...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >The determination of protonation states in proteins
【24h】

The determination of protonation states in proteins

机译：质子化作用状态的决心蛋白质

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The protonation states of aspartic acids and glutamic acids as well as histidine are investigated in four X-ray cases: Ni,Ca concanavalin A at 0.94 ?, a thrombin-hirugen binary complex at 1.26 ? resolution and two thrombin-hirugen-inhibitor ternary complexes at 1.32 and 1.39 ? resolution. The truncation of the Ni,Ca concanavalin A data at various test resolutions between 0.94 and 1.50 ? provided a test comparator for the `unknown' thrombin-hirugen carboxylate bond lengths. The protonation states of aspartic acids and glutamic acids can be determined (on the basis of convincing evidence) even to the modest resolution of 1.20 ? as exemplified by our X-ray crystal structure refinements of Ni and Mn concanavalin A and also as indicated in the 1.26 ? structure of thrombin, both of which are reported here. The protonation-state indication of an Asp or a Glu is valid provided that the following criteria are met (in order of importance). (i) The acidic residue must have a single occupancy. (ii) Anisotropic refinement at a minimum diffraction resolution of 1.20 ? (X-ray data-to-parameter ratio of 3.5:1) is required. (iii) Both of the bond lengths must agree with the expectation (i.e. dictionary values), thus allowing some relaxation of the bond-distance standard uncertainties required to 0.025 ? for a `3' determination or 0.04 ? for a `2' determination, although some variation of the expected bond-distance values must be allowed according to the microenvironment of the hydrogen of interest. (iv) Although the Fo - Fc map peaks are most likely to be unreliable at the resolution range around 1.20 ?, if admitted as evidence the peak at the hydrogen position must be greater than or equal to 2.5 and in the correct geometry. (v) The atomic B factors need to be less than 10 ?2 for bond-length differentiation; furthermore, the C=O bond can also be expected to be observed with continuous 2Fo - Fc electron density and the C-OH bond with discontinuous electron density provided that the atomic B factors are less than approximately 20 ?2 and the contour level is increased. The final decisive option is to carry out more than one experiment, e.g. multiple X-ray crystallography experiments and ideally neutron crystallography. The complementary technique of neutron protein crystallography has provided evidence of the protonation states of histidine and acidic residues in concanavalin A and also the correct orientations of asparagine and glutamine side chains. Again, the truncation of the neutron data at various test resolutions between 2.5 and 3.0 ?, even 3.25 and 3.75 ? resolution, examines the limits of the neutron probe. These various studies indicate a widening of the scope of both X-ray and neutron probes in certain circumstances to elucidate the protonation states in proteins.
机译：天冬胺酸和的质子化作用状态氨基戊二酸和组氨酸调查在四个x光情况下:倪,Cathrombin-hirugen伴刀豆球蛋白为0.94 ?在1.26二进制复杂吗?thrombin-hirugen-inhibitor三元配合物在1.32和1.39吗?倪,伴刀豆球蛋白各种测试数据分辨率在0.94和1.50之间?测试比较器“未知”thrombin-hirugen羧酸盐键的长度。质子化作用的天冬胺酸和谷氨酸酸可以确定的基础上甚至适度的令人信服的证据)解决1.20 ?晶体结构改进的镍和锰伴刀豆球蛋白A和也表示在1.26吗?报告在这里。一个Asp或Glu是有效的提供满足以下标准(在秩序重要性)。单一的入住率。最小衍射分辨率为1.20 ?data-to-parameter比3.5:1)是必需的。(3)债券的长度都必须同意期望(即字典值),因此允许一些放松的键长标准的不确定性要求0.025吗?“3”的决心还是0.04 ?的决心,虽然有些变化必须允许预期的键长值根据氢的微环境感兴趣的。最有可能是不可靠的分辨率范围约1.20 ?,如果承认氢的峰位置必须证据大于或等于2.5的正确的几何形状。键长小于10 ? 2分化;也会与连续观测2 fo - Fc电子密度和c哦债券不连续的电子密度,提供原子小于大约20 B因素? 2和轮廓水平增加。决定性的选择是进行不止一个实验中,如多个x射线晶体学实验和理想的中子晶体学。中子蛋白质的互补的技术的晶体学提供了证据质子化作用组氨酸和酸性残留在伴刀豆球蛋白也是正确的方向的天冬酰胺,谷氨酰胺的一面链。在不同的测试分辨率在2.5和3.0之间?,甚至3.25和3.75吗?中子探测器的极限。研究显示的范围扩大在某些情况下x射线和中子探测器阐明蛋白质的质子化作用状态。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号