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1.
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. 相似文献
2.
The quantum yields of singlet oxygen formation (ØΔ) by the quenching of triplet states of organic sensitizers are measured at various concentrations of the sensitizers by using the time-resolved thermal lens method. Above a certain concentration, ØΔ is independent of the sensitizer concentration. Below the threshold, ØΔ gradually decreases as the concentration of the sensitizer decreases. The extrapolation of ØΔ to zero concentration indicates that singlet oxygen formation is not necessarily dominant in the quenching process even for the 3ππ* state in benzene. 相似文献
3.
Paul C. Beaumont Michael A. J. Rodgers Barry J. Parsons Glyn O. Phillips 《Photochemistry and photobiology》1985,42(5):605-608
Abstract— The yield of singlet oxygen (1 Δg ) from some furocoumarins in the presence of DNA has been measured using time resolved techniques. For both psoralen and 4'-aminomethyl-4,5',8-trimethylpsoralen, increasing DNA concentration leads to a decrease in the yield of singlet oxygen. In addition, there is a linear dependence between the yield of singlet oxygen and the observed triplet yield determined by laser flash photolysis. In view of this observation it seems unlikely that singlet oxygen production occurs from these two furocoumarins when they are complexed with DNA. Preliminary, albeit inconclusive, results for 8-methoxypsoralen are also presented. 相似文献
4.
Salvatore Cannistraro Albert van de Vorst Giulio Jori† 《Photochemistry and photobiology》1978,28(2):257-259
Abstract— EPR studies of the porphyrin-sensitized photooxidation of 2, 2, 6,6-tetramethyl-piperidine to the nitroxide demonstrate that all the porphyrins examined are able to generate 1 O2 , although the efficiency of the photoprocess is dependent on the nature of the side chains. Incorporation of metal ions into the porphyrin molecule depresses or even inhibits the formation of 1 O2 . Comparison of these results with previously obtained kinetic data points out that the efficiency of porphyrins as photosensitizes is controlled by the lifetime of their lowest triplet state. 相似文献
5.
J. Decuyper N. Houba-Héin C. M. Calberg-Bacq A. Van De Vorst 《Photochemistry and photobiology》1984,40(1):149-151
Abstract In contrast to previous results obtained with the nitroxide radical detection technique, generation of the specific 1 O2 oxidation product of cholesterol shows that photoexcited acridine orange produces singlet oxygen. 相似文献
6.
Abstract —The kinetic behavior of the ESR Signal II in spinach chloroplasts has been studied under steady-state illumination and under flash conditions. In controls Signal II exhibits biphasic decay following cessation of illumination—a moderately fast phase (t1/2 10-60s) and a slow phase (t1/2? 2–3 h). Addition of 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (DCMU), o-phenanthroline, NH4Cl or gramicidin had no effect on the decay of Signal II; however, agents such as antimycin A, carbonyl cyanide-m-chlorophenylhydrazone (CCCP), NH2OH or tris washing greatly accelerated the decay of Signal II. Flash photolysis-electron spin resonance experiments on Jensen-Bassham type chloroplasts reveal the presence of a previously unnoticed decay component in the g ? 2 region. This species is formed in less than 1 ms and exhibits a decay half life of ?6-10s. The spectral profile corresponds to the steady-state Signal II spectrum. This new transient is formed in approximately equimolar amounts to Signal I. The results are discussed in terms of two prevalent hypotheses—one which would place the Signal II component on the reducing side of PSII and another which would place the Signal II component on the oxidizing side. 相似文献
7.
Direct measurements of the decay of singlet oxygen phosphorescence at 1270 nm were made in human plasma diluted with various amounts of deuterium oxide. The Stern-Volmer plot of the singlet oxygen lifetimes was linear up to 15% plasma concentration (vol/vol). Extrapolation of these measurements to 100% plasma content gave a singlet oxygen lifetime of 1.04 +/- 0.03 microseconds in human plasma. Biological molecules accounted for 77% of the total singlet oxygen quenching while water accounted for 23% of the quenching. The contributions of various types of biological molecules to the total singlet oxygen quenching were calculated from their plasma concentrations and their quenching constants. Plasma proteins quenched most of the singlet oxygen. Uric acid also quenched a significant amount of singlet oxygen (12%). Tocopherols, carotenoids, ascorbic acid and bilirubin made only small contributions to the total singlet oxygen quenching (less than or equal to 4%). 相似文献
8.
