ABNORMAL FIBROUS ASSEMBLIES OF ALZHEIMER'S DISEASE

成对螺旋细丝的分子组织，淀粉样斑块 核心和脑血管淀粉样蛋白分离自阿尔茨海默病(AD) 将使用X射线衍射和电子显微镜对大脑进行研究。 高分辨率的X=射线图案将从分离的 异常纤维集合体与体外培养模式的比较 与AD具有序列同源性的合成多肽的组装 淀粉样β蛋白。 为了获得适合于此类比较的模式，程序集 将通过将颗粒或浓缩溶液暴露于 2特斯拉的外磁场。磁感应取向 具有相似的丝状结构(与丝状噬菌体一样多样， 完整的视网膜杆、核酸和镰状细胞血红蛋白纤维) 以前已被证明可显著提高 衍射数据。X射线从我们的各种纤维组件中散射出来 也会通过改变沐浴的电子密度来增强 培养基，使用阴性染色，标记反应性氨基酸残基 用重金属。对比度适中且定向良好的颗粒将 允许检测到因包装 纤维内和纤维沿线的结构单元。准确测定 X射线反射的间隔和积分宽度将 提供衍射区的大小和长度的测量 组成该结构的多肽链。 确定结构单元的尺寸和空间组织 包括成对的螺旋细丝、AD淀粉样蛋白和体外组件 将阐明我们对它们的形成、相互关系、 和稳定性，并将提供关于它们可能如何与或 来源于神经元中正常存在的细胞骨架成分。的 更普遍的兴趣，我们的发现也将与系统性 淀粉样变性，以及蛋白质折叠问题。

The molecular organization of paired helical filaments, amyloid plaque cores, and cerebrovascular amyloid isolated from Alzheimer's disease (AD) brain will be studied using X-ray diffraction and electron microscopy. High-resolution X=ray patterns will be obtained from isolates of the abnormal fibrous assemblies for comparison with patterns from in vitro assemblies of synthetic polypeptides having sequence homologies with the AD amyloid beta-protein. To obtain patterns that are suitable for such comparisons, the assemblies will be oriented by exposure of pellets or concentrated solutions to an external magnetic field of 2 Tesla. The magnetically-induced orientation of similar filamentous structures (as diverse as filamentous bacteriophage, whole retinal rods, nucleic acids, and sickle cell hemoglobin fibers) has been previously shown to substantially enhance the quality of the diffraction data. The X-ray scatter from our various fibrous assemblies will also be enhanced by altering the electron density of the bathing medium, using negative stains, and labeling reactive amino acid residues with heavy metals. Appropriately contrasted and well-oriented pellets will allow the detection of weak scatter that arises from the packing of the structural units within and along the fibres. Accurate determination of the spacings and of the integral widths of the X-ray reflections will provide a measure of the sizes of the diffracting regions and the lengths of the polypeptide chains constituting the structure. Determining the dimensions and spatial organization of the structural units that comprise paired helical filaments, AD amyloids and in vitro assemblies will illuminate our understanding of their formation, interrelationships, and stability, and will provide insight on how they might be related to or derive from normally occurring cytoskeletal components in the neuron. Of more general interest, our findings will also be relevant to the systemic amyloidoses, and to the problem of protein folding.