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Shi Nian-Qing Prahl Kristine Hendrick Jim Cruz Jose Lu Ping Cho Jae-Yong Jones Sharon Jeffries Thomas 《Applied biochemistry and biotechnology》2000,84(1-9):201-216
Pichia stipitis CBS 6054 will grow on d-xylose, d-arabinose, and l-arabinose. d-Xylose and l-arabinose are abundant in seed hulls of maize, and their utilization is important in processing grain residues. To elucidate
the degradation pathway for l-arabinose, we obtained a mutant, FPL-MY30, that was unable to grow on d-xylose and l-arabinose but that could grow on d-arabinitol. Activity assays of oxidoreductase and pentulokinase enzymes involved in d-xylose, d-arabinose, and l-arabinose pathways indicated that FPL-MY30 is deficient in d-xylitol dehydrogenase (D-XDH), d- and l-arabinitol dehydrogenases, and d-ribitol dehydrogenase. Transforming FPL-MY30 with a gene for xylitol dehydrogenase (PsXYL2), which was cloned from CBS 6054 (Gen Bank AF127801), restored the D-XDH activity and the capacity for FPL-MY30 to grow on
l-arabinose. This suggested that FPL-MY30 is critically deficient in XYL2 and that the d-xylose and l-arabinose metabolic pathways have xylitolas a common intermediate. The capacity for FPL-MY30 to grow on d-arabinitol could proceed through d-ribulose. 相似文献
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采用TLHT势和经典分子动力学方法研究了稀有气体原子(He,Ne,Ar,Kr,Xe)进入带缺陷的单壁纳米碳管(SWCNT)的动力学过程,计算出了稀有气体原子分别从管壁和管口入射时,它们能封装在SWCNT中的能量阈值Ek0,并与理想结构情形做了比较.结果表明:随着管壁缺陷半径r的增加,Ek0减小;当r<4.5 ?时,给定合适的初始动能,稀有气体原子能封装在纳米碳管中;而r=4.5 ?时,稀有气体原子不能封装在碳管中,且此时缺陷对Ar,Kr和Xe的输运特性有很大影响.
关键词:
纳米碳管
缺陷
稀有气体原子
分子动力学模拟 相似文献
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THE ANALYSIS OF RADIOACTIVE DECAY CURVES (Ⅰ) TWO-COMPONENT DECAY CURVES——INTRODUCTION OF A NON-CLASSICAL METHOD OF ANALYSIS 下载免费PDF全文
In present paper, a non-classical method ("λ" method) of analyzing the two-component radioactive decay curve was developed. The use of the relationship between the apparent decay constant λ(t) and the time t in fitting is to be distinguished from the use of the relationship between the total activity A(t) and t in fitting by the classical method ("A" method). In "λ" method, there are three unknowns while in "A" method there are four, thus the former is simpler than the latter. 相似文献
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采用TLHT势和经典分子动力学方法研究了稀有气体原子进入单壁纳米碳管(SWCNT)的动力学过程,计算得出SWCNT能吸入稀有气体原子(He,Ne,Ar,Kr,Xe)的管径阈值r0分别为6.3 ?,7.0 ?,8.6 ?,8.6 ?,8.6 ?,同时计算了对应的每种稀有气体原子能封装在不同管径的SWCNT中的最大初始动能Ek0.计算给出有趣的结果是封装在纳米碳管中的稀有气体原子在管中不停地作周期性振荡,振荡周期与原子进入管中的能量无关,振幅与原子进入管中的能量有关,即振幅随着入射能量的增加而增加.分析表明:给定合适类型的碳管,具有很小初始动能的稀有气体原子可在碳管中稳定的周期性振荡,其振荡频率可达GHz. 相似文献
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