摘要:

Abstract—Electronically excited triplet species generated during the peroxidase catalyzed aerobic oxidation of appropriate substrates efficiently elicit fluorescence from acceptors in micelles, as shown with 9, 10‐dibromoanthracene and chlorophyll solubilized by various surfactants. In the case of 9, 10‐dibromoanthracene excited by triplet acetone, phosphorescence also can be detected near O2depletion.The significant implications of this study are that micelle‐solubilized chlorophyll is an excellent detector of enzyme‐generated triplet carbonyl species, as confirmed with several systems, and that the use of micelles make it possible to extend ‘photobiochemistry without light’ to other photobiologically important, yet water insolu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03375.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The absorption spectra, lifetimes, extinction coefficients and intersystem crossing quantum yields of the lowest tripletT1of 4‐thiouridine have been determined both in acetonitrile and in water. An ordering of1,3(n,π)* and1,3(π,π)* states is suggested. Triplet quenching rate constants with various pyrimidine bases or amino acids are re

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03376.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The self‐sensitized photooxidation of mesodiphenylhelianthrene in various solvents has been investigated. The involvement of1O2as the reactive intermediate in the formation of the endoperoxide has been demonstrated by the quenching of the photooxidation by the efficient1O2‐quencher β‐carotene. The rate constant for the addition of1O2to mesodiphenylhelianthrene has been determined to bekR≅ 1010M‐1s‐1, which is the highest value hitherto known in the literature. The probability factorp, which describes the concentration independent part of the overall quantum yield, has been measur

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03377.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Porphyrins appended in themesopositions with 1,2‐diazole, indole and quinoline are shown to exhibit enhanced fluorescence quantum yields relative tomesotetraphenyl porphyrin. The singlet emission yields decrease with the number of appended heterocyclic bases. An intramolecular charge transfer resonance mechanism has been advanced to interpret these resu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03378.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The chemical structure of the major product that resulted from illumination of ethanolic solutions of dibromothymoquinone was deduced using13C‐and1H‐nuclear magnetic resonance spectroscopy. The photoproduct is 2,5‐dibromo‐3‐allyl‐6‐methyl‐p‐dihydrobenzoquinone. The inhibition of photosynthetic electron transport by the photoreduced compound was found to be roughly equivalent to inhibition by nonirradiated

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03379.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Action spectra for the lethal effects of ultraviolet light (254–434 nm) irradiation delivered under aerobic or anaerobic conditions toEscherichia coliRT2 (specifically sensitive to near‐UV radiation;>320 nm) andE. coliRT4 (near‐UV resistant) were prepared. Negligible oxygen dependence was observed for both strains below about 315 nm. The oxygen enhancement ratio (OER) for RT4 increased above this wavelength to the longest wavelength used, whereas for RT2 there was a greater increase in the OER to a large peak at 365 nm, then a progressive decrease at longer wavelengths. The results are consistent with the possibility that the sensitivity of strain RT2 to near‐UV radiation may be due to hyperproduction of photosensitizer, operating via photodynamic type reactions involving excited species

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03380.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The two‐cell mouse embryo has a unique cell cycle of a short DNA synthesis (S) phase and an extremely long post‐DNA synthesis (G2) phase. An attempt was made to investigate the radiation biology of the long G2phase using UV radiation as a probe. Two cell mouse embryos, at various positions in the cell cycle, were UV‐irradiated in phosphate‐buffered saline. The embryos were cultured for a few hours to 3 days to assay for their cell proliferative characteristics. The embryos were most sensitive to the killing action of UV radiation in the late G2phase. The embryos divided more than two times after low UV fluences before dying and experienced G2phase delays.These results can be contrasted to the situation in somatic cells, in which the action of UV radiation is S phase selective. One possibility is that the target for the action of UV radiation is different in two‐cell mouse embryos from that in somatic cells and that the target is similar to that for X

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03381.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The effect of UV‐B irradiation on the development ofDictyostelium discoideumfrom amoebae to mature sorocarps was studied. Radiation with wavelength ≤ 310 nm was very efficient in retarding and inhibiting the development especially when the organisms were exposed during the first 12 h. At a wavelength of 280 nm an irradiation of 1 h at an irradiance of<0.2 W m‐2was sufficient to completely inhibit sorocarp development. The fluence‐dependence shows as well that the development ofD. discoideumis a very sensitive system to indicate UV‐B irradiation. Furthermore, since the sorocarp development is concluded within 48 h it can serve as a fast bioassay for hazardous levels of increased UV‐B irradiation which have been predicted as a result of the ozone reduction in the stratosphere due to the manmade production and emission of chlorof

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03382.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Formation of crosslinks in DNA by various mono‐ and bifunctional furocoumarins plus UVA light in mouse embryo fibroblasts was evaluated by a NaI density gradient centrifugation method. Angelicin and 3‐carbethoxypsoralen did not form any crosslinks: however, angelicin was slightly carcinogenic for mouse skin, whereas 3‐carbethoxypsoralen was not carcinogenic. Psoralen induced DNA crosslinking, in a dose‐dependent fashion and was highly carcinogenic for mouse skin. In contrast to the psoralen‐induced photoadducts (120 per 106nucleotides) which were left unrepaired, 41% of the 3‐carbethoxypsoralen adducts (30 per 106nucleotides) were removed during 1 h of dark po

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03383.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—We have previously demonstrated that 8‐methoxypsoralen (8‐MOP)‡ plus UVA is able to inactivate the three enzymatic activities ofE. coliDNA polymerase I and that oxygen is required for these reactions (M. Grangeret al., (1982)Photochem. Photobiol.,36, 175–180). We now show that UV‐A irradiation produces a covalent incorporation of the psoralen derivative into the enzyme either in the presence or in the absence of oxygen. The excited psoralen binds directly to the protein in an oxygen‐independent reaction; no complex was detected in the absence of irradiation. Fluorescence measurements reveal that at least two photoadducts are formed.The 8‐MOP‐photomodified enzyme is still fully active but further irradiation leads to an inhibition of the 5′→ 3′ polymerase activity whereas the 5′→ 3′ exonuclease activity is not affected. A major part of the inhibition reaction is shown to be oxygen‐dependent but singlet oxygen quenchers have no effect on the kinetics. This oxygen‐dependent reaction is attributed to a photosensitization, due to covalently bound 8‐MOP, of neighbouring amino acids through an intermediate reactive oxygen species which is not singlet oxygen. The oxygen‐independent reaction is attributed to a direct photosensitization thro

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03384.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY