On the nucleation and growth of amyloid beta-protein fibrils: Detection of nuclei and quantitation of rate constants
On the nucleation and growth of amyloid beta-protein fibrils: Detection of nuclei and quantitation of rate constants
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DOI：
10.1073/pnas.93.3.1125
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发表时间：
1996-02-06
影响因子：
11.1
通讯作者：
Teplow, DB
中科院分区：
文献类型：
--
作者：
Lomakin, A;Chung, DS;Teplow, DB
我们研究了合成的淀粉样β-蛋白-（1-40）片段（A β）在0.1M HCl中的纤维形成。在低pH下，A β形成纤维的速率可通过准弹性光散射光谱进行详细监测。用圆二色光谱和电子显微镜检查的原纤维显示，它们与淀粉样斑块中发现的那些高度相似。我们确定的流体动力学半径的A β聚集体在整个过程中的原纤维成核和生长。高于约0.1 mM的A β浓度，伸长的初始速率和原纤维的最终尺寸与A β浓度无关。低于0.1 mM的A β浓度，初始伸长速率与肽浓度成比例，并且所得原纤维显著长于在较高浓度下形成的原纤维。我们还发现，表面活性剂n-十二烷基六氧六环乙二醇单醚（C（12）E（6））以浓度依赖性的方式减缓原纤的成核和伸长。我们的观察结果与A β纤维形成模型一致，该模型包括以下关键步骤：（i）肽胶束在高于某一临界A β浓度时形成，（ii）原纤维在这些胶束内或在异质核（种子）上成核，和（iii）原纤维通过单体与原纤维末端的不可逆结合而生长，我们的数据的解释使我们能够确定原纤维核和A β胶束的大小和原纤维成核率我们的方法提供了一种用于定量测定A β原纤维形成的有力手段。
We have studied the fibrillogenesis of synthetic amyloid beta-protein-(1-40) fragment (A beta) in 0.1 M HCl, At low pH, A beta formed fibrils at a rate amenable to detailed monitoring by quasi-elastic light-scattering spectroscopy. Examination of the fibrils with circular dichroism spectroscopy and electron microscopy showed them to be highly similar to those found in amyloid plaques. We determined the hydrodynamic radii of A beta aggregates during the entire process of fibril nucleation and growth. Above an A beta concentration of approximate to 0.1 mM, the initial rate of elongation and the final size of fibrils were independent of A beta concentration. Below an A beta concentration of 0.1 mM, the initial elongation rate was proportional to the peptide concentration, and the resulting fibrils were significantly longer than those formed at higher concentration. We also found that the surfactant n-dodecylhexaoxyethylene glycol monoether (C(12)E(6)) slowed nucleation and elongation of fibrils in a concentration-dependent manner. Our observations are consistent with a model of A beta fibrillogenesis that includes the following key steps: (i) peptide micelles form above a certain critical A beta concentration, (ii) fibrils nucleate within these micelles or on heterogeneous nuclei (seeds), and (iii) fibrils grow by irreversible binding of monomers to fibril ends, Interpretation of our data enabled us to determine the sizes of fibril nuclei and A beta micelles and the rates of fibril nucleation (from micelles) and fibril elongation, Our approach provides a powerful means for the quantitative assay of A beta fibrillogenesis.