摘要:

AbstractHydrogen peroxide,t‐butyl hydroperoxide, di‐t‐butyl peroxide and dibenzoyl peroxide efficiently quench the fluorescence of 2,3‐dimethylnaphthalene incorporated into sodium dodecyl sulfate and cetyltrimethylammonium chloride micelles. Potassium persulfate only is effective when the probe is incorporated into a cationic micelle. The binding constant of the peroxides and the intramiccllar quenching rate constants have been evaluated for all the systems considered and the data are compared to that obtained in homogeneous solution. It is concluded that, even for processes which are not diffusion controlled, the quenching process is slower in the m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04469.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe fluorescent states of tetratolylporphyrin and its zinc complex in acetone were quenched by various kinds of quinones. The transient effect for the collisional quenching caused the upward deviation of the plots of the inversed fluorescence intensities of the porphyrinsvsthe quinone concentrations. A charge‐transfer interaction between the porphyrins in the singlet excited states and the quinones was suggested from the dependence of the quenching rate constants on the electron affinities of the quinone

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04470.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Dipyrromethenones, which include xanthobilirubinic acid (I), its methyl ester (II) and theendo‐vinyl analog of neoxanthobilirubinic acid methyl ester (“half bilirubin” methyl ester) (III) bind to human serum albumin (HSA) and thereby exhibit greatly increased fluorescence as well as induced circular dichroism in their long wavelength transitions. As determined from fluorescence studies, the “tightness” of the binding to HSA is,inter alia, inversely related to the inherent solubility of the dipyrromethenone in aqueous buffer. Fast (ps) configurational isomerization (Z→E) is the major pathway for decay of the first excited (singlet) states of the HSA‐bound dipyrromethenones. A quantum yield of − 0.4 is associated with theZ→Eisomerization. Binding to HSA enhances the lifetimes of the less thermodynamically stableE‐isomers. The results of these studies of “half bilirubins” allow a clear evaluation of the effects of protein binding upon the photophysics and ph

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04471.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe singlet oxygen quantum yield (ϕ1o2) of 11 purified fluorescein derivatives was determined by reaction with singlet oxygen acceptors in aqueous and ethanolic solutions; in both solvents ϕ1o2was enhanced with increasing halogenation. Tryptophan and 2,2,6,6‐tetramethylpiperidone were found to be unadapted for the determination of ϕ1o2, in our systems; however, the use of 9.10‐dipropionic anthracene acid andp‐nitrosodimethylaniline in conjunction with imidazole derivatives was suitable for1O2detection in water. Both methods lead to results in excellent agreement. As in ethanol. ϕ1o2, was equal to the triplet state quantum yield (ϕT), the comparison between the two solvents showed that ϕTin water was greater than in ethanol. The comparison between our values obtained with polychromatic light with published data obtained with monochromatic light suggests that the triplet quantum yield of fluorescein derivatives is wavelength

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04472.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe ability of tryptophan in peptides to photosensitize the oxidation of methyl linoleate (ML) was evaluated. Purified ML was irradiated (λ>270 nm) alone or in the presence of a tryptophan‐containing peptide in ethanol solution. Oxidation was monitored by measuring the dienc hydroperoxides formed from ML by high performance liquid chromatography. N‐acetylphenylalanyltryptophan (NAPT) and N‐acetyltryptophan were about 2‐fold more effective as photosensitizers than leucyltryptophan and tryptophylleucine. N‐acetylphenylalanyltryptophan photolyzed in ethanol to form multiple photoproducts including N‐formylkynurenine‐type compounds. However, the NAPT photoproducts did not photosensitize the oxidation of ML and N‐formylkynurenine was about 8% as effective as NAPT. Sodium azide partially quenched the photooxidation se

