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排序方式: 共有377条查询结果,搜索用时 31 毫秒
51.
In bacteria, selenocysteine (Sec) is incorporated into proteins via the recoding of a particular codon, the UGA stop codon in most cases. Sec-tRNASec is delivered to the ribosome by the Sec-dedicated elongation factor SelB that also recognizes a Sec-insertion sequence element following the codon on the mRNA. Since the excess of SelB may lead to sequestration of Sec-tRNASec under selenium deficiency or oxidative stress, the expression levels of SelB and tRNASec should be regulated. In this bioinformatic study, I analyzed the Rhizobiales SelB species because they were annotated to have a non-canonical C-terminal extension. I found that the open reading frame (ORF) of diverse Alphaproteobacteria selB genes includes an entire tRNASec sequence (selC) and overlaps with the start codon of the downstream ORF. A remnant tRNASec sequence was found in the Sinorhizobium meliloti selB genes whose products have a shorter C-terminal extension. Similar overlapping traits were found in Gammaproteobacteria and Nitrospirae. I hypothesized that once the tRNASec moiety is folded and processed, the expression of the full-length SelB may be repressed. This is the first report on a nested tRNA gene inside a protein ORF in bacteria. 相似文献
52.
53.
Akinobu Takaki Tetsuya Yasunaka Takahito Yagi 《International journal of molecular sciences》2015,16(8):17494-17513
Hepatitis B often progresses to decompensated liver cirrhosis requiring orthotopic liver transplantation (OLT). Although newer nucleos(t)ide analogues result in >90% viral and hepatitis activity control, severely decompensated patients still need OLT because of drug-resistant virus, acute exacerbation, or hepatocellular carcinoma. Acute hepatitis B is also an indication for OLT, because it can progress to fatal acute liver failure. After OLT, the hepatitis B recurrence rate is >80% without prevention, while >90% of transplant recipients are clinically controlled with combined hepatitis B immunoglobulin (HBIG) and nucleos(t)ide analogue treatment. However, long-term HBIG administration is associated with several unresolved issues, including limited availability and extremely high cost; therefore, several treatment protocols with low-dose HBIG, combined with nucleos(t)ide analogues, have been investigated. Another approach is to induce self-producing anti-hepatitis B virus (HBV) antibodies using an HBV envelope (HBs) antigen vaccine. Patients who are not HBV carriers, such as those with acutely infected liver failure, are good candidates for vaccination. For chronic HBV carrier liver cirrhosis patients, a successful vaccine response can only be achieved in selected patients, such as those treated with experimentally reduced immunosuppression protocols. The present protocol for post-OLT HBV control and the future prospects of newer treatment strategies are reviewed. 相似文献
54.
Dai‐Ming Tang Cui‐Lan Ren Ling Zhang Ying Tao Peng Zhang Wei Lv Xiang‐Ling Jia Xiaojuan Jiang Guangmin Zhou Takahito Ohmura Ping Huai Feng Li Yoshio Bando Dmitri Golberg Quan‐Hong Yang 《Advanced functional materials》2019,29(19)
It is essential to understand the size scaling effects on the mechanical properties of graphene networks to realize the potential mechanical applications of graphene assemblies. Here, a “highly dense‐yet‐nanoporous graphene monolith (HPGM)” is used as a model material of graphene networks to investigate the dependence of mechanical properties on the intrinsic interplanar interactions and the extrinsic specimen size effects. The interactions between graphene sheets could be enhanced by heat treatment and the plastic HPGM is transformed into a highly elastic network. A strong size effect is revealed by in situ compression of micro‐ and nanopillars inside electron microscopes. Both the modulus and strength are drastically increased as the specimen size reduces to ≈100 nm, because of the reduced weak links in a small volume. Molecular dynamics simulations reveal the deformation mechanism involving slip‐stick sliding, bending, buckling of graphene sheets, collapsing, and densification of graphene cells. In addition, a size‐dependent brittle‐to‐ductile transition of the HPGM nanopillars is discovered and understood by the competition between volumetric deformation energy and critical dilation energy. 相似文献
55.
Tsutomu Osawa Koji Koganei Noriyasu Ito Masayuki Kitano Tadao Harada Osamu Takayasu 《Catalysis Letters》2005,100(3-4):189-193
Nickel oxide was prepared by the decomposition of nickel hydroxide and then the nickel oxide was reduced to form the nickel catalyst. The properties of the nickel oxide and the reduced nickel were studied in relation to the enantio-differentiating ability (e.d.a.) of a tartaric acid-NaBr-modified reduced nickel catalyst. The modified nickel catalyst prepared from nickel oxide with less non-stoichiometric oxygen produced a high e.d.a. for the hydrogenation of methyl acetoacetate. The high crystallinity of the nickel oxide and the resultant nickel would be required to attain a high e.d.a. 相似文献
56.
Tomohito Hamazaki Eisuke Takazakura Kenzo Osawa Masaharu Urakaze Saburo Yano 《Lipids》1990,25(9):541-545
Eicosapentaenoic acid (EPA) ethyl ester (1.8 g/d) was administered to 16 diabetic patients (5 insulin-dependent and 11 noninsulin-dependent
diabetics) for 6 mon. EPA in total plasma fatty acids increased from 4.0±2.4 mol% (mean±SD) to 7.5±3.1 mol% (p<0.001). Albumin
excretion, measured with spot urine, was significantly reduced from 65 to 36 mg/g creatinine (geometric means, p<0.001). Fasting
blood sugar levels, glycohemoglobin, body weight and blood pressure did not change significantly during the study. There were
also no significant changes in serum levels of creatinine, urea nitrogen, total cholesterol and triglycerides. Although no
overt hemorrhage was observed in the patients, hematocrit was reduced from 42.6±2.8% to 41.0±3.9% (p<0.02). Ten other similar
diabetic patients (4 insulin-dependent and 6 non-insulin-dependent diabetics) were followed as a reference group, not concomitantly,
for 6 mon with neither EPA ethyl ester nor placebo. The parameters mentioned above were not changed significantly in this
group during 6 mon. EPA administration might retard the appearance of overt diabetic nephropathy. 相似文献
57.
We propose a new design artifact for the calibration of ball-plates, which are used to assess the performance of coordinate-measuring machines (CMMs) and to calibrate those. Though transferring a length standard is necessary for ball-plate calibration, gauge-blocks are usually used for it. We think that the gauge-blocks are not appropriate gauges for transferring the length standard because of their shape. Therefore, we develop a new artifact, which we call a ball step-gauge. The ball step-gauge consists of a steel bar having the shape of an H and seven ceramic balls. It is rigid and lightweight. In addition, it can be calibrated precisely using special equipment with a laser interferometer; thus it can be used as a transfer length standard in the ball-plates calibration; furthermore, we discuss the uncertainties in measurements using the new interferometric equipment we developed. 相似文献
58.
Niidome T Akiyama Y Shimoda K Kawano T Mori T Katayama Y Niidome Y 《Small (Weinheim an der Bergstrasse, Germany)》2008,4(7):1001-1007
Gold nanorods showing surface plasmon (SP) bands in the near-IR region are used as bioimaging probes that respond to near-IR light in mice. The SP bands of intravenously injected polyethylene glycol-modified gold nanorods are directly monitored from the mouse abdomen by using a spectrophotometer equipped with an integrating sphere. The absorbance at 900 nm from the gold nanorods immediately increases after injection and reaches a plateau. The injection of phosphatidylcholine-modified gold nanorods also increases the absorbance at 900 nm, but the absorbance decreases single exponentially with a 1.3-min half-life. In vivo spectral changes of gold nanorods depend on the surface characteristics, and can be observed in real time using simple spectroscopic measurements. 相似文献
59.
The effects of lemon flavonoids, as crude flavonoids prepared from lemon juice, were investigated in diabetic rats. The oxidative
stress of eriocitrin (eriodictyol 7-O-β-rutinoside) and hesperidin (hesperetin 7-O-β-rutinoside) on streptozotocin-induced diabetic rats was investigated. Diabetic rats were given a diet which contained 0.2%
crude flavonoids, 0.2% eriocitrin, and 0.2% hesperidin. After the 28-d feeding period, the concentration of the thiobarbituric
acid- reactive substance in the serum, liver, and kidney of diabetic rats administered crude flavonoids, eriocitrin, and hesperidin
significantly decreased as compared with that of the diabetic group. The levels of 8-hydroxydeoxyguanosine, which is exchanged
from deoxyguanosine owing to oxidative stress, in the urine of diabetic rats administered eriocitrin and hesperidin significantly
decreased as compared with that of the diabetic rat group. Crude flavonoids, eriocitrin, and hesperidin suppressed the oxidative
stress in the diabetic rats. These results demonstrated that dietary lemon flavonoids of eriocitrin and hesperidin play a
role as antioxidant in vivo. 相似文献
60.
Masatake Kawada Zen‐Ichiro Kawasaki Kenji Matsu‐ura Toshio Musashiya Satoru Kuroki Teruya Osawa Hiroki Tanaka 《Electrical Engineering in Japan》2000,132(1):38-45
Partial discharge (PD) within voids in a solid insulating system is a symptom and/or a direct cause of deterioration of a generator winding. It is reported that PD is a very short duration current and/or voltage pulse, about 1 to 5 ns. Generally PD emits an electromagnetic wave which is a broadband range signal (≈ gigahertz). Therefore, we developed a new system for detecting the electromagnetic wave, especially microwaves (gigahertz) associated with a material defect of the winding. From the point of view of preventing accidents of insulation breakdown, it is important to assess the condition of the winding. We applied our system to a dielectric breakdown test to learn the relation between the characteristics of the microwaves and the insulation condition of the winding. The dielectric breakdown test is believed to be useful for estimating the minimum breakdown voltage which is a criterion of the insulation condition of the winding. Experimental results showed that this system was able to assess the insulation condition by measuring the number of pulses and the amplitude of the microwaves per voltage cycle. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 38–45, 2000 相似文献