In situ atomic force microscopy study of Alzheimer's β-amyloid peptide on different substrates:: New insights into mechanism of β-sheet formation
In situ atomic force microscopy study of Alzheimer's β-amyloid peptide on different substrates:: New insights into mechanism of β-sheet formation
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DOI：
10.1073/pnas.96.7.3688
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发表时间：
1999-03-30
影响因子：
11.1
通讯作者：
Holtzman, DM
中科院分区：
文献类型：
--
作者：
Kowalewski, T;Holtzman, DM
我们应用原位原子力显微镜直接观察阿尔茨海默氏β-淀粉样肽（A β）与两种模型固体表面接触的聚集：亲水性云母和疏水性石墨。聚集的时间过程之后是与10-500 μ M A β在PBS（pH 7.4）中的溶液接触的表面的连续成像。脆弱的纳米级聚集体的A β的可视化是可能的通过应用的轻敲模式的成像，这最大限度地减少了探针尖端和样品之间的横向力，A β聚集体的大小和形状，以及它们的形成动力学，表现出明显的依赖于表面的物理化学性质。在亲水性云母上，A β形成颗粒状的假胶束聚集体，其在较高A β浓度下具有形成线性组装体的趋势，这让人想起最近在文献中描述的原纤维种类。相比之下，在疏水石墨上，A β形成均匀的细长片。这些折叠的尺寸与具有垂直于聚集体长轴的延伸肽链的β-折叠的尺寸一致。A β的片层沿着彼此成120度的沿着三个方向取向，类似于石墨表面的晶体学对称性。这种基底模板自组装可能是β-片层与α-螺旋相比的区别特征。这些研究表明，原位原子力显微镜能够直接评估淀粉样蛋白在生理液体中的聚集，并表明A β原纤维的形成可能是由水溶液和疏水底物界面处的相互作用驱动的，如体内膜和脂蛋白颗粒中所发生的那样。
We have applied irt situ atomic force microscopy to directly observe the aggregation of Alzheimer's beta-amyloid peptide (A beta) in contact with two model solid surfaces: hydrophilic mica and hydrophobic graphite, The time course of aggregation was followed by continuous imaging of surfaces remaining in contact with 10-500 mu M solutions of A beta in PBS (pH 7.4). Visualization of fragile nanoscale aggregates of A beta was made possible by the application of a tapping mode of imaging, which minimizes the lateral forces between the probe tip and the sample, The size and the shape of A beta aggregates, as well as the kinetics of their formation, exhibited pronounced dependence on the physicochemical nature of the surface. On hydrophilic mica, A beta formed particulate, pseudo-micellar aggregates, which at higher A beta concentration had the tendency to form linear assemblies, reminiscent of protofibrillar species described recently in the literature. In contrast, on hydrophobic graphite A beta formed uniform, elongated sheets. The dimensions of those sheets were consistent with the dimensions of beta-sheets with extended peptide chains perpendicular to the long axis of the aggregate. The sheets of A beta were oriented along three directions at 120 degrees to each other, resembling the crystallographic symmetry of a graphite surface, Such substrate-templated self-assembly may be the distinguishing feature of beta-sheets in comparison with alpha-helices. These studies show that in situ atomic force microscopy enables direct assessment of amyloid aggregation in physiological fluids and suggest that A beta fibril formation may be driven by interactions at the interface of aqueous solutions and hydrophobic substrates, as occurs in membranes and lipoprotein particles in vivo.