Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
Proc Natl Acad Sci U S A. 2013 May 21;110(21):8543-8. doi: 10.1073/pnas.1220711110. Epub 2013 May 6.
Surface-assisted self-assembly of amyloid-like peptides has received considerable interest in both amyloidosis research and nanotechnology in recent years. Despite extensive studies, some controlling factors, such as salts, are still not well understood, even though it is known that some salts can promote peptide self-assemblies through the so-called "salting-out" effect. However, they are usually noncontrollable, disordered, amorphous aggregates. Here, we show via a combined experimental and theoretical approach that a conserved consensus peptide NH2-VGGAVVAGV-CONH2 (GAV-9) (from representative amyloidogenic proteins) can self-assemble into highly ordered, multilayered nanofilaments, with surprising all-upright conformations, under high-salt concentrations. Our atomic force microscopy images also demonstrate that the vertical stacking of multiple layers is highly controllable by tuning the ionic strength, such as from 0 mM (monolayer) to 100 mM (mainly double layer), and to 250 mM MgCl2 (double, triple, quadruple, and quintuple layers). Our atomistic molecular dynamics simulations then reveal that these individual layers have very different internal nanostructures, with parallel β-sheets in the first monolayer but antiparallel β-sheets in the subsequent upper layers due to their different microenvironment. Further studies show that the growth of multilayered, all-upright nanostructures is a common phenomenon for GAV-9 at the mica/water interface, under a variety of salt types and a wide range of salt concentrations.
近年来，在淀粉样变研究和纳米技术领域，表面辅助的类淀粉样肽自组装受到了相当大的关注。尽管进行了广泛的研究，但有些控制因素，如盐，仍然没有得到很好的理解，尽管人们知道一些盐可以通过所谓的“盐析”效应促进肽自组装。然而，它们通常是不可控的、无序的、无定形的聚集体。在这里，我们通过结合实验和理论的方法表明，一种保守的共识肽 NH2-VGGAVVAGV-CONH2（GAV-9）（来自代表性的淀粉样蛋白）可以在高盐浓度下自组装成高度有序的多层纳米丝，具有令人惊讶的全直立构象。我们的原子力显微镜图像还表明，通过调节离子强度，如从 0 mM（单层）到 100 mM（主要是双层），再到 250 mM MgCl2（双层、三层、四层和五层），可以高度控制多层的垂直堆叠。然后，我们的原子分子动力学模拟揭示了这些单独的层具有非常不同的内部纳米结构，第一层具有平行的β-折叠，但随后的上层具有反平行的β-折叠，这是由于它们所处的不同微环境所致。进一步的研究表明，在云母/水界面上，在多种盐类和广泛的盐浓度下，GAV-9 生长为多层、全直立纳米结构是一种普遍现象。
