摘要:

Abstract—The formation of singlet molecular oxygen (1O2) by sensitization of the furocoumarins 5‐methoxypsoralen (5‐MOP), 8‐methoxypsoralen (8‐MOP) and psoralen complexed with DNA was investigated. From the results it is concluded that 5‐MOP complexed with native DNA is able to generate1O2, even in a larger extent than 5‐MOP free in solution. Also, with 8‐MOP and especially with psoralen,1O2formation by the complexed compound could be observed. The1O2formation sensitized by covalently bound furocoumarin was demonstrated with psoralen as a model compound. 4′,5′‐Dihydropsoralen, a model compound for the UVA light absorbing 4′,5’monoadducts of furocoumarins to DNA, is

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09060.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—The geometric requirements for intramolecular fluorescence quenching of indole by carboxylic acid and amide functions have been determined in rigid norbornyl ([2.2,1]bicycloheptenyl) skeleton:transandcis3‐(3′‐indolyl) norbornene 2‐dimethylcarboxamides or carboxylic acids. The reference compound was the 3‐(3′‐indolyl) N‐dimethylpropionamide or ‐propanoic acid. The quenching occurs mainly in protic solvents. In theciscompounds, the quantum yields are strongly decreased when compared to thetransand open chain compounds. As determined by the pH dependence of fluorescence of the acids, it is in the acid form—COOH that the fluorescence is quenched; in the ionized species ‐CO−2, only small quenching is observed. The Ksof Stern‐Volmer equations are very small for thecisbicyclic acid and amide, the indole nucleus being shielded on one side only. The results support the hypothesis that small rearrangement of the peptide bond in protein conformation changes may

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09061.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—A mutant ofSaccharomyces cerevisiaewas isolated which has a low capability for photoreactivating UV‐induced lethal damage. The DNA photolyase activity of the cell‐free extract is much less than in a wild‐type strain.In vivocomplementation of photoreactivation was demonstrated in crosses withphr1mutant strains. Tetrad analysis and backcrosses suggest that this new mutation defines a second chromosomal genePHR2which is loosely linked to theP

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09062.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Spectral transmittance of 400–865 nm radiation through various human structures, including the skull with scalp, the chest wall, abdominal wall and scrotum, is presented. There is essentially no visible light of wavelengths shorter than 500 nm transmitted through the chest or the abdominal wall. In contrast, 10−5–10−4of blue light can reach the brain and testes. Transmittance of all tissues increases progressively with wavelength from 600 to 814nm. The maximal transmittances are 10−2–10−1for skulls and scrota, and 10−3–10−2for chest and abdominal walls. Tissue thickness, optical absorption and scattering are majo

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09063.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—In this study, we examine some of the photobiologic and immunologic characteristics of the suppression of contact hypersensitivity (CHS) by UV radiation. BALB/c mice were irradiated on the shaved dorsal skin with FS40 sunlamps and sensitized 5 days later by applying a contact sensitizer lo the shaved abdomen. The suppression of CHS resulting from exposure to a given total dose of UV radiation was unaffected by changes in dose fractionation over a 5‐day period and by changes in dose‐rate over a 10‐fold range. Elimination of wavelengths below 315 nm with a mylar filter abrogated the suppressive effect of the sunlamps, even when the same total energy was administered. Irradiation of unshaved mice required 14 times more energy to produce 50% suppression than was required for shaved mice, suggesting that the exposed skin is the primary target of this effect. Contact sensitization of UV‐irradiated, but not unirradiated, mice induced the appearance of antigen‐specific suppressor T lymphocytes in their spleen. The photobiologic and immunologic similarities between the suppression of CHS by UV radiation and the UV‐mediated suppression of tumor rejection that we described previously suggest that these two immunosuppressive effects of UV exposure share certain steps in t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09064.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—A detailed experimental study of the effect of intensity of a 6 ps excitation pulse on the decay kinetics and yield from phycobilisomes (PBsomes) is presented. The fluorescence from thec‐phycoerythrin (PE) emission from PBsomes was found to decay as a single exponential with a time of 31 ± 4ps for an excitation intensity1014photons/cm2. The decrease in yield with increased intensity in this case occurred at a higher intensity than in the isolated phycobiliprotein PE. The fluorescence yield of the PC and APC emission component was also found to decrease markedly with increasing excitation intensity. This is in contrast to the case of the isolated phycobiliprotein APC which showed only a slight quenching of the fluorescence. The higher quenching observed for the APC emission in the PBsome evidences the higher effective absorption of APC via energy transfer from PE to PC

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09065.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—The partially purified blue light‐sensitive membrane‐associated flavin‐cytochrome complex from etiolated corn coleoptiles shows a unique sharp α‐band at 555 nm in its light‐minus‐dark difference spectrum at liquid nitrogen temperature. This band is clearly distinguishable from the α‐bands found in fractions enriched for mitochondria and endoplasmic reticulum respectively. The photoactive membrane fraction is shown to have ATPase activity that is not stimulated by K+and that is not inhibited by oligomycin. Other than flavin fluorescence at 525 nm obtained upon excitation at 450 nm, there is a second fluorescent component with emission at 430 nm on excitation at 350 nm. The mid‐point potential of the Triton X‐100 solubilizedb‐cytochrome, measured by simultaneously monitoring the reduction of the pyocyanine 600‐800 nm peak and the appearance of the 427 nm Soret peak of theb‐cytochrome upon titration with dithionite in the presence of ferricyanide, is estimated to be −65 mV. The kinetics of the blue light‐induced reduction and dark rcoxidation of the 6‐cytochrome suggest that the mid‐point potential of theb‐cytochrome is not af

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09066.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—C‐phycocyanin fromSynechococcussp. (Anacystis nidulans) shows photoreversible absorption changes when dissolved in buffer containing 75% ethylene glycol (vol/vol). Irradiation with red light (638 nm) causes a 7.5% decrease in absorbance around the absorption maximum (620 m), while the absorbance around 500 nm increases. Subsequent irradiation with green light (500 nm) partially reverses this change. Final photoreversibility at around 620 nm amounts to ca. 2.5% of the maximum absorbance. These reactions are ascribed to two interconvertible species PCrand PCg, the former with a higher absorbance in the red. the latter in the green. The rate of dark reversion from PCgto PCris strongly enhanced by ferricyanide. It is proposed that with this reagent, dark reversion occurs via an oxidized form of PCg. Furthermore, ferricyanide in the presence of ethylene glycol is capable of reversibly oxidizing part of the chromophores of C‐phycocyanin, presumably to a radical. In the absence of ethylene glycol, however, ferricyanide causes total irreversible bleaching of the pigment in the dark. The induced photoreversibility of C‐phycocyanin is ascribed to the perturbing action on the protein structure by ethylene glycol in high concentrations. This solvent proved the most suitable perturbant of several compounds

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09067.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—The action spectrum of phototaxis inDaphnia magna(Crustacea) was measured in a chamber which simulated a natural angular distribution of underwater light. A 17% step‐down in irradiance was used to stimulate the phototactic response at all wavelengths and irradiances tested. Peaks in the spectral response curves depended on the fluence rate to which the zooplankton were acclimated. The wavelength of maximum response (Zmax) shifted from yellow‐green at the highest acclimation fluence rate (5.1 × 10−2Wm−2) to blue‐violet at moderate rates. At low acclimation fluence rates, the blue‐violet maximum was retained and another maximum developed in the red. At the lowest fluence rate (1.6 × 10−5Wm−2), the blue‐violet and red maxima were lost and another maximum developed in the near ultraviolet. The action spectrum indicates the presence of three, and possibly four, photopigments with Zmax, at ∼405, 440, 570 and 690nm. The 440 and 690nm maxima may belong to the same photopigment; however, this was not tested. Changes in zooplankton swimming speed, caused either by large changes in irradiance or by mechanical stimuli, were accompanied by changes in the strength of the phototactic response to the −17% stimulus at any irradiance level for white and monochromatic light, and indicated the presence of a mechanism connecting swimming s

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09068.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Phycoerythrocyanin is a biliprotein found in very few blue‐green algae. Its properties have been examined under three conditions: in whole cells, in light‐harvesting organelles (the phycobilisomes). and as an isolated protein. Absorption and fluorescence bands characteristic of the isolated protein are essentially the same as those in intact cells of the blue‐green algaAnabaena variabilis.The same spectroscopic hallmarks are observed in purified phycobilisomes. Dissociation of these physobilisomes at low‐phosphate concentrations resulted in increased phycoerythrocyanin fluorescence. This time‐dependent increase in fluorescence demonstrates the function of this biliprotein in excitation‐energy transfer to the other biliproteins when the organelles are intact. The relative stabilities of the various heteroprotein bonds within the phycobilisomes are shown to possess differing phosphate ion dependencies. Studies on the isolated protein fromMastigocladus laminosusinclude fluorescence measurements at both 23 and‐196°C, as is generally observed with biliproteins, although phycoerythrocyanin has complex visible absorption and excitation spectra, only a single emission

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb09069.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY