Synthesis and reaction of <i>ortho</i>-fluoronitroaryl nitroxides. Novel versatile synthons and reagents for spin-labelling studies

Hankovszky, H. O.; Hideg, Kálmán; Lovas, M. J.; Jerkovich, Gyula; Rockenbauer, Antal; Győr, M.; Sohar, P.

doi:10.1139/v89-214

Cited by 17 publications

(14 citation statements)

References 16 publications

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“…The synthesis and voltage dependence of TNP-based probes has not been described previously. However, spin-labels based on dinitrophenol have been synthesized (46,47). To our knowledge, the voltage-dependence of these derivatives has not been characterized, and they also could be useful probes of membrane potential.…”

Section: 97±02xl0-3s-'mentioning

confidence: 99%

Probes of membrane electrostatics: synthesis and voltage-dependent partitioning of negative hydrophobic ion spin labels in lipid vesicles

Franklin

Cafiso

Flewelling

et al. 1993

Biophysical Journal

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Two spin-labeled derivatives of the hydrophobic anion trinitrophenol have been synthesized and characterized in lipid vesicles. In the presence of lipid vesicles, the electron paramagnetic resonance (EPR) spectra of these probes are a composite of both membrane-bound and aqueous populations; as a result, the membrane-aqueous partitioning can be determined from their electron paramagnetic resonance spectra. The effect of transmembrane potentials on the membrane-aqueous partitioning of these spin-labeled hydrophobic ions was examined in phosphatidylcholine vesicles formed by extrusion. Inside positive membrane potentials promote an increase in the binding of these probes that is quantitatively accounted for by a simple thermodynamic model used previously to describe the partitioning of paramagnetic phosphonium ions. The transmembrane migration rates of these ions are dependent on the dipole potential, indicating that these ions transit the membrane in a charged form. The partitioning of the probe is also sensitive to the membrane surface potential, and this dependence is accurately accounted for using the Gouy-Chapman Stern formalism. As a result of the membrane dipole potential, these probes exhibit a stronger binding and a more rapid transmembrane migration rate compared with positive hydrophobic ion spin labels and provide a new set of negatively charged hydrophobic ion probes to investigate membrane electrostatics.

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Section: 97±02xl0-3s-'mentioning

confidence: 99%

Probes of membrane electrostatics: synthesis and voltage-dependent partitioning of negative hydrophobic ion spin labels in lipid vesicles

Franklin

Cafiso

Flewelling

et al. 1993

Biophysical Journal

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“…The optimal geometry of the compounds was approximated by 9 (2R,6S )-2,6-Dimethyl-2,6-diphenylpiperidin-1-yloxy [14] 10 (2R,6R )-2,6-Dimethyl-2,6-diphenylpiperidin-1-yloxy [20] 11 cis-2,5-Bis(4-hydroxy-3-nitrophenyl)-2,5dimethylpyrrolidin-1-yloxy [14] 12 trans-2,5-Bis(4-hydroxy-3-nitrophenyl)-2,5-dimethylpyrrolidin-1-yloxy 124190-06-3 [19] 13 2,2,6,6-Tetramethyl-piperidin-1-yloxy ( TEMPO ) 2564-83-2 semi-empirical calculations on the AM1 level. The optimal geometry of the compounds was approximated by 9 (2R,6S )-2,6-Dimethyl-2,6-diphenylpiperidin-1-yloxy [14] 10 (2R,6R )-2,6-Dimethyl-2,6-diphenylpiperidin-1-yloxy [20] 11 cis-2,5-Bis(4-hydroxy-3-nitrophenyl)-2,5dimethylpyrrolidin-1-yloxy [14] 12 trans-2,5-Bis(4-hydroxy-3-nitrophenyl)-2,5-dimethylpyrrolidin-1-yloxy 124190-06-3 [19] 13 2,2,6,6-Tetramethyl-piperidin-1-yloxy ( TEMPO ) 2564-83-2 semi-empirical calculations on the AM1 level.…”

mentioning

confidence: 99%

“…4-Azido-2,2,6,6-tetramethylpiperidin-1-yloxy[14] 3 Bis[4-(tert-butyl)phenyl]nitroxide 3454900-3[15] 4 cis-3-Benzoyl-2,2,5,5-tetramethyl-4phenylpyrrolidin-1-yloxy 119580-56-2[16] 5 4-Iodo-2,2,6,6-tetramethylpiperidin-1-yloxy[14] 6 4-Bromo-2,2,6,6-tetramethylpiperidin-1-yloxy 3225-25-0[17] 7 4-(2,5-Dihydro-2,5-dioxo-1H-pyrrol-1-yl)-2,2,6,6-tetramethylpiperidin-1-yloxy 15178-63-9[18] 8 2-(4-Fluoro-3-nitrophenyl)-2,5,5trimethylpyrrolidin-1-yloxy 124189-86-2[19] …”

mentioning

confidence: 99%

Quenching of Porphyrin Triplet and Singlet Oxygen by Stable Nitroxide Radicals: Importance of Steric Hindrance

Vidóczy¹,

Baranyai²

2001

HCA

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Dedicated to Professor AndreÂ M. Braun on the occasion of his 60th birthdayTo study the nature of quenching, we used stable nitroxide radicals (most of which contain piperidine or pyrrolidine rings) as quenchers of triplet hematoporphyrin as well as of singlet molecular oxygen. A characteristic feature of quenching triplet porphyrin is a near-diffusion-limited rate constant, whereas the rate constant for quenching singlet oxygen is about three orders of magnitude lower. Accessibility of the nitroxide moiety in radicals was characterized quantitatively based on semi-empirical calculations (at AM1 level), with the use of van der Waals radii of the species. While variation in the rate constant values for quenching triplet porphyrin can be fully explained by the steric hindrance of the neighbouring groups of the nitroxide radical, no such effect can be observed in quenching singlet oxygen.

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“…The nitroxides, 1-6, were synthesized by the reactions outlined as follows (16)(17)(18)(19)(20)(21) Nitroxides 1-4 were isolated from the respective reaction mixtures by silica gel column chromatography using ethyl acetate/benzene (1/3) as eluant.…”

Section: Methodsmentioning

confidence: 99%

Styrene Polymerization Mediated by Five-Membered Cyclic Nitroxides

Yamada¹,

Miura²,

Nobukane³

et al. 1998

ACS Symposium Series

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To evaluate the structural effect of nitroxides on the living free radical polymerization of styrene, substituted pyrrolidinyloxyls and an oxazolidinyloxyl were synthesized and employed as mediators at 110 °C.All the cyclic nitroxides, except oxazolidinyloxyl were found to control different extents the molecular weight (M n ) and polydispersity (M w /M n ) of the polystyrene samples obtained. Among the nitroxides synthesized, 2,2,3,3,5-pentamethyl-5-phenylpyrrolidinyloxyl and 2,3,3,5-tetramethyl-2,5-diphenylpyrrolidinyloxyl, are of particular interest because polystyrene samples with M n > 100000 and M w /M n < 1.5 were obtained whereas 2,2,6,6-tetramethylpiperidinyloxyl yielded polymers with considerably lower M n and slightly lower M w /M n under similar conditions. The polymerization in the presence of oxazolidinyloxyl radical was found to proceed almost without any influence of the nitroxide.The living free radical polymerization (LFRP) of styrene (St) mediated by 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) has drawn much attention, because LFRP enables to control molecular weight and molecular weight distribution of the polymer by preservation of the activity of propagating radical through the reversible deactivation by TEMPO (7-7). Indeed, the propagating species rapidly reacts with TEMPO to form an alkoxyamine as dormant species that can regenerate the propagating radical and TEMPO upon thermally activated dissociation. The formation of the reversible bond from the propagating radical and TEMPO reduces the steady state concentration of the active radicals and leads to the diminution of the probability of uncontrolled bimolecular termination. Overview of TEMPO Mediated PolymerizationRecently, it has been revealed that thermal initiation of St, bimolecular termination, chain transfer to the reactive dimer produced by thermal initiation of St, and degradation of the alkoxyamine into an unsaturated group at polymer chain end and a hydroxyamine occur concurrently in the LFRP system (5-8).Furthermore, the 'Corresponding author 200

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Synthesis and reaction of ortho-fluoronitroaryl nitroxides. Novel versatile synthons and reagents for spin-labelling studies

Cited by 17 publications

References 16 publications

Probes of membrane electrostatics: synthesis and voltage-dependent partitioning of negative hydrophobic ion spin labels in lipid vesicles

Probes of membrane electrostatics: synthesis and voltage-dependent partitioning of negative hydrophobic ion spin labels in lipid vesicles

Quenching of Porphyrin Triplet and Singlet Oxygen by Stable Nitroxide Radicals: Importance of Steric Hindrance

Styrene Polymerization Mediated by Five-Membered Cyclic Nitroxides

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