Intramolecular Quenching of Excited Singlet States in a Series of Fluorescamine- Derivatized Nitroxides

Herbelin, Sarah E.; Blough, Neil V.

doi:10.1021/jp980977e

Cited by 75 publications

(66 citation statements)

References 22 publications

(81 reference statements)

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“…[1][2][3] Intermolecular quenching may occur through chance collisions between an excited molecule and a nitroxide radical. A tether between the fluorophore and the radical moiety increases encounters between the fluorophore and the radical, which increases the efficacy of fluorescence quenching.…”

Section: Introductionmentioning

confidence: 99%

The First Example of an Azaphenalene Profluorescent Nitroxide

Blinco¹,

McMurtrie²,

Bottle³

2007

Eur J Org Chem

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The synthesis of the first example of an azaphenalene‐based fused aromatic nitroxide TMAO, [1,1,3,3‐tetramethyl‐2,3‐dihydro‐2‐azaphenalen‐2‐yloxyl, (5)], is described. This novel nitroxide possesses some of the structural rigidity of the isoindoline class of nitroxides, as well as some properties akin to TEMPO nitroxides. Additionally, the integral aromatic ring imparts fluorescence that is switched on by radical scavenging reactions of the nitroxide, which makes it a sensitive probe for polymer degradation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Section: Introductionmentioning

confidence: 99%

The First Example of an Azaphenalene Profluorescent Nitroxide

Blinco¹,

McMurtrie²,

Bottle³

2007

Eur J Org Chem

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“…Ac-Tempo does not exert fluorescence from the acridine moiety (Fig. 1B) due to the quenching produced by electron exchange interactions between the Tempo radical and the excited state of acridine (18). The fluorescence quenching of Ac-Tempo can be eliminated upon conversion of the nitroxide moiety into a non-paramagnetic species, e.g.…”

Section: Biochemical Evidence For Selective Interactions Of Ac-tempo mentioning

confidence: 99%

“…Ac-Tempo contains two chemical moieties conjugated by a peptide bond, namely fluorescent acridine and a stable paramagnetic nitroxide radical called Tempo, and, similar to Sphinx, it inherits duality of their physical properties. The nitroxide radical, however, quenches the fluorescence of acridine through an intramolecular intersystem crossing induced by electron exchange (18). We established that the reaction of GS ⅐ radicals with the nitroxide moiety of Ac-Tempo converts it to the corresponding piperidine, which therefore eliminates the quenching to yield a readily measurable fluorescence from acridine moiety and the disappearance of a typical EPR signal from the nitroxide radical.…”

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confidence: 92%

Glutathione Propagates Oxidative Stress Triggered by Myeloperoxidase in HL-60 Cells

Borisenko

Martin

Zhao

et al. 2004

Journal of Biological Chemistry

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Glutathione acts as a universal scavenger of free radicals at the expense of the formation of the glutathionyl radicals (GS ⅐ ). Here we demonstrated that GS ⅐ radicals specifically interact with a reporter molecule, paramagnetic and non-fluorescent 4-((9-acridinecarbonyl)-amino)-2,2,6,6-tetramethylpiperidine-1-oxyl (Ac-Tempo), and convert it into a non-paramagnetic fluorescent product, identified as 4-((9-acridinecarbonyl)amino)-2,2,6,6-tetramethylpiperidine (Ac-piperidine). Horseradish peroxidase-, myeloperoxidase-, and cyclooxygenasecatalyzed oxidation of phenol in the presence of H 2 O 2 and GSH caused the generation of phenoxyl radicals and GS ⅐ radicals, of which only the latter reacted with Ac-Tempo. Oxidation of several other phenolic compounds (e.g. etoposide and tyrosine) was accompanied by the formation of GS ⅐ radicals along with a characteristic fluorescence response from Ac-Tempo. In myeloperoxidase-rich HL-60 cells treated with H 2 O 2 and phenol, fluorescence microscopic imaging of Ac-Tempo revealed the production of GS ⅐ radicals. A thiol-blocking reagent, N-ethylmaleimide, as well as myeloperoxidase inhibitors (succinyl acetone and azide), blocked formation of fluorescent acridine-piperidine. H 2 O 2 /phenolinduced peroxidation of major classes of phospholipids in HL-60 cells was completely inhibited by Ac-Tempo, indicating that GS ⅐ radicals were responsible for phospholipid peroxidation. Thus, GSH, commonly viewed as a universal free radical scavenger and major intracellular antioxidant, acts as a pro-oxidant during myeloperoxidase-catalyzed metabolism of phenol in HL-60 cells.Thiols are said to fulfill important antioxidant functions in cells and biological fluids. In particular, glutathione, the most abundant intracellular low molecular weight thiol, regulates the content of H 2 O 2 and organic (lipid) hydroperoxides via glutathione peroxidase-catalyzed reactions. GSH is also commonly presumed to act as a universal free radical sink toward a wide variety of different types of free radicals (1-5). Although scavenging of reactive radicals by GSH is believed to be an important antioxidant function of the latter, it may render effective protection only if the sulfur-centered glutathionyl radicals (GS ⅐ ) 1 formed in the scavenging reactions do not further propagate free radical generation. On the contrary, pro-oxidant activity of GSH should be expected if GS ⅐ radicals are reactive enough to interact with and cause damage to vital intracellular molecules.In fact, experiments in model systems indicate that GS ⅐ radicals can abstract hydrogen atoms from carbohydrates such as 2-deoxy-D-ribose and initiate irreversible DNA damage (6). Thiyl radicals are also capable of hydrogen abstraction from ␣-amino C-H bonds of amino acids with the consequent formation of carbon-centered radicals (7). However, reactions of thiyl radicals with carbohydrates and amino acids are reversible; moreover, carbon-centered radicals of carbohydrates and amino acids are stronger oxidants than thiyl radicals, suggesting tha...

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“…Blough and co-workers have shown that these covalently-linked nitroxidefluorophore adducts can be employed as very sensitive optical sensors of radical/redox reactions (8)(9)(10)(11). Scaiano and co-workers have also developed a number of prefluorescent probes allowing radical and/or antioxidant detection in homogeneous and heterogeneous systems (12)(13)(14).…”

Section: Introductionmentioning

confidence: 99%

Study on the interaction between nitroxide free radical and conjugated polyelectrolytes by fluorimetry

Dou

2008

Luminescence

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In this work, we studied the fluorescence quenching of the anionic conjugated polyelectrolyte PPE-SO 3 by the paramagnetic species 2,2,6,6-tetramethylpiperidine-N-oxide free radical (TEMPO) in aqueous solution. At low quencher concentration the Stern-Volmer constant is 94 mol/L; as the quencher concentration increases the Stern-Volmer plots become superlinear. Ascorbic acid is used to reduce TEMPO to the corresponding hydroxylamine and the PPE-SO 3 fluorescence is fully recovered. Under a large excess of ascorbic acid over TEMPO, the rise of fluorescence followed pseudo-first-order kinetics. IntroductionConjugated polyelectrolytes (CPEs) are π-conjugated polymers that feature ionic solubilizing side groups (1). These materials show many of the interesting and useful properties exhibited by π-conjugated polymers, such as high fluorescence quantum yields, unique solution behaviour, the ability to interact electrostatically with other charged species, and an extraordinarily high sensitivity to fluorescence quenchers (2). This latter property has been exploited in sensing experiments, in which a variety of organic and inorganic analytes and biomolecules can be detected at picomolar concentration levels (3-6).Nitroxides are persistent free radicals frequently used as radical scavengers or as quenchers of excited states (7). Blough and co-workers have shown that these covalently-linked nitroxidefluorophore adducts can be employed as very sensitive optical sensors of radical/redox reactions (8-11). Scaiano and co-workers have also developed a number of prefluorescent probes allowing radical and/or antioxidant detection in homogeneous and heterogeneous systems (12)(13)(14).However, there is no report of studies on the interaction between nitroxides radicals and conjugated polyelectrolytes until now and the mechanism is also not clear. In an effort to construct highly sensitive optical probes of radical/redox species, we sought to exploit both the radical trapping and fluorescence quenching properties of the nitroxides by constructing a system that contains nitroxides and conjugated polyelectrolytes.In this work, we studied the fluorescence quenching of the sulphonate-substituted poly(phenylene ethynylene) PPE-SO 3 by the paramagnetic species 2,2,6,6-tetramethylpiperidine-N-oxide free radical (TEMPO) in aqueous solution (structures in Fig. 1). PPE-SO 3 is a water-and alcohol-soluble polymer that exhibits a strong blue or green fluorescence (15, 16). The possible mechanism of fluorescence quenching was studied. Additionally, chemical reduction of the TEMPO to a diamagnetic hydroxylamine can lead a fluorescence recovery of PPE-SO 3 . ExperimentalChemicals PPE-SO 3 was synthesized according to a previously described method (16), and the structure (Fig. 1)

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Intramolecular Quenching of Excited Singlet States in a Series of Fluorescamine- Derivatized Nitroxides

Cited by 75 publications

References 22 publications

The First Example of an Azaphenalene Profluorescent Nitroxide

The First Example of an Azaphenalene Profluorescent Nitroxide

Glutathione Propagates Oxidative Stress Triggered by Myeloperoxidase in HL-60 Cells

Study on the interaction between nitroxide free radical and conjugated polyelectrolytes by fluorimetry

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