摘要:

Abstract—Breaks induced in purified DNA by 334‐nm ultraviolet (UV) radiation are enhanced 30 times when 2‐thiouracil (s2Ura) is present during aerobic irradiation. This enhancement by s2Ura is maximally effective at a concentration of about 1 mM.Anoxic irradiation reduces the s2Ura‐enhanced breakage by 90%, indicating a Type II photosensitization. Benzoate, glycerol, diazabicyclo[2.2.2.]octane (DABCO) and histidine all inhibit formation of s2Ura photosensitized breaks, unlike diethylenetriaminepenta‐acetic acid (DETAPAC) and catalase, which do not. The relationships between the concentration of DABCO. benzoate and histidine and their protection against induction of single strand breaks (SSBs) were similar, with little inhibition below 10 mMand maximal inhibition near 0.1Mfor all compounds. Irradiation of the DNA‐s2Ura mixture dissolved in D2O instead of H2O enhanced the rate of induction of SSBs in DNA by 334‐nm light almost five times. Addition of superoxide dismutase (40, 80 and 200 μg/ml) decreased the rate of induction of breaks in DNA by 334‐nm radiation plus s2Ura (in H2O) by about 40%. Boiled superoxide dismuta

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03573.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Sulfonated phthalocyanine and a series of its metal chelates in combination with red light irradiation led to the degradation of L‐tryptophan in oxygenated aqueous solution. The photoproducts and the rate of transformation of L‐tryptophan are compared with hematoporphyrin and rose bengal sensitized photooxidation. In all cases the primary photoproducts are characterized ascisandtrans‐3a‐hydroperoxy‐l,2,3,3a,8,8a‐hexahydropyrrolo[2,3‐b]indole‐2‐carboxylic acid. Support for the involvement of singlet excited oxygen is obtained from azide inhibition and the formation of the specific singlet oxygen product with cholesterol. We observed the contribution of another pathway in the case of th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03574.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Metallophthalocyanines (MPc) and tetrasubstituted magnesium phthalocyanines (MgPcR4) were investigated as sensitizers for the photoreduction of methylviologen (MV2+) under visible light(420–800 nm) irradiation using disodium ethylenediaminetetraacetic acid (Na2EDTA) as an electron donor in dimethyl formamide (DMF)‐water mixture. Magnesium phthalocyanine and aluminium phthalocyanine were found to be the most efficient sensitizers among nine MPc's examined (M = 2Li, 2Na, Mg, Ca, Al(Cl), Fe, Ni, Co, and Zn). The following sequence of the efficiency among MgPc and MgPcR4's was obt

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03575.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Substitution of bromodeoxyuridine for thymidine in the DNA of mammalian cells sensitizes them to a range of wavelengths of ultraviolet light. Cells are also sensitized to photochemical reactions involving dyes such as Hoechst 33258, which is used to produce differential staining of chromatids according to their bromodeoxyuridine content. Irradiation with 313 nm light of human and hamster cells containing bromodeoxyuridine in their DNA produced single‐strand breaks, detectable by alkaline elution, but no DNA‐protein cross‐links. Irradiation with 360 nm light in the presence of Hoechst 33258 produced extensive DNA‐protein cross‐linkage as well as single‐strand breaks. These cross‐links were observed in DNA containing bromodeoxyuridine incorporated by either semiconservative or repair replication, and may provide a method for identification of proteins in close proximity to replication forks or repair sites. When the protein was removed with proteinase K, bromodeoxyuridine in repair patches after irradiation by doses of ultraviolet (254 nm) light as low as 0.26 J/m2could readily be detected. Hoechst 33258‐mediated photolysis, therefore, provides a sensitive new technique for measuring repair replication after ultraviolet

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03576.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Theanthraquinone–2‐sulfonate photo‐sensitized splitting ofcis‐syn1,3‐dimethylthymine dimer gives rise to large CIDNP effects in the reaction product 1,3‐dimethylthymine. The polarization originates from a radical ion pair formed by electron transfer from the dimer to the triplet state sensitizer. In a deoxygenated solution the sign of the polarization of theC–6 proton is reversed compared to the predicted one on account of the CIDNP sign rules. In an aerated solution the correct sign is observed. This can be accounted for by assuming reduction of the lifetime of the radical pair in the presence of oxygen. The time‐resolved photo‐CIDNP technique was used to study the time dependence of the 1,3‐dimethylthymine signal. To account for this time‐dependence a cation radical disproportionati

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03577.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The steady state and time resolved fluorescence of the drug and chromosomal staining agent, 4′,6‐diamidino‐2‐phenylindole dihydrochloride, DAPI, was examined under different solvent conditions. In solutions between pH 3 and pH 9 the fluorescence spectral maximum of DAPI was found at 460 nm. The fluorescence decayed with double exponential kinetics, with decay times of 2.86 and 0.144 ns, at all wavelengths below 550 nm. At 550 nm single exponential decay kinetics with a lifetime of 0.153 ns was observed. The fluorescence spectrum could be resolved into two components, the 2.86 ns component having a spectral maximum near 450 nm and the 0.144 ns component having a spectral maximum near 490 nm. The results are rationalized in terms of there being two different configurations of DAPI, one of which undergoes a rapid protonation of the indole ring by proton transfer from the 6‐amidinium group in the excited singlet state. The 0.144 ns component is assigned as the fluorescence from the excited state of the protonated indole ring. The results provide an explanation of the fluorescence enhancement in DAPI‐nucleic a

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03578.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The spectroscopic properties of hematoporphyrin, hematoporphyrin‐dimethyl ester, uroporphyrin and uroporphyrinoctamethyl ester, incorporated into unilamellar liposomes of dipalmitoylphos‐phatidylcholine, have been studied with the aim to assess the distribution of porphyrins within the various liposomal compartments.The results obtained indicate that the highly hydrosoluble uroporphyrin is partitioned in the endoliposomal aqueous pool while its octamethylester is homogeneously distributed in the inner lipid monolayer. Hematoporphyrin and its dimethylester show an heterogeneous distribution within the phospholipid bilayer. At T = 25°C these porphyrins are preferentially located in the outer phospholipid monolayer.Detailed studies on hematoporphyrin indicate that the distribution between the inner and outer phospholipid monolayer is a function of temperature and liposome dimensions. In particular, the increase of temperature above the critical temperature for the liquid‐gel phase transition of the liposomes causes a partial shift of the porphyrin molecules toward the inner phospholipid monolayer. Moreover, the increase of liposome dimensions leads to a greater accessibility of porphyrin to the externa

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03579.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Ultraviolet absorption and fluorescence spectra of 4′‐amino phenylalanine (Aphe) and of some peptides and esters containing Aphe, are characterized. Based on these results, the applicability of Aphe for fluorescence structural investigations of peptides is evaluated. The use of Aphe as an acceptor in fluorescence energy transfer measurements offers the possibility of facilitating the determination of donor fluorescence quantum yield (φD) in the absence of energy transfer which usually turns out to be difficult in systems containing donor and acceptor moities. The Aphe residue in peptides also allows a better insight into intramolecular intera

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03580.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Evidence of complex formation between pyrene and polar solvent molecules has been obtained by monitoring the S1,← S0and S2← S0absorption spectra of pyrene. The solvents employed are propionitrile, valeronitrile, dichloromethane, and dioxane. The stabilization energy is found to be small relative to general hydrogen bond energies, but somewhat high relative to the Boltzmann energy. These are in good accord with the findings of Lianos and Georghiou [Photochem. Photobiol.30,355 (1979)] that pyrene forms 1:1 molecular complexes with several dipolar solvents in the ground

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03581.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The phototoxic response induced by hematoporphyrin derivative and irradiation was evaluated in mice congenitally deficient in the fifth component of complement (C5), those congenitally deficient in mast cells, and in cyclophosphamide‐treated, leukopenic mice. Hematoporphyrin derivative, 10 mg/kg, was injected intraperitoneally, and 6 h later, the animals were irradiated (6.5 kj/m2at396–407 nm). Phototoxicity was quantified by measurement of the increase in ear‐thickness. In control mice, at the end of the irradiation (0 h), an increase in the ear‐thickness of28–37% was noted; it reached a peak of51–81 % at 24 h. The phototoxic response in C5‐deficient mice was markedly suppressed both at 0 h and at 24 h (P vscontrol,<0.02 and<0.05, respectively), while mast cell‐deficient mice has a suppressed response at 24 h (P vscontrol,<0.001). In both groups of mice, the intensity of dermal mononuclear and polymorphonuclear infiltrates was not different from that of the respective controls. The response in leukopenic mice was suppressed at both 24 h and 48 h (P<0.001). These results indicate that intimate and complex interactions among the complement system, mast cells, and leukocytes are necessary for the complete manifestation of the ph

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb03582.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY