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41.
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The techniques of chemical ligation have attracted great attention as an alternative to enzymatic joining of DNA ends. Here we introduce the photoligation of anthracene-modified ODN conjugates through anthracene cyclodimer formation. The effect of the positions and the kinds of single base mismatch on the template was evaluated using eight templates with one-base displacements. We found out that the yield of the ligation was affected by mispairing in a position-dependent manner. Such results would be attributed to the disruption of the local structure at the ligation site.  相似文献   
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Different initial cell concentrations of a recombinant flocculent Saccharomyces cerevisiae MA-R4 were evaluated for their effects on xylose fermentation and glucose–xylose cofermentation. A high initial cell concentration greatly increased both the substrate utilization and ethanol production rates. During xylose fermentation, the highest rates of xylose consumption (2.58 g/L h) and ethanol production (0.83 g/L h) were obtained at an initial cell concentration of 13.1 g/L. During cofermentation, the highest rates of glucose consumption (14.4 g/L h), xylose consumption (2.79 g/L h), and ethanol production (6.68 g/L h) were obtained at an initial cell concentration of 12.7 g/L. However, a high initial cell density had no positive effect on the maximum ethanol concentration and ethanol yield mainly due to the increased amount of by-products including xylitol. The ethanol yield remained almost constant (0.34 g/g) throughout xylose fermentation (initial cell concentration range, 1.81–13.1 g/L), while it was slightly lower at high initial cell concentrations (9.87 and 12.7 g/L) during cofermentation. The determination of the appropriate initial cell concentration is necessary for the improvement of substrate utilization and ethanol yield.  相似文献   
45.
Void formation at the interface between thick AlN layers and (0 0 0 1) sapphire substrates was investigated to form a predefined separation point of the thick AlN layers for the preparation of freestanding AlN substrates by hydride vapor phase epitaxy (HVPE). By heating 50–200 nm thick intermediate AlN layers above 1400 °C in a gas flow containing H2 and NH3, voids were formed beneath the AlN layers by the decomposition reaction of sapphire with hydrogen diffusing to the interface. The volume of the sapphire decomposed at the interface increased as the temperature and time of the heat treatment was increased and as the thickness of the AlN layer decreased. Thick AlN layers subsequently grown at 1450 °C after the formation of voids beneath the intermediate AlN layer with a thickness of 100 nm or above self-separated from the sapphire substrates during post-growth cooling with the aid of voids. The 79 μm thick freestanding AlN substrate obtained using a 200 nm thick intermediate AlN layer had a flat surface with no pits, high optical transparency at wavelengths above 208.1 nm, and a dislocation density of 1.5×108 cm−2.  相似文献   
46.
Click Cu(I)‐catalyzed polymerizations of diynes that contained ester linkages and diazides were performed to produce polyesters (click polyesters) of large molecular weights [(~1.0–7.0 ) × 104], that contained main‐chain 1,4‐disubstitued triazoles in excellent yields. Incorporation of triazole improved the thermal properties and magnified the even‐odd effect of the methylene chain length. We also found that, by changing the positions of the triazole rings, the thermal properties of the polyesters could be controlled. The use of in situ azidation was a safe reaction, as explosive diazides are not used. In addition, the microwave heating was found to accelerate the polymerization rates. This is the first study that has applied click chemistry for the synthesis of a series of polyesters. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4207–4218, 2010  相似文献   
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Radical additions of S-thiophosphinyl dithiocarbonate to terminal aromatic alkynes afford (E)-1-aryl-1-thio-2-thiophosphinylethene derivatives regio- and stereoselectively in high yields. The transformations of the products are also described.  相似文献   
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