摘要:

Abstract—Mechanism of the photogeneration of hydrogen peroxide and superoxide ion from tryptophan (Trp) and its photooxidation products was investigated. Near‐ultraviolet irradiation of 3a‐hydro‐peroxypyrrolidinoindole, an intermediate in the photooxidation of Trp, has been shown to generate hydrogen peroxide efficiently under aerobic conditions. Irradiation of N‐formylkynurenine in the presence of 3α‐hydroxypyrrolidinoindole also produced hydrogen peroxide. The formation of superoxide ion in both reactions has been confirmed, whereas the reaction of Trp with chemically generated singlet oxygen did not produce any detectable amount of su

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03822.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Voltage transients are generated across lipid bilayer membranes by light flashes as a result of photophysical processes in sorbed dyes which displace electrical charges. A theory is presented which indicates that: (i) the fraction of sorbed dye which displaces charge from one flash can be determined by the fractional reduction in the photovoltage amplitude resulting from a second and identical flash, providing the second flash occurs before dye excited by the first flash returns to its equilibrium condition. (ii) The photoeffect quantum efficiency can be determined from the fraction of dye displacing charge, the light intensity and the dyes' optical absorption cross section. Apparatus constraints required different experimental procedures for dyes with different excited state life times, which are discussed. Experimental results are presented for an azo dye, 3,3'‐bis(α‐(trimethyiammonium)methyl)azobenzenebromide (Bis‐Q), three carbocyanine dyes in the series 3,3'‐dimethyl‐2,2'‐oxacarbocyanine‐iodide (diO‐C1‐3), an amino‐pyridinium dye, 4‐(p‐(dimethyl‐amino)styryl)‐1‐rnethyl‐pyridinium‐iodide (di‐1‐ASP), and a xanthene dye, 2',4',5',7'‐tetraiodofluorescein (erythrosin), the sodium salt of which is known as F, D and C red number 3. The dyes' optical absorption cross section values are uncertain owing to solvent and orientational effects in membranes. Photoeffect quantum efficiency values obtained by calculating optical absorption cross sections from the dyes' molar extinction coefficients in aqueous solutions are: Bis‐Q (0.08), diO‐C1‐3 (0.31), diO‐C2‐3 (0.22), d

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03823.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Type C chloroplasts were deposited on the surface of an SnO2optically transparent electrode glass plate with polyvinyl alcohol plus bovine serum albumin as immobilizing supports. This electrode, on illumination of 250 J/m2in an electrolyte solution, generated anodic photo current more than 150 nA per 10 μg chlorophyll/cm2of the SnO2glass plate at a potentiostatic condition of + 0.5 V against a saturated calomel electrode, and gave rise to an open circuit potential up to 300 mV. The photocurrent output was enhanced as high as 60‐fold under the short circuit condition by the addition of an artificial electron carrier, l‐methoxy‐5‐methylphenazinium methyl sulfate, to the electrolyte solution. With the electrode poised at +0.5 V against a saturated calomel electrode, the enhancement effect was exhibited as high as 13‐fold in the presence of 2,6‐dichlorophenol indophenol. A photocurrent spectrum coincides well with an absorption spectrum of the chloroplast film electrode. Effects of heat‐treatment, photosynthetic inhibitors, and electrolyte's pH on the magnitude of the photocurrent were studied in detail. Water molecule, a primary electron donor in the chloroplast photosystems, contributes to the large majority of photocurrent generation. A minor output was observed with the electrode coated with completely inactivated chloroplasts, probably due to the chlorophyll ph

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03824.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Free radical intermediates appearing during illumination of aqueous suspensions of tungsten oxide were detected by electron spin resonance using the technique of spin trapping. Solutions irradiated contained methanol, formaldehyde, sodium formate and sodium hydrogen carbonate. Signals assigned to the spin adducts of the •H, •OH, •CO2‐and •CH2OH radicals

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03825.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The action spectrum (313–435 nm) for killing Chinese hamster ovary cells containing bromo‐deoxyuridine substituted DNA and treated with Hoechst 33258 was very similar to the absorption spectrum of the dye bound to chromatin, indicating that sensitization was mediated through direct absorption of radiation by the dye. The ratio of sensitization cross sections for 365 nm (plus dye) to 313 nm (no dye) was approx. 30 while this ratio for strand breakage was about one. These results are in agreement with the hypothesis that strand breaks are not the major class of lethal photoproducts induced via Hoechst 33258 sensitiz

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03826.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The near‐UV (NUV, 300 400 nm) sensitivity of logarithmically growingEscherichia colicells of the fatty acid auxotroph K1060 increases with the number of carbon‐carbon double bonds in the fatty acid used as supplement. Cultures of K.1060 grown to stationary phase on unsaturated fatty acids of the same chain length but differing in the number of carbon‐carbon double bonds per molecule differed only marginally in their NUV sensitivity. The clear NUV‐sensitizing effect of increasing double bonds in the fatty acid supplement used to support logarithmic growth implies that the membrane may be an important NUV target only for logarithmically growing cells. Based on these observations, our previous suggestion that inefficient conversion of fatty acids in the membrane to their cyclopropane analogs as an explanation for the NUV‐sensitizing effect of thenurmutation on stationaryE. colicell populations mu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03827.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Morphological abnormality due to the UV irradiation of sperm and its modification by photoreactivation (PR) were studied in the sea urchin,Hemicentrotus pukherrimus.When sperm was UV‐irradiated and allowed to fertilize unirradiated eggs, the effect of the UV was manifested as an abnormal morphology of embryos in the gastrula or later stages. The UV‐induced morphological abnormality was prevented by photoreactivation when the fertilized eggs were illuminated with visible light. In the experiments on a stage‐dependent change of PR effectiveness, it was found that an illumination sufficed to effect a nearly complete PR when applied up to the onset of the first DNA synthetic phase, while the PR effectiveness declined thereafter. Illumination after the completion of DNA synthesis had little effect

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03828.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The levels of DNA excision repair, as measured by unscheduled DNA synthesis (UDS) and the UV‐endonuclease sensitive site assay, were compared in cells derived from human fetal brain and dermal tissues. The level of UDS induced following ultraviolet (UV) irradiation was found to be lower (approx. 60%) in the fetal brain cells than in fetal dermal cells. It was determined, using the UV‐endonuclease sensitive site assay to confirm the UDS observation, that 50% of the dimers induced by UV in fetal dermal cells were repaired in 8h, while only 15% were removed in the fetal brain cells during the same period of time. Even after 24 h, only 44% of the dimers induced by UV in the fetal brain cells were repaired, while 65% were removed in the dermal cells. These data suggest that cultured human fetal brain cells exhibit lower levels of excision repair compared to cultured human fetal dermal

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03829.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Data are presented from 14 sites where continuous measurements of the sun's shortest ultraviolet radiation reaching the earth's surface have been made for four or more years. Average daily dose per month and its variability from year to year is shown for each station. Some of the many influences affecting these measurements can be discerned by station intercomparisons. No consistent long term change in solar UV‐B radiation reaching the ground is evid

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03830.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Reaction center (RC) complexes isolated from the photosynthetic bacteriumRhodopseudomonas sphaeroidesR‐26 were dried as a film onto platinum and semiconductor (SnO2) electrodes. The light‐induced primary charge separation which occurs across the biological complex couples electrically with the SnO2but not with the metal electrode on the time scale of observation. As the working electrode in a two‐electrode photoelectrochemical cell, RC‐coated SnO2generated photovoltages as high as 80 mV and photocurrents as high as 0.5µA·cm2when exposed to light of λ>600nm. The number of quinone molecules per RC strongly influences the photovoltage and photocurrent observed. Photo‐effects generated by RC electrodes persist after several days of storage; however, the kinetics and polarity of the effects are subject to change. The potential use of RC electrodes lies more as a new probe of photosynthetic electron transport rather than as a solar energy conversion device because modification to the RCs and their environment affect the electrical properties of the cell. An energy‐level model is proposed to explain how the photoelectrochemica

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb03831.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY