摘要:

Abstract—Bioluminescence from the oxidation of acetaldehyde by bacterial luciferase ofPhotobacterium fischerihas been demonstrated for the first time and its efficiency has been compared with that of nonanal and other short chain aldehyde

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09522.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Irradiation of 2,2‐bis‐(4‐hydroxyphenyl)‐propane (bisphenol‐A) with UV light causes photo‐decomposition of the compound. Spin‐trapping with α‐phenyl‐N‐tert‐butyl‐nitrone showed that free radicals were cleaved from the molecule. No direct ESR‐spectroscopic information concerning the structure of the remaining radical skeleton could be obtained. Gas chromatographic mass spectrometric analysis of the decomposition products indicated the existence of a semiquinone structure following cleavage of a methyl radical from 2,2‐bis‐4–(hydroxyphenyl)‐propane. The capacity of2,2‐bis‐(4‐hydroxyphenyl)‐propane to give rise to radicals

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09523.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The photophysical behaviour of new pyrrolocoumarins with different substituents on the nitrogen are reported. The photophysical properties of these pyrrolocoumarins are generally in agreement with those of the psoralens: a strong absorption (240–400 nm), a weak fluorescence (400–680 nm) characterized by a short singlet lifetime, and a rather strong phosphorescence at 77 K (480–600 nm). The absorption and fluorescence properties were investigated in several solvents. The shift of the fluorescence maximum is interpreted on the basis of the solvatochromic parameters π*, α and β. The triplet‐triplet absorption spectra also depend on the nature of the solvent, while the triplet excited state has a lifetime of a few microseconds at room temperature (concentration 2.5 × 10−4M). Some absorption and fluorescence characteristics of the 4′,5′‐dihydropyrrolocoumarins, which are suitable models for the 4′,5′‐monoadducts to py

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09524.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The ability of UV‐irradiation (254 nm) to induce formation of RNA‐protein crosslinks in tobacco mosaic virus (TMV) particles have been studied by Cs2SO4density gradient centrifugation, analytical centrifugation, nitrocellulose filter binding and two‐dimensional peptide mapping. RNA‐protein crosslinks were found to be formed on UV‐irradiation of TMV, but the parallel process of UV‐induced RNA chain breakage complicated their quantitation. Using speciall devised equations, the quantum yield of RNA‐protein crosslink formation was found to be 0.65 × 10−5and that of RNA chain break for

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09525.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Oxygen consumption, photoinduced by visible light, and sensitized by novel anthrapyrazole antitumor agents has been observed. Generation of singlet oxygen upon irradiation of ethanolic solutions of the drugs with visible light (480–520 nm) was demonstrated using a specific1O2acceptor, 2.5‐dimethylfuran and a quencher, sodium azide. An electron paramagnetic resonance method was employed to measure the rate of oxygen consumption. Significant differences were found in the sensitizing properties among the anthrapyrazoles studied. Intramolecular hydrogen bonding within the chro‐mophore is one of the structural factors that determine the efficacy of a given anthrapyrazole in1O2ge

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09526.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Cell electrophoresis was used to detect the effect of far‐UV or near‐UV radiation on the cell surface charge of the pathogenic protozoanTritrichomonas foerus. Either far‐UV or near‐UV radiation interfered with the surface charge ofT. foetusat fluences which inhibited cell growth by 50%. Both UV‐radiations induced a significant decrease on surface charge ofT. foetus, as evaluated by measurement of its electrophoretic mobility (EPM). Determinations of EPM of protozoa in solution of low ionic strength indicated that the decrease in the EPM induced by far‐UV is much less pronounced than that observed for near‐UV o

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09527.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—4ells from patients with the sun sensitive cancer‐prone disease, xeroderma pigmentosum (XP) have defective repair of UV damaged DNA with reduced excision of the major photoproduct, the cyclobutane type pyrimidine dimer. Other (non‐dimer) photoproducts, have recently been implicated in UV mutagenesis. Utilizing an expression vector host cell reactivation assay, we studied UV damaged transfecting DNA that was treated byin vitrophotoreactivation to reverse pyrimidine dimers while not altering other photoproducts. We found that the reduced expression of a UV damaged transfecting plasmid in XP complementation group A cells is only partially reversed by photoreactivation.E. coliphotolyase treatment of pSV2catSVgpt exposed to 100 or 200 J m−2of 254 nm radiation removed 99% of the T4 endonuclease V sensitive sites. Transfection of XP12BE(SV40) cells with photoreactivated pSV2catSVgpt showed residual inhibition corresponding to 25 to 37% of the lethal hits to the cat gene. This residual inhibition corresponds to the fraction of non‐dimer photoproducts induced by UV. This result implies that XP12BE(SV40) cells do not repair most of the non‐dimer photoprod

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09528.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Fluorescence and circular dichroic properties of bovine a‐crystallin have been monitored to detect changes in the structural integrity of the protein following photoreactions in the presence of sensitizer, either methylene blue or N‐formylkynurenine. Methylene blue‐sensitized photooxidation causes a change in the tertiary structure as manifested in the near‐UV CD; this is observed within 0.5 h of irradiation during which time tryptophan emission decreases rapidly. Using inhibitors specific for active species of oxygen, it has been shown that singlet oxygen predominantly causes this change but the sensitizer molecules also have some role in this process. Upon 6 h of irradiation in the presence of methylene blue under both aerobic and anaerobic conditions, the thiol groups that were in a non‐polar region of the protein are exposed to polar environments. In conformity with these fluorescence results. near‐UV CD (tertiary structure) suffers a drastic alteration whereas the far‐UV CD (secondary structure) remains virtually unchanged. The studies with inhibitors indicate that sensitizer molecule itself is primarily responsible for this process. This major change in the conformation has been explained by suggesting that a large portion of the protein unfolds in the photosensitized reaction, thereby altering microenviron‐ments, orientation, and intermolecular interactions of different amino acids. N‐formylkynurenine also shows some changes in the near‐UV CD, presumably, caused by H2O2generated in the photosensitized reaction. But the major alteration in the microenvironments of thiol groups and in the near‐UV CD, as observed in the case of methylene blue, does not occur even when the protein is irradiated for 6 h in the presence of N

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09529.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Photolysis of α‐crystallin in the presence of riboflavin under both aerobic and anaerobic conditions causes a rapid decrease in Trp emission; photooxidation most likely occursvianon‐covalent complex formation between the sensitizer molecule and the substrate. However, the change in the tertiary structure of the protein, as manifested in the near‐UV CD, is very different between aerobic and anaerobic photolysis. Riboflavin‐sensitized reaction under aerobic condition causes a major change in the microenvironments of thiol groups as well as in the near‐UV CD, whereas under anaerobic condition the change in the near‐UV CD is much less and SH‐group environments remain unaltered. The sensitizer in this photoinduced change in conformation of the protein is very select

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09530.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—A fast light‐induced light scattering transient in the presence of Mg2+and GTP is observed from bovine rod outer segment suspension. This transient is studied at various temperatures, degrees of photo‐bleaching and GTP concentration. The kinetic analysis of this signal at low photo‐bleaching (∼ 5%) reveals two different processes which are consecutive rather than simultaneous. The rate of both processes depends upon the extent of photo‐bleaching and indicates that each process requires a photolyzed rhodopsin intermediate. At low temperature, the rate constant of both the processes increases with the extent of photo‐bleaching while at higher temperatures it decreases. The calculated activation energy of both processes decreases with increasing photo‐bleaching. It has also been observed that with decreasing GTP concentration, the rates of both processes decrease indicating that the two processes though first order are most likely bimolecular, first order in both GTP and the photolytic rhodopsin intermediate (m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09531.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY