Azam Anum, Leong Timothy G, Zarafshar Aasiyeh M, Gracias David H
Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD, USA.
PLoS One. 2009;4(2):e4451. doi: 10.1371/journal.pone.0004451. Epub 2009 Feb 12.
Nature utilizes self-assembly to fabricate structures on length scales ranging from the atomic to the macro scale. Self-assembly has emerged as a paradigm in engineering that enables the highly parallel fabrication of complex, and often three-dimensional, structures from basic building blocks. Although there have been several demonstrations of this self-assembly fabrication process, rules that govern a priori design, yield and defect tolerance remain unknown. In this paper, we have designed the first model experimental system for systematically analyzing the influence of geometry on the self-assembly of 200 and 500 microm cubes and octahedra from tethered, multi-component, two-dimensional (2D) nets. We examined the self-assembly of all eleven 2D nets that can fold into cubes and octahedra, and we observed striking correlations between the compactness of the nets and the success of the assembly. Two measures of compactness were used for the nets: the number of vertex or topological connections and the radius of gyration. The success of the self-assembly process was determined by measuring the yield and classifying the defects. Our observation of increased self-assembly success with decreased radius of gyration and increased topological connectivity resembles theoretical models that describe the role of compactness in protein folding. Because of the differences in size and scale between our system and the protein folding system, we postulate that this hypothesis may be more universal to self-assembling systems in general. Apart from being intellectually intriguing, the findings could enable the assembly of more complicated polyhedral structures (e.g. dodecahedra) by allowing a priori selection of a net that might self-assemble with high yields.
自然界利用自组装来构建从原子尺度到宏观尺度的各种结构。自组装已成为工程领域的一种范例，它能够通过基本构建单元高度并行地制造复杂的、通常是三维的结构。尽管已经有多个关于这种自组装制造过程的实例，但控制先验设计、产率和缺陷容忍度的规则仍然未知。在本文中，我们设计了首个模型实验系统，用于系统地分析几何形状对由拴系的多组分二维（2D）网络自组装成200微米和500微米的立方体及八面体的影响。我们研究了所有能够折叠成立方体和八面体的11种二维网络的自组装情况，并观察到网络的紧凑程度与组装成功率之间存在显著的相关性。我们用两种紧凑程度的度量方法来衡量这些网络：顶点或拓扑连接的数量以及回转半径。通过测量产率和对缺陷进行分类来确定自组装过程的成功率。我们观察到随着回转半径减小和拓扑连通性增加，自组装成功率提高，这类似于描述紧凑性在蛋白质折叠中作用的理论模型。由于我们的系统与蛋白质折叠系统在尺寸和规模上存在差异，我们推测这一假设可能对一般的自组装系统更具普遍性。除了在学术上引人入胜之外，这些发现还可能通过允许事先选择可能高产自组装的网络，从而实现更复杂多面体结构（如十二面体）的组装。
