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排序方式: 共有125条查询结果,搜索用时 15 毫秒
1.
In the photosynthetic green filamentous bacterium Chloroflexus aurantiacus, excitation energy is transferred from a large bacteriochlorophyll (BChl) c antenna via smaller BChl a antennas to the reaction center. The effects of substituted 1,4-naphthoquinones on BChl c and BChl a fluorescence and on flash-induced cytochrome c oxidation were studied in whole cells under aerobic conditions. BChl c fluorescence in a cell suspension with 5.4 microM BChl c was quenched to 50% by addition of 0.6 microM shikonin ((R)-2-(1-hydroxy-4-methyl-3-pentenyl)-5,8-dihydroxy-1, 4-naphthoquinone), 0.9 microM 5-hydroxy-1,4-naphthoquinone, or 4 microM 2-acetyl-3-methyl-1,4-naphthoquinone. Between 25 and 100 times higher quinone concentrations were needed to quench BChl a fluorescence to a similar extent. These quinones also efficiently inhibited flash-induced cytochrome c oxidation when BChl c was excited, but not when BChl a was excited. The quenching of BChl c fluorescence induced by these quinones correlated with the inhibition of flash-induced cytochrome c oxidation. We concluded that the quinones inhibited electron transfer in the reaction center by specifically quenching the excitation energy in the BChl c antenna. Our results provide a model system for studying the redox-dependent antenna quenching in green sulfur bacteria because the antennas in these bacteria inherently exhibit a sensitivity to O(2) similar to the quinone-supplemented cells of Cfx. aurantiacus. 相似文献
2.
Purification of basic FGF receptors from rat brain 总被引:4,自引:0,他引:4
T Imamura Y Tokita Y Mitsui 《Biochemical and biophysical research communications》1988,155(2):583-590
Receptor molecules for basic fibroblast growth factor (bFGF) were isolated from rat brain by a novel and rapid procedure and characterized. Purification was performed by wheatgerm agglutinin (WGA) gel affinity chromatography in combination with bFGF gel affinity chromatography, utilizing a novel elution method involving heparin. The eluted proteins were active in binding bFGF and were separated as two bands with respective molecular masses of 140 kDa and 110 kDa on SDS-PAGE. More than half of this bFGF-binding activity was lost after 16 h at 4 degrees C. Thus, bFGF receptors were purified as labile glycoconjugates. 相似文献
3.
M R Raju S G Carpenter N Tokita J Howard 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1985,48(2):271-276
The variation in radiosensitivity across the cell cycle after exposure to neon ions and 60Co gamma-rays is reported for cultured hamster cells. The cells were first synchronized by mitotic selection, then resynchronized in the region of the G1/S boundary by treatment with 10(-3)M hydroxyurea. Although the use of hydroxyurea improves the synchrony, it does sensitize cells at the G1/S boundary to some degree. The cells were exposed at the plateau and the distal peak position of a neon ion beam modified by a 10 cm wide ridge filter. The results indicate that the variation (ratio of maximum to minimum survival after fixed doses of radiation that are approximately matched to produce similar cell killing) was approximately 80 to 100-fold for 60Co gamma-rays and neon ions at the plateau, and 25-fold for distal peak neon ions. While the r.b.e. of distal peak neon ions decreased rapidly with increasing dose for cells in late S-phase, the r.b.e. is independent of dose for cells at the G1/S boundary. 相似文献
4.
I Ono I Ishiwata T Nakaguchi M Soma N Tokita C Ishiwata M Mukai S Nozawa H Ishikawa 《Human cell》1989,2(3):272-277
The malignant schwannoma cell line (HKMS) was established from the subcutaneous tumor of Axilla region of a 48-year-old Japanese woman. The HKMS line has the following biological properties. 1. The HKMS cells were spindle in shape and showed neoplastic and pleomorphic features. The monolayer sheet of HKMS cells showed the resemble cell-arrangement with that of the original tumor tissue. 2. The cells showed a stable growth and the serial passages were successively carried out 150 times within 3 years. Their population doubling time is about 40 hours. 3. The chromosome number varied widely, and the modal number was stable at the 78-80. The marker chromosomes were present. 4. The cells were transplanted into the subcutis of nude mice and produced the malignant schwannoma. 相似文献
5.
I Ono I Ishiwata T Nakaguchi K Ohara N Tokita M Soma C Ishiwata S Nozawa H Ishikawa 《Human cell》1989,2(4):416-422
We cultured an aspiration fluid of the sternal bone marrow of the patient having adrenal neuroblastoma and established a neuroblastoma cell line (HSNB). The HSNB line has the following biological properties. 1. They are small round in shape and proliferate in flotation while forming cell aggregate, and often they attach the bottom of plastic dish and process the nerve-like fibers. A rough-endoplasmic reticulum are poorly developed, however, a lot of free ribosomes are scattered in the cytoplasm. In the peripheral area of the cells, small spherical secretory granules (60-140 nm in diameter) are existed. One characteristic of this cell is existence of microtubules in the cell-projections. 2. They show a stable growth and the doubling time is about 50 hours. 3. Their chromosome number varied widely and the mode is 46. The double minute chromosomes were present in 50% of cells. 4. When they are transplanted in the cheek pouch of hamster, they produced the neuroblastoma. 5. They produce neuron specific enolase. 6. N-myc gene was amplified ca 250 folds. 相似文献
6.
