Purification, crystallization and preliminary crystallographic investigations of selenium-containing phycocyanin from selenium-rich algae (Spirulina platen sis)

The selenium-containing phycocyanin from the selenium-rich algae (Spirulina platensis) has been crystallized in two crystal forms by the hanging-drop vapor diffusion techniques. A chro-matographic procedure of gel filtration and anion exchange was used for purification. Form I crystal with space group P21 and cell parameters a =108.0 A, b = 117.0 A, c = 184.0 A, β = 90.2° and 12(αβ) units in the asymmetric unit was obtained by using (NH4)2SO4 as precipitant. These crystals diffract up to 2.8 A. Form II crystal obtained by using PEG4000 as precipitant belongs to space group P63 with unit cell constants a = 155.0 A, c = 40.3 A, γ=120.0° and one(αβ) unit in the asymmetric unit. The crystals diffract beyond 2.9 A. The possible stacking forms of phycocyanin molecules in the first crystal form were discussed.     

Structure of desheptapeptide (B24-B30) insulin in a new crystal form

The structure of desheptapeptide (B24-B30) insulin (DHPI) in a new crystal form (form B) has been determined and refined to 0.2 nm resolution. The crystals were obtained under the same crystallization condition as previously reported crystal form (form A). The overall structures of the two crystal forms are similar but obvious differences can be observed in crystal packing and local conformation. The crystal structures of the two forms show that the two independent molecules in an asymmetric unit from a DHPI dimer, and the dimer formation buries more than 18.20 and 16.95 nm~2 of solvent accessible surfaces for form A and form B DHPI, respectively, the largest among insulin and insulin analogs ever reported. Close examination at crystal packing shows that the dimer-forming surface of DHPI, namely Surface Ⅱ, is normally present in the association of insulin and insulin analogs in their crystal structures. The results demonstrate that Surface Ⅱ is crucially important for the formation of two crystal form     

用于生物大分子晶体结构修正的差值Fourier综合程序系统

在国产大型通用电子计算机013上建立了用于生物大分子晶体结构晶体学修正的差值Fourier综合程序系统。该程序包括坐标和温度因子增量的自动分析和计算,配合适当的人工干预可使繁杂而艰苦的修正过程连续进行,实现了差值Fourier修正的半自动化。应用本程序系统对1.8埃分辨率的胰岛素晶体结构进行了十一轮差值Fourier修正。偏离因子R值从38.8%降到21.0%。修正后的Fourier图提供了包括蛋白质和水在内的更精细的结构信息。     

用于生物大分子晶体结构修正的差值Fourier综合程序系统

在国产大型通用电子计算机013上建立了用于生物大分子晶体结构晶体学修正的差值Fourier综合程序系统。该程序包括坐标和温度因子增量的自动分析和计算,配合适当的人工干预可使繁杂而艰苦的修正过程连续进行,实现了差值Fourier修正的半自动化。应用本程序系统对1.8埃分辨率的胰岛素晶体结构进行了十一轮差值Fourier修正。偏离因子R值从38.8%降到21.0%。修正后的Fourier图提供了包括蛋白质和水在内的更精细的结构信息。     

蛋白质分子立体化学的自动分析——Ⅱ.构象分析

这是关于蛋白质分子立体化学自动分析方法报道的第二篇,介绍用扭角来定量描述蛋白质分子的构象,以及从原子坐标自动计算构象角的方法和程序。     

2．5分辨率单斜Al－（L－丙氨酸）胰岛素晶体结构研究

空间群为Ｐ２１的Ａ１－（Ｌ－丙氨酸）胰岛素晶胞内,一个不对称单位含有一个六聚体,应用差值Ｆｏｕｒｉｅｒ技术,立体化学制最小二来技术和Ｘ—ＰＬＯＲ程序并辅以电子密度图的人工拟合,解析了分辨率ＡＩ—（Ｌ－丙氨酸）胰岛素（Ａｌ－Ｌ－ＡｌａⅠ）的晶体结构。最终Ｒ因子为２０．６％,与标准键长与键角的均方根偏差分别为和４．１９°,从电子密度图与模型的拟合来看,六聚体中每条Ａ链的Ａｌ位置替换的Ｌ—Ａｌａ清晰可见,每条Ｂ链Ｎ端Ｂ１—Ｂ８伏段都为α螺旋构象,形成了Ｂ１—Ｂ１９的连续α螺旋段。     

单斜Al－（L－丙氨酸）胰岛素初步晶体学研究

用微量气相扩散方法在含酚的柠檬酸缓冲体系中,得到了可供Ｘ射线晶体学分析用的Ａｌ－（Ｌ－丙氨酸）胰岛素晶体,晶体衍射能力为２．５Ａ。经Ｘ射线衍射分析确定,该晶体属于单斜晶系,空间群为Ｐ２_１,晶胞参数：ａ＝６１．５Ａ,ｂ＝６２．２Ａ,ｃ＝４８．３Ａ,α＝γ＝９０．０°,β＝１１０．９°。晶胞中每个结晶学不对称单位含有一个Ａｌ－（Ｌ－丙氨酸）胰岛素六聚体。     

经各向异性温度因子修正后的1.2A分辨率的猪胰岛素晶体结构——温度因子的结构信息,水分子,氢原子和氢键体系

本文主要报道在1.2(?)高分辨率利用限制立体化学参数的倒易空间最小二乘技术对胰岛素的非氢原子进行各向异性温度因子修正后的结果。在修正后的电子密度图上,少数原子电子密度的各向异性分布有明显表现;80％的氢原子的电子密度有不同程度的反映;修正建立的包括水和溶剂体系,氢原子和氢键在内的胰岛素分子的精确结构模型,为各种胰岛素类似物结构的分析和比较,以及结构与功能关系的研究提供了可靠的,精度的参照和基础。     

决明子中一种新的降脂蛋白的纯化与生化特性

决明子是一种传统中药,具有降低血清胆固醇的作用。通过凝胶排阻及离子交换层析技术从决明子中分离出一种具有抑制胆固醇合成作用的新蛋白Peak Ⅱ-3,将之命名为新决明子蛋白。质谱分析表明该蛋白分子量为19.7kD,等电聚焦（IEF）电泳结果显示其等电点为4.80。SDS-PAGE及等电聚焦电泳的结果均为单一条带,表明新蛋白为均一组分。对该蛋白N-端进行测序,结果为IPYISASFPLNIEFPSE,用BLAST在NCBI-BLASTP库中搜索没有找到同源蛋白。圆二色谱结果显示该蛋白具有12.5％的α螺旋,55.6％的β折叠,31.9％的无规卷曲。     

Multi-isomorphous replacement phasing of the earthworm fibrinolytic enzyme component A from <Emphasis Type="Italic">Eisenia fetida</Emphasis>

Earthworm fibrinolytic enzyme component A (EFEa) from Eisenia fetida, a protein functioning not only as a direct fibrinolytic enzyme, but also as a plasminogen activator, has been crystallized in P212121 space group with 3 proteinmolecules per asymmetric unit. Four heavy atom derivatives were prepared using a mother liquor containing 1.4 mol@L-1 Li2SO4 and 0.1 mol@L-1 MOPS buffer (pH7.2) and used to solve the protein's diffraction phase. The heavy atom binding sites in the derivative crystals were determined using difference Patterson and difference Fourier methods and were refined in combination to yield the initial protein's structure phase at 0.25 nm resolution. The non-crystallographic symmetryrelationship of the three independent protein molecules in the asymmetric unit was determined using the correlative heavy atom sites and used for the averagingof the initial electron density. As a result, the electron density was significantly improved, providing a solid foundation for subsequent structure determination.