摘要:

AbstractA number of trp–containing peptides (gly‐l‐trp,l‐ala‐l‐trp,l‐trp‐gly and N‐acetyl‐trp) have been photolyzed under anaerobic conditions. Analysis of the resultant photoproduct mixtures suggests the intermediacy of an hydrated electron in the case of trp‐gly and N‐acetyl‐trp. Amino acid trp peptides deaminate with a concomitant cyclization to the 4‐position of the indole. This appears to occur via a short‐lived radical indole complex. Little difference was detected between photoproduct mixtures using either vycor or a Corning CS‐0‐54 (cut off ca. 295 nm) as filters. Thus these reactions can occur both above and

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05315.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThein vitrophotochemical behaviour of benzo[a]pyrene (BP) in presence of short and long chain carboxylic acids is studied. The direct irradiation (295–400 or 320–400 nm) of BP in solution in the presence of saturated carboxylic acids destroys more than 70% of this carcinogen in 72 h with a 150 W Xe arc lamp. Consumption of BP alone under similar conditions is less than 10%. The principal product resulting from direct interaction of BP with carboxylic acids is characterized as 6‐acyloxybenzo[a]pyrene by means of UV, IR, NMR and mass spectroscopy. The other pathways of destruction may involve polymerization. Saturated fatty acids are shown to favour photoacyloxyation, while unsaturated fatty acids appear to facilitate polymerization of BP. The effect of different factors, such as the carboxylic acid involved, solvent, and wavelength on photoacyloxylation reaction as well as on the consumption of BP is discussed. Photoinduced interaction of BP with carboxylic acids seems to involve radical cation as well as free radicals of the hydrocarbon. Biological properties of BP esters in terms of primary irritancy and carcinogenic activity have also been tested by mouse skin assay. Both long and short chain esters do not show any carcinogenic activity; conversely, long chain esters are shown to be more severe irritants as compared to short chain esters

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05316.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA rubrene derivative has been synthesized as a new trap for singlet oxygen in aqueous solution. Photooxygenation and evolution of the endoperoxide under various conditions have been investigated. This trap may be used either as a colorimetric test or as a specific one by isolation of the endoperoxide.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05317.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA continuous argon laser has been used to study the self‐sensitized photooxidation of potassium rubrene‐2,3,8,9‐tetracarboxylate in oxygen‐saturated H2O and D2O. An analysis of the data obtained in concentrated solutions leads to an unexpected high value of the ratio of1O2lifetimes in D2O and H2O,Td2o/Th2o =17 ± 1. Results obtained in diluted aqueous solutions are interpreted in terms of a re‐encounter of1O2and ground state substrate molecules generated in the same triplet—triplet anni

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05318.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTwo common methods of obtaining nanosecond time‐resolved spectra (TRES) are compared. TRES measured directly are distorted owing to convolution of the fluorescence signal with the exciting pulse but can be obtained with ease. Undistorted TRES, constructed from deconvoluted decay curves, suffer from poor spectral resolution, require much experimental and computation time to produce and may not be completely free from distortions. Nevertheless, they must be used for quantitative calculations. It is recommended that the method of obtaining TRES should be determined by the type of information require

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05319.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractUptake of ala in exponentially grown and starved cells ofEscherichia coliB/r is inhibited by monochromatic far–UV (254–310 nm) and near UV (310–405 nm) light. The action spectrum for inhibition of ala uptake is similar to that found earlier for gly uptake, showing a maximum at 280 nm and a significant but much lower action throughout the near–UV region. The action spectra suggest that the chromophores for inactivation of ala and gly uptake lie in the carrier proteins and that these proteins are similar. Kinetic studies, in unirradiated bacteria, show that (a) theKmfor ala uptake (11 μM) is about twice that for gly uptake (4.9 μM), (b) theKmfor ala uptake does not change in the presence of gly, although the Kmaxdoes decrease, and (c) other amino acids, such as ser and phe, have no effect on theKmorVmaxof the ala uptake system. These data suggest that ala and gly are transported by the same carrier protein, with the binding sites for ala and gly on different

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05320.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe interaction of near‐UV light and a photosensitizer, 8‐methoxypsoralen (8‐MOP), was studied in the Chinese hamster ovary cell/hypoxanthine‐guanine phosphoribosyl transferase system; cell survival (cloning efficiency) and mutation induction (resistance to 6‐thioguanine) were quantified. Exposure of cells to either 8‐MOP up to 20 μg/ml(93 μM) or near–UV light up to 40000 J/m2had no effect on either survival or mutation frequency. Preincubation of cells with 8–MOP from 5 to 120 min prior to irradiation with various fluences did not affect cell survival or mutation frequency. Survival decreased and mutation frequency increased linearly when either the 8‐MOP concentration or fluence was increased while the other factor was held as a constant. Mutation frequency appears to show reciprocity relative to the product of 8‐MOP concentration times fluence of near–UV light [(μg/ml)·(J/m2)] throughout a range apparently limited by high cell lethality. The observed pooled data on mutation,f(x), as a function of (μg/ml)·(J/m2),x, fit a linear dose–response line,f(x) = (34.2 + 0.05x) × 10‐6. Cell survival, however, does not ap

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05321.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractMeasurements were performed to determine the action spectrum and dose dependence for photoreactivation ofE. coliBs‐1cells after γ‐irradiation. The similarities between photoreactivation after UV‐ and after γ‐irradiation in action spectra, kinetics, and other characteristics indicate that the increased survival of γ‐irradiated cells after illumination with photoreactivating light is the result of true photoenzy

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05322.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe formation of colonies in solid medium was used as a criterion of viability to determine the effect of ultraviolet radiation onTrichomonas vaginalis.Both viability (colony) counts and total cell (hemocytometer) counts were used to estimate physiological ages of cell populations to be irradiated. Washed‐cell suspensions in 0.6% saline were exposed to far‐ (254 nm) and near‐UV (300–400 nm) radiation and dose‐response survival curves were constructed from colony counts. The effect of far‐UV was found to be independent of growth phase with the D0for exponential, early stationary, and late stationary cells 2.6, 2.7, and 2.7 J/m2, respectively. Survival to near‐UV increased with the age of cells with the estimated D50being 216 J/m2for exponential cells, 1360 J/m2for early stationary cells, and 4200 J/m2for late stationary cells. Exponential cells ofTrichomonas gallinaeirradiated with near‐UV had a D50of 340 J/m2. T.vaginalisis highly sensitive to far‐UV relative to protozoa.T. vaginalisandT. gallinaeare highly sensitive to near‐UV relative to o

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05323.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractViral DNA was irradiated in the presence of proteins and assayed for loss of biological activity. Several proteins were found to enhance the inactivation of transfecting ability by UV radiation. The sensitization caused by a particular protein depends upon its amino acid composition. Experiments done at low molar ratios of protein to DNA indicate that a protein‐induced lesion could be a highly efficient means of inactivatio

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05324.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY