ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08891.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—A critical review of photochromism in triphenylmethane derivatives and some related compounds is presented. Most of the triphenylmethane compounds reported to be photochromic as well as some of those reported as non‐photochromic are mentioned. Compounds were included only if the conditions under which the observations were made were reasonably well described. Qualitative observations of photochromism are predominant since very little quantitative data are available. Physical properties of the compounds and/or their solutions which appear to be related to photochromism are discussed including conductivity, dielectric constant and dipole moment. Among other topics discussed are mechanisms and kinetic stud

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08892.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Extracts ofNeurospora crassacontain photoreactivating enzyme by the criteria of ability to split thymine‐containing dimers and to increase the transforming ability of u.v.‐irradiatedHemophilus influenzaeDNA. The latter activity is heat‐labile and is destroyed by trypsin. The action spectrum of suchin vitrophotoreactivation is a simple one (with a single maximum at 405 nm in the range 313 to 436 nm), differing from the more complicatedin vitrospectra for yeast andEscherichia coli.However, thein vitro Neurosporaspectrum coincides closely with thein vivospectrum for this organism, suggesting that there is little or no “indirect” photoreactivation inNeurospora.It is concluded that theNeurosporaphotoreactivating enzyme is probably of a different type than those of yeast andEsche

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08893.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—The lumincscence arising from L‐tryptophane and L‐tyrosine in aqueous solutions at 77d̀K during irradiation with u.v.‐light and with X‐rays has been studied. The spectra obtained with the two types of radiation were largely similar, differing only in that the yields of phosphorescence relative to fluorescence were considerably enhanced in the case of X‐irradiation. The decay times observed for the exponentially decaying phosphorescence, being 6.6 sec and 2.7 sec for tryptophane and tyrosine respectively, were the same for both kinds of irradiation. The G‐value of the X‐ray induced luminescence was about 10 for both tryptophane and tyrosine. Thus, about 30 per cent of the total energy absorbed from X‐rays in these compounds was re‐emitted as light.It was concluded that the X‐ray induced fluorescence and phosphorescence originate from the same levels as does the luminescence caused by u.v.‐light, i.e. the lowest excited singlet and the lowest triplet level of the aromatic structure of these compounds. In the case of X‐irradiation the enhanced ratios between the yields of phosphorescence and fluorescence indicated that some process other than excitation directly from the ground state contributed considerably to the luminescence yields. Assuming this process to be a recombination between the ionized molecule and its electron, it was calculated that the contribution to the luminescence yield from excitations directly from the ground state relative to that from ionizations, was neg

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08894.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Previous workers have reported that, in a variety of cells, ultraviolet microbeam irradiation of cytoplasm adjacent to the mitotic spindle causes the spindle to diminish or disappear and have postulated that this effect is mediated by a spindle “poison” produced photochemically from a cytoplasmic precursor. In the present work, a microbeam action spectrum for this effect has been obtained to aid in the identification of this mediator material. A small portion of the cytoplasm ofAmbystoma(salamander) tissue‐culture cells was irradiated in early metaphase with ultraviolet microbeams of various wavelengths and intensities but of the same diameter (8 μ). Spindle destruction was scored by observing diminution of its image as seen with a polarization microscope. In addition, the time of anaphase was recorded so that an action spectrum for anaphase delay was also obtained. These two action spectra are quite similar and are nearly parallel to the absorption spectrum of a tyrosine‐containing protein. A few proteins are discussed which might mediate t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08895.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—The quantum yields of phosphorescence and fluorescence and the phosphorescence lifetime have been determined for biacetyl in benzene, p‐xylene, n‐heptane, and water, and for benzil in n‐heptane at 22d̀C. The following values for the fluorescence quantum yield and natural phosphorescence lifetime were obtained: For biacetyl in benzene, 2.7 times 10‐3and 7.8 msec, in p‐xylene, 2.5 times 10‐3and 10.8 msec, in n‐heptane, 2.9 times 10‐3and 10.8 msec, in water, 1.1 times 10‐3and 10.0 msec, and for benzil in n‐heptane, 1.1 t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08896.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Near ultraviolet (365 nm) and green‐yellow (546‐579nm) radiations repress the growth of liquid cell cultures of Ginkgo pollen and of monolayer cultures of HeLa. The deleterious effects of green‐yellow wavelengths can be negated by red radiation; near‐u.v.‐induced growth repressions are insensitive to visible light photorestoration. These wavelengths do not interact synergistically and evoke different kinetics

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08897.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY