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排序方式: 共有274条查询结果,搜索用时 15 毫秒
91.
92.
Novel functions of complex carbohydrates elucidated by the mutant mice of glycosyltransferase genes 总被引:4,自引:0,他引:4
Furukawa K Takamiya K Okada M Inoue M Fukumoto S Furukawa K 《Biochimica et biophysica acta》2001,1525(1-2):1-12
Complex carbohydrates consist of carbohydrate moieties and protein or lipid portions, resulting in the formation of glycoproteins, proteoglycans or glycosphingolipids. The polymorphic carbohydrate structures are believed to contain profound biological implications which are important in cell-cell or cell-extracellular matrix interactions. A number of studies to delineate the roles of carbohydrates have been performed, and demonstrated definite changes in their profiles, cellular phenotypic changes or, sometimes, morphological and functional changes in tissues after modification of their structures. Recent successes in the isolation of glycosyltransferase genes and their modification enzyme genes has enabled clearer demonstrations of the roles of complex carbohydrates. In particular, genetic modification of glycosyltransferase genes in mice can elucidate the biological significances of their products in vivo. Here, we summarize recent advances in the understanding of the roles of complex carbohydrates provided from studies of gene knock-out mice of glycosyltransferase and modification enzyme genes focusing on novel functions which had not been expected. 相似文献
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Kazuhiko Takamiya 《Bioscience, biotechnology, and biochemistry》2013,77(5):481-489
The single injection of levulinic acid oxime (250 mg/rat) or α-ketoglutaric acid oxime (250 mg/rat) on rats, carrying radioactive cesium, promoted both urinary and fecal excretion of this radionuclide. The administration of levulinic acid oxime (sodium salt) decreased the cesium retention by liver. The administration of the oxime did not have influence on the urinary excretion of sodium and potassium in normal rats. The toxicity of the oxime was low. The LD50 of α-ketoglutaric acid oxime was 3500 mg/kg (mice, intraperitoneally). (The LD50 of levulinic acid oxime has already been indicated as 2040 mg/kg (mice, intravenously). 相似文献
96.
AppA is a novel blue-light receptor that controls photosynthetic gene expression in the purple bacterium Rhodobacter sphaeroides. The photocycle reaction of the light-sensing domain, BLUF, is unique in the sense that a few hydrogen bond rearrangements are accompanied by only slight structural changes of the bound chromophore. However, the exact features of the hydrogen bond network around the active site are still the subject of some controversy. Here we present biochemical and genetic evidence showing that either Gln63 or Trp104 in the active site of the BLUF domain is crucial for light sensing, which in turn controls the antirepressor activity of AppA. Specifically, the Q63L and W104A mutants of AppA are insensitive to blue light in vivo and in vitro, and their activity is similar to that of the light-adapted wild-type AppA. Based on spectroscopic and structural information described previously, we conclude that light-dependent formation and breakage of the hydrogen bond between Gln63 and Trp104 are critical for the light-sensing mechanism of AppA. 相似文献
97.
Shunsuke Yamamoto Akiko Orimo Hideo Ohkita Hiroaki Benten Shinzaburo Ito 《Liver Transplantation》2012,2(2):229-237
The origin of open‐circuit voltage (VOC) was studied for polymer solar cells based on a blend of poly(3‐hexylthiophene) (P3HT) and seven fullerene derivatives with different LUMO energy levels and side chains. The temperature dependence of J–V characteristics was analyzed by an equivalent circuit model. As a result, VOC increased with the decrease in the saturation current density J0 of the device. Furthermore, J0 was dependent on the activation energy EA for J0, which is related to the HOMO–LUMO energy gap between P3HT and fullerene. Interestingly, the pre‐exponential term J00 for J0 was larger for pristine fullerenes than for substituted fullerene derivatives, suggesting that the electronic coupling between molecules also has substantial impact on VOC. This is probably because the recombination is non‐diffusion‐lmilited reaction depending on electron transfer at the P3HT/fullerene interface. In summary, the origin of VOC is ascribed not only to the relative HOMO–LUMO energy gap but also to the electronic couplings between fullerene/fullerene and polymer/fullerene. 相似文献
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Hashimoto M Takamiya S Yokota T Nakajima Y Yamakura F Sugio S Aoki T 《Archives of biochemistry and biophysics》2008,471(1):42-49
The anaerobic parasitic nematode Ascaris suum has an oxygen-avid hemoglobin in the perienteric fluid, the biological function of which remains elusive. Here, we report that Ascaris cytochrome b5 is expressed specifically in the intestinal parasitic stage and is secreted into the perienteric fluid, thus co-localizing with Ascaris hemoglobin. We also found that cytochrome b5 reduces Ascaris non-functioning ferric methemoglobin more efficiently than mammalian methemoglobin. Furthermore, a computer graphics model of the electron transfer complex between Ascaris cytochrome b5 and Ascaris hemoglobin strongly suggested that these two proteins are physiological redox partners. Nitric oxide has been reported to react easily with oxygen captured in hemoglobin to form nitrate, but not toxic free radicals, which may result in production of methemoglobin for the cytochrome b5 to regenerate functional ferrous hemoglobin. Therefore, our findings suggest that Ascaris cytochrome b5 is a key redox partner of Ascaris hemoglobin, which acts as an antioxidant. 相似文献
100.
Takamiya K Imanaka T Ota Y Akamine M Shibata S Shibata T Ito Y Imamura M Uwamino Y Nogawa N Baba M Iwasaki S Matsuyama S 《Radiation and environmental biophysics》2008,47(3):343-348
The upper and lower limits of the excitation function of the 63Cu(n,p)63Ni reaction were experimentally determined, and the number of 63Ni nuclei produced in copper samples exposed to atomic bomb neutrons in Hiroshima was estimated by using the experimental
excitation functions and the neutron fluences given in the DS02 dosimetry system. The estimated number of 63Ni nuclei was compared with that measured and with that calculated using the DS02 dosimetry system and the corresponding ENDF/B-VI
cross section. In comparison with DS02, there is about a 60% maximum difference in 63Ni production at the hypocenter when the experimental upper cross section values are used. The difference becomes smaller
at greater distances from the hypocenter and decreases, for example, to less than 30 and 5% when using the upper and lower
experimental cross sections at 1,000 m, respectively. 相似文献