Catalytic efficiencies, percentages of rates of product formation per NADPH oxidized, and rates of product formation per O2 consumed of ionic mutants of cytochrome P450 1A2 (P450 1A2) were studied. Efficiencies of Lys99Glu, Lys453Glu, and Arg455Glu mutants for the hydroxylation reaction toward 7-ethoxycoumarin in the reconstituted system were much lower than that of the wild type (less than 17%), which corresponds to lower turnover numbers for these mutants. In contrast, the catalytic efficiencies for the hydroxylation reaction toward methanol of the three mutants were more than 45% that of the wild type in spite of these mutants' lower turnover numbers. Turnover numbers and catalytic efficiencies of Arg137Leu and Lys401 Glu mutants toward both substrates were comparable to those of the wild type. The electron-transfer rate from the reductase to the heme of P450 1A2 was decreased by 30% upon addition of excess methanol, while it was not influenced by addition of excess 7-ethoxycoumarin. The turnover numbers toward both 7-ethoxycoumarin and methanol as well as the rate constant of electron transfer were decreased by 25-40% by raising the concentration of KCl from 0 to 300 mM in the reconstituted system containing 50 mM potassium phosphate buffer. The turnover numbers toward both substrates of the above-mentioned five ionic mutants caused by tert-butyl hydroperoxide in the absence of the reductase and NADPH were comparable to those of the wild type. The effect of phospholipid constituents on the catalytic activity toward 7-ethoxycoumarin of the wild type was also studied.(ABSTRACT TRUNCATED AT 250 WORDS)
The off the Pacfic coast of Tohoku Earthquake caused an unprecedented and widespread soil liquefaction event especially in the southern part of the Kanto district. An improved understanding of the complex liquefaction processes involved and especially identification of the liquefaction layer, is needed to understand and mitigate against such events. We report here for the first time the application of X-ray computerized tomography (CT) scanning to core samples of the soft and water-saturated near-surface formations subjected to liquefaction. Our results clearly show images of the different sedimentary units and their internal structure, including ripple laminations and load casts. One unit was identified where the original sedimentary structures have been completely obliterated, which we interpret to be the zone of liquefaction. Our results show that X-ray CT scanning is a potentially useful tool for soil liquefaction research in the fields of geology and engineering.
Following typhoons, floods, earthquakes and volcanic eruptions, it is often necessary to undertake emergency works under the continual threat of secondary disasters. In order to execute these works as safely as possible, it is important to rapidly characterize ground conditions at the disaster sites. In order to achieve this, a portable cone penetration testing apparatus that could be attached to a two-armed, remotely operated robot was developed.This paper outlines the development of the remotely controlled cone penetration test system and the test results obtained to confirm the applicability of the apparatus to real-world situations.
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