In situ atomic force microscopy study of Alzheimer's beta-amyloid peptide on different substrates: new insights into mechanism of beta-sheet formation.
In situ atomic force microscopy study of Alzheimer's beta-amyloid peptide on different substrates: new insights into mechanism of beta-sheet formation.
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DOI：
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发表时间：
1999
影响因子：
11.1
通讯作者：
T. Kowalewski;D. Holtzman
中科院分区：
文献类型：
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作者：
T. Kowalewski;D. Holtzman
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（Abeta）与两个模型固体表面接触的聚集：亲水性云母和疏水性石墨。在聚集的时间过程之后，对保持与10-500 μ M Abeta在PBS（pH 7.4）中的溶液接触的表面进行连续成像。通过应用轻敲成像模式，使Abeta的脆弱纳米级聚集体的可视化成为可能，该模式最大限度地减少了探针尖端和样品之间的横向力。Abeta聚集体的大小和形状，以及它们形成的动力学，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，Abeta形成颗粒状、假纤维状聚集体，其在较高Abeta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物种。相反，在疏水石墨上，Abeta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。Abeta片沿彼此成120度的沿着三个方向取向，类似于石墨表面的晶体对称性。这种以底物为模板的自组装可能是β-折叠与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聚集在生理液体中，并表明Abeta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 in situ atomic force microscopy to directly observe the aggregation of Alzheimer's beta-amyloid peptide (Abeta) 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 microM solutions of Abeta in PBS (pH 7.4). Visualization of fragile nanoscale aggregates of Abeta 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 Abeta aggregates, as well as the kinetics of their formation, exhibited pronounced dependence on the physicochemical nature of the surface. On hydrophilic mica, Abeta formed particulate, pseudomicellar aggregates, which at higher Abeta concentration had the tendency to form linear assemblies, reminiscent of protofibrillar species described recently in the literature. In contrast, on hydrophobic graphite Abeta 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 Abeta 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 Abeta 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.