 Destruction of Stearic Acid Nitroxyl Radicals Mediated by Photoexcited Merocyanine 540 in Liposomal and Micellar SystemsHoebeke, Maryse  ; Seret, Alain ; Piette, Jacques et alin Biochemistry (1993), 32(10), 2730-2736 Fatty acid spin labels have been included into liposomes and micelles, in order to study the photochemical behavior of merocyanine 540 toward nitroxyl radicals situated at various depths in the bilayer or ... [more ▼] Fatty acid spin labels have been included into liposomes and micelles, in order to study the photochemical behavior of merocyanine 540 toward nitroxyl radicals situated at various depths in the bilayer or the surfactant layer. Visible illumination of the dye, either free in ethanol or bound to liposomes or micelles, leads to the reduction of the electron spin resonance signal of the label. The efficiency of the interaction between merocyanine 540 and spin labels depends on the depth at which the nitroxyl moiety is localized in the micelle or vesicle. Fluorescence measurements indicate that the first excited singlet state of merocyanine 540 is not directly implicated in the reaction mechanism. Flash photolysis experiments conducted in aqueous solutions of hexadecyltrimethylammonium bromide micelles show that the presence of nitroxyl radical decreases the rate constant of triplet decay in a concentration-dependent fashion. The corresponding quenching rate constant (kq) is determined for the different spin labels. The kq values and the reduction rates of ESR signal show the same dependence on the localization of the nitroxyl moiety in the micelles. [less ▲] Detailed reference viewed: 28 (1 ULg)Photophysical investigation of Rose Bengal in aqueous sodium taurocholate solutionsSeret, Alain ; in Journal of Photochemistry & Photobiology B : Biology (1993), 17(1), 47-56 The photophysics of rose bengal has been studied in aqueous sodium taurocholate solutions with or without 0.6 mol NaCl dm−3. The ground and first excited singlet states solubilize only in the aggregates ... [more ▼] The photophysics of rose bengal has been studied in aqueous sodium taurocholate solutions with or without 0.6 mol NaCl dm−3. The ground and first excited singlet states solubilize only in the aggregates formed by sodium taurocholate, whereas the first triplet state solubilizes both in the bulk phase and in the aggregates. A lower limit of the corresponding entry and exit rate constants ke and ks, respectively has been estimated: ke ≥ 5 X 106 dm3 mol−1 s−1 (2x107 dm3 mol−1 s−1 with 0.6 mol NaCl dm−3) and ks ≥ 105 s−1. The triplet state as well as the semioxidized radical react with the taurocholate anion. The former reaction leads to the formation of semireduced dye. The latter is responsible for the detection of only semioxidized radicals which move freely in the aqueous phase. The results are compared with those obtained previously in aqueous sodium dodecyl sulphate solutions and the possible biological implication is discussed. [less ▲] Detailed reference viewed: 19 (1 ULg)Merocyanine 540 (MC540) in cetyltrimethylammonium bromide: a flash photolysis and an electron spin resonance studyHoebeke, Maryse ; Seret, Alain ; Piette, Jacques et alPoster (1992, September) Detailed reference viewed: 28 (3 ULg)Singlet Oxygen Quantum Yield of Sulfur and Selenium Analogs of PsoralenSeret, Alain ; Piette, Jacques ; et alin Photochemistry and Photobiology (1992), 56(3), 409-412 The quantum yield of singlet oxygen production by eight newly synthesized sulfur and selenium analogs of psoralen irradiated with UV-A (366 nm) has been determined in CCl4 with the help of the steady ... [more ▼] The quantum yield of singlet oxygen production by eight newly synthesized sulfur and selenium analogs of psoralen irradiated with UV-A (366 nm) has been determined in CCl4 with the help of the steady state luminescence technique. The new psoralen derivatives are generally better singlet oxygen producers than psoralen itself. In particular, the replacement of selenophene for furan and/or of thiopyrone for pyrone induces an important enhancement of the singlet oxygen quantum yield. [less ▲] Detailed reference viewed: 22 (1 ULg)Photochemical reactions of Rose Bengal as a probe of bile salts aggregation processSeret, Alain ; Poster (1992, July) Detailed reference viewed: 26 (0 ULg)The aggregation pattern of sodium taurocholate in water as probed by electronic states and radicals of Rose BengalSeret, Alain ; Conference (1991, July 09) Detailed reference viewed: 8 (0 ULg)Triplet Yield of Merocyanine 540 in Water Is Wavelength DependentSeret, Alain ; Hoebeke, Maryse ; in Photochemistry and Photobiology (1990), 52(3), 601-604 Monomers and aggregates of Merocyanine 540 (MC540) in water are able to photoisomerize. The shape of the photoisomer absorption spectrum is very similar to that of the ground state. Triplet state of MC540 ... [more ▼] Monomers and aggregates of Merocyanine 540 (MC540) in water are able to photoisomerize. The shape of the photoisomer absorption spectrum is very similar to that of the ground state. Triplet state of MC540 in water has been produced by energy transfer from triplet anthracene and displays a broad absorption spectrum between 600 and 700 nm. The triplet state may also be produced by direct excitation of MC540 with UV light. However, when the dye is excited by visible light, no triplet state absorbance in the red could be detected so that the triplet yield of MC540 in water seems to be excitation wavelength dependent. [less ▲] Detailed reference viewed: 20 (4 ULg)Solubility properties of Eosin Y and Rose Bengal triplet state in sodium dodecyl sulfate micellar solutionsSeret, Alain ; in Journal of Physical Chemistry (1990), 94(13), 5293-5299 Solubility properties of the Eosin Y and Rose Bengal triplet states in aqueous solutions of sodium dodecyl sulfate have been explored by means of flash photolysis and electron paramagnetic resonance ... [more ▼] Solubility properties of the Eosin Y and Rose Bengal triplet states in aqueous solutions of sodium dodecyl sulfate have been explored by means of flash photolysis and electron paramagnetic resonance techniques. Eosin Y triplet state does not associate with the surfactant aggregates while the Rose Bengal triplet state appears to be in dynamic equilibrium between the micellar and aqueous pseudophases. The corresponding equilibrium constant depends on the detergent concentration between the critical micelle concentration and about 60 mol dm-3. The exit rate constant of the Rose Bengal triplet state out of a micelle is found to decrease in this concentration range. This is attributed to an increase of the hydrophobic character of the sodium dodecyl sulfate micelle resulting from its partial dehydratation. Between 60 and 200 mmol dm-3, the equilibrium and exit rate constants seem to be constant. [less ▲] Detailed reference viewed: 108 (1 ULg)Activation of human immunodeficiency virus type 1 by an oxidative stressLegrand-Poels, Sylvie ; VAIRA, Dolorès ; PINCEMAIL, Joël et alin AIDS Research and Human Retroviruses (1990) Detailed reference viewed: 1 (0 ULg)Reactivation of HIV-1 after an oxidative stressPiette, Jacques ; ; Vaira, Dolorès et alin Free Radicals in Biology and Medicine (1990), 9(Suppl. A), 5 Detailed reference viewed: 5 (0 ULg)Rose Bengal triplet state behaviour in sodium dodecyl sulfate micellesSeret, Alain ; Piette, Jacques ; Poster (1989, August) Detailed reference viewed: 29 (1 ULg)The photochemistry of the semi-oxidized form of Eosin Y and Rose Bengal in aqueous sodium dodecyl sulphate solutionsSeret, Alain ; in Journal of Photochemistry & Photobiology A : Chemistry (1988), 43(2), 193-206 In aerobic aqueous solutions, the semi-oxidized form of the halofluorescein dyes disappears via a bimolecular reaction with itself and via the formation of an adduct with OH− ions. In aerobic aqueous ... [more ▼] In aerobic aqueous solutions, the semi-oxidized form of the halofluorescein dyes disappears via a bimolecular reaction with itself and via the formation of an adduct with OH− ions. In aerobic aqueous solutions of sodium dodecylsulphate, semi-oxidized rose bengal is solubilized in the micelles, and its exit rate from the micellar aggregates is lower than 60 s−1. The properties of semi-oxidized eosin Y in sodium dodecylsulphate solutions are interpreted in terms of a model based on an adsorption equilibrium between water-bound and micelle-bound dye radicals. This equilibrium depends on the surfactant concentration between the critical micelle concentration and 80 mmol dm−3. Over this range, the reactivity of the semi-oxidized form with itself and towards hydrophilic quenchers decreases when the surfactant concentration is increased. The reaction of the semi-oxidized form with itself is involved in the bleaching of these dyes and the photoproduct is clearly able to react with the semi-oxidized radical of the xanthene dyes. [less ▲] Detailed reference viewed: 15 (0 ULg)Singlet Oxygen Production and Photoisomerization: Two Competitive Processes for Merocyanine 540 Irradiated with Visible LightHoebeke, Maryse ; Seret, Alain ; Piette, Jacques et alin Journal of Photochemistry & Photobiology B : Biology (1988), 1(4), 437-446 The quantum yields of singlet oxygen production by merocyanine 540 have been measured during visible light irradiation performed in methanol and ethanol. These appear to be one hundred times smaller than ... [more ▼] The quantum yields of singlet oxygen production by merocyanine 540 have been measured during visible light irradiation performed in methanol and ethanol. These appear to be one hundred times smaller than the quantum yield for rose bengal measured under the same conditions. Flash photolysis experiments demonstrate the ability of merocyanine 540 molecules to isomerize under visible light irradiation: the isomerization quantum yields are about 0.65 in both ethanol and methanol. This information combined with the fluorescence quantum yield data account for the low values for singlet oxygen production. [less ▲] Detailed reference viewed: 30 (2 ULg)Flash photolysis of Eosin in aqueous micellar dispersionsSeret, Alain ; ; in Chemical Physics Letters (1987), 135(4,5), 427-431 The flash photolysis technique was employed to study the properties of eosin triplet state in aqueous micellar solutions. Increasing the concentration of cetyltrimethylammonium bromide from 10−6 M to the ... [more ▼] The flash photolysis technique was employed to study the properties of eosin triplet state in aqueous micellar solutions. Increasing the concentration of cetyltrimethylammonium bromide from 10−6 M to the CMC leads to a dramatic decrease of triplet absorbance and to the appearance of a very fast decay process of triplet state resulting from the formation of dye-rich induced micelles. From the CMC to 10−2 M, the absorbance and the lifetime of triplet state increase progressively. [less ▲] Detailed reference viewed: 19 (1 ULg)Nitroxide reduction by electron transfer from the Eosin triplet state: electron paramagnetic resonance and flash photolysis studiesSeret, Alain ; ; in Journal of Photochemistry (1987), 38 The paramagnetism loss of nitroxide, photosensitized by eosin, was analysed in basic aqueous and micellar media using electron paramagnetic resonance (EPR) spectroscopy. In cetyltrimethylammonium bromide ... [more ▼] The paramagnetism loss of nitroxide, photosensitized by eosin, was analysed in basic aqueous and micellar media using electron paramagnetic resonance (EPR) spectroscopy. In cetyltrimethylammonium bromide micelles and sodium bis(2-ethylhexyl)sulphosuccinate—n-heptane microemulsions, the paramagnetism decay curves are monoexponential. This is not the case in neat water and sodium dodecylsulphate micelles, for which more complex decays were recorded. It is concluded from flash photolysis measurements that the eosin triplet state is physically quenched by nitroxide and that the latter can be reduced by electron transfer either from the triplet state or from the semireduced form of eosin. This sequence of reactions was confirmed by experiments in micellar media and leads to an understanding of the EPR results. [less ▲] Detailed reference viewed: 24 (0 ULg)Photophysical properties of Eosin dianion in cationic micellar solutionsSeret, Alain ; ; in Archives Internationales de Physiologie et de Biochimie (1986, November), 94(4), 15 Detailed reference viewed: 22 (0 ULg)Singlet oxygen production by UV and visible photoexcited porphyrins under different states of aggregationSeret, Alain ; ; in Photobiochemistry and Photobiophysics (1986), 12 Tryptophan photosensitization was used to determine the quantum yield of singlet oxygen production by porphyrins irradiated with ultraviolet or visible light in phosphate buffer at pH 7.0. From a ... [more ▼] Tryptophan photosensitization was used to determine the quantum yield of singlet oxygen production by porphyrins irradiated with ultraviolet or visible light in phosphate buffer at pH 7.0. From a preliminary study of aggregation of these dyes, it was established that uroporphyrin, hematoporphyrin and deuteroporphyrin allowed to investigate the behaviour of monomers, dimers and higher aggregates, respectively. The photosensitization results show that monomers and polymers produce singlet oxygen with very similar yields. Inclusion of Zn2+ and Cu2+ metal ions on deuteroporphyrin inhibits partially (factor 3) and totally the singlet oxygen production. [less ▲] Detailed reference viewed: 72 (4 ULg)Effects of micellar adsorption on the photosensitizing properties of xanthènes dyesHoebeke, Maryse ; ; et alin Journal of photochemistry (1986), 35 Detailed reference viewed: 1 (1 ULg) |
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