Abstract— The production of free radicals by reaction of 2,2,6,6-tetramethyl-4-piperidinol with singlet oxygen was studied by EPR spectroscopy. The rate constant of the amine was found to be equal to 8 ×105 M -1 s-1 in ethanol and to 4 × 107 M-1 s-1 in phosphate buffer (pH 8). Competition experiments were performed with singlet oxygen quenchers such as NaN3 , DABCO and the quenching rate constants were found to be consistent with the literature values. The EPR method proved to be a valuable technique to study the reaction of singlet O2 with the sterically hindered amine without any interfering effect. 相似文献
9.
Abstract— The hematoporphyrin-sensitized production of singlet molecular oxygen, O2 (1 Δg ), has been investigated in methanol and in aqueous solution. The quantum yield for formation of O2 (1 Δg ) (ΦΔ ) has been measured by both steady-state (oxygen consumption) and time-resolved (near-infrared luminescence) methods. In methanol, both techniques indicate that ΦΔ = 0.76 and the value remains independent of sensitizer concentration over a wide range. This finding is consistent with the dye persisting in a monomelic form in methanol solution. In contrast, ΦΔ decreases markedly with increasing sensitizer concentration in water due to dimerization of the dye. Analysis of the steady-state data indicates ΦΔ values of 0.74 and 0.12, respectively, for monomer and dimer. It is further shown that the efficiency whereby quenching of the triplet state by O2 results in generation of O2 (1 Δg ) is substantially lower for the dimer than for the corresponding monomer. Because monomer and dimer possess quite different absorption spectral profiles, the efficacy for photodynamic action with hematoporphyrin exhibits a pronounced wavelength dependence. 相似文献
10.
A. A. Krasnovsky Jr M. A. J. Rodgers M. G. Galpern B. Rihter M. E. Kenney E. A. Lukjanetz 《Photochemistry and photobiology》1992,55(5):691-696
Using the direct measurement of the photosensitized luminescence of singlet molecular oxygen (1O2) the rate constants (kq) have been determined for 1O2 quenching by the monomeric molecules of the following phthalocyanines and naphthalocyanines in chloroform: tetra-(4-tert-butyl) phthalocyanine (I); octa-(3,6-butoxy) phthalocyanine (II), tetra-(6-tert-butyl)-2,3 naphthalocyanine (III), aluminium tetra-(1-tert-phenyl)-2,3 naphthalocyanine (IV), tri-(n-hexyl-siloxy) derivatives of silicon- (V), tin- (VI), aluminium- (VII) and gallium- (VIII) 2,3 naphthalocyanine. The following kq values were obtained (kq x 10(-8) M-1 s-1): 2.9 (I), 59 (II), 100 (III), 20 (IV), 3.9 (V), 53 (VI), 33 (VII), 110 (VIII). As most of the quenchers have the low-lying triplet levels, a contribution of the quenching mechanism based on the energy transfer from 1O2 to these levels has been analysed. A formula is proposed describing the relation between kq values caused by this mechanism, and photophysical constants of the quencher triplet state. This formula was applied to phthalocyanines, naphthalocyanines, beta-carotene and bacterochlorophyll a. The data suggest that the energy transfer can fully explain the activity of V and strongly contributes into the activities of II, III and VI-VIII. A charge transfer interaction might be an additional mechanism involved in 1O2 quenching by compounds studied. As some phthalocyanines and naphthalocyanines are strong physical quenchers of singlet oxygen they can be used as efficient inhibitors for photodestructive processes in photochemical systems. 相似文献
11.
JEFFREY R. KANOFSKY 《Photochemistry and photobiology》1991,53(1):93-99
Time resolved measurements of singlet oxygen phosphorescence at 1270 nm were made from unsealed red cell ghosts, labeled with 5-(N-hexadecanoyl)aminoeosin and suspended in deuterium oxide buffer. The singlet oxygen emission lifetime was long, 23 +/- 1 microseconds. The lifetime of the singlet oxygen phosphorescence from intact unsealed ghosts was not a measure of the singlet oxygen lifetime within the red cell ghost membrane, however. The prolonged singlet oxygen emission was due to singlet oxygen escaping from the thin membrane into the buffer, since the emission lifetime was significantly shortened by adding azide ion or water to the deuterium oxide buffer. The lifetime of singlet oxygen within the red cell ghosts membrane was estimated by dispersing the ghosts with detergent and then measuring the singlet oxygen lifetime in deuterium oxide buffers containing various dilutions of the dispersed ghosts. Apparent singlet-oxygen quenching constants were measured using four different photosensitizing dyes and two different detergents. The apparent quenching constant was independent of the dye used, but varied significantly with different detergents. Extrapolation of this data to "100%" ghost concentration gave a singlet oxygen lifetime from 24 and 130 ns. A ghost concentration of "100%" was defined as that concentration of red cell ghost molecules which would be contained within a red cell ghost membrane pellet containing no buffer solutions. Most of the singlet oxygen quenching was due to proteins. Lipids extracted from red cell ghosts accounted for only 2-7% of the total singlet oxygen quenching. 相似文献
12.
THE PHOTOCHEMICAL YIELD OF SINGLET OXYGEN FROM PORPHYRINS IN DIFFERENT STATES OF AGGREGATION 总被引:4,自引:0,他引:4
Abstract— Aqueous solutions of hematoporphyrin and hematoporphyrin derivatives were exposed to light. When present in such solutions tryptophan is degraded by a singlet oxygen mechanism. This is true for excitation at 396 nm, where porphyrin monomers have their absorption maximum, as well as for excitation at 360 nm, where porphyrin aggregates seem to absorb strongly. The quantum yield of singlet oxygen production is similar within 25% for excitation at 396 and 360 nm while the fluorescence quantum yield is more than a factor 2 lower for excitation at 360 nm than for excitation at 396 nm. Photoexcitation of the clinically used hematopotophyrin derivatives photofrin I and photofrin II produces singlet oxygen with significantly smaller yields than photoexcitation of hematoporphyrin. Thus, the aggregates present in solutions of photofrin I and photofrin II are of a different nature than those present in aqueous solutions of hematoporphyrin. 相似文献
13.
本工作用氯甲基化的苯乙烯系的树脂和四-(对-氨基苯)卟啉及其Mg2+、Cd2+、Ni2+、Cu2+的络合物,合成了一组高分子的金属卟啉敏化剂。并用9,10-二甲基蒽作为1O2受体,测定了它们光敏化产生1O2的相对能力,分别为1.0、1.56、0.73、0.25、0.21。表明高分子卟啉镁具有较强的敏化能力,是一种良好的敏化剂,其他三种过渡金属元素,特别是具有顺磁性的Ni和Cu,对卟啉光敏化能力起了明显的抑制作用。 相似文献
14.
N. J. de Mol G. M. J. Beijersbergen
van
Henegouwen 《Photochemistry and photobiology》1979,30(3):331-335
Abstract— The formation of singlet molecular oxygen (lO2) by energy transfer from the excited 8-meth-oxypsoralen (8-MOP) molecule was investigated. This was done in several ways: (a) In the reaction of irradiated 8-MOP with the 1O2 acceptor 2-methyl-2-pentene, the characteristic oxidation products were identified. (b) The rate of the 8-MOP sensitized photooxidation of 3, 4-dihydroxy phenylalanine (dopa), which appeared to be also a useful 1O2 acceptor, was larger in D2O than in H2O. (c) The β-values for reaction of 1O2with dopa in the presence of 8-MOP or of methylene blue as 1O2 generators were in accordance with each other. The consequences of 1O2 formation by 8-MOP sensitization is discussed for the clinical use of this compound. 相似文献
15.
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
16.
John L. Seed Kathleen G. Specht † Thomas A. Dahl ‡ W. Robert Midden § 《Photochemistry and photobiology》1989,50(5):625-632
Singlet oxygen activates the mutagenicity of several benzo[a]pyrene (BP) derivatives in the absence of mammalian metabolic action. This has been demonstrated using a separated-surface-sensitizer system for generating chemically pure singlet oxygen, eliminating most of the complications that arise with singlet oxygen generation by conventional photosensitization. Salmonella typhimurium bacteria were exposed to singlet oxygen in the presence of certain BP derivatives and the mutation frequency determined with an azaguanine forward mutation assay. The mutation frequency was increased by exposure to singlet oxygen compared to light-only controls for those BP derivatives that were saturated at either the 7,8 or 9,10 positions but not both. The increase in mutation frequency depends on both the concentration of BP derivative and on the dose of singlet oxygen. Mutation frequency was also significantly increased when bacteria were treated with a solution of trans-7,8-dihydrodiol-BP that had been separately exposed to singlet oxygen, unequivocally demonstrating that the mutagenicity is due to the formation of a product of BP derivative oxidation by singlet oxygen and that this product has a lifetime at least on the order of minutes in acetonitrile. The requirement for singlet oxygen rather than some other form of reactive oxygen was confirmed by determination of the gas phase lifetime of the intermediate responsible for activating mutagenicity. This was performed by measuring the dependence of the mutation frequency on the distance separating the sensitizer from the target. This gives a value of 88 +/- 35 ms, which is in excellent agreement with the mean value of 89 ms calculated from previous independent determinations of the gas phase lifetime of singlet oxygen reported in the literature. 相似文献
17.
Abstract— A general method for the determination of the extent of the singlet oxygen (1O2) quenching by sensitizer in the dye-sensitized photooxygenation of olefins is used in the case of rose bengal (RB) in methanol and oil-soluble chlorophyll (M) in benzene with 2-methyl-2-pentene and tetramethylethylene as acceptors. Unlike RB, M which contains only a low percentage of pure chlorophyll (Chi), quenches 1O2. It is shown that this very cheap mixture can be used for kinetic studies and that the chemical quenching of 1O2 by M is very weak with respect to the physical quenching. The upper limit for the rate constants of physical and chemical quenching of 1O2 by Chi is estimated. 相似文献
18.
I. B. C. Matheson R. D. Etheridge Nancy R. Kratowich John Lee 《Photochemistry and photobiology》1975,21(3):165-171
Abstract— The physical quenching of singlet molecular oxygen (1 Δg ) by amino acids and proteins in D2 O solution has been measured by their inhibition of the rate of singlet oxygen oxidation of the bilirubin anion. Steady-state singlet oxygen concentrations are produced by irradiating the oxygenated solution with the 1–06 μm output of a Nd-YAG laser, which absorbs directly in the electronic transition 1 Δg + 1 v →3 Σg - . The rate of quenching by most of the proteins studied is approximated by the sum of the quenching rates of their amino acids histidine, tryptophan and methionine, which implies that these amino acids in the protein structure are all about equally accessible to the singlet oxygen. The quenching constants differ from those obtained by the ruby-laser methylene-blue-photosensitized method of generating singlet oxygen, or from the results of steady-state methylene-blue-photosensitized oxidation, where singlet oxygen is assumed to be the main reactive species. The singlet oxygen quenching rates in D2 O, pD 8, are (107 ℒ mol-1 s-1 ): alanine 0–2, methionine 3, tryptophan 9, histidine 17, carbonic anhydrase 85, lysozyme 150, superoxide dismutase 260, aposuperoxide dismutase 250. 相似文献
19.
S. R. Fahrenholtz F. H. Doleiden A. M. Trozzolo A. A. Lamola 《Photochemistry and photobiology》1974,20(6):505-509
Abstract —D-α-tocopherol was found to be an effective quencher of 1 O2 molecules ( k = 2.5 times 108 →mol-1 s-1 in pyridine) by measuring its effect on the autosensitized photooxidation of rubrene. The quenching process was shown to be almost entirely 'physical', that is, α-tocopherol deactivated about 120 1 O2 molecules before being destroyed. The results suggest that this process may be a mechanism for the protective effect of α - tocopherol in photodynamic action. 相似文献
20.
DIRECT DETECTION OF SINGLET OXYGEN SENSITIZED BY HAEMATOPORPHYRIN AND RELATED COMPOUNDS 总被引:1,自引:0,他引:1
J. P. Keene D. Kessel E. J. Land R. W. Redmond T. G. Truscott 《Photochemistry and photobiology》1986,43(2):117-120
Abstract— Direct time-resolved detection of the luminescence at 1270 nm from 'singlet oxygen' was used to estimate the quantum yield of singlet oxygen production (ΦΔ ) from a series of related porphyrins in benzene and in D2 O. From this and available data the fraction of oxygen quenching interactions leading to singlet oxygen production (SΔ ) was derived in most cases. A marked increase in ΦΔ value was observed for di-haematoporphyrin ester (DHE) in cetyltrimethyl ammonium bromide/D2 O solution in comparison to D2 O alone, this increase is attributed to a major structural alteration of DHE on introduction of the detergent. 相似文献