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04473.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The photosensitized inactivation of subtilisin BPN' by free hematoporphyrin (HP) followed exponential kinetics with positive mechanistic tests for the involvement of singlet oxygen (1O2) as the principal intermediate. The photoinactivation quantum yield was 0.029 at 390 nm in oxygen‐saturated, D2O buffer at pH 7.0. The effects of HP binding were investigated for tryptophan oxidation in bovine serum albumin (BSA) and human serum albumin (HSA) at high protein:HP concentration ratios where the HP was>97% complexed. The reaction kinetics were non‐exponential and mimick a second‐order process in the initial stages. The rate of HP photobleaching was 30‐fold faster for complexed HP compared with free HP, which was shown to account for the observed kinetics. Mechanistic tests showed that1O2was the dominant photooxidizing intermediate of tryptophan residues and that it was not involved in the accompanying photobleaching of HP. The quantum yield for tryptophan oxidation in BSA was 0.11 at 390 nm in oxygen‐saturated, D2O buffer at pH 8.0. The reactivity of HSA was approximately 2‐fold lower than BSA for equivalent conditions. Estimates of the reaction cross sections led to 3 Å2for the inactivation of subtilisin BPN' by1O2and 20 Å2for the oxidation of tr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04474.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractPretreatment of human cells with near UV radiation (UVA) in fluences exceeding 5 × 104Jm−2caused a decrease in the amount of the unscheduled DNA synthesis induced by far UV radiation (UVC). The DNA repair synthesis, as measured by the incorporation of [3H] ‐thymidine, is reduced by nearly a factor of 2 for a UVA radiation exposure of 1.5 × 105Jm−2. Since solar UVA fluence rate is rather independent of latitude, this figure corresponds to a UVA exposure time of 50‐60 min from noon sunlight in the su

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04475.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractWe examined the production of pyrimidine dimers by UV radiation in different intracellular forms of simian virus 40 DNA. Virus and chromatin or previrions were selectively labeled with [l4C]‐thymidine and [3H]‐thymidine, respectively, in the same monolayer of infected cells. Viral DNA was extracted immediately after irradiation, and pyrimidine dimers were detected as sites sensitive to the UV‐endonuclease encoded by bacteriophage T4. No difference in the number of dimers introduced into chromatin, previrions. or virions was det

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04476.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA wild‐typeEscherichia coliK‐12 strain was irradiated using monochromatic radiation in the range 254 to 405 nm. A measure of the cell membrane damage induced at each wavelength was investigated by comparing cell viability after irradiation on nutrient agar and on minimal medium containing either a low or high inorganic salt concentration. An action spectrum for lethality and for cell membrane damage was then determined. From 254 to 310 nm lethality closely corresponded to the absorption spectrum of DNA, and there was no indication of membrane damage. However, above a wavelength of 310 nm, the direct absorption of radiation by DNA could not account for the sensitivity observed. Moreover, at wavelengths longer than 310 nm, cell membrane damage was induced and by an increasing factor up to a peak at 334 nm. At the longer wavelengths of 365 and 405 nm, there was a gradual decrease from the peak of damage to cell membranes induced by 334 nm radiation. These results indicate that cell membrane damage may contribute significantly to near‐UV radiation‐induced cell lethality in wild‐typeE.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04477.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Action spectra for UV‐induced lethality as measured by colony forming ability were determined both for a normal human skin fibroblast strain (lBR) and for an excision deficient xeroderma pigmentosum strain (XP4LO) assigned to complementation group A using 7 monochromatic wavelengths in the range 254‐365 nm. The relative sensitivity of the XP strain compared to the normal skin fibroblasts shows a marked decrease at wavelengths longer than 313 nm. changing from a ratio of about 20 at the shorter wavelengths to just greater than 1.0 at the longer wavelengths. The action spectra thus indicate that the influence on cell inactivation of the DNA repair defect associated with XP cells is decreased and almost reaches zero at longer UV wavelengths. This would occur, for example, if the importance of pyrimidine dimers as the lethal lesion decreased with increasing wavelength. In common with other studies both in bacterial and mammalian cells, our results are consistent with pyrimidine dimers induced in DNA being the major lethal lesion in both cell strains over the wavelength range 254‐313 nm. However, it is indicated that different mechanisms of inactivation operate at wavelengths longer than

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb04478.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY