DNP-enhanced solid-state NMR spectroscopy is shown to maintain performance over a wide range of s... more DNP-enhanced solid-state NMR spectroscopy is shown to maintain performance over a wide range of sample spinning rates up to 40 kHz.
A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) ar... more A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) are investigated as exogenous polarization sources for dynamic nuclear polarization (DNP) solid-state NMR at 9.4 T and with ca. 100 K sample temperatures. The impact of electron relaxation times on the DNP enhancement (ε) is examined, and we observe that longer inversion recovery and phase memory relaxation times provide larger ε. All radicals are tested in both bulk 1,1,2,2-tetrachloroethane solutions and in mesoporous materials, and the difference in ε between the two cases is discussed. The impact of the sample temperature and magic angle spinning frequency on ε is investigated for several radicals each characterized by a range of electron relaxation times. In particular, TEKPol, a bulky derivative of bTbK with a molecular weight of 905 g•mol -1 , is presented. Its high-saturation factor makes it a very efficient polarizing agent for DNP, yielding unprecedented proton enhancements of over 200 in both bulk and materials samples at 9.4 T and 100 K. TEKPol also yields encouraging enhancements of 33 at 180 K and 12 at 200 K, suggesting that with the continued improvement of radicals large ε may be obtained at higher temperatures.
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
The dinitroxide bis(TEMPO) bisketal (bTbk) was shown to crystallize into open frameworks whose st... more The dinitroxide bis(TEMPO) bisketal (bTbk) was shown to crystallize into open frameworks whose structures were determined by single-crystal X-ray diffraction. We show that bTbk can be used as a supramolecular building block for the hosting of a plethora of guests inside the 1D channels of its paramagnetic framework, including other radicals such as TEMPO or 2-azaadamantane-N-oxyl. C 60 and C 70 were also found to be easily included in this open framework during its crystallization. This resulted in welldefined, nanostructured assemblies of composite radical crystals (bTbk/toluene/C 60 or C 70 )o r( bTbk/toluene/TEMPO) by a very simple dissolution/crystallization process with tunable guest content. Selective C 60 extraction was also demonstrated directly from fullerene soot.
Scheme 1. The reduction of TEMPOL by sodium ascorbate, leading to the formation of a delocalized ... more Scheme 1. The reduction of TEMPOL by sodium ascorbate, leading to the formation of a delocalized sodium ascorbyl radical and diamagnetic TEMPOL-H.
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Using a novel phosphorylated spin trap, 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO... more Using a novel phosphorylated spin trap, 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), an analog of the commonly used trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), we have investigated the reactions of sulfur-centered radicals produced from the oxidation of thiols and sulfite by peroxynitrite. The predominant species trapped in all cases are the corresponding sulfur-centered radicals, i.e. glutathionyl radical (GS ⅐ ) from glutathione (GSH), N-acetyl-DL-penicillamine thiyl radical ( ⅐ S-NAP) from N-acetyl-DL-penicillamine (NAP) and sulfite anion radical (SO 3 . ) from sulfite. These radicals consume molecular oxygen forming either peroxyl or superoxide anion radicals. GS ⅐ , ⅐ S-NAP, and SO 3 . -derived radicals react with ammonium formate to form the carbon dioxide anion radical (CO 2 . ). Further support of spin adduct assignments and radical reactions are obtained from photolysis of S-nitrosoglutathione and S-nitroso-Nacetyl-DL-penicillamine. We conclude that the direct reaction of peroxynitrite with thiols and sulfite forms thiyl and sulfite anion radicals, respectively, by a hydroxyl radical-independent mechanism. Pathological implications of thiyl radical formation and subsequent oxyradical-mediated chain reactions are discussed. Oxygen activation by thiyl radicals formed during peroxynitrite-mediated oxidation of glutathione may limit the effectiveness of GSH against peroxynitrite-mediated toxicity in cellular systems.
We describe the synthesis and biological applications of a novel nitrogen‐15‐labeled nitrone spin... more We describe the synthesis and biological applications of a novel nitrogen‐15‐labeled nitrone spin trap, 5‐ethoxycarbonyl‐5‐methyl‐1‐pyrroline N‐oxide ([15N]EMPO) for detecting superoxide anion. Superoxide anion generated in xanthine/xanthine oxidase (100 nM min−1) and NADPH/calcium‐calmodulin/nitric oxide synthase systems was readily detected using EMPO, a nitrone analog of 5,5′‐dimethyl‐1‐pyrroline N‐oxide (DMPO). Unlike DMPO‐superoxide adduct (DMPO–OOH), the superoxide adduct of EMPO (EMPO–OOH) does not spontaneously decay to the corresponding hydroxyl adduct, making spectral interpretation less confounding. Although the superoxide adduct of 5‐(diethoxyphosphoryl)‐5‐methyl‐pyrroline N‐oxide is more persistent than EMPO–OOH, the electron spin resonance spectra of [14N]EMPO–OOH and [15N]EMPO–OOH are less complex and easier to interpret. Potential uses of [15N]EMPO in elucidating the mechanism of superoxide formation from nitric oxide synthases, and in ischemia/reperfusion injury are...
Thermolysis of alpha-alkoxyamino propionanilides produces indolinones, whereas thermal reaction o... more Thermolysis of alpha-alkoxyamino propionanilides produces indolinones, whereas thermal reaction of N-allylaniline derivatives with various Tordo-type alkoxyamines results in formation of indolines in the radical regime. [reaction: see text]
G. Olive et al."2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide": Evaluation o... more G. Olive et al."2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide": Evaluation of the spin trapping properties. p1 2-ETHOXYCARBONYL-2-METHYL-3,4-DIHYDRO-2H-PYRROLE-1-OXIDE: EVALUATION OF THE SPIN TRAPPING PROPERTIES. Abstract: The 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide (EMPO), an easily prepared pyrroline-N-oxide has been tested as free radical scavenger. Spin adducts of superoxide, hydroxyl radical and other free radicals were characterized in phosphate buffer at pH 7.0 and 5.6. At pH 7 in phosphate buffer, the EMPO/O2 spin adduct was estimated to be about 5 times more persistent than its DMPO analogue. Furthermore, its decay does not produce the EMPO / HO • adduct.
Spin trapping with cyclic nitrones coupled to electron spin resonance (ESR) is recognized as a sp... more Spin trapping with cyclic nitrones coupled to electron spin resonance (ESR) is recognized as a specific method of detection of oxygen free radicals in biological systems, especially in culture cells. In this case, the detection is usually performed on cell suspensions, which is however unsuitable when adhesion influences free radical production. Here, we performed ESR detection of superoxide with four spin traps (5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide, DEPMPO; 5-diisopropoxyphosphoryl-5-methyl-1-pyrroline N-oxide, DIPPMPO; (4R*, 5R*)-5-(diisopropyloxyphosphoryl)-5-methyl-4-[({[2-(triphenylphosphonio)ethyl]carbamoyl}oxy)methyl]pyrroline N-oxide bromide, Mito-DIPPMPO; and 6-monodeoxy-6-mono-4-[(5-diisopropoxyphosphoryl-5-methyl-1-pyrroline-N-oxide)-ethylenecarbamoyl-(2,3-di-O-methyl) hexakis (2,3,6-tri-O-methyl)]-β-cyclodextrin, CD-DIPPMPO) directly on RAW 264.7 macrophages cultured on microscope coverslip glasses after phorbol 12-myristate 13-acetate (PMA) stimulation. Dis...
Physical chemistry chemical physics : PCCP, Jan 7, 2014
Grafting reactive molecular complexes on dehydroxylated amorphous silica is a strategy to develop... more Grafting reactive molecular complexes on dehydroxylated amorphous silica is a strategy to develop "single-site" heterogeneous catalysts. In general, only the reactivity of isolated silanols is invoked for silica dehydroxylated at 700 °C ([SiO(2-700)]), though ca. 10% of the surface silanols are in fact geminal Q2-silanols. Here we report the reaction of allyltributylstannane with [SiO(2-700)] and find that the geminal Q2-silanols react to form products that would formally arise from vicinal Q3-silanols that are not present on [SiO(2-700)], indicating that a surface rearrangement occurs. The reorganization of the silica surface is unique to silica dehydroxylated at 700 °C or above. The findings were identified using Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) combined with DFT calculations.
DNP-enhanced solid-state NMR spectroscopy is shown to maintain performance over a wide range of s... more DNP-enhanced solid-state NMR spectroscopy is shown to maintain performance over a wide range of sample spinning rates up to 40 kHz.
A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) ar... more A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) are investigated as exogenous polarization sources for dynamic nuclear polarization (DNP) solid-state NMR at 9.4 T and with ca. 100 K sample temperatures. The impact of electron relaxation times on the DNP enhancement (ε) is examined, and we observe that longer inversion recovery and phase memory relaxation times provide larger ε. All radicals are tested in both bulk 1,1,2,2-tetrachloroethane solutions and in mesoporous materials, and the difference in ε between the two cases is discussed. The impact of the sample temperature and magic angle spinning frequency on ε is investigated for several radicals each characterized by a range of electron relaxation times. In particular, TEKPol, a bulky derivative of bTbK with a molecular weight of 905 g•mol -1 , is presented. Its high-saturation factor makes it a very efficient polarizing agent for DNP, yielding unprecedented proton enhancements of over 200 in both bulk and materials samples at 9.4 T and 100 K. TEKPol also yields encouraging enhancements of 33 at 180 K and 12 at 200 K, suggesting that with the continued improvement of radicals large ε may be obtained at higher temperatures.
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
The dinitroxide bis(TEMPO) bisketal (bTbk) was shown to crystallize into open frameworks whose st... more The dinitroxide bis(TEMPO) bisketal (bTbk) was shown to crystallize into open frameworks whose structures were determined by single-crystal X-ray diffraction. We show that bTbk can be used as a supramolecular building block for the hosting of a plethora of guests inside the 1D channels of its paramagnetic framework, including other radicals such as TEMPO or 2-azaadamantane-N-oxyl. C 60 and C 70 were also found to be easily included in this open framework during its crystallization. This resulted in welldefined, nanostructured assemblies of composite radical crystals (bTbk/toluene/C 60 or C 70 )o r( bTbk/toluene/TEMPO) by a very simple dissolution/crystallization process with tunable guest content. Selective C 60 extraction was also demonstrated directly from fullerene soot.
Scheme 1. The reduction of TEMPOL by sodium ascorbate, leading to the formation of a delocalized ... more Scheme 1. The reduction of TEMPOL by sodium ascorbate, leading to the formation of a delocalized sodium ascorbyl radical and diamagnetic TEMPOL-H.
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Using a novel phosphorylated spin trap, 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO... more Using a novel phosphorylated spin trap, 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), an analog of the commonly used trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), we have investigated the reactions of sulfur-centered radicals produced from the oxidation of thiols and sulfite by peroxynitrite. The predominant species trapped in all cases are the corresponding sulfur-centered radicals, i.e. glutathionyl radical (GS ⅐ ) from glutathione (GSH), N-acetyl-DL-penicillamine thiyl radical ( ⅐ S-NAP) from N-acetyl-DL-penicillamine (NAP) and sulfite anion radical (SO 3 . ) from sulfite. These radicals consume molecular oxygen forming either peroxyl or superoxide anion radicals. GS ⅐ , ⅐ S-NAP, and SO 3 . -derived radicals react with ammonium formate to form the carbon dioxide anion radical (CO 2 . ). Further support of spin adduct assignments and radical reactions are obtained from photolysis of S-nitrosoglutathione and S-nitroso-Nacetyl-DL-penicillamine. We conclude that the direct reaction of peroxynitrite with thiols and sulfite forms thiyl and sulfite anion radicals, respectively, by a hydroxyl radical-independent mechanism. Pathological implications of thiyl radical formation and subsequent oxyradical-mediated chain reactions are discussed. Oxygen activation by thiyl radicals formed during peroxynitrite-mediated oxidation of glutathione may limit the effectiveness of GSH against peroxynitrite-mediated toxicity in cellular systems.
