共查询到20条相似文献,搜索用时 93 毫秒
1.
Takuo Shiraishi Masao Makiuchi Katsuko Kakinuma Humio Inaba 《Photochemistry and photobiology》1998,68(1):16-19
Abstract— We report the detection of a weak near-infrared light emission originating from 8 nM singlet molecular oxygen (1 O2 ) produced in a mixture of 1 m M hypochlorite (OC1- ) and 8 n M hydrogen peroxide (H2 O2 ). The measurements were made with a highly sensitive detection system for ultraweak light emission in the 1.0-1.5 μm wavelength region. The emission intensity exhibited linear dependence for H2 O2 concentrations in the range of 8-670 n M . The mixture containing a lower concentration (33 μ M ) of OCl- pseudocontinuously emitted near-infrared light for 5 s. The rate constant for 1 O2 production obtained from the kinetic analysis agrees with that previously reported. Our results demonstrate the possibility of measuring very low concentrations of 1 O2 in a OCi-/H2 O2 mixture as well as 1 O2 production in intact living systems. 相似文献
2.
LUMIFLAVIN-SENSITIZED PHOTOOXYGENATION OF INDOLE 总被引:1,自引:0,他引:1
Abstract— The lumiflavin-sensitized photooxygenation of indole in aqueous solutions has been investigated by means of steady light photolysis and flash photolysis. The semiquinone of lumiflavin and the half-oxidized radical of indole were formed by the reaction between triplet lumiflavin and indole (3.7 times 109 M -1 s-1 ). The semiquinone anion radical of lumiflavin reacted with oxygen to form superoxide radical. The triplet state of lumiflavin also reacted with oxygen forming singlet oxygen, 1 O2 . But the reaction between 1 O2 and indole (7 times 107 M_l s_1 ; estimated from steady light photolysis using Rose Bengal as a sensitizer) was far less efficient than the reaction between indole and triplet lumiflavin. The quantum yield of the lumiflavin-sensitized photooxygenation of dilute indole via radical processes was much higher than that via 1 O2 processes, though appreciable 1 O2 was formed. 相似文献
3.
Dolores J. Fatur † Richard H. C. San † Allan J. Davison † Hans F. Stich † 《Photochemistry and photobiology》1987,45(3):413-420
Abstract— Maximum chemiluminescence in a system containing 6-hydroxydopamine (6-OHDA) and H2 O2 required the addition of Fe2+ :EDTA, oxygen, and lucigenin. In this system luminescence was strongly inhibited by catalase (91% inhibition) or 50 m M mannitol (83%), whereas superoxide dismutase or ascorbate did not significantly change the reaction rate. In the absence of lucigenin, 50 m M mannitol (78%), catalase (76%), or ascorbate (73%) inhibited strongly, while superoxide dismutase inhibited by 60%. Removing EDTA from the lucigenin-containing system caused a 79% decrease in luminescence, while the substitution of desferoxamine for EDTA decreased luminescence by 55%. In the presence of desferoxamine plus EDTA the luminescence increased by 30% in comparison with that seen with EDTA alone. Luminescence in the system containing 6-hydroxydopamine, H2 O2 , Fe2+ :EDTA and lucigenin required the presence of oxygen (93% inhibition anaerobically), consistent with a mechanism involving reductive oxygenation of the lucigenin. It is concluded that luminescence in the presence of lucigenin involves a substantial contribution from H2 O2 and Fe2+ mediated by a mannitol-sensitive intermediate (conceivably Fenton-derived hydroxyl radicals). In the absence of lucigenin, superoxide and an ascorbate-labile component are additional important participants in the process. 相似文献
4.
Abstract— β-Carotene, at concentrations 0.1 m M , inhibits the formation of hydroperoxides and other oxidation products in a refined petroleum oil exposed to Pyrex-filtered UV. The effect appears to be due to 1 O2 quenching. A mechanism incorporating 1 O2 and radical processes is proposed as a model for environmental photooxidation of petroleum. 相似文献
5.
Danuta Slawinska Janusz Slawinski Krzysztof Polewski Wojciech Pukacki 《Photochemistry and photobiology》1979,30(1):71-80
Abstract— Peroxidation of tannins with alkaline H2 O2 is accompanied by weak chemiluminescence in the spectral region 480–800 nm. o-Di and tri-hydroxy groups of polyphenols undergo oxidation by a free-radical mechanism and a green intermediate anion-radical with absorption Δmax = 600 nm is formed. The radical mechanism is supported by the low activation energy 14–20 kJ/mol and the quenching effect of radical scavengers. The reaction of the green intermediate with peroxy anions is the chemiluminescence rate limiting step. In the presence of a-hydroxy-methylperoxide formed from H2 O2 and formaldehyde, the alkaline peroxidation of tannins is accompanied by strong red luminescence (420–800 nm). The base catalyzed decomposition of peroxides gives only a weak red emission (460–800 nm). Light intensity is enhanced in D2 O by a factor 6.5. Quenchers of O2 (1 Δg ) and 1,3-di-phenylisobenzofurane diminish light intensity in non-aqueous solutions. The data suggest 1 O2 participation in the observed chemiluminescence. Thermo-chemical calculations give —ΔH values from 250–1000 kJ/mol for one elementary reaction step which limits the mechanism of chemi-enereization. Chemiexcitation of tannins is relevant to biochemical mechanisms of aerobic degradation of aromatic compounds, energy utilization as well as to defense and resistance processes in plants. 相似文献
6.
Abstract— The possibility of 1 O2 (1 Δg ) participation in the oxidation of polyphenols and quinones has been investigated in two systems: (1) the system involving autooxidation leading to oxidative polymerization and destruction, and (2) the modified Trautz-Schorigin reaction, i.e. oxidation of polyphenols and HCHO with H2 O2 in concentrated alkaline solutions. The red band with maximum at 635 nm observed in chemiluminescence of pyrocatechol, adrenaline, pyrogallol, gallic acid, adrenochrome and p -benzoquinone corresponds to the transition 2O2 (1 Δg ) → 2O2 (3 Σ- g ). Emission bands in the range 475–540 nm arise from the superposition of the 2O2 (1 Δg ) → 2O2 (3 Σ- g ) transition and radiative deactivation of excited oxidation products. In system (2) chemiluminescence has a broad band from 580 nm beyond 800 nm and much higher intensity than in system (1). Formaldehyde was found to enhance light emission in system (1) by a factor of about 30. The influence of solvents, including D2 O in which 1 O2 has varying lifetimes, on kinetics of chemiluminescence as well as quenching effect of β-carotene, hydroquinone, cysteine, bilirubin and biliverdin strongly support the involvement of 1 O2 in the chemiluminescence of both systems. 相似文献
7.
Michael Price Stanley R. Terlecky David Kessel 《Photochemistry and photobiology》2009,85(6):1491-1496
Although the first reactive oxygen species (ROS) formed during irradiation of photosensitized cells is almost invariably singlet molecular oxygen (1 O2 ), other ROS have been implicated in the phototoxic effects of photodynamic therapy (PDT). Among these are superoxide anion radical (• O2 − ), hydrogen peroxide (H2 O2 ) and hydroxyl radical (• OH). In this study, we investigated the role of H2 O2 in the pro-apoptotic response to PDT in murine leukemia P388 cells. A primary route for detoxification of cellular H2 O2 involves the peroxisomal enzyme catalase. Inhibition of catalase activity by 3-amino-1,2,4-triazole led to an increased apoptotic response. PDT-induced apoptosis was impaired by addition of an exogenous recombinant catalase analog (CAT- skl) that was specifically designed to enter cells and more efficiently localize in peroxisomes. A similar effect was observed upon addition of 2,2'-bipyridine, a reagent that can chelate Fe+2 , a co-factor in the Fenton reaction that results in the conversion of H2 O2 to • OH. These results provide evidence that formation of H2 O2 during irradiation of photosensitized cells contributes to PDT efficacy. 相似文献
8.
TEMPORAL and SPECTRAL SEPARATION OF SINGLET OXYGEN LUMINESCENCE FROM NEAR INFRARED EMITTING PHOTOSENSITIZERS 总被引:1,自引:0,他引:1
Dirk U. Näther John R. Gilchrist Thomas Gensch Beate Röder 《Photochemistry and photobiology》1993,57(S1):1056-1059
Abstract— The luminescence emission of singlet molecular oxygen (1 O2 ) generated by bacteriopheophytin a, a near-infrared-emitting photosensitizer, was measured using a new high-sensitivity spectrometer system for time- and spectral-resolved near-infrared detection. The instrument uses a low energy pulsed nitrogen laser (40 μJ per pulse) to excite the photosensitizer optically and is capable of a time resolution of 40 ns per data point and an instrument response function of 350 ns FWHM (full width at half maximum). The use of a low-energy (and relatively low cost) source provides sufficient system sensitivity to measure time-resolved spectra in the near infrared with high spectral and temporal resolution. The simultaneous detection, with high accuracy and repeatability, of both the temporal and spectral dependence of the photoprocesses of 1 O2 generation, especially with near-infrared-emitting photosensitizers, may further stimulate the current intensive investigations concerning the activity of 1 O2 to biomolecules. 相似文献
9.
MECHANISM OF PHOTOSENSITIZATION BY PHEOPHORBIDE a STUDIED BY PHOTOHEMOLYSIS OF ERYTHROCYTES AND ELECTRON spIN RESONANCE SPECTROSCOPY 总被引:1,自引:0,他引:1
Abstract Phcophorbide a (PPa), a causal substance of food intoxication, when excited by exposure to light wavelengths of over 600 nm, caused the photohemolysis of goat erythrocytes in proportion to the incubation time of the cells. The addition of N-3 , an effective scavenger of 1 O2 , to the medium markedly inhibited the hemolysis of erythrocytes in a concentration-dependent manner, whereas the addition of superoxide dismutase (SOD) and catalase, inhibitors of O- 2 and H2 O2 generation, respectively, to the medium had little effect on it.
Methods for converting1 O2 to a nitroxide radical by 2,2,6,6-tetramethyl-4-piperidone (TMPD) and for trapping O- 2 and OH by 5,5-dimethyl-l-pyrroline-A'-oxide (DMPO) were employed to observe directly these activated oxygens by electron spin resonance (ESR). The methods provided evidence that only 1 O2 , was produced by PPa, which was excited by light wavelengths of over 600 nm. Both the addition of N3 to the solution and the removal of oxygen from the solution inhibited the generation of 1 O2 .
These results led us to conclude that1 O2 was mainly responsible for the hemolysis of erythrocytes by photoexcited PPa. 相似文献
Methods for converting
These results led us to conclude that
10.
STEADY-STATE NEAR-INFRARED DETECTION OF SINGLET MOLECULAR OXYGEN: A STERN-VOLMER QUENCHING EXPERIMENT WITH SODIUM AZIDE 总被引:2,自引:1,他引:2
Abstract— A sensitive near-infrared detection system incorporating improvements to existing methodologies has been used to characterize the sodium azide quenching of the steady-state luminescence of singlet molecular oxygen at 1270 nm. Stern-Volmer plots which were linear up to 80% quenching of the 1 O2 generated by rose bengal and eosin Y yielded a rate constant of 5.8 ± 0.1 times 108 M −1 s−1 for the quenching of 1 O2 in water, while the rate constants obtained in deuterium oxide with the same sensitizers were 6.28 times 108 M −1 s−1 and 6.91 times 108 M −1 s−1 respectively. A flow system minimized the effects of photobleaching of the rose bengal. With a mercury arc light source, the instrument can be used in photosensitization experiments to detect low levels of 1 O2 production in aqueous media. 相似文献
11.
M. Delmelle 《Photochemistry and photobiology》1978,27(6):731-734
Abstract— All -trans retinal is dissolved in alcohols and illuminated at 365 nm in the presence of a singlet oxygen acceptor, 2,5-dimethylfuran. Illumination produces the photosensitized oxidation of the acceptor which is measured by the disappearance of its 215 nm absorption band. A kinetic study is carried out and βDMF is 1.6 × 10- -4 M . The quantum yield of 1 O2 production from the light-excited retinal is estimated to 0.096. The retinal sensitized photooxidation of dimethylfuran is inhibited by a 1 O2 quencher, 1,4-diazabicyclo(2,2,2)-octane, and enhanced by deuteration of the solvent. Deuterated solvents are known to increase 1 O2 lifetime.
The production of1 O2 from retinal is briefly discussed in relation to the damage which may be induced by light in the visual cells. 相似文献
The production of
12.
Abstract— The rate constant for quenching of 1 O2 by azide ion in water was determined to be (5.0 ± 0.4) × 108 M −1 s−1 using a variety of sensitizers (including humic acids) and 1 O2 acceptors. The apparent second-order rate constant decreases with pH below pH 5.5 in accordance with the protonation of azide ion to form hydrazoic acid (p K a = 4.6). Quenching by hydrazoic acid is at least 2 orders of magnitude slower than by azide ion. Greater than 99% of all interactions between 1 O2 and azide ion involve physical quenching rather than chemical reaction. Humic acid triplets are not significantly quenched by azide ion at concentrations less than 2 m M , allowing azide ion quenching to be used as a diagnostic test for the intermediacy of 1 O2 in photosensitized oxidations in natural surface waters. 相似文献
13.
Abstract— In experiments on the interception of reactive intermediates of strongly oxidizing character in dye (S) sensitized photooxidations using p -nitrosodimethylaniline (RNO) as a selective scavenger, it has been observed that some substrates (A) or 1 O2 acceptors (like imidazole derivatives) induce the bleaching of RNO as followed spectrophotometrically at 440 nm. Since singlet oxygen (1 O2 ) does not react chemically with RNO, this bleaching is a consequence of 1 O2 capture by the imidazole ring which results in the formation of a trans-annular peroxide intermediate [1 O2 ] capable of inducing the bleaching of RNO (-RNO). In the absence of RNO, [1 O2 ] decomposes or rearranges into the final oxygenation product 1 O2 : 1 Δg Thus, the system imidazole plus RNO can be used as a sensitive and selective test for the presence of 1 O2 in aqueous solutions. The method can also be applied in the presence of sensitizing dyes which, under visible irradiation, can partially bleach RNO even in the absence of imidazole derivatives. In such a case, the bleaching of RNO is strongly increased by the presence of imidazoles with a characteristic dependence on their concentration. The separation of the product of RNO bleaching by thin layer chromatography can serve as additional proof of the presence of 1 O2 in the system. The imidazole plus RNO method has been applied to a number of sensitizing and non-sensitizing dyes. 相似文献
14.
PROOXIDANT and ANTIOXIDANT EFFECTS OF ASCORBATE ON PHOTOSENSITIZED PEROXIDATION OF LIPIDS IN ERYTHROCYTE MEMBRANES 总被引:1,自引:0,他引:1
Albert W. Girotti James P. Thomas John E. Jordan 《Photochemistry and photobiology》1985,41(3):267-276
Abstract— Continuous blue light irradiation of resealed erythrocyte ghosts at 37°C in the presence of uroporphyrin or protoporphyrin results in 1 O2 -mediated (azide inhibitable) lipid peroxidation and membrane lysis. Lipid peroxidation was assessed by thiobarbituric acid reactivity and by quantitation of total hydroperoxides, while lysis was measured in terms of trappedglucose–6-P release. Low concentrations of ascorbate, AH- (e.g. 0.5 m M ). present at the start of irradiation, significantly enhanced the rates of lysis and peroxidation, whereas relatively high concentrations of AH- (e.g. 15 m M ) inhibited both processes. By way of contrast. AH- produced only a dose-dependent inhibition of the photoinactivation of lysozyme, added as an extramembranous target. No significant AH- induced lipid peroxidation was observed in dark or light controls, plus porphyrin or minus porphyrin, respectively. Stimulation of peroxidation and lysis by low levels of AH- was enhanced by added Fe(III), abolished by EDTA. but unaffected by catalase or superoxide dismutase. A plausible explanation for these results is as follows. At low concentrations of AH- prooxidant activity is favored. Redox metal-mediated breakdown of photoperoxides occurs, which tends to amplify lipid peroxidation. Neither O2 - nor H2 O2 appears to be involved. At significantly high concentrations, AH- acts predominantly as an antioxidant by intercepting 1 O2 and/or sensitizer triplet, or by scavenging free radical intermediates of lipid peroxidation. 相似文献
15.
Piotr J. Bilski M. A. Wolak V. Zhang D. E. Moore C. F. Chignell 《Photochemistry and photobiology》2009,85(6):1327-1335
Lamotrigine (LTG) [3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine], an anticonvulsant and antidepressant drug Lamictal® , produces a (photo)toxic response in some patients. LTG absorbs UV light, generating singlet oxygen (1 O2 ) with a quantum yield of 0.22 in CH2 Cl2 , 0.11 in MeCN and 0.01 in D2 O. A small production of superoxide radical anion was also detected in acetonitrile. Thus, LTG is a moderate photosensitizer producing phototoxicity and oxidizing linoleic acid. LTG is a weak 1 O2 quencher ( k q = 3.2 × 105 m −1 s−1 in MeCN), but its photodecomposition products in dimethyl sulfoxide (DMSO) quenched 1 O2 very efficiently. Upon intense UV irradiation from a xenon lamp, LTG was photobleached rapidly in DMSO and slowly in acetonitrile, alcohol and water. The rate increased significantly when laser pulses at 266 nm were employed. The photobleaching products generated 1 O2 twice as strongly as LTG. Photobleaching was usually accompanied by the release of chloride anions, which increased in the presence of ascorbic acid. This suggests the formation of aryl radicals via dechlorination, a process which may be responsible for the photoallergic response observed in some patients. Our results demonstrate that LTG is a moderate generator of 1 O2 prone to photodechlorination, especially in a reducing environment, which can contribute to the reported phototoxicity of LTG. 相似文献
16.
Irina G. Gazaryan Maya Yu. Rubtsova Yuri L. Kapeliuch José Neptuno Rodriguez-Lopez L. Mark Lagrimini Roger N. F. Thorneley 《Photochemistry and photobiology》1998,67(1):106-110
The properties of a newly isolated anionic tobacco peroxidase from transgenic tobacco plants overexpressing the enzyme have been studied with respect to the chemiluminescent reaction of luminol oxidation. These were compared to the properties of horseradish peroxidase in the cooxidation of luminol and p -iodophenol, the enhanced chemiluminescence reaction. The pH, luminol and hydrogen peroxide concentrations were optimized for maximum sensitivity using the tobacco enzyme. The detection limit for the latter under the optimal conditions (2.5 m M luminol, 2 m M hydrogen peroxide, 100 m M Naborate buffer, pH 9.3) was about 0.1 p M , which is at least five times lower than that for horseradish peroxidase in enhanced chemiluminescence with p -iodophenol. The rate constants for the elementary steps of the enzyme-catalyzed reaction have been determined: k 1 = 4.9 × 106 M −1 s1 , k 2 = 7.3 × 106 M −1 s−1 , k 3 = 2.1 × 106 M −1 s−1 (pH 9.3). The similarity of these rate constants is unusual for plant peroxidases. The high catalytic activity of tobacco peroxidase in the luminescent reaction is explained by the high reactivity of its Compound II toward luminol and the high stability of the holoenzyme with respect to heme dissociation. This seems to be a unique property of this particular enzyme among other plant peroxidases. 相似文献
17.
The steady-state UVA (350 nm) photolysis of ( E )-β-ionone ( 1 ) in aerated toluene solutions was studied by 1 H NMR spectroscopy. The formation of the 1,2,4-trioxane ( 2 ) and 5,8-endoperoxide ( 5 ) derivatives in the ratio of 4:1 was observed. Time-resolved laser induced experiments at 355 nm, such as laser-flash photolysis, photoacoustic and singlet oxygen 1 O2 phosphorescence detection, confirmed the formation of the excited triplet state of 1 with a quantum yield Φ T = 0.50 as the precursor for the generation of singlet oxygen 1 O2 ( Φ Δ = 0.16) and the isomeric α-pyran derivative ( 3 ), which was a reaction intermediate detected by NMR. In turn, the reaction of 1 O2 with 1 and 3 occurred with rate constants of 1.0 × 106 and 2.5 × 108 m −1 s−1 to yield the oxygenated products 5 and 2 , respectively, indicating the relevance of the fixed s-cis configuration in the α-pyran ring in the concerted [2+4] cycloaddition of 1 O2 . 相似文献
18.
The photooxidation of N,N -diethylhydroxylamine (DEHA) by Rose Bengal (RB) has been investigated in micellar and nonmicellar aqueous solutions. We measured the quantum yield of oxygen consumption forming H2 O2 and monitored two intermediates, the superoxide and diethylnitroxide radicals. When the pH was vaned, the quantum yield of oxidation remained constant for 6 < pH < 10.5, decreased in acidic pH, and increased considerably in NaOH solution; these changes could be attributed to the protonation and dissociation processes of the >N-OH moiety of DEHA. The formation of diethylnitroxide radical was enhanced by superoxide dismutase or strong alkaline solution. Around neutral pH, the oxidation proceeded mainly via electron transfer from DEHA to the RB triplet ( k q = 107 M -1 s-1 ) with little 1 O2 participation ( kq < 105 M -1 s-1 ). However, when RB was incorporated into micelles in alkaline solution, the contribution of the singlet oxygen pathway increased at the expense of electron transfer, which was inhibited by the less polar micellar environment. Dark autoxidation of DEHA was accelerated by heavy metal impurities and increased very strongly in NaOH solution. 相似文献
19.
N. J. de Mol G. M. J. Beijersbergen van Henegouwen 《Photochemistry and photobiology》1981,33(6):815-819
Abstract— The production of singlet oxygen (1 O2 ) by a series of furocoumarins with different skin sensitizing abilities has been investigated with methods already proven to be suitable to establish the ability of 8-methoxypsoralen (8-MOP) to generate 1 O2 .
The following compounds: 5-methoxypsoralen (5-MOP), psoralen, 4,5',8-trimethylpsoralen (TMP) and 5,8–dimethoxypsoralen (5,8–DMOP), are able to generate1 O2 when irradiated with long–wave ultraviolet light. With the photobiologically inactive angelicin no 1 O2 production has been found. The relative extent of 1 O2 formation has been determined for the various furocoumarins and has been compared with literature data for the skin photosensitizing effect. The observed relation between experimental data on the one side and the literature data on the other side is discussed. 相似文献
The following compounds: 5-methoxypsoralen (5-MOP), psoralen, 4,5',8-trimethylpsoralen (TMP) and 5,8–dimethoxypsoralen (5,8–DMOP), are able to generate
20.
Abstract— The use of cyclic 1,3-dienes and polycyclic aromatic hydrocarbons as xenobiotic substrates for the interception of electronically excited (singlet) molecular oxygen (1 O2 ) in biological systems is reviewed and criticized, and the possibility of utilization of reactive endogenous substrates for 1 O2 interception is considered. The common sterols, cholesterol, 5α-cholest-7-en-3β-ol, and 5α-lanost-8-en-3β-ol each give oxidation products with 1 O2 different from those with ground-state molecular oxygen that can be distinguished from one another by simple chromatographic means. 相似文献