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61.
62.
Inohara-Ochiai M Hasegawa S Iguchi S Ashikari T Shibano Y Hemmi H Nakayama T Nishino T 《Journal of Bioscience and Bioengineering》2002,93(6):575-583
The monomeric multimetal-binding beta-galactosidase of Saccharopolyspora rectivirgula (srbg), a glycosyl hydrolase family-2 enzyme, has a unique sequence consisting of 192 amino acid residues with no similarity to known proteins. This 192-residue sequence (termed the "iota [iota] sequence") appears to be inserted into a sequence homologous to the active-site domain of the Escherichia coli lacZ enzyme (lacZbg). To assess the effects of the t sequence at specific sites of beta-galactosidase on the catalytic functioning and molecular properties of beta-galactosidase, deletion or insertion mutants of beta-galactosidases were constructed, expressed in LacZ- E. coli strains, and characterized: srbgdelta in which the iota sequence was deleted from srbg, and lacZbgI, in which the 192-residue iota sequence was inserted into the corresponding position (between Asp591 and Phe592) in the active-site domain of lacZbg. srbgdelta was a catalytically inactive, dimeric protein which retained multimetal-binding characteristics, suggesting that the iota sequence is very important for maintaining the structure necessary for the catalytic functioning and the monomeric structure of srbg but is not responsible for the unique metal ion requirements of srbg. On the other hand, lacZbgI existed as a mixture of a monomer, a tetramer, and higher multimers. The monomeric species was inactive, whereas the tetramer and other multimers were catalytically active (V(max )K(m) value, 25% of that of lacZbg) and highly specific for beta-D-galactoside. The tetrameric lacZbgI was activated by Mg2+ and Mn2+ with lowered metal affinities, and the stoichiometry of metal binding was unchanged from that of lacZbg. These results, along with the published stereo structure of lacZbg, suggest that, in lacZbgI, the inserted 192-residue iota peptide could fold independently of the lacZbg domains into a "sub-domain," lying distant from the active site and subunit interfaces. 相似文献
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64.
BNKLT无铅压电陶瓷中频滤波器的研制 总被引:1,自引:0,他引:1
采用本组发明的[Bi0.5(Na1-x-yKxLiy)0.5]TiO3(BNKLT)系无铅压电陶瓷,研制了单片式中频陶瓷滤波器。该体系陶瓷具有较高的使用温度,在160℃以上仍具有较强压电性。利用此体系材料,采用轮廓振动模式,制作了插损约为3 dB,中心频率约为530 kHz,带宽约为8.8 kHz,左、右选择性均良好的无铅压电陶瓷单片式中频滤波器。除中心频率以外,各项指标均与村田公司同类含铅陶瓷中频滤波器(SFU系列)产品相当,具有良好的应用前景。 相似文献
65.
66.
介绍了一种新型的宽带x波段七端口环行器组件,当信号从输入端输入时可分成若干个分支信道输出,组件的总插入损耗(6个信道)≤3.5Db,各输出信道之间的反向损耗α_≥30Db,可用于频率变换技术。 相似文献
67.
The nanocomposite films were prepared by direct intercalation of poly (ethylene oxide) and PEO into MoO3 xerogel via sol-gel route,The electrochromic behavior and the chemical conditionws of Li^ ions were investigated by cyclic voltammograms,UV-visible spectral transmittance and XPS,The tesults show that the cycling efficiency and the reversibility of insertion/extraciton of Li^ ions in (PEO)1 MoO3 .nH2O nanocomposite film were improved.The intercalation of PEO into MoO3 xerogel modulated the wavelength range of electrochromism and enhanced the electrochromic efficiney,Two different chemical conditions of Li^ ions existing in the interlayer and interstitial positions of MoO3 lattice were observed in MoO3 XEROGEL AND (PEO)1 MoO3.nH2O naocomposite films. 相似文献
68.
从引纬、控制、自动化装置等主要部分入手,阐述了国内外喷气织机在各个阶段的技术发展过程,目前的水平以及今后的发展方向。 相似文献
69.
70.
Kusumoto M Suzuki R Nishiya Y Okitsu T Oka M 《Journal of Bioscience and Bioengineering》2004,97(6):406-411
IS1203v is an insertion sequence (IS) which is identical to the most abundant IS elements in the genome of Escherichia coli O157:H7. However, there is no sequence homologous to IS1203v in the genome of E. coli K-12. We constructed a system to analyze the excision frequency of IS1203v, and demonstrated that the frequency in E. coli O157:H7 was approximately 10(5) times higher than that in E. coli K-12. We also investigated the excision frequencies of IS1203v in various E. coli isolates, and showed that the excision frequencies of IS1203v-possessing strains were approximately 10(3) times higher than those of IS1203v-nonpossessing strains. The results suggest that the IS1203v-possessing strains use a common system to enhance IS1203v excision. 相似文献