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1.
THE CHROMOPHORES AS ENDOGENOUS SENSITIZERS INVOLVED IN THE PHOTOGENERATION OF SINGLET OXYGEN IN SPINACH THYLAKOIDS 总被引:1,自引:0,他引:1
Abstract— The photogeneration of singlet oxygen (1 O2 ) from thylakoids and the chromophores involved as endogenous sensitizers were investigated using chloroplasts and thylakoids isolated from spinach. The blue light-induced inhibition kinetics of photosynthetic electron transport and that of CTvCF, ATPase were also studied. The spectral dependence of the generation of 1 O2 from thylakoid membranes, measured by the imidazole plus RNO method, clearly demonstrated that the Fe-S centers play an important role in 1 O2 generation, acting as sensitizers in thylakoids. The photoinhibition of the electron transport in isolated chloroplasts was strikingly depressed by a lipid-soluble '02 quencher and enhanced by deuterium oxide substitution, indicating that the inhibition processes are mainly mediated by 1 O2 which is produced via photodynamic activation. The involvement of chloroplast cytochromes in the production of 1 O2 was deduced from the action spectrum for the photodynamic inhibition of the electron carrier chain. The results obtained from the kinetic studies appear consistent with the involvement of some components such as the Fe-S centers and cytochrome chromophores of the carrier chain in the generation of 1 O2 . 相似文献
2.
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
3.
Abstract— The possible association of photodynamic sensitization with photoinhibition damage to the photosystem II complex (PS II) has been investigated using isolated intact thylakoids from pea leaves. For this study singlet oxygen (1 O2 ), photoproduced by endogenous chromophores that are independent of the function of PS II, was assumed to be the major reactive intermediate involved in the photoinhibition process. When thylakoid samples preincubated with rose bengal were subjected to exposure to relatively weak green light (500–600 nm) under aerobic conditions, PS II was severely damaged. The pattern of the rose bengal-sensitized inhibition of PS II was similar to that of high light-induced damage to PS II: (1) the secondary quinone (QB )-dependent electron transfer through PS II is inactivated much faster than the QB -independent electron flow, (2) PS II activity is lost prior to degradation of the D1 protein, (3) diuron, an herbicide that binds to the QB domain on the D1 protein, prevents D1 degradation, and (4) PS II is damaged to a greater extent by the deuteration of thylakoid suspensions but to a lesser extent by the presence of histidine. Furthermore, it was observed that destroying thylakoid Fe-S centers resulted in a marked reduction of high light-induced PS II damage. These results may suggest that the primary processes of photoinhibition are mediated by 1 O2 and that Fe-S centers, which are located in some membrane components, but not in PS II, play an important role in photogenerating the activated oxygen immediately responsible for the initiation of photodamage to PS II. 相似文献
4.
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
5.
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
6.
Abstract— In view of the increasing attention to 1 O2 (1 Δg ) participation in the photodynamic action, different types of genetic changes in Saccharomyces cerevisiae by acridine orange sensitization were compared with respect to the response to N3 - , a well known quencher of 1 O2 . The induction of mitotic crossing over with respect to ade 2 locus and mitotic gene conversion at trp 5 locus were suppressed by the addition of N3 - suggesting the involvement of 1 O2 as a major intermediate. However, the induction of reverse mutation at ilv 1 was only slightly suppressed. These results may indicate that there are two types of photodynamic DNA damage; one is produced via 1 O2 and the other via non-1 O2 reaction pathway which lead to mitotic gene conversion and mitotic crossing over, and to mutation, respectively. 相似文献
7.
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
8.
Chang Sook Kim Gwang Hyun Han Jin Man Kim Jin Jung 《Photochemistry and photobiology》1993,57(S1):1069-1074
Abstract— A comparative study was carried out on the in situ susceptibilities to photoinactivation of the photosystem I (PS I) and II (PS II) complexes of spinach thylakoids treated with efficient type II sensitizers. While the presence of the exogenous sensitizers caused a substantial increase in the extent of photoinactivation of whole chain electron transport, it did not affect PS I activity of thylakoids in light but exerted an enhanced photoinactivating effect only on PS II. The measurements of the action spectrum for the inhibition of PS II activity of the sensitizer-incorporated thylakoids and that for the generation of singlet oxygen (1 O2 ) from them revealed that photosensitized inactivation of PS II is directly related to the photoproduction of 1 O2 in thylakoid membranes. The results obtained in the present work clearly demonstrate an exceptional sensitivity of PS II to 1 O2 , providing circumstantial evidence that high light-induced damage to PS II may result from photosensitization reactions mediated by 1 O2 , which is not necessarily produced within the PS II complex. 相似文献
9.
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
10.
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
11.
Abstract— The autoxidation of the catecholamine neurotoxin 6-hydroxydopamine (20 μ M ) gave rise to a chemiluminescence which was greatly stimulated by FeSO4 (20 μ M ) or by hydrogen peroxide addition (20 μ M to 2 m M ). The luminescence of both 6-hydroxydopamine alone or 6-hydroxydopamine plus hydrogen peroxide was strongly inhibited by catalase and by superoxide dismutase (both at 10 μg/m/); bovine serum albumin at 10 μg/m/ had no inhibitory effect. The luminescence was also strongly inhibited by several potent hydroxyl radical trapping agents and also by low concentrations of the 1 O2 quencher DABCO (l,4-diazabicyclo-2.2.2.-octane). Chemiluminescence was greatly enhanced in D2 O, a solvent in which 1 O2 has a prolonged lifetime. These data demonstrate the involvement of hydrogen peroxide, the superoxide radical and the hydroxyl radical in the chemiluminescence. The data are also consistent with some role for 1 O2 . 相似文献
12.
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
13.
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
14.
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
15.
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
16.
SINGLET OXYGEN FORMATION BY SENSITIZATION OF FUROCOUMARINS COMPLEXED WITH, OR BOUND COVALENTLY TO DNA 总被引:1,自引:0,他引:1
N. J. de Mol G. M. J. Beijersbergen van Henegouwen B. van Beele 《Photochemistry and photobiology》1981,34(6):661-666
Abstract— The formation of singlet molecular oxygen (1 O2 ) by sensitization of the furocoumarins 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP) and psoralen complexed with DNA was investigated. From the results it is concluded that 5-MOP complexed with native DNA is able to generate 1 O2 , even in a larger extent than 5-MOP free in solution. Also, with 8-MOP and especially with psoralen, 1 O2 formation by the complexed compound could be observed. The 1 O2 formation sensitized by covalently bound furocoumarin was demonstrated with psoralen as a model compound. 4',5'-Dihydropsoralen, a model compound for the UVA light absorbing 4',5'monoadducts of furocoumarins to DNA, is also able to generate 1 O2 . 相似文献
17.
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
18.
Philippe Richard Aleksander Blum Leonard I. Grossweiner 《Photochemistry and photobiology》1983,37(3):287-291
—The photosensitized inactivation of subtilisin BPN' by free hematoporphyrin (HP) followed exponential kinetics with positive mechanistic tests for the involvement of singlet oxygen (1 O2 ) as the principal intermediate. The photoinactivation quantum yield was 0.029 at 390 nm in oxygen-saturated, D2 O buffer at pH 7.0. The effects of HP binding were investigated for tryptophan oxidation in bovine serum albumin (BSA) and human serum albumin (HSA) at high protein:HP concentration ratios where the HP was > 97% complexed. The reaction kinetics were non-exponential and mimick a second-order process in the initial stages. The rate of HP photobleaching was 30-fold faster for complexed HP compared with free HP, which was shown to account for the observed kinetics. Mechanistic tests showed that 1 O2 was the dominant photooxidizing intermediate of tryptophan residues and that it was not involved in the accompanying photobleaching of HP. The quantum yield for tryptophan oxidation in BSA was 0.11 at 390 nm in oxygen-saturated, D2 O buffer at pH 8.0. The reactivity of HSA was approximately 2-fold lower than BSA for equivalent conditions. Estimates of the reaction cross sections led to 3 Å2 for the inactivation of subtilisin BPN' by 1 O2 and 20 Å2 for the oxidation of tryptophan in BSA. 相似文献
19.
20.
PHOTOSENSITIZATION BY ANTITUMOR AGENTS—1. PRODUCTION OF SINGLET OXYGEN DURING IRRADIATION OF ANTHRAPYRAZOLES WITH VISIBLE LIGHT 总被引:1,自引:0,他引:1
Krzysztof Reszka Petros G. Tsoungas J. William Lown 《Photochemistry and photobiology》1986,43(5):499-504
Abstract— Oxygen consumption, photoinduced by visible light, and sensitized by novel anthrapyrazole antitumor agents has been observed. Generation of singlet oxygen upon irradiation of ethanolic solutions of the drugs with visible light (480–520 nm) was demonstrated using a specific 1 O2 acceptor, 2.5-dimethylfuran and a quencher, sodium azide. An electron paramagnetic resonance method was employed to measure the rate of oxygen consumption. Significant differences were found in the sensitizing properties among the anthrapyrazoles studied. Intramolecular hydrogen bonding within the chro-mophore is one of the structural factors that determine the efficacy of a given anthrapyrazole in 1 O2 generation 相似文献