0.1:1) (11). familiar with. The lifetimes of spin adducts are longer for MPPO
In order to improve on the shortcomings of DMPO, some than for DMPO and the rate constants of spin trapping are similar. An interesting additional feature is associated with the derivatives have been prepared and the spin-trapping chemdetection of two spin-adduct spectra in some cases. The major istry explored. Thus, 3,3,5,5-tetramethylpyrroline-N-oxide component is assigned to the trans addition product ( with re-(M 4 PO) was synthesized to increase the stability of the cyspect to the phenyl group ) in the case of carbon-centered radiclic nitrone and its spin adducts (12). The 3,3-diethyl-5,5cals. The minor component is assigned to the cis adduct. In the dimethylpyrroline-N-oxide (E 2 PO) and 5-alkyl-5-methylsuperoxide / peroxyl radical adduct, however, the reverse appyrroline-N-oxide (MRPO, where R ร
n-propyl, n-hexyl, pears to be the case. Only one EPR spectrum is detected in the and n-dodecyl) were prepared to make DMPO more lipohydroxyl radical adduct of MPPO. แญง 1996 Academic Press, Inc. phyllic (13, 14). Other derivatives of similar structure have also been reported (15)(16)(17)(18).
The nitronyl hydrogen in DMPO has been replaced