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Characteristics of dislocations in protein crystals

蛋白质晶体位错的特征

基本信息

批准号：
18560648
负责人：
KOJIMA Kenichi
金额：
$ 2.4万
依托单位：
Yokohama City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

The object of this research is to understand characteristics of dislocations in protein crystals. We have attacked the problems by means of two ways. One is to observe clear images of dislocations and to determine the Burgers vectors by synchrotron X-ray topography. The other is to estimate the elastic energy of dislocations and the mechanical strength by an ultrasonic pulse echo method and an indentation method.Crystal defects, especially dislocations, in hen egg-white lysozyme crystals that are a typical protein crystal that have - multiple polymorphisms, for example tetragonal, orthorhombic and monoclinic forms were investigated by means of synchrotron white and monoclinic-beam X-ray topography. The observed topographic images of dislocations were much clearer compared to those of any protein crystals that have been reported so far. It was demonstrated that millimeter-size crystals larger than extinction length for X-ray topographic reflections are required to obtain clear images, t … More hat is, direct images for protein crystals. In addition the weak beam technique was found to be useful for obtaining clear images. Straight, curved and loop-type dislocations were clearly resolved on the topographs. This shows that dislocations observed in common inorganic and organic with small molecules can also be introduced even in protein crystals. The shapes and distributions of dislocations strongly depended on the crystal polymorphisms. This suggests that the growth mechanisms in the different crystal forms studied could differ. Therefore, X -ray topography provides a useful tool for the characterization of protein crystal dislocations.We have succeeded the measurement of all components of elastic constants in hen egg-white lysozyme crystals using an ultrasonic pulse echo method. The measurements of the sound velocity were performed using (110) , (101) and (001) crystal surfaces. Consequently, all the six elastic constants of the dehydrated tetragonal HEW lysozyme crystals were determined to be C_<11>= C_<22>= 12.44 GPa, C_<12> =7.03 GPa, C_<13>= C_<28> =8.36 GPa, C_<88> =12.79 GPa, C_<44>=C_<55> =2.97 Gpa and C_<66>=2.63 Gpa, respectively.In addition, Mechanical properties of high quality tetragonal hen egg-white lysozyme single crystals, which are one of protein crystals were investigated by the indentation method. The indentation marks were clearly observed on the crystal surface and no elastic recovery of them occurred. The value of the micro-Vickers hardness in wet condition was estimated to be about 20 MPa at room temperature. The hardness greatly depended on the amount of water (intra-crystalline water) contained in the crystals. The hardness increased with increasing evaporation time to air at room temperature. It reached the maximum at about 260 MPa, which is 20 times as much as that in the wet condition. The origin of such a change in hardness was explained in terms of the dislocation mechanisms in lysozyme single crystals. Less

本研究的目的是了解蛋白质晶体中位错的特征。我们从两个方面着手解决这些问题。一种是用同步辐射X射线形貌术观察位错的清晰图像并确定Burgers矢量。利用同步辐射白色和单斜束X射线形貌术研究了鸡蛋-白色溶菌酶晶体中的晶体缺陷，特别是位错，该晶体是一种典型的蛋白质晶体，具有多晶型，如四晶型、正交晶型和单斜晶型。观察到的位错的形貌图像比迄今为止报道的任何蛋白质晶体都要清晰得多。结果表明，要获得清晰的X射线形貌反射图像，需要大于消光长度的毫米级晶体， ...更多信息也就是蛋白质晶体的直接图像。此外，弱束技术被认为是有用的，以获得清晰的图像。在形貌图上可以清楚地分辨出直位错、弯位错和环型位错。这表明，即使在蛋白质晶体中也可以引入在常见的无机和有机小分子中观察到的位错。位错的形状和分布强烈依赖于晶体的多形性。这表明所研究的不同晶体形式的生长机制可能不同。因此，X射线形貌术为蛋白质晶体位错的表征提供了一个有用的工具。我们用超声脉冲回波法成功地测量了鸡蛋清溶菌酶晶体的弹性常数的所有分量。声速的测量使用（110）、（101）和（001）晶体表面进行。结果表明，脱水后的溶菌酶晶体的6个弹性常数分别为C <11>= C <22>= 12.44 GPa、C <12>=7.03 GPa、C <13>= C = <28>8.36 GPa、C = <88>12.79 GPa、C <44>= C = <55>2.97 GPa和C <66>=2.63 GPa。在晶体表面上观察到清晰的压痕，并且没有发生弹性回复。湿态显微维氏硬度值在室温下约为20 MPa。硬度很大程度上取决于晶体中所含的水（晶内水）的量。在室温下，硬度随着蒸发时间的增加而增加。在260 MPa左右达到最大值，是湿态的20倍。这种硬度变化的起源解释在溶菌酶单晶的位错机制。少