PDF(Pubmed)
Abstract：
The hierarchic assembly of fibrillar collagen into an extensive and ordered supramolecular protein fibril is critical for extracellular matrix function and tissue mechanics. Despite decades of study, we still know very little about the complex process of fibrillogenesis, particularly at the earliest stages where observation of rapidly forming, nanoscale intermediates challenges the spatial and temporal resolution of most existing microscopy methods. Using video rate scanning atomic force microscopy (VRS-AFM), we can observe details of the first few minutes of collagen fibril formation and growth on a mica surface in solution. A defining feature of fibrillar collagens is a 67-nm periodic banding along the fibril driven by the organized assembly of individual monomers over multiple length scales. VRS-AFM videos show the concurrent growth and maturation of small fibrils from an initial uniform height to structures that display the canonical banding within seconds. Fibrils grow in a primarily unidirectional manner, with frayed ends of the growing tip latching onto adjacent fibrils. We find that, even at extremely early time points, remodeling of growing fibrils proceeds through bird-caging intermediates and propose that these dynamics may provide a pathway to mature hierarchic assembly. VRS-AFM provides a unique glimpse into the early emergence of banding and pathways for remodeling of the supramolecular assembly of collagen during the inception of fibrillogenesis.
摘要：
纤维状胶原蛋白分层组装成广泛而有序的超分子蛋白质原纤维对于细胞外基质功能和组织力学至关重要。尽管经过了几十年的研究,我们对纤维形成的复杂过程仍然知之甚少，特别是在观察快速形成的最早阶段，纳米级中间体挑战了大多数现有显微镜方法的空间和时间分辨率。使用视频速率扫描原子力显微镜（VRS-AFM），我们可以在溶液中的云母表面上观察到胶原蛋白原纤维形成和生长的最初几分钟的细节。纤维状胶原蛋白的定义特征是沿着原纤维的67nm周期性条带，这是由单个单体在多个长度尺度上的有序组装所驱动的。VRS-AFM视频显示了小原纤维从初始均匀高度到在几秒钟内显示典型条带的结构的同时生长和成熟。原纤维主要以单向方式生长，生长尖端的磨损末端锁住相邻的原纤维。我们发现,即使在极早的时间点，生长中的原纤维的重塑通过鸟笼中间体进行，并提出这些动力学可能提供成熟的分层组装途径。VRS-AFM提供了对在原纤维形成开始期间胶原的超分子组装的重塑的条带和途径的早期出现的独特一瞥。
