摘要:

Abstract—Time resolved emission spectra have been measured ofAnabaena variabiliscells which were grown under different light conditions. The spectra of algae photoinhibited with strong white light for 6 h as well as of algae irradiated with blue light are similar to those of the control (weak white light). Cells that were photobleached with strong white light or red light (5 days each) show dramatic changes in their time resolved emission spectra. The contributions of long‐lived components to the time resolved emission spectra are large in photobleached cells. In both the reference sample and in photoinhibited cells the short‐lived components with lifetimes in the picosecond range prevail which indicates efficient energy transfer within the antenna pigments. The results upon photobleaching are discussed in terms of a functional decoupling of the phycobilisome rods from the core while photoinhibition does not influence the pigment composition and the molecular organization of the antenna pig

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02700.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The role of the replicative state of DNA and of the photosynthetic electron transport system in determining UV‐sensitivity of A.nidulansunder conditions of non‐photoreactivation (by incubating the cells for 24 h in the dark following UV‐irradiation) has been investigated. Both the DNA synthesis data and the data on survival levels during cell cycle synchrony forced by light to dark and dark to light transitions showed that the differential UV‐sensitivity was not correlated with the replicative state of the DNA as suggested earlier. However, incubation in the light with the herbicides 2/3‐4, dichlorophenyl/‐l, 1‐dimethyl urea (DCMU) and 2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine (atrazine) which are known to inhibit electron transport by specifically binding to the high turnover B protein of photosynthetic electron transport system II (PSII), enhanced the UV‐resistance with kinetics similar to those of a culture transferred from light to dark. We interpret this result as implicative of PSII as the second lethal target in the case of cyanobacteria. The inactivation of electron transport activity of PSII as measured by the fall in DCMU‐sensitive fluorescence yield during post‐UV dark incubation supports this hypothesis. It is proposed that in wild type cells the survival under conditions of non‐photoreactivation following UV‐irradiation is essentially determined by the level of dark‐repair of damage to PSII and that the 32 kD B protein may have a role in dark‐repair of damage to the electron transport system. This hypothesis explains the paradox of negative liquid holding recovery phenomenon under conditions which promote exci

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02701.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Amorphous chlorophyll a obtained by electrodeposition(Chl–678) undergoes a bathoch‐romic shift upon solvation with gaseous alcohol at ambient temperatures. The process is reversible when the alcohol is removed. With 1‐propanol, the red band of Chi a is displaced from 678 nm to 701 nm and a new aggregate is formed,Chl–701. To determine the nature of the new aggregate, the IR carbonyl bands of Chi are monitored. The free ketone massive band ofChl–678, situated at 1691 cm‐1, is decreased upon solvation to the profit of the associated ketone carbonyl massive band which absorbs at 1656 cm‐1. The bandwidths of the massive bands are much greater than the typical value of a carbonyl band of a ketone in solution. This is an indication that the massive bands are composed of overlapping bands. In order to determine the number and the position of the bands, the Fourier self‐deconvolution technique has been used to enhance the spectral characteristics of the infrared spectra. The band fitting technique is then used on the original spectra to determine the difference in intensity between the bands ofChl–678 and those ofChl–701. The interpretation of the resolved IR spectra shows that the amorphous sample is composed of open dimers linked together by the CO‐Mg coordinate bonds. When the solvated species are formed, these coordinate bonds are not ruptured and one molecule of alcohol for two molecules of chlorophyll is linked to these molecules by an hydrogen bond between the hydrogen of the alcohol and the available ketone and by a coordinate bond between the available Mg and the oxygen of the alcohol. Closed

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02702.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—We determined the polarized and isotropic visible/UV absorption spectra of chlorophylla(Chia) and pheophytina(Pheoa) oriented in the lamellar phase of glycerylmonooctanoate/H2O. Resolution into mutually perpendicular X‐ and Y‐polarized absorption spectra of the pigments was achieved assuming that the transition moments of Chiaand Pheoaare located in the plane of the chromophores. The polarized spectra were deconvoluted into harmonic progressions and the resultant assignment of band positions in the long‐wavelength region was found to correlate well with independent spectral measurements, such as the polarisation of fluorescence. However, the correlation of the experimentally determined transitions with the results of theoretical calculations is not straightforward. The overall conclusions are of fundamental interest in the determination of orientations of the tetrapyrrole macrocycle in lipid lamellae and pigment‐protein structures of photosynthetic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02703.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Weak luminescence was detected using photon counting equipment, from oxygenated, liquid cultures ofEscherichia coliduring two stages of its growth cycle. The first period of emission occurred during the exponential phase of growth and comprised a UV(210–330 nm) band and a visible region(450–620 nm) band, the total intensity being (1.65 ± 0.12) x 103counts s‐1. The second period of emission occurred during the stationary phase of growth and comprised only a visible region(450–620 nm) band of intensity (8.72 ± 0.15) x 103counts s‐1. When the growth temperature was raised from 306.15 to 310.15 K, the above emission intensities were approximately halved, but the spectra were not changed significantly. No luminescence was observed at either temperature when theE. coliwas grown anaerobically. The visible region luminescence was attributed to excited carbonyl groups and excited singlet O2dimers formed during the decomposition of lipid peroxides. The UV component was tentatively assigned to oxidative side reactions accompanying the synthesi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02704.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Photophysical and photodynamic properties of a ehlorin type molecule derived from hydroxyethylvinyldeuteroporphyrin are presented. It photosensitizes singlet oxygen production as efficiently as mesotetraphenylporphin. The high absorptions of both its ground and triplet states in the red (660 nm) make it a potent photosensitizer which might act not only by photo‐oxidation via singlet oxygen but also by radicals produced via sequential biphotonic absorpt

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02705.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Diploid yeast cells exposed to UV‐light of different wavelengths in the region between 254 and 313 nm were assessed for their ability of delayed plating recovery. They were either held in non‐nutrient suspension (‘liquid holding’) or on non‐nutrient agar before final plating. Thus it was possible to distinguish between real and apparent recovery due to cell multiplication. The experiments showed that no delayed plating recovery was found beyond 295 nm wa

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02706.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—We measured excision repair of ultraviolet radiation (UVR)‐induced pyrimidine dimers in DNA of the corneal epithelium of the marsupial,Monodelphis domestica, using damage‐specific nucleases fromMicrococcus luteusin conjunction with agarose gel electrophoresis. We observed that 100 J‐2of UVR from aFS–40 sunlamp(280–400 nm) induced an average of 2.2 ± 0.2 times 10‐2endonuclease‐sensitive sites per kilobase (ESS/kb) (pyrimidine dimers) and that ∼ 50% of the dimers were repaired within 12 h after exposure. We also determined that an exposure of 400 J m‐2was needed to induce comparable numbers of pyrimidine dimers (2.5 times 10‐2) in the DNA of skin ofM. domestica in vivo. In addition, we found that 50% of the dimers were also removed from the epidermal cells ofM. domesticawithin 12 h after exposure. A dose of 100 J m‐2was necessary to induce similar levels of pyrimidine dimers (2.0 ± 0.2 times 10‐2) in the DNA of the cultured marsupial cell line P

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02707.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02708.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY