摘要:

Abstract—Neuroblasts of the grasshopper,Chortophaga viridifasciata(DeGeer), in culture were exposed to 4–15 J/m2of monochromatic ultraviolet radiation in middle prophase and timed to prometaphase (breakdown of the nuclear membrane). At wavelengths 265 and 280 nm the times recorded for the treated cells were significantly less than those for the matched control cells. Wavelength 225 nm produced neither significant acceleration nor deceleration of mitotic rate.Evidence from the present experiment does not implicate any particular chromophore in this response, though similar results of a previous microbeam study of neuroblasts point to the nucleic acid or protein of the nucleolus as the possible effective mater

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06540.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—E. coliK‐12 wild‐type cells plated immediately after UV irradiation had a much lower survival on minimal medium solidified with agar‐agar No. 3 (Oxoid), purified agar (Difco) or ionagar (Colab) than on plates solidified with laboratory‐washed Noble agar (Difco). An intermediate survival was obtained on plates solidified with unwashed Noble agar (Difco). When irradiated cells were incubated in liquid minimal medium for various times before subsequent plating on agar‐agar No. 3, their survival increased rapidly and became identical to the survival of cells plated on washed Noble agar. The same phenomenon was found withpolA1 cells, but no differences in survival on the different agars were observed withuvrB, exrA, recAorrecBcells. These‐ data suggest that a repair process dependent on theuvrB, recA, recBandexrA(but not thepolA) gene products is inhibited when UV irradiatedE. coliK‐12 cells are plated on minimal medium solidified with agar‐agar No. 3, purified agar or ionagar. This implies that theuvrgene‐dependent excision‐repair process consists of at least two branches, one controlled by thepolAgene and a second controlled by therecA, recB and exrAgenes and inhibitable by a substance present in certain agars. For maximum sensitivity, experiments designed to study chemical inhibitors of repair should use agar plates that do not them

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06541.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—A spectrophotometer using the photon‐counting method is described. The sample cuvette is mounted on a table which can be displaced in theXandYdirections, permitting investigation of absorption and self‐absorption processes within the cuvette. Fluorescence detection is performed at right angles to the direction of the exciting beam, the analysis grating being driven by a stepping motor. The apparent spectrum is fed into a multichannel analyser and printed. Corrections are made to the data provided by the printer. Signal‐to‐noise ratio, fluorescence spectra and fluorescence excitation spectra are discussed in more detail for the case of more concentrated solutions. This very high sensitivity device allows room‐temperature investigation of the fluorescent emission from neutral aqueous solutions of nucleic acid bases, nucleosides, nucleotides, dinucleotides etc., quantum yields for these molecules being of the order of 10‐4. A table of minimum concentration values of some commonly used fluorescent pr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06542.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Ultraviolet irradiation of pyrimidine and 4‐ and 5‐methylpyrimidine in methanol at 113 K gave the corresponding semiquinone radicals in a monophotonic process. It is likely that this process involves ann* triplet state of the photoexcited pyrimi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06543.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—From flash photolyses of methyl formate (HCOOCH3),d‐methyl formate (DCOOCH3), methyl formate‐d3(HCOOCD3) and fully ***deuterated methyl formate (DCOOCD3) in the vapour phase at room temperature, the relative efficiencies of the formyl and methoxyl radicals in producing formaldehyde have been deter

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06544.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The properties of delayed fluorescence (DF) of proteins are studied in parallel with their properties of recombination luminescence, produced after ultraviolet excitation and photoionization of chromophoric residues at low temperature, in water‐ethylene glycol glasses. It is shown that the DF emission of proteins, originating from tryptophan residues, is produced via triplet‐triplet absorption processes, photoionization of tryptophan residues, and recombination of the charged species. Electron scavengers that reduce the DF yield act differently upon the DF emission and the recombination luminescence as a consequence of the protein structure. Influence of energy transfer on the protein DF yield is also empha

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06545.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The synchronized asexual cycle inProtosiphon botryoidesKlebs is described. A blue light (430 nm) inhibition of zoospore production can be photoreversed by green light (550 nm). Similarly, a green light (550 nm) stimulation of zoospore production can be photoreversed by blue (430 nm) light. 430 nm light also shortens the period of zoospore motility, and 550 nm light lengthens this perio

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06546.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Light‐induced EPR signals can be observed in moss spores and pollen grains. Their characteristics are studied in this paper. The modification of these signals during spore maturation or various physical and chemical treatments shows that they probably originate in the spore or pollen grain wall. This hypothesis is confirmed by the similarity between the spore (or isolated spore wall) absorption spectrum and the light‐induced signal action spe

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06547.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Absorption, fluorescence, and circular dichroism (CD) spectra have been obtained for a mucopolysaccharide—cationic dye complex. The dye acridine orange exhibits a blue shift in its absorption maximum and a red shift in its fluorescence maximum when mixed with chondroitin sulfate A in aqueous solution. The spectral shifts of the dye appear to be reversed by addition of salt, divalent cations being more effective than monovalent cations. The complex exhibits induced optical activity in the visible absorption spectrum of acridine orange. The biphasic nature of the CD curve is compatible with interpretations involving chromophore coupl

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06548.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Lipid model membrane systems, liposomes, may be oxidized by both toluidine blue Osensitized photo‐oxidation and radiofrequency‐discharge‐generated singiet oxygen. Oxidation can be followed by the appearance of lipid peroxides, malondialdehyde formation, and ultimately by the lysis of the liposomes. Inhibition of oxidation is observed in both systems using either β‐carotene or DABCO. These observations are consistent with the view that type II (singlet oxygen) reactions are involved in this photodyna

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06549.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY