DEPMPO: an efficient tool for the coupled ESR-spin trapping of alkylperoxyl radicals in water

Abstract

Peroxidation is an important process both in chemistry and biology, and peroxyl radicals play a crucial role in various pathological situations involving lipid and protein peroxidation. A few secondary and tertiary peroxyl radicals can be detected directly by Electron Spin Resonance (ESR). However, primary and secondary alkylperoxyl radicals have extremely short lifetimes and their direct observation is impossible in biological samples. DMPO has been used to trap alkylperoxyl radicals generated in biological systems and the characterization of DMPO-alkylperoxyl spin adducts has been claimed by different authors. However, it was then clearly shown that all the assignments made previously to DMPO-OOR adducts were actually due to DMPO-OR adducts. We have investigated the potential of DEPMPO to characterize the formation of alkylperoxyl radicals in biological milieu. Various DEPMPO-OOR (R = Me, primary or secondary alkyl group) spin adducts were unambiguously characterized and the formation of DEPMPO-OOCH(3) was clearly established during the reaction of tert-butylhydroperoxide with chloroperoxidase and cytochrome c.

ESR study of the spin adducts of three analogues of DEPMPO substituted at C4or C3

“…T 3 equilibrium. This steric effect can explain an average geometry close to 3 T 4 for the 2R,4S,5R-adduct and close to 4 T 3 for the other enantiomer. In the rest of the text, for the signals obtained with 7t, 6 and 8 nitrones, we report the solutions of simulation with the highest regression coefficients.…”

“…Synthesis of ethyl 2-cyano-4-diethoxypentanoate 2 is described, 11 but we obtained 2 via the quantitative transacetalisation of ethyl 2-cyano-4-oxopentanoate 1, which was synthesized from chloroacetone and ethyl cyanoethanoate. 12 The yield (36% not optimized) of the reduction step of the cyano and ester functions of 2 using LiAlH 4 was lowered by formation of by-products such as some conjugated oxoenamines. The amino function of 2-aminomethyl-4-diethoxypentan-1-ol 3 was let to react with the carbonyl function delivered by HCl to afford the expected 4-hydroxymethyl-1-methyl-2-pyrroline 4.…”

“…9 As it was demonstrated by Pople and Cremer, 15 the intrinsic flexibility of the 5-membered nitroxide ring can be characterized by the amplitude and phase of the ring deformation. Because of the dihedral rules followed by the -coupling of the electron of the nitroxide, (see table 2 calculated for DEPMPO-OOH 16 ) the major set, in this first simulation solution of the 7c-OOH t signal, has the A p and A H values characteristic for pseudo-axial phosphoryl group and pseudo-equatorial H of a twist envelope ( 3 T 4 for 2R,4S,5R-nitroxyde or 4 T 3 for 2S,4R,5R-nitroxyde). Therefore the OOH group is also pseudo-axial and the hydromethyl group is equatorial.…”

Sterilization of bacteria suspensions and identification of radicals deposited during plasma treatment

“…DEPMPO is the most efficient spin trap for the detection of various short lived free radicals, which could be generated in the same system [16]. The DEPMPO free radical adducts give rise to characteristic EPR spectra as shown in [17]. The Fe(II) (DTCS) 2 complex traps nitric oxide radicals (NO•) and forms the ferrous nitrosyl complex Fe(NO)(DTCS) 2 which gives a characteristic three line EPR spectrum [18].…”

Aerobic one-step oxidation of benzene to phenol on copper exchanged HZSM5 zeolites: A mechanistic study

“…(4) a superoxide anion can react with a benzene radical cation from the benzene adsorption to form a phenyl peroxy radical. Furthermore, two PhOO • radicals can dimerize and via elimination of dioxygen two PhO • radicals can be formed [15,16]:…”