Structure and dynamics of self-assembling β-sheet peptide tapes by dynamic light scattering
Structure and dynamics of self-assembling β-sheet peptide tapes by dynamic light scattering
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DOI：
10.1021/bm000080z
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发表时间：
2001-06-01
影响因子：
6.2
通讯作者：
Boden, N
中科院分区：
文献类型：
--
作者：
Aggeli, A;Fytas, G;Boden, N
可以设计寡聚肽，其在溶液中经历一维自组装以形成厚度为单个分子且长度为微米的β-折叠带。(1)在本文中，我们提出了第一个系统的调查的大小，形状，动力学，和相互作用的β-折叠带形成的自组装的24个残基的肽，K24，在2-氯乙醇，在很宽的范围内的肽浓度c（c：10（-7）-1 mM），使用光子相关光谱。磁带的行为像半柔性链的持久性长度为几百纳米和更长的轮廓长度，即使在c接近0.1纳米。偏振的依赖于q的光散射强度I符合长轴物体的模型，长轴和短轴α近似为630 nm，β近似为40 nm。这是一个意想不到的结果，鉴于以前的理论预测，带状聚合物可以在溶液中形成扁圆的硬币状结构。(2)这种实验观察到的行为归因于P-带的明显扭曲和弯曲，这不允许它们形成硬币状结构，而是它们有利于形成细长聚合物。在c* 接近10（-2）mM时，可以看到条带开始重叠并形成具有异常大的网格尺寸的网络（例如，约400 nm，15 μ M），远大于那些传统的聚合物。随着肽浓度的增加，网格尺寸减小，网络成为一个物理凝胶在c接近0.4 mM。这些semidilute解决方案的特征在于一个主要的松弛模式与合作扩散的纠缠带网络，和一个较弱的较慢的模式，与凝胶簇的形成。Xi的浓度依赖性（Xi（c）类似于c（-0.34））比高斯或溶胀链的预期标度（高斯链的Xi（c）类似于c（-1），或溶胀链的Xi（c）类似于c（-3/4）弱得多，但与刚性棒的预期标度并不一致。基于光散射强度I和合作扩散系数D的浓度依赖性，发现合作摩擦系数f（c）显示出比半稀释柔性和半柔性聚合物溶液（f（c）类似于c（0.5））更强的浓度依赖性（f（c）类似于c（1.34））。(3)因此，我们可以得出结论，缠结带网络的行为近似于半刚性聚合物。
Oligomeric peptides can be designed which undergo one-dimensional self-assembly in solution to form beta-sheet tapes a single molecule in thickness and micrometers in length.(1) In this paper, we present the first systematic investigation of the size, shape, dynamics, and interactions of beta-sheet tapes formed by a self-assembling 24-residue peptide, K24, in 2-chloroethanol, over a wide range of peptide concentrations c (c: 10(-7)-1 mM), using photon correlation spectroscopy. The tapes behave like semiflexible chains with persistence lengths of several hundred nanometers and much longer contour lengths, even at c approximate to 0.1 nM. The polarized q-dependent light-scattering intensity I fits a model of a prolate object with major and minor axes alpha approximate to 630 nm and beta approximate to 40 nm. This is an unexpected result in view of the previous theoretical predictions that tapelike polymers could form oblate coinlike structures in solution.(2) This experimentally observed behavior is attributed to the pronounced twist and bend of the P-tapes, which do not allow them to form the coinlike structures, but instead they favor the formation of elongated polymers. At c* approximate to 10(-2) mM, the tapes are seen to start overlapping and forming networks with unusually large mesh sizes (e.g., ca. 400 nm at 15 muM), much larger than those of conventional polymers. With increasing peptide concentration the mesh size decreases and the network becomes a physical gel at c approximate to 0.4 mM. These semidilute solutions are characterized by one main relaxation mode associated with the cooperative diffusion of the entangled tape network, and a weaker slower mode, associated with gel cluster formation. The concentration dependence of xi (xi(c) similar to c(-0.34)) for is much weaker compared to the expected scaling for Gaussian or swollen chains (xi(c) similar to c(-1) for Gaussian chains, or xi(c) similar to c(-3/4) for swollen ones), but is not inconsistent with the expected scaling for rigid rods. On the basis of the concentration dependencies of the light-scattering intensity I and of the cooperative diffusion coefficient D, the cooperative friction coefficient f(c) is found to display a stronger concentration dependence (f(c) similar to c(1.34)) than in the case of semidilute flexible and semiflexible polymer solutions (f(c) similar to c(0.5)).(3) Thus, we may conclude that the network of entangled tapes approximates in its behavior that of semirigid polymers.