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本文报道正交晶系的天花粉蛋白晶体系生长自酸性溶液(pH～5.4),其空间群是P_(2_12_12_1),a=38.23,b=76.18,c=79.12。每个不对称单位内含一个分子量为26000,由234个氨基酸残基组成的蛋白分子。用浸泡法获得了两个重原子衍生物:K_2PtCl_4和K_2HgI_4。采用多对同晶置换加反常散射的联合概率法求得母体相角,计算了5分辨率的电子密度图。从图上可分辨出每个独立分子的界面。初步结果表明,与生长自碱性溶液(pH～8.6)的单斜晶体中的分子相比,分子在酸性条件下没有发生剧烈的构象变化。
In this paper, the orthorhombic Trichosanthin crystal system grows from acidic solution (pH ~ 5.4), its space group is P_ (2_12_12_1), a = 38.23, b = 76.18, c = 79.12. Each asymmetric unit contains a protein molecule with a molecular weight of 26,000 consisting of 234 amino acid residues. Two heavy atom derivatives were obtained by soaking method: K_2PtCl_4 and K_2HgI_4. The phase angle of the matrix was calculated by the joint probabilistic method of multiple pairs of isomorphous substitution and anomalous scattering, and the electron density of 5 was calculated. The interface of each individual molecule can be discerned from the graph. The preliminary results show that the molecule does not undergo violent conformational changes under acidic conditions compared to molecules in monoclinic crystals grown from alkaline solution (pH ~ 8.6).