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At least 613 records · Page 34Linked to original sources
PubMed2000

Structural and environmental requirements for quenching of singlet oxygen by cyanine dyes

Singlet-oxygen quenching constants were measured for 19 cyanine dyes in acetonitrile. The most efficient quenchers were 1-butyl-2-[2-[3-[(1-butyl-6-chlorobenz-[cd]indol-2(1H)- ylidene)ethylidene]-2-chloro-1-cyclohexen-1-yl]ethenyl]-6-chlorobenz[cd] indolium and 6-chloro-2-[2-[3-(6-chloro-1-ethylbenz[cd]indol-2(1H)-ylidene) ethylidene]-2-phenyl-1-cyclopenten-1-yl]ethenyl]-1-ethyl-benz[cd]indolium, having quenching constants with diffusion-controlled values of 2.0 +/- 0.1 x 10(10) and 1.5 +/- 0.1 x 10(10) M-1 s-1, respectively. There was a trend toward increased quenching constants for cyanine dyes with the absorption band maxima at longer wavelengths. However, the quenching constants correlated better with the oxidation potentials of the cyanine dyes, suggesting that quenching proceeds by charge transfer rather than energy transfer. The quenching constants for 1,1',3,3,3',3'-hexamethylindotricarbocyanine perchlorate and 1,1'-diethyl-4,4'-carbocyanine iodide were measured in several solvents as well as in aqueous solutions of detergent micelles. In different solvents, the quenching constants varied by as much as a factor of 50. The quenching constants were largest in solvents with the highest values on the pi* scale of Kamlet, Abboud, Abraham and Taft. This was consistent with quenching occurring by charge transfer. Within cells, cyanine dyes concentrate in membrane-bound organelles. The quenching constants were substantial within detergent micelles. To the extent that micelles are models for biological membranes, cyanine dyes may be effective biological singlet-oxygen quenchers.

Journal Article↗
PubMed1981

Singlet oxygen and ultraweak chemiluminescence in rat skin.

The intensity of ultraweak chemiluminescence (CL) was estimated in rat epidermal homogenate with a technique utilizing UV irradiation (in vitro and in vivo). CL markedly increased in the homogenate after irradiation. The CL intensity was enhanced to 300% by the substitution of deuterium oxide for H2O, and it was reduced to 50% when diazabicyclo-octane, a scavenger for singlet oxygen, was added. It was concluded that the weak CL would be attributable to singlet oxygen, and the determination of the lipoperoxide in skin tissue by the method of the CL counting system was discussed.

Animals↗
PubMed1987

The ene reaction of singlet oxygen with olefins.

The reactions of singlet oxygen (1O2) with cis and trans butenes-1,1,1-d3, at -80 degrees C in Freon-11, show a product isotope effect (kH/kD) of 1.38 and 1.25 respectively. Isomerization of the starting materials or formation of dioxetanes were not observed during the course of the photooxygenation. Together with the isotope effects on the reactions of tetramethylethylene-d6 isomers with singlet oxygen, these results require the reversible formation of a perepoxide or charge transfer intermediate.

Alkenes↗
PubMed1992

Correlations between the rate constant of singlet oxygen quenching by imidazole derivatives and anti-inflammatory activity in rats.

The second-order rate constants, k delta, for quenching of molecular singlet oxygen O2 (1 delta g) by nonsteroidal anti-inflammatory imidazole drugs have been determined using time-resolved phosphorescence detection of singlet oxygen. A linear correlation was observed between log k delta (ranging from 7.90 to 8.50) and the anti-inflammatory activity of these compounds (ranging from ED50 = 15 to 300 mg/kg), as measured in rats by Jørgensen and Dyrsting [United States Patent 4,424,229 (1984)]. The correlation between this physico-chemical parameter measured in vitro and a biological activity measured in vivo might be useful in screening other types of candidate anti-inflammatory drugs. The rate constant (k delta) can be considered as a quantitative expression of the electron-donating power of the imidazole drug, as suggested by a correlation of log k deta (ranging from 6.02 to 7.45) with Hammett substituent parameters observed in the case of 2-substituted imidazoles.

Animals↗
PubMed2005

[Visible absorption spectra and resonance Raman spectra of n-pi* singlet-triplet transition of p-benzoquinone in CS2].

The visible absorption spectra of p-benzoquinone (PBQ) in CS2 were measured, and a weak absorption band around 507 nm attributed to n-pi* singlet-triplet transition was denonstrated. Using the resonance Raman effect excited in liquid-core optical fiber which can enhance Raman intensity by 6-9 orders of magnitude, the authors obtained the 514.5 nm excited resonance Raman (RR) spectra of PBQ at 1439 cn(-1) in the concentration range from 10(-3) to 10(-6) mol x L(-1). The new characteristic RR band is attributed to the symmetric C==O stretch (v(C==O)) of n-pi* singlet-triplet transition of PBQ. The resonance Raman shift is blue-shifted with decreasing concentration. The results of this paper are helpful for understanding the relationship between the electric structure and the photophysical properties of PBQ, and for obtaining more abundant structural information of molecules.

English Abstract↗
PubMed1975

Spectroscopic evidence for the generation of singlet oxygen in the reduced nicotinamide adenine dinucleotide phosphate-dependent microsomal lipid peroxidation system.

In the presence of Fe3+-ADP and NADPH, washed rat liver microsomes at 37 degrees and at pH 7.5 emitted ultraweak light with the peroxidative cleavage of endogenous lipid. The main light-emitting species of this system was analyzed spectroscopically in the visible region and estimated to be singlet oxygen. The addition of superoxide dismutase or catalase did not inhibit the light emission significantly. It is unlikely therefore that superoxide anion and OH are involved in the generation of singlet oxygen in the present system.

Adenosine Diphosphate↗
PubMed1979

Photoactivation of the nematicidal compound alpha-terthienyl from roots of marigolds (Tagetes species). A possible singlet oxygen role.

The nematicidal compound alpha-terthienyl from roots of Tagetes species generates upon irradiation with near ultraviolet light reactive oxygen species on which the in vitro nematicidal activity depends. This system was studied by following the inhibition of glucose-6-phosphate dehydrogenase by photoactivated alpha-terthienyl and protection of the enzyme activity in the absence of oxygen and by various additions. Addition of mannitol, benzoate, superoxide dismutase or catalase did not have any effect nor did H2O2. This suggests that OH., O-.2, and H2O2 are not the reactive oxygen species involved. The enzyme was protected against photoactivated alpha-terthienyl in air-saturated solutions by singlet oxygen quenchers such as histidine, methionine, tryptophan, bovine serum albumin, and NaN3. Furthermore, inactivation of the enzyme was about 3.5 times faster in D2O than in H2O. When alpha-terthienyl in CH2Cl2 was irradiated in the presence of the olefin adamantylideneadamantane, a stable dioxetane was formed which decomposed to adamantanone when heated above its melting point. These results indicate a singlet oxygen-mediated process.

Animals↗
PubMedDate not supplied

[Role of singlet-excited and triplet states in chlorophyll photooxidation].

Effect of p-benzoquinone concentration [Q] on the yield of ion-radicals during photooxidation of chlorophyll a with p-benzoquinone was studied by the method of impulse photoconductivity. It has been shown that in the studied range [Q] = 10(-6)--10(-1) M the relationship delta n ([Q]) has a bell-like shape with the maximum at [Q] approximately 10(-3) M. From the relationship obtained the ratio beta = delta ns/delta nt of the contributions of singlet--excited (Chl) and triplet (Chl) states of the pigment into the total yield of ion-radicals is evaluated: for [Q] less than or equal to 10(-1) M beta less than or approximately 10(-3). Primary contribution of the triplet state to the formation of ion-radical is explained, first, by a larger, as compared to the singlet-excited state, life time of the state Chl in solution and second, by the fact that the ion-radical pair 3(Chl+Q-) in the triplet state regenerates less effectively to Chl+Q, than the pair (Chl+Q-).

Benzene Derivatives↗
PubMed1994

A simple in vitro method to detect singlet oxygen and to compare photodynamic activity using alkaline phosphatase.

A simple, sensitive and reliable in vitro method based on photodynamic inactivation of alkaline phosphatase to detect singlet oxygen and for evaluating relative photosensitizing efficiencies of photosensitizers such as hematoporphyrin (Hp) and phthalocyanines has been developed and compared with photobleaching of p-nitroso dimethyl aniline (RNO) and photooxidation of L-tryptophan. Inactivation of alkaline phosphatase is dependent both on light fluence and sensitizer concentration. Scavengers like mannitol and azide anion indicated the involvement of singlet oxygen in the deactivation of alkaline phosphatase, since azide anion provided concentration dependent protection whereas mannitol had no effect and that compared to ordinary water, photoinactivation of alkaline phosphatase was three times higher in 65% D2O. Alkaline phosphatase appears to be resistant to free radical attack (particularly to OH radicals) since hydrogen peroxide alone or in presence of ferrous ions did not reduce the enzyme activity and mannitol or azide anion gave no significant protection when alkaline phosphatase was irradiated with Co-60 gamma rays up to 2 K Gy. With the present method using red light, the chloroaluminium phthalocyanine sulphonates prepared by sulphonation showed higher and the corresponding condensation product lower photodynamic activity; Hp being intermediate and Mn- and Gd-phthalocyanines had no photodynamic activity.

Alkaline Phosphatase↗
PubMed1994

Cross-linking of dermal collagen induced by singlet oxygen.

Changes were studied in dermal collagen induced by singlet oxygen, which was generated by a bilirubin-photosensitized reaction. An increase in the ratio of high-molecular-weight components (beta- and r-components) against the alpha-chain of collagen after irradiation manifested in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sodium azide, a singlet oxygen quencher, inhibits the alteration of the molecular size by the photochemical reaction. These data suggest that chronic sunlight irradiation may contribute to cross-links of dermal collagen.

Animals↗
PubMed1993

[Scavenging action of green tea extracts on singlet oxygen and preventive effect on lipid peroxidation].

Singlet oxygen (1O2) produced by illuminated photosensitizer Rose Bengal was detected by its bleaching effect on N,N-dimethylnitrosoaniline(DMNA). The 1O2 could be scavenged by green tea extracts (GTE), with the scavenging action being obvious at the early stage of photosensitized oxidation. The higher the concentration of GTE in the photooxidation reaction system, the stronger the 1O2 scavenging action. The scavenging effect of the fresh GTE solution on singlet oxygen was better than that of old solution. The preventive effects of GTE on lipid peroxidation induced by 1O2 in ghosts and microsomal membranes were also observed. Malondialdehyde (MDA) production was found to be completely inhibited by a high concentration of GTE in the reaction system.

Animals↗
PubMed1997

[Singlet oxygen therapy].

Physico-chemical concept of the singlet oxygen therapy application using photochemically sensibilized air or drinking a water, already barbaturized by an activated singlet oxygen of air, is adduced. Therapy technology and examples of its clinical application in the treatment of several pathologic processes for the free-radicals correction are depicted.

Antioxidants↗
PubMedDate not supplied

Quantitative generation of singlet (1 delta g) oxygen from acidified aqueous peroxynitrite produced by the reaction of nitric oxide and superoxide anion.

Simple acidification of aqueous alkaline peroxynitrite quantitatively generates singlet (1 delta g) molecular oxygen, detected and quantitated spectroscopically (1270 nm). This observation provides a chemical basis for physiological cytotoxicity of ONOO- generated in the diffusion - controlled reaction of cellular NO. and O2-. The experiments consist of (i) chemical generation of ONOO- from NO. gas and KO2 powder in alkaline aqueous solution; (ii) absorption spectral identification of ONOO- in the near-UV with maximum at 301 nm; (iii) spectroscopic identification of 1O2 by its emission band at 1200-1340 nm with maximum at 1275 nm; and (i.v.) quantification of 1O2 generated in ONOO-/H+ reaction by comparison of the chemiluminescence intensity at 1270 nm with that from H2O2/OCI- reaction that generates 1O2 with unit efficiency at alkaline pH. 1O2 was generated with unit efficiency with respect to ONOO- concentration by the ONOO-/H+ reaction.

Drug Stability↗
PubMedDate not supplied

Imaging of ultra-weak bio-chemiluminescence and singlet oxygen generation in germinating soybean in response to wounding.

Ultra-weak bio-chemiluminescence (UBC) from germinating soybean (Glycine max L. Merr) cotyledon under mechanical wounding was observed using a high-sensitivity imaging system based on an ICCD detector and a highly sensitive single photon counter (SPC) device. The UBC imaging showed that the intensity at the injury location on a wounded cotyledon was obviously enhanced as compared with that at the non-injured point. The UBC intensity of wounded cotyledons was initially very high and reached a stationary state after about 5 min. Wounding-induced emission could be suppressed by wounding in the presence of sodium azide. Deuterium oxide amplified the emission intensity. It was concluded that singlet oxygen ((1)O(2)) was the main cause of the emission during the wounding phase.

Cotyledon↗
PubMed2004

18O-Labeled lipid hydroperoxides and HPLC coupled to mass spectrometry as valuable tools for studying the generation of singlet oxygen in biological system.

Decomposition of lipid hydroperoxides (LOOH) is known to generate toxic products capable to induce tissue injury. We have recently confirmed that decomposition of LOOH into peroxyl radicals is a potential source of singlet oxygen ((1)O(2) in biological system. Using (18)O-labeled linoleic acid hydroperoxide (LA(18)O(18)OH) in the presence of Ce(4+) or Fe(2+), we observed the formation of (18)O-labeled (1)O(2) ((18)[(1)O(2)]) by chemical trapping of (1)O(2) with 9,10-diphenylanthracene (DPA) and detecting the corresponding (18)O-labeled DPA endoperoxide (DPA(18)O(18)O) by HPLC coupled to tandem mass spectrometry (HPLC-MS/MS). (18)O-Labeled alcohol and ketone were also detected providing further evidence for the generation of (1)O(2) by the Russell mechanism. Similarly the reaction of LA(18)O(18)OH with peroxynitrite also generated (18)[(1)O(2)].In conclusion, these results indicates that the use of (18)O-labeled LOOH associated with HPLC-MS/MS can be an useful tool to clarify mechanistic features involved in the reaction of LOOH in biological media.

Chromatography, High Pressure Liquid↗
PubMed2001

The effects of singlet oxygen produced by photodynamic action on the mitochondrial permeability transition differ in accordance with the localization of the sensitizer.

We have examined whether the effects of singlet oxygen (1O2) produced by photodynamic action on the mitochondrial permeability transition (PT) can be modulated by the localization of photosensitizers in irradiated mitochondria. We have previously shown that oxidation due to 1O2 photogenerated in hematoporphyrin (HP)-loaded mitochondria can prevent opening of the PT pores, likely after degradation of some critical histidines (Salet et al, 1997, J. Biol. Chem. 272, 21938-21943). Equally, in the present study we have irradiated mitochondria in the presence of a structurally different photosensitizer producing 1O2, namely 4,5',8-trimethylpsoralen (TMP). Fluorescence studies show that TMP binds to protein sites which differ from those of HP. In sharp contrast with HP, TMP-driven photodynamic action triggers per se pore opening. Interestingly, this inducing effect is inhibited when TMP-treated mitochondria are irradiated after addition of mersalyl, a specific reagent protecting thiol groups of the inner mitochondrial membrane that are oriented toward the external hydrophilic phase. This fact suggests that 1O2-mediated thiol oxidation is responsible for TMP-photoinduced pore opening. Taken together, these findings suggest that 1O2 can activate or inactivate a cellular function such as mitochondrial PT depending on the site where it is produced in the mitochondrial membrane.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Rapid reaction of singlet molecular oxygen (1O2) with p-aminobenzoic acid (PABA) in aqueous solution.

The reaction of singlet molecular oxygen (1O2) with p-aminobenzoic acid (PABA) is quite rapid. The rate constant for reaction of 1O2 with PABA was measured in buffered aqueous solution by the method of competition kinetics and found to be 8.9 x 10(8) M-1 sec-1. The results of a Stern-Volmer analysis indicate that additional loss of 1O2 does not occur through physical quenching by PABA. Although illuminated PABA solutions are known to form 1O2, it appears that PABA is also a very efficient sink for 1O2.

4-Aminobenzoic Acid↗
PubMed1997

Photochemical formation of singlet molecular oxygen ((1)O2) in illuminated 6-methylcoumarin solutions.

Use of the fragrance 6-methylcoumarin (6-MC) in cosmetic products has declined significantly due to numerous reports of photoallergic contact dermatitis associated with its use. We have determined that 6-MC undergoes direct photolysis with an estimated half-life of 83 minutes when illuminated with mid-latitude U.S., noon-centered, equinox sunlight and a quantum yield for photolysis at 313 nm of phi = 3 x 10(-3). The work presented here also provides evidence that singlet molecular oxygen ((1)O2) is formed in illuminated solutions containing 6-MC. An estimated value of phi = 0.01 is reported for the (1)O2 quantum yield at 313 nm. Formation of (1)O2 is significant because it is known to react with a variety of biomolecules and it is possible that (1)O2 formation is at least partially responsible for reports of 6-MC photoallergenicity and phototoxicity.

Coumarins↗