Detection and characterization of hydroxyl radical adducts by mass spectrometry

Abstract

The study of the influence of free radicals in the biological process depends primarily on the capacity to detect these reactive species. In this work we have studied the application of mass spectrometry to the identification of hydroxyl radical species. The detection and identification by collisional activation mass-analyzed ion kinetic energy spectrometry (CA-MIKES) of a spin adduct of DMPO with the hydroxyl radical [(DMPO + O) + H]+ (m/z 130) has demonstrated that mass spectrometry can be a powerful tool in the detection and identification of spin adducts of DMPO with hydroxyl radical species. We were also able to detect the capture of secondary free radicals using ethanol by detecting and identifying the corresponding adduct [(DMPO + ethanol) + H]+. Other spin adducts have also been detected and identified. We consider that the use of mass spectrometry is a relevant technique for the detection of free hydroxyl radicals, especially in complex mixtures, since mass spectrometry is able to discriminate these adducts in such situations. Moreover, using this approach, it was possible to identify new spin adducts.

Identification of oxidation products and free radicals of tryptophan by mass spectrometry

“…The elimination of two hydrogen radicals from the DMPO moieties leads to the formation of an intramolecular seven membered ring, which suggests that DMPO molecules are present in this structure in positions in the vicinity. The intramolecular seven-membered ring is a structure which is similar to previously proposed adducts formed between two and three DMPO with radical hydroxyl [15]. …”

“…Radicals are very unstable species, but in the presence of spin traps they form a stable adduct with the trap. Previous work has shown that mass spectrometry is a good method to detect the stable adducts of DMPO with hydroxyl radicals [15]. Following the same methodology, new adducts of DMPO and radical species resulting from tryptophan oxidation under Fenton reaction conditions were detected and identified by mass spectrometry.…”

“…The structural information given by this technique is limited, so there is a need for new techniques that provide more information about the origin and location of radical. Recently, it has been shown that mass spectrometry is a suitable technique to detect the stable adducts formed by radicals and spin adducts of DMPO [13][14][15], POBN [16,17], and other [18 -20] spin traps. NMR has also been used in determining the sites of reaction of the hydroxyl radical and in identifying the oxidation products [21,22].…”

Characterization of Free Radical Spin Adducts of 5-Diisopropyloxy-Phosphoryl-5-Methyl-1-Pyrroline-N-Oxide Using Mass Spectrometry and 31P Nuclear Magnetic Resonance

“…Mass spectrometry (MS) has been shown to be a suitable tool to identify and verify spin adducts. these techniques were applied to the characterization of radical adducts of the nitrones benzylidene(tert-butyl)azane oxide (PBN) 15,16 , 4-{[tertbutyl(oxido)imino]-methyl} pyridine 1-oxide (PoBN), [17][18][19][20] 2,2 dimethyl-3,4-dihydropyrroline N-oxide (DMPo), [21][22][23][24][25][26][27] N-arylc,c-dimethoxycarbonylnitrones 28 and (2-methyl-1-oxido-3,4-dihydro-2H-pyrrol-2-yl) phosphonate (DEPMPo). 29 the mass spectrometric analyses were performed on the isolated radical spin adducts using high-performance liquid chromatography (HPLc) or with on-line chromatographic system such as HPLc or Gc.…”

“…[15][16][17][18][19][20][21] recently, the structural determination of free radical spin adducts from a complex mixture has been reported without any preliminary separation. [22][23][24][25][26][27][28][29] Each method presents different advantages and disadvantages. Isolation with chromatographic systems is a long procedure and does not permit the analysis of the initial paramagnetic spin adducts.…”