We describe the synthesis and biological applications of a novel nitrogen‐15‐labeled nitrone spin... more We describe the synthesis and biological applications of a novel nitrogen‐15‐labeled nitrone spin trap, 5‐ethoxycarbonyl‐5‐methyl‐1‐pyrroline N‐oxide ([15N]EMPO) for detecting superoxide anion. Superoxide anion generated in xanthine/xanthine oxidase (100 nM min−1) and NADPH/calcium‐calmodulin/nitric oxide synthase systems was readily detected using EMPO, a nitrone analog of 5,5′‐dimethyl‐1‐pyrroline N‐oxide (DMPO). Unlike DMPO‐superoxide adduct (DMPO–OOH), the superoxide adduct of EMPO (EMPO–OOH) does not spontaneously decay to the corresponding hydroxyl adduct, making spectral interpretation less confounding. Although the superoxide adduct of 5‐(diethoxyphosphoryl)‐5‐methyl‐pyrroline N‐oxide is more persistent than EMPO–OOH, the electron spin resonance spectra of [14N]EMPO–OOH and [15N]EMPO–OOH are less complex and easier to interpret. Potential uses of [15N]EMPO in elucidating the mechanism of superoxide formation from nitric oxide synthases, and in ischemia/reperfusion injury are...
Thermolysis of alpha-alkoxyamino propionanilides produces indolinones, whereas thermal reaction o... more Thermolysis of alpha-alkoxyamino propionanilides produces indolinones, whereas thermal reaction of N-allylaniline derivatives with various Tordo-type alkoxyamines results in formation of indolines in the radical regime. [reaction: see text]
G. Olive et al."2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide": Evaluation o... more G. Olive et al."2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide": Evaluation of the spin trapping properties. p1 2-ETHOXYCARBONYL-2-METHYL-3,4-DIHYDRO-2H-PYRROLE-1-OXIDE: EVALUATION OF THE SPIN TRAPPING PROPERTIES. Abstract: The 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide (EMPO), an easily prepared pyrroline-N-oxide has been tested as free radical scavenger. Spin adducts of superoxide, hydroxyl radical and other free radicals were characterized in phosphate buffer at pH 7.0 and 5.6. At pH 7 in phosphate buffer, the EMPO/O2 spin adduct was estimated to be about 5 times more persistent than its DMPO analogue. Furthermore, its decay does not produce the EMPO / HO • adduct.
Spin trapping with cyclic nitrones coupled to electron spin resonance (ESR) is recognized as a sp... more Spin trapping with cyclic nitrones coupled to electron spin resonance (ESR) is recognized as a specific method of detection of oxygen free radicals in biological systems, especially in culture cells. In this case, the detection is usually performed on cell suspensions, which is however unsuitable when adhesion influences free radical production. Here, we performed ESR detection of superoxide with four spin traps (5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide, DEPMPO; 5-diisopropoxyphosphoryl-5-methyl-1-pyrroline N-oxide, DIPPMPO; (4R*, 5R*)-5-(diisopropyloxyphosphoryl)-5-methyl-4-[({[2-(triphenylphosphonio)ethyl]carbamoyl}oxy)methyl]pyrroline N-oxide bromide, Mito-DIPPMPO; and 6-monodeoxy-6-mono-4-[(5-diisopropoxyphosphoryl-5-methyl-1-pyrroline-N-oxide)-ethylenecarbamoyl-(2,3-di-O-methyl) hexakis (2,3,6-tri-O-methyl)]-β-cyclodextrin, CD-DIPPMPO) directly on RAW 264.7 macrophages cultured on microscope coverslip glasses after phorbol 12-myristate 13-acetate (PMA) stimulation. Dis...
Physical chemistry chemical physics : PCCP, Jan 7, 2014
Grafting reactive molecular complexes on dehydroxylated amorphous silica is a strategy to develop... more Grafting reactive molecular complexes on dehydroxylated amorphous silica is a strategy to develop "single-site" heterogeneous catalysts. In general, only the reactivity of isolated silanols is invoked for silica dehydroxylated at 700 °C ([SiO(2-700)]), though ca. 10% of the surface silanols are in fact geminal Q2-silanols. Here we report the reaction of allyltributylstannane with [SiO(2-700)] and find that the geminal Q2-silanols react to form products that would formally arise from vicinal Q3-silanols that are not present on [SiO(2-700)], indicating that a surface rearrangement occurs. The reorganization of the silica surface is unique to silica dehydroxylated at 700 °C or above. The findings were identified using Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) combined with DFT calculations.
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Papers by Paul Tordo