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The three dimensional structure of des-pentaptide insulin has been solved at a resolu-tion of 2.4A. The structure determination was achieved without the use of heavy atom de-rivatives, by using only the phase information obtained from the seattering (both real andimaginary) of X-rays by cadmium ions present in the native crystal. Using this phase in-formation, a map, with figure of merit 0.56, was produced which enabled an initial modelof the protein to be constructed. Because of the novelty of this approach to the solutionof the phase problem the procedures used are explained in some detail. 相似文献
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Trichosanthin crystals grown at pH 5.4 are orthorhombic P2_12_12_1 with cell dimension α=38.23, b=76.18 and c=79.12. Each asymmetric unit contains one protein molecule of 234 amino acid residues (M. W. 26,000). The structure has been solved at 5 resolution by conventional MIR method with two heavy-atom derivatives. The preliminary result suggests that the protein molecule in acidic solution does not have dramatic conformational change, compared with that in alkali solution. 相似文献
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本文报道起始模型对于X射线实验观测量和已知立体化学观测量作约束参数最小二乘修正的结果.经修正和扩展的模型,不仅包括DPI分子的全部非氢原子和一个镉原子,而且还加进49个水分子.由反常散射和模型信息概率相联合得到相角,各项系数按相角可靠性加权,其2F_o-F_c Fourier综合给出清晰的结果,无明显的对试用模型的偏向.最后得到的模型有合理的立体化学,同理想键长的均方根偏离是0.027A;同观测X射线散射相当吻合,对 10—2.4A分辨率的全部数据其偏离因子R=0.182. 相似文献
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根据科技产品由简单到复杂再到简而精,体积也由小到大再到小而精的这一螺旋上升的发展规律,以及电声器材随着使用环境和规模的变化,对电声器材提出新的使用需求的形势下,指出电声器材为适应这种需求,将来会按大、小、宽、轻、精这五个方面形成发展趋势。并从理论上和实际生产中,提出实现这五个方面的具体途径和要求。列举了电声器材相关参数的相互制约作用,指出设计师怎样从中寻求平衡。同时,也预期将来有新的电声理论的出现而给电声器材性能的突破进一步指明方向。 相似文献
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本文证明λ阻遏蛋白的电荷分布显示,分子的静电极性可能加速蛋白质向DNA分子的非特异性结合.分布于阻遏蛋白分子前26个残基的一片正电荷区可能提供一个非特异性结合面.此外,在许多DNA-蛋白质特异性识别过程中,蛋白质以二聚体为活力单位与DNA结合.这很可能也是由于有利于静电作用的缘故。 相似文献
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The charge distribution of λ-repressor suggests that the molecular electrostatic polarity may accelerate the non-specific binding of the protein to the DNA molecule. The repressor molecule has a patch of positive charge within the first 26 residues which may contribute a non-specific binding surface. In addition, electrostatics may play an important role and account for why proteins form and use dimers in many specific DNA-protein recognition processes. 相似文献
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通过对声柱指向性的分析,结合高音波导柱面波的形成,得出了线阵列应该有低音和高音两个不同指向性的结论,这与传统形式音箱的技术指标中只有高音指向性是有区别的。指出目前人们对线阵列指向性认识的误区,进而提出在进行线阵列声场调试过程中应该注意的问题。 相似文献
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