共查询到20条相似文献,搜索用时 0 毫秒
1.
Thérèse Montenay-Garestier ‡ Francine Brun Claude Hélène 《Photochemistry and photobiology》1976,23(2):87-91
Abstract— Low temperature luminescence studies have provided evidence for interactions between the disulfide group of cystamine and adenine bases in cystamine-poly(A) complexes and in cystamine-adenosine aggregates. A quenching of adenine phosphorescence by cystamine was observed. At room temperature complex formation between cystamine and poly(A) was followed by proton magnetic resonance, absorption spectrophotometry and fluorescence using competition with a fluorescent peptide to monitor the binding process. These base-disulfide interactions could be involved in the photochemistry of protein-nucleic acid complexes. 相似文献
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Shingo Minato Tetsuo Osa Masahiko Morita Asao Nakamura Hiroshi Ikeda Fujio Toda Akihiko Ueno 《Photochemistry and photobiology》1991,54(4):593-597
The intramolecular excimer formation of 6A,6B-, 6A,6C-, 6A,6D-, and 6A,6E-bis(2-naphthyl-sulfonyl)-γ-cyclodextrins (1, 2, 3, and 4, respectively) and 6A.6B-, 6A,6C-, and 6A,6D-bis(2-naphthyl-sulfonyl)-β-cyclodextrins (5, 6, and 7, respectively) has been studied in 10% ethylene glycol aqueous solution. The two naphthyl rings are co-included in the γ-cyclodextrin cavities of1–4, and marked excimer emission was observed for 2, 3, and 4. On the other hand, almost pure monomer emission was observed for 5, 6, and 7 due to inclusion of one of two naphthyl rings in the β-cyclodextrin cavities. Compounds 2, 3, 6, and 7 showed remarkable guest-induced enhancement in the excimer emission, and this property was used for detecting several organic compounds with remarkable molecular recognition. 相似文献
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Abstract. The triplet-triplet absorption spectra of psoralen, xanthotoxin, angelicin and bergapten have been determined using the technique of pulse radiolysis and laser flash photolysis in benzene and water. The extinction coefficients of the triplet transitions have been measured and used to determine the singlet → triplet intersystem crossing quantum yields for 353 nm excitation. These yields vary considerably in passing from benzene to water as solvent. The highest yields were obtained for psoralen and angelicin in water, being 0.45 and 0.33, respectively. Reaction rate constants of the psoralen and angelicin triplets with various pyrimidine and purine nucleic acid bases and amino acids have been measured. The high reactivities support the suggestion that the photosensitising properties of furocou-marins are mediated by the corresponding furocoumarin triplet states. The similarly high S → T quantum yields, and triplet reactivities with pyrimidines of psoralen and angelicin, also support the suggestion that the observed differences in photosensitising properties of these two psoralens may be due to their differing geometries, which allow psoralen itself to intercalate DNA more easily than angelicin. The efficient reactions also found for psoralen and angelicin triplets with amino acids suggest that such triplets in vivo may also react with these components. Significant damage may thus be caused to protein as well as nucleic acid components of the cell. 相似文献
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Nicholas J. Turro Tsuneo Okubot† Gregory C. Weed 《Photochemistry and photobiology》1982,35(3):325-329
Abstract— The emission of several 1,3-bichromophoric(BC) systems has been investigated in aqueous solutions containing various cyclodextrins (CD's). In all cases where molecular models reveal that the correspondence of the size and shape of the eclipsed conformation of the BC system and the cavity CD is high, a stable CD (host)-BC (guest) complex is formed and in these cases, the ratio of excimer to monomer emission intensity UE/IM) is much larger than that found in homogeneous solution. The effect of application of high pressure on the IE /IM ratio was investigated, as was the influence of 02 quenching of excimer and monomer in homogeneous solutions, in aqueous micellar solutions, and in aqueous solutions of CD complexes. A strong protection from 02 quenching is observed in the latter case. 相似文献
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INHIBITION OF NUCLEIC ACID SYNTHESIS IN CELLS EXPOSED TO 200 MICROMETER RADIATION FROM THE FREE ELECTRON LASER 总被引:1,自引:0,他引:1
Vertebrate tissue culture cells were exposed to 200 um wavelength radiation (1CO W/cm2 ) from a free electron laser (FEL) of the electrostatic generator type. Cell cultures demonstrated no morphological alterations but a statistically significant (P .05) proportion of the cells exhibited inhibition of DNA synthesis. This study demonstrates the first biological effects of the FEL and the feasibility of performing biological investigations with this device. 相似文献
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Abstract— In our earlier papers we described the recovery of U.V. irradiated L-strain cells by means of nucleic acids. In an attempt to get better insight in the mechanism(s) leading to this recovery we studied the effect of native DNA on the metabolism of nucleic acids of recipient cells. In these experiments we have found that the label isologous DNA-C14 is incorporated in DNA of normal and irradiated recipient cells. The rate of DNA-C14 label incorporation in the DNA of irradiated recipient cells is slower than in the unirradiated controls. The presence of thymidine in the incubation media reduces the incorporation rate of DNA-C14 . When the irradiated cells have been growing in a medium containing isologous DNA in presence of thymidine or heterologous DNA the recovery effect was not observed. 相似文献
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醋酸锌与草酸的分步固相反应 总被引:2,自引:0,他引:2
The solid state reaction of zinc acetate with oxalic acid was found to be two-step reactions. It was a double reaction which the second reaction takes place before the first ceased. The method of isothermal TG wasn′t fit to this type of reaction because of the limitation of the volatilization rate of acetic acid at the low heat temperature, but the method of isothermal electric conductivity exhibited its superiority. 相似文献
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Abstract— Photochemical and γ-ray-induced reactions of purines with amines are described. These lead to the appropriate 8-substituted purines. The photoproducts were obtained in yields of up to 100% by the use of a variety of photosensitizers, including peroxides. A free radical mechanism is proposed for these reactions.
Such reactions may be relevant to the problem of the nature of DNA-protein cross-links induced by ultraviolet radiation. 相似文献
Such reactions may be relevant to the problem of the nature of DNA-protein cross-links induced by ultraviolet radiation. 相似文献
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In the study of chemical evolution, experiments simulating primitive earth conditions have shown that many compounds of biological significance can be produced from simple precursors. In an attempt to search for the origin of polycarboxylic acids, the UV irradiation of aqueous acetic acid was performed. Among the products detected were succinic, citric and malonic acids which are key compounds in metabolic pathways, suggesting that these compounds might have been formed on the primitive Earth prior to life itself. 相似文献
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固体超酸POSA催化醇脱水制烯 总被引:1,自引:0,他引:1
固体超酸由于其优良的催化性能,近年来倍受重视。其中以全氟骨架的磺酸树脂Nafion H应用最广。POSA(全氟辛基磺酸,C_8F_(17)SO_3H)也是一种化学性质稳定、易回收的固体超酸,具有与Nafion H相似的氟碳链磺酸结构。 相似文献
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Abstract—The triplet-triplet absorption spectra of coumarin, 5.7 dimethoxycoumarin and the furocoumarin 4'5' dihydropsoralen. a model for 4'5' psoralen-pyrimidine mono adducts, have been determined by the techniques of pulse radiolysis and laser flash photolysis. The extinction coefficients of the triplet transitions have been measured and used to determine the singlet → triplet intersystem crossing quantum yields for 347 nm excitation in water. Reaction rate constants for coumarin and 4'5' dihydropsoralen triplets with various pyrimidine and purine nucleic acid bases, and amino acids, have been measured. Long-lived transient absorptions detected after quenching coumarin and 4'5' dihydropsoralen triplets with tryptophan are assigned to mixtures of the corresponding coumarin radical anion and the tryptophan radical cation. The spectra of the radical anions of coumarin and 4'5' dihydropsoralen were established using pulse radiolysis of the coumarins in aqueous formate. It is suggested that coumarins and furocoumarin triplets are quenched by nucleic acid bases and amino acids via a chargetransfer mechanism. 相似文献
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B. Verček B. Stanovnik M. Tišler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):315-316
Abstract Substituted or unsubstituted thioureido heterocycles can be successfully used for the formation of a new thiadiazole or thiazole ring. For example, a fused thiadiazolo ring is formed either from carbethoxythioureido- or carbethoxymethylthioureido-heterocycles (I). The reaction proceeds by oxidative cyclization and can be performed in the presence of various oxidizing agents. On the other hand, some reducing agents convert II back into I. A particular case represents the reaction between 2-chloro-3-aminopyridine and carbethoxy isothiocyanate giving directly III (R = = COOEt), although the reaction must proceed via an intermediate like I (n = O). 相似文献
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从葡萄糖—乳酸溶液中提取乳酸的离子交换工艺 总被引:5,自引:0,他引:5
本文就乳酸发酵-发离联合体系中离子交换工艺过程进行了研究。用间歇法测定了乳酸的交换等温线,并对离子交换柱上交换曲线和解吸曲线进行了测定和研究。实验结果是令人满意的。 相似文献
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利用柠檬酸去除污泥中重金属的新工艺 总被引:4,自引:0,他引:4
经柠檬酸络合后采用离子交换法处理污泥中的重金属,该方法包括3个步骤:浸提过程、固液分离、浸提液的净化和循环。对影响浸提液的净化和循环步骤中的主要影响因素进行了研究。结果表明,732型阳离子交换树脂性能优异,对重金属的离子交换率接近100%;以5%HCl溶液为洗脱剂,动态逆流操作条件下,Cu、Ni和Zn的洗脱率分别达到88.85%、86.15%和88.40%;以铝片为置换剂,对重金属Pb、Cd、Cu、Ni都能得到90%以上的置换率。循环实验表明,处理后污泥中的重金属含量符合《农用污泥中污染物控制标准》(GB4284-84),柠檬酸可以实现循环使用。 相似文献