Department of Chemistry, The State University of New York at Geneseo College, Geneseo, NY 14454, USA.
Int J Mol Sci. 2019 Oct 28;20(21):5354. doi: 10.3390/ijms20215354.
The adsorption of amyloidogenic peptides, amyloid beta 1-40 (Aβ), alpha-synuclein (α-syn), and beta 2 microglobulin (β2m), was attempted over the surface of nano-gold colloidal particles, ranging from d = 10 to 100 nm in diameter (). The spectroscopic inspection between pH 2 and pH 12 successfully extracted the critical pH point (pH) at which the color change of the amyloidogenic peptide-coated nano-gold colloids occurred due to aggregation of the nano-gold colloids. The change in surface property caused by the degree of peptide coverage was hypothesized to reflect the ΔpH, which is the difference in pH between bare gold colloids and peptide coated gold colloids. The coverage ratio (Θ) for all amyloidogenic peptides over gold colloid of different sizes was extracted by assuming Θ = 0 at ΔpH = 0. Remarkably, Θ was found to have a nano-gold colloidal size dependence, however, this nano-size dependence was not simply correlated with . The geometric analysis and simulation of reproducing Θ was conducted by assuming a prolate shape of all amyloidogenic peptides. The simulation concluded that a spiking-out orientation of a prolate was required in order to reproduce the extracted Θ. The involvement of a secondary layer was suggested; this secondary layer was considered to be due to the networking of the peptides. An extracted average distance of networking between adjacent gold colloids supports the binding of peptides as if they are "entangled" and enclosed in an interfacial distance that was found to be approximately 2 nm. The complex nano-size dependence of Θ was explained by available spacing between adjacent prolates. When the secondary layer was formed, Aβ and α-syn possessed a higher affinity to a partially negative nano-gold colloidal surface. However, β2m peptides tend to interact with each other. This difference was explained by the difference in partial charge distribution over a monomer. Both Aβ and α-syn are considered to have a partial charge (especially δ+) distribution centering around the prolate axis. The β2m, however, possesses a distorted charge distribution. For a lower Θ (i.e., Θ <0.5), a prolate was assumed to conduct a gyration motion, maintaining the spiking-out orientation to fill in the unoccupied space with a tilting angle ranging between 5° and 58° depending on the nano-scale and peptide coated to the gold colloid.
尝试在直径为 10 至 100nm 的纳米金胶体颗粒表面吸附淀粉样肽，包括淀粉样β 1-40（Aβ）、α-突触核蛋白（α-syn）和β2 微球蛋白（β2m）。在 pH 2 到 pH 12 之间的光谱检测成功地提取了关键 pH 点（pH），即由于纳米金胶体的聚集，淀粉样肽包覆的纳米金胶体的颜色发生变化。由肽覆盖率引起的表面性质变化被假设反映了ΔpH，即裸金胶体和肽包覆金胶体之间的 pH 差异。通过假设在ΔpH=0 时Θ=0，提取了所有淀粉样肽在不同尺寸金胶体上的覆盖率（Θ）。值得注意的是，Θ 被发现与纳米金胶体尺寸有关，但这种纳米尺寸的依赖性并不简单地与相关。通过假设所有淀粉样肽均为长形，对Θ的重现几何分析和模拟进行了。模拟得出的结论是，需要一个长形的尖刺取向，才能重现提取的Θ。建议涉及一个二级层；这个二级层被认为是由于肽的网络。提取相邻金胶体之间的网络平均距离支持肽的结合，就好像它们“缠绕”并包含在大约 2nm 的界面距离内。Θ 的复杂纳米尺寸依赖性由相邻长形之间的可用间距解释。当形成二级层时，Aβ 和 α-syn 对部分负电的纳米金胶体表面具有更高的亲和力。然而，β2m 肽倾向于相互作用。这种差异可以通过单体上的部分电荷分布差异来解释。Aβ 和 α-syn 都被认为具有部分电荷（特别是δ+）分布，围绕长形轴集中。然而，β2m 具有扭曲的电荷分布。对于较低的Θ（即Θ<0.5），假设长形进行回旋运动，保持尖刺取向，用 5°至 58°的倾斜角度填充未占据的空间，这取决于纳米尺度和肽涂覆到金胶体上的程度。