Takeshi Wada Kiyoshi Inageda Keiichi Aritomo Ken-ichi Tokita Hiroshi Nishina Katsunobu Takahashi 《Nucleosides, nucleotides & nucleic acids》2013,32(6):1301-1314
Abstract Structure of cyclic adenosine diphosphoribose (cADPR) was reinvestigated by using 1H, 13C, and 31P NMR spectroscopy. The 1H-1H coupling constants and NOE data suggested that the adenosine and ribose moieties have a predominant C2′-endo conformation and an unusual flat conformation, respectively. 相似文献
7.
Almost all of the methodologies developed to date to assay the potential mutagenicity of chemical substances are based on detection of altered phenotypic traits. The alternative approach of directly screening the whole genome for mutations is not feasible because of the logistics of carrying out mass sequencing of genes. Here we describe a novel and highly sensitive mutation assay, which we term the 'genome profiling-based mutation assay' (GPMA) that directly detects mutations generated in genomic DNA. We used GPMA to detect mutations caused by known mutagens such as AF2 and ethidium bromide even at concentrations of 30 ppb. The number of mutations detected was dependent on the number of generations in culture and the concentrations of the mutagens. Almost complete agreement was observed between GPMA and the Ames test in the discrimination of mutagens (63 out of 64). Owing to the high sensitivity of GPMA, the effects of long-term and low-dose exposures and the influence of chemicals of low solubility can also be screened. Thus, genotype-based GPMA can complement the Ames test, which is the standard technology in this field and is based on phenotypic traits. 相似文献
8.
Yamauchi S Tokita Y Aono S Matsui F Shuo T Ito H Kato K Kasahara K Oohira A 《The Journal of biological chemistry》2002,277(23):20583-20590
Neuroglycan C (NGC) is a brain-specific transmembrane chondroitin sulfate proteoglycan. In the present study, we examined whether NGC could be phosphorylated in neural cells. On metabolic labeling of cultured cerebral cortical cells from the rat fetus with (32)P(i), serine residues in NGC were radiolabeled. Some NGC became detectable in the raft fraction from the rat cerebrum, a signaling microdomain of the plasma membrane, with cerebral development. NGC from the non-raft fraction, not the raft fraction, could be phosphorylated by an in vitro kinase reaction. The phosphorylation of NGC was inhibited by adding to the reaction mixture a recombinant peptide representing the ectodomain of NGC, but not by adding a peptide representing its cytoplasmic domain. NGC could be labeled by an in vitro kinase reaction using [gamma-(32)P]GTP as well as [gamma-(32)P]ATP, and this kinase activity was partially inhibited by 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole, a selective inhibitor of casein kinase II. In addition to the intracellular phosphorylation, NGC was also phosphorylated at the cell surface by an ectoprotein kinase. This is the first report to demonstrate that NGC can be phosphorylated both intracellularly and pericellularly, and our findings suggest that a kinase with a specificity similar to that of casein kinase II is responsible for the NGC ectodomain phosphorylation. 相似文献
9.
Oohira A Kushima Y Tokita Y Sugiura N Sakurai K Suzuki S Kimata K 《Archives of biochemistry and biophysics》2000,378(1):78-83
The effects of glycosaminoglycans (GAG) on cell-to-substratum adhesion and neurite elongation were examined in primary cultures of fetal rat hippocampal neurons using tissue culture dishes coated with GAGs coupled to dipalmitoylphosphatidylethanolamine (PE), a novel probe for biological functions of GAGs. Both chondroitin sulfate conjugate to PE (CS-PE) and hyaluronic acid conjugate to PE (HA-PE) promoted neurite elongation from neurons in a dose-dependent manner when immobilized onto polylysine-coated dishes at various concentrations up to 1.0 microg/ml. The coating of CS-PE or HA-PE at a concentration higher than 1.0 microg/ml resulted in failure of neurite extension and adhesion of neurons to the substrata. In contrast, heparin conjugate to PE (HP-PE) did not exert any effects on neurite elongation or on cell attachment at these concentrations. These findings suggest that GAGs serve as a modulator for neurite elongation during neuronal network formation in the developing central nervous system. 相似文献
10.
Matthew C. L. Keith Xian-Liang Tang Yukichi Tokita Qian-hong Li Shahab Ghafghazi Joseph Moore IV Kyung U. Hong Brandon Elmore Alok Amraotkar Brian L. Ganzel Kendra J. Grubb Michael P. Flaherty Gregory Hunt Bathri Vajravelu Marcin Wysoczynski Roberto Bolli 《PloS one》2015,10(4)