摘要:

AbstractUV irradiation of desferoxamine (Desferal) produced a well resolved electron spin resonance spectrum that we attributed to a nitroxide radical on the basis of thegvalue and hyperfine splitting constants. Of related hydroxylamines, only N, N‐dialkyl or N‐isopropyl and larger branched N‐alkyl derivatives formed nitroxides and UV was not needed; smaller N‐alkyl and N, N‐dicarbonyl derivativeswereinert to UV. Of related acetohydroxamates, the N‐methyl and N‐ethyl derivatives required UV irradiation for radical formation; the other, larger branched N‐alkyl derivatives readily formed free radicals without UV. Nitroxides from hydroxamates, as represented by UV‐irradiated desferoxamine, were predominant at acidic pH values; those from hydroxylamines, as represented by N, N‐dimethyl hydroxylamine, were so at alkaline values. The results were related to the electron donating and withdrawing properties of the N‐substituting groups and the derealization of

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04069.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPhotoreactions of aqueous solutions of synthetic water‐soluble porphyrins were studied by the1H and13C CIDNP technique. Strong polarizations, which were very sensitive to the presence of added acid, were observed on the cationic porphyrins (TMePyPH2‐TAPPH2) when irradiated through continuous UV‐visible light. They resulted from the reverse electron transfer between the semi‐oxidized and the semi‐reduced species of the derivative.When the experiments were carried out in the presence of nucleobases, guanine (and its derivatives) was the only residue that was polarized. This is thoroughly interpreted in terms of a reversible electron transfer reaction leading to guanine photooxidation by the porphyrin excited triplet state. It was shown to be drastically pH‐dependent and was correlated to the redox potential of the porphyrin. It was not affected by the incident wavelength. The reaction proceeded through the intermediate formation of the correlated radical‐ion pair: porphyrin radical anion‐guanine radical cation. This study suggested that a Type I (free radical) reaction could be one of the primary processes in DNA photosensitizatio

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04070.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractOn irradiation of solutions of anthryl‐substituted cobalt(III) cage complexes, [(l‐(anthryl‐9‐methylamino)‐8‐methyl‐3,6,10,13,16,19‐hexaazabicyclo [6.6.6] eicosane) cobalt(III)]3+or [(l‐(4‐an‐thryl‐9)‐3‐aza‐butyl‐l‐amino)‐8‐methyl‐3,6,10,13,16,19‐hexaazabicyclo [6.6.6] eicosane)cobalt (III)]3* in the presence of ethylenediaminetetraacetic acid and platinum catalysts hydrogen was produced. These complexes act as coupled photosensitizers (anthracene moiety) and electron relays (cobalt cage) to produce H2viaenergy trapping and intramolecular electron transfer initially. The intensity of fluorescence and the photochemical reactivity favour the latter complex and the excited singlet state of the anthracene chromophore is invoked as the intermediate state lead

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04071.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe photoallergens bithionol (BT) and fentichlor (FT) generated free radical photoproducts upon UV photolysis which were observable by direct electron spin resonance (ESR). Both the yield and the type of free radical photoproducts were affected by pH, and to some extent, concentration of oxygen and concentrations of the photosensitizers. At pH 8.5, bithionol (0.9 mM) generated a semiquinone type free radical (BI)viaa mechanism which probably involves substitution of the 4‐chlorine by hydroxyl to form the corresponding hydroquinone followed by oxidation. The photolysis of 4‐chlorophenol, 4‐chlorocatechol and 2,2'‐methylene‐bis(4‐chlorophenol) also generated the corresponding semiquinone radicals, suggesting that this mechanism is shared by other 4‐chlorophenols. At pH 8.5, only photoproduct BI was observed during the irradiation of BT; FT related photoproducts were not observed at this pH. However, at higher pH values (pH 10.7 or pH 12), FT photoproducts were also observed in addition to BI upon prolonged irradiation. Moreover, the yield of BI increased drastically at higher pH. Oxygen did not play any role at pH 10.7, although it enhanced the yield of BI at pH 8.5. At pH 8.5, irradiated fentichlor generated, in roughly equal amounts, a semiquinone radical (Fla) and an unidentified species which contained two inequivalent protons (FII). At higher pH values (pH 10.7 and pH 12), at least four species were observed. All of the species are believed to be semiquinone radicals and two have been unambiguously identified. The yield of FI increased by a factor of 50 as the pH was increased from 8.5 to 12. Oxygen played only a minor role at pH 10.7 and above. However, at pH 8.5, it also enhanced th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04072.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSparteine, the tetracyclic saturated amine alkaloid, is highly fluorescent in n‐hexane solution (Φf= 0.64; ζ= 63 ns) and has a large Stokes shift [λmax(abs) = 203 nm; λmax(fluor) = 325 nm]. Its isomer, α‐isosparteine, has similar properties: Φf= 0.55; ζf= 50 ns; λmax(fluor) = 338 nm. Oxidized derivatives, such as lupanine, thermopsine, and α‐diplospartyrine, are weakly fluorescent. Based on a comparison with spectroscopic and photophysical properties of the monoamine, quinolizidine, it is concluded that the excitation energy is delocalized over the two N‐atoms in starteine and a‐isosparteine. The self quenching rate constant for sparteine,ca.1 times 107M‐1s‐1, is about 100 times smaller than that for quinolizidine, consistent with excited state derealization. The significant fluorescence quenching in lupanine is rationalized by the fact that N‐methyl‐2‐piperidone mfe/molecularly quenches the fluorescence of quinolizidine at nearly the diffusion controlled rate in ‐hexane. Comparisons are made with the fluorescence properties of other diamines such as N, N'‐dimethylbispidine and

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04073.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPhcophorbidea(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 of1O2, 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‐2and H2O2generation, respectively, to the medium had little effect on it.Methods for converting1O2to a nitroxide radical by 2,2,6,6‐tetramethyl‐4‐piperidone (TMPD) and for trapping O‐2and 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 only1O2, was produced by PPa, which was excited by light wavelengths of over 600 nm. Both the addition of N3to the solution and the removal of oxygen from the solution inhibited the generation of1O2.These results led us to conclude that1O2was mainly responsible for the hemolysis of erythrocy

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04074.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe cytotoxic and mutagenic effects of chloroaluminum phthalocyanine (CAPC) plus red light have been measured in strains of L5178Y mouse lymphoma cells which differ in their DNA repair capacities. Strain LY‐R, deficient in the excision repair of UV‐induced dimers, was found to be relatively more sensitive to the cytotoxic effects of CAPC plus light, whereas strain LY‐S, deficienl in the repair of DNA double‐strand breaks, was more sensitive than strain LY‐R to the mutagenic effects of the treatment. Mutation frequencies were measured in LY‐S and LY‐R sub‐strains which were heterozygous or hemizygous at the thymidine kinase (tk) locus. The mutation frequency at thetklocus induced in the heterozygous strain LY‐SI by CAPC plus light was lower than that induced by an equitoxic dose of ionizing radiation but similar to that induced by an equitoxic dose of UVC radiation: The mutation frequency at the F., dose of CAPC plus light was approximately 1100 per 106surviving cells. The induced frequency in strain LY‐S1 was much higher than in eithertk+l‐heterozygous orik+10hemizygous strains of LY‐R. The rate and extent of incorporation of CAPC by the LY‐R strains was somewhat greater than for strain LY‐S1 at early times after CAPC addition, but by the time the cells were irradiated (18 h after CAPC addition) the difference was not great enough to account for the difference in cytotoxicity. It is possible that the cytotoxic and mutagenic lesions differ and that either the quantities of the respective lesions induced or the efficiencies of repair of the respective lesions differ inversely in the two strains.light have been measured in strains of L5178Y mouse lymphoma cells which differ in their DNA repair capacities. Strain LY‐R, deficient in the excision repair of UV‐induced dimers, was found to be relatively more sensitive to the cytotoxic effects of CAPC plus light, whereas strain LY‐S, deficienl in the repair of DNA double‐strand breaks, was more sensitive than strain LY‐R to the mutagenic effects of the treatment. Mutation frequencies were measured in LY‐S and LY‐R sub‐strains which were heterozygous or hemizygous at the thymidine kinase (tk) locus. The mutation frequency at thetklocus induced in the heterozygous strain LY‐SI by CAPC plus light was lower than that induced by an equitoxic dose of ionizing radiation but similar to that induced by an equitoxic dose of UVC radiation: The mutation frequency at the F., dose of CAPC plus light was approximately 1100 per 106surviving cells. The induced frequency in strain LY‐S1 was much higher than in eithertk+l‐heterozygous orik+10hemizygous strains of LY‐R. The rate and extent of incorporation of CAPC by the LY‐R strains was somewhat greater than for strain LY‐S1 at early times after CAPC addition, but by the time the cells were irradiated (18 h after CAPC addition) the difference was not great enough to account for the difference in cytotoxicity. It is possible that the cytotoxic and mutagenic lesions differ and that either the quantities of the respective lesions induced or the efficiencies of repair of the

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04075.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe resolution of the absorption spectra in the Q band (480 nm‐620 nm) spectral region of monomeric and dimeric hematoporphyrin species present in aqueous solutions has been achieved using absorption, fluorescence and computer analysis methods. The absorption maxima of the dimer in this spectral region are red shifted about 12 nm with respect to those of the monomer. The significance of this finding in relationship to the well documented blue shift of hematoporphyrin aggregate observed in the Soret band region (λmalx∼400 nm) of the absorption spectrum is discu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04076.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAntibodies were raised in rabbits against purified endonuclease V, the product of the bacteriophage T4denVgene, which incises DNA at the site of UV‐induced pyrimidine dimers. These antibodies cross‐reacted with the purified UV‐DNA endonuclease fromM. luteusin both enzyme‐linked immunosorbent assay and Western assays. However, no sequence similarity was detected between thedenVgene andM. luteusDNA by hybridization. The two endonucleaes are remarkably similar in enzymatic activity, and their antigenic similarities have been preserved despite differences in their DNA se

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04077.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe phototoxicity of various drugs (chlorpromazine (CPZ), metronidazole (MET), 8‐methoxypsoralen (8‐MOP), azathioprine (AZA) and the azathioprine metabolites, 6‐mercaptopurine (6‐MP), methylnitrothio‐imidazole (MNTI), methylnitroimidazole (MNI)) was determined in hairless (Skh‐hrl) mice exposed to a light source with broad emission (290–700 nm). Chlorpromazine, MET, 8‐MOP, AZA, MNI and 6‐MP were phototoxic, as determined by the oedematous response of skin, at doses comparable to those used clinically.The effects of long‐term drug therapy and UV radiation on skin carcinogenesis were then determined. Chlorpromazine and MET, and to a lesser extent AZA, MNTI and 6‐MP, enhanced photocarcinogen‐esis. In each case, both the tumour yield and the proportion of malignant:benign skin tumours were increased. The results of this study imply that prolonged treatment of mice with low‐level phototoxins predispos

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04078.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY