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排序方式: 共有169条查询结果,搜索用时 46 毫秒
61.
Wang ZW Lai CB Chang CH Chiang CJ Chao YP 《Journal of agricultural and food chemistry》2011,59(12):6534-6542
The L-arabinose (Ara)-controlled T7 expression system was previously constructed by creation of an Escherichia coli BL21(BAD) strain. The production of recombinant proteins in this strain was stringently regulated and reached a high level upon induction with Ara. Nevertheless, this system is still associated with inherent problems of interference with glucose and of the all-or-nothing induction profile at a subsaturating level of Ara. In this study, these problems were circumvented by modifying the physiological traits of BL21(BAD) strain. This was followed by deletion of ptsG gene and the araFGH and araBAD operon. The former encodes the glucose transporter while the latter two gene operons produce proteins responsible for Ara uptake and catabolism. In addition, the expression of genomic araE (encodes the Ara transporter) was constitutively enhanced. The resulting strain was designated BAD-5. By expression of the faster degrader GFP(LAA) at a subsaturating level of Ara, 80% of BAD-5 strain was found visually bright in the presence or absence of glucose. A further analysis by flow cytometry showed a uniform distribution of GFP expression for BAD-5 strain. In marked contrast, BL21(BAD) strain exhibiting visual brightness was less than 10% of the cell population and remained dark in the presence of glucose. Moreover, a saturated level of luciferase from Renilla reniformis (Rluc) could be readily obtained in BAD-5 strain at 20 μM Ara regardless of glucose. Rluc in BL21(BAD) strain was produced in an Ara dose-dependent manner, and the protein production became arrested when glucose was present. Overall, it illustrates the usefulness of the improved system for overproduction of recombinant proteins in an efficient, homogeneous, and glucose-insensitive way. 相似文献
62.
Lee TT Huang YF Chiang CC Chung TK Chiou PW Yu B 《Journal of agricultural and food chemistry》2011,59(13):7353-7359
The main objective of this research was to study the characteristics of starch granules and their influences on in vitro and pig prececal starch digestion of corn, dehulled barley, wheat, and potato. Scanning electron microscopy was used to study the starch endosperm structure in the parent material as well as in vitro starch digestion. The results showed that corn starch granules were polyhedral, with a diameter ranging from 2 to 10 μm, whereas those of dehulled barley and wheat were spherical, with a diameter ranging from 5 to 20 μm. Potato had the largest starch granules among starch sources reported herein, with oval spheres of 10-50 μm in diameter. In vitro starch hydrolysis showed that starch granules of corn degraded faster than the starch of dehulled barley and wheat, with the potato starch being degraded the slowest. The in vivo digestibility trial using ileal-cannulated pigs confirmed the starch degradation of grains. The in vitro (x, %) and in vivo (y, %) digestibility were highly correlated [y = 6.5304x - 538.48 (R(2) = 0.9924)]. On the basis of the results, in vitro starch hydrolysis might be useful in predicting in vivo prececal starch digestibility. The digestion kinetic characteristics of different starch sources might be employed to evaluate the starch digestive rate at the pig ileum. 相似文献
63.
Osteoporosis is a major skeletal disease associated with loss of estrogen in postmenopausal women. In this study, Lactobacillus paracasei subsp. paracasei NTU 101 (NTU 101F) and Lactobacillus plantarum NTU 102 (NTU 102F) were used as starters to ferment soy skim milk. This was then used as a nutritional supplement for 8 weeks to ovariectomized (OVX) mice. This study reveals that soy skim milk fermented with lactobacilli can increase the contents of aglycone isoflavones, soluble calcium, and vitamin D(3). The trabecular bone volumes and trabecular number of the distal femur in mice fed NTU 101F increased by a factor of 1.48 and 1.74 compared with the OVX group. The bone network density and thickness of the distal metaphyseal trabecular in mice fed NTU 101F and Fosamax was significantly greater than that of OVX mice. These results suggest that fermented soy skim milk can attenuate bone loss in OVX mice and lower the risk of osteoporosis. 相似文献
64.
In this study, chitosan (CS) grafted by glycidyltrimethylammonium chloride (GTMAC) to form GTMAC-CS was synthesized, chemically identified, and rheologically characterized. The Maxwell Model can be applied to closely simulate the dynamic rheological performance of the chitosan and the GTMAC-CS solutions, revealing a single relaxation time pertains to both systems. The crossover point of G′ and Gʺ shifted toward lower frequencies as the CS concentration increased but remained almost constant frequencies as the GTMAC-CS concentration increased, indicating the solubility of GTMAC-CS in water is good enough to diminish influence from the interaction among polymer chains so as to ensure the relaxation time is independent of the concentration. A frequency–concentration superposition master curve of the CS and GTMAC-CS solutions was subsequently proposed and well fitted with the experimental results. Finally, the sol-gel transition of CS is 8.5 weight % (wt %), while that of GTMAC-CS is 20 wt %, reconfirming the excellent water solubility of the latter. 相似文献
65.
66.
Climate change can have a serious impact on water resources. The main agricultural product in southern Taiwan is rice, the planting of which consumes far more water than other crops. This makes agriculture in Taiwan especially vulnerable to climate change. In this study, we used the generalized watershed loading functions (GWLF) hydrological model to simulate the discharge of the Kaoping River under climate change scenarios A2 and B2 as released by the Intergovernmental Panel on Climate Change. We discussed the potential impact of climate change on water resources based on the results of GWLF simulations carried out using rainfall and temperature data from five general circulation models (GCMs). The simulation results indicate that river discharge in the wet season increases significantly, and decreases in the dry season. The discharge variations from using the various GCMs as inputs fall within the range of ?26 to +15 % for the dry season and ?10 to +82 % for the wet season. The variation in available water will seriously impact the first period rice farming (the period between the beginning of January and the end of May) in southern Taiwan. Consequently, effective reduction in conveyance loss in the irrigation canal systems and proper fallowing of paddy fields will be the main challenges to Taiwan’s agricultural sector for alleviating the impact of climate change. For further decision making, we show the effects of adapting to climate change by various degrees of the following two methods: fallowing paddy fields to various degrees and reducing conveyance loss in irrigation canal systems. 相似文献
67.
A new approach to selecting a regionalized design hyetograph by principal component analysis and analytic hierarchy process 总被引:1,自引:0,他引:1
Designing storm hyetographs is the essential element of hydrologic modeling analysis and storm water drainage design. In order to reasonably use storm hyetograph design in an un-gauged area, a regional representative hyetograph from an alternative and uniform area must be found. A new approach is proposed in this study to select a regional design storm hyetograph using principal component analysis (PCA) and analytic hierarchy process (AHP). The proposed approach combines both PCA and cluster analysis techniques. Furthermore, the AHP method is also used to establish the regional design hyetograph. A case study applied in the area of northern Taiwan shows that our method can successfully categorize the area into three homogenous zones. A representative regional hyetograph can be obtained by selecting the largest priority vector or by the weighted average of rain gauges in each zone. 相似文献
68.
Jui-Hsin Su Yu-Cheng Chen Mohamed El-Shazly Ying-Chi Du Chiang-Wen Su Chia-Wei Tsao Li-Lian Liu Yalan Chou Wen-Been Chang Yin-Di Su Michael Y. Chiang Yao-Tsung Yeh Mei-Chin Lu 《Marine drugs》2013,11(9):3168-3185
A dibromotyrosine derivative, (1′R,5′S,6′S)-2-(3′,5′-dibromo-1′,6′-dihydroxy-4′-oxocyclohex-2′-enyl) acetonitrile (DT), was isolated from the sponge Pseudoceratina sp., and was found to exhibit a significant cytotoxic activity against leukemia K562 cells. Despite the large number of the isolated bromotyrosine derivatives, studies focusing on their biological mechanism of action are scarce. In the current study we designed a set of experiments to reveal the underlying mechanism of DT cytotoxic activity against K562 cells. First, the results of MTT cytotoxic and the annexin V-FITC/PI apoptotic assays, indicated that the DT cytotoxic activity is mediated through induction of apoptosis. This effect was also supported by caspases-3 and -9 activation as well as PARP cleavage. DT induced generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) as indicated by flow cytometric assay. The involvement of ROS generation in the apoptotic activity of DT was further corroborated by the pretreatment of K562 cells with N-acetyl-cysteine (NAC), a ROS scavenger, which prevented apoptosis and the disruption of MMP induced by DT. Results of cell-free system assay suggested that DT can act as a topoisomerase II catalytic inhibitor, unlike the clinical anticancer drug, etoposide, which acts as a topoisomerase poison. Additionally, we found that DT treatment can block IKK/NFκB pathway and activate PI3K/Akt pathway. These findings suggest that the cytotoxic effect of DT is associated with mitochondrial dysfunction-dependent apoptosis which is mediated through oxidative stress. Therefore, DT represents an interesting reference point for the development of new cytotoxic agent targeting IKK/NFκB pathway. 相似文献
69.
Neuropeptide Y (NPY) is the most important appetite regulator. This study aimed to establish an in vitro NPY mRNA expression model for screening essences to determine if they are an appetite stimulator or inhibitor. We cultured the olfactory nerve cells Rolf B1.T for 2 days and then treated the cells with the known appetite inhibitor limonene and stimulator linalool. It was found that linalool could significantly stimulate NPY mRNA expression in 10 min, and limonene had the opposite effect. Similar results were also found in primary olfactory ensheathing cells isolated from rats. Further clinical trials using human subjects found that, when 10 min of treatment was applied, linalool indeed increased the serum NPY level in human peripheral blood. Limonene, on the other hand, decreased the serum NPY level. Thus, NPY mRNA expression in Rolf B1.T cells could be used as an in vitro model for screening essences that may affect appetite. 相似文献
70.
Yung-Chieh Wang Yu-Pin Lin Chun-Wei Huang Li-Chi Chiang Hone-Jay Chu Wen-Sheng Ou 《Water, air, and soil pollution》2012,223(5):2719-2742
This work develops a system dynamic simulation model for free-water surface constructed wetlands, as well as provides appropriate values for the parameters of constructed wetland management. The system dynamic model is calibrated and validated by using data from a 1-year study of a constructed wetland in Tainan of southern Taiwan. Additionally, the major parameters that affect the simulation output are obtained via sensitivity analysis by using generalized likelihood uncertainty estimation (GLUE). A high R 2 and Nash?CSutcliffe coefficient of efficiency between the simulated and measured outflow values indicate that in addition to reproducing the changing trends of dissolved oxygen (DO), 5-day biological oxygen demand (BOD5), total nitrogen (TN), total suspended sediment (TSS), and total phosphorous (TP) concentrations, the model can simulate the variations of DO, BOD5, and TSS. Taken into account the interactions among parameters, the GLUE method successfully obtained the model sensitive parameters from the Monte Carlo parameter sets. Sensitivity analysis results indicate that the parameters of microorganisms are sensitive factors that affect DO, BOD5, and TN, while sediment diameter largely influences TP and TSS. Further elucidating environmental microorganisms would increase the model accuracy and provide a valuable reference for constructed wetland management and design. 相似文献