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71.
Tatsuo Iwasa Kazuo Takeda Fumio Tokunaga Peter S. Scherrer Lester Packer 《Bioscience reports》1982,2(11):949-958
To elucidate the role of tyrosine residues in the shift of max and the light-driven proton pump of bacteriorhodopsin~ the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and i t was stable in the dark for several hours at –65°C.Four batho-intermediates were formed by irradiation with green light (500 nm) at –170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at –170°C. Four corresponding meta-intermediates were also formed by irradiation at –60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin. 相似文献
72.
A contractile ring and cortical changes found in the dividing Tetrahymena pyriformis 总被引:1,自引:0,他引:1
Tomoyoshi Yasuda Osamu Numata Kazuo Ohnishi Yoshio Watanabe 《Experimental cell research》1980,128(2):407-417
A contractile ring consisting mainly of microfilaments was found in the fission zone of dividing Tetrahymena pyriformis. Diameters of the microfilaments were widely distributed from 2.5 to 15 nm. Ring-associated structures such as lateral stripes, linkers and beads with siender tails were recognized. Lateral stripes arranged at regular intervals of about 84 nm on some parts of microfilament bundles were found in both tangential and transverse sections, suggesting that they correspond to bands fastening the contractile ring microfilaments. Linkers that connect individual lateral stripes to the epiplasmic layer were present. Beads or beads with slender tails were found to be arranged on some microfilaments.The results of the present paper also indicate that drastic morphological changes occur in the cortex of the fission zone, especially in the epiplasmic layer, accompanying contraction of the division furrow. The epiplasmic layer which was proved to be a compact filamentous network in this study has been known to exist at the periphery of cytoplasm in immediate contact with one of the cell surface membranes, the inner alveolar membrane; however, in the fission zone of the dividing ceil, it was frequently separated from the membrane and subsided into the cytoplasm. The subsided epiplasmic layer was then loosened and dispersed. The subsidence of the epipiasmic layer appears to be caused by the force generated by the contraction of the contractile ring and transmitted with the linkers to the epiplasmic layer. The changes observed in the epiplasmic layer are presumably indispensable for the rigid cortical layer contraction involved in cytokinesis of Tetrahymena. 相似文献
73.
74.
Coumarin, a specific inhibitor of the biosynthesis of celluloseof higher plant cell walls, inhibited the cellulose formationof Acetobacter xylinum. The degree of inhibition reached 55%in the presence of 1 mM coumarin, which causes 70% inhibitionin the case of plant cellulose. (Received April 12, 1976; ) 相似文献
75.
Transient electric birefringence measurements on poly(L -lysine hydrobromide) in methanol–water mixtures have been carried out at various solvent compositions in the vicinity of the helix–coil transition region (from 87 to 98 vol % methanol). Anomalous birefringence transients were observed between 90 and 95 vol % methanol above a threshold field strength. A distinct difference between the responses to weak and strong electric fields was noticed over a narrow range of the solvent composition. The effects of polymer concentration and temperature on the field-strength dependence of the birefringence were studied at a solvent composition of 90 vol % methanol where the anomalous transients appeared most clearly. The double logarithmic plots of the steady-state specific birefringence versus the square of field strength for different concentrations and temperatures could be superimposed by shifting them horizontally along the abscissa. The threshold field strength which was determined from the shift factor decreased with decreasing concentration. The results provide further evidence that strong electric fields can cause a helix–coil transition in this system under favorable conditions. 相似文献
76.
77.
Spruce leaves greened in darkness were devoid of three of the five thermoluminescence bands found for mature leaves. These bands were developed rapidly by exposure of the dark-grown leaves to continuous light. The development of these bands was studied by illumination with repetitive flashes at varied intervals. Flashes at intervals of 1 s were the most effective in inducing these bands. Those at shorter or longer intervals were less effective. It was deduced from these data that the development of these bands is a multiquantum process which involves at least two photo-events with a dark reaction between them. 相似文献
78.
The antibiotic cordycepin (3'-deoxyadenosine), a known specificinhibitor of nucleic acid synthesis and polyadenylation of RNA,remarkably retarded decrease in the chlorophyll and proteincontents of senescing tobacco leaf disks. The effectivenessof cordycepin, at its optimum concentration (ca. 4 x 105M), was 53% as effective as a cytokinin, benzyladenine at 106M. Adenosine and 2'-deoxyadenosine had no anti-senescence action. (Received May 29, 1975; ) 相似文献
79.
and
1986. Complete resistance to challenges with Hymenolepis nana cysticercoids derived from mouse, rat and beetle in mice. International Journal for Parasitology 16: 623–628. When BALB/c and dd strains of mice were given eggs of Hymenolepis nana, they all became completely resistant not only to challenge with mouse-derived cysticercoids but also to challenges with rat-derived and beetle-derived cysticercoids. Serum IgG antibodies at 47–60 days post egg inoculation reacted strongly with these three different host-derived cysticercoids when examined by IFA test, but IgA and IgM isotypes reacted very weakly. Antibodies of infected mouse sera (IgG, IgM and IgA were examined) reacted not only with the protoscolex (scolex of the excysted juvenile) but also with the outer cyst wall. By contrast, uninfected mouse sera and immune sera prepared seven days post cysticercoid inoculation did not react at all. Antigens of both cyst wall and protoscolex appeared to be of parasite origin and not of host origin, and appeared similar in parasites from the different host species. 相似文献
80.
Toxicity of free proline revealed in an arabidopsis T-DNA-tagged mutant deficient in proline dehydrogenase 总被引:5,自引:0,他引:5
The toxicity of proline (Pro) to plant growth has raised questions despite its protective functions in response to environmental stresses. To evaluate Pro toxicity, we isolated an Arabidopsis T-DNA-tagged mutant, pdh, that had a defect in Pro dehydrogenase (AtProDH), which catalyzes the first step of Pro catabolism. The pdh mutant showed hypersensitivity to exogenous application of < or =10 mM L-Pro, at which wild-type plants grew normally. A dose-dependent increase in internal free Pro accumulation was observed in pdh plants during external Pro supply. These results do not just prove the toxicity of Pro, but also suggest that AtProDH is the only enzyme acting as a functional ProDH in ARABIDOPSIS: To further analyze the targets of Pro toxicity, we compared the expression of thousands of genes by pdh plants with that by wild-type plants by cDNA microarray analysis. Most genes were unaffected. Here we demonstrate Pro toxicity by using the pdh mutant and discuss a cause-and-effect action between an excess of free Pro and growth inhibition in ARABIDOPSIS. 相似文献