The self-assembly of protein complexes is at the core of many fundamental biological processes¹, ranging from the polymerization of cytoskeletal elements, such as microtubules², to viral capsid formation and organelle assembly³. To reach a comprehensive understanding of the underlying mechanisms of self-assembly, high spatial and temporal resolutions must be attained. This is complicated by the need to not interfere with the reaction during the measurement. As self-assemblies are often governed by weak interactions, they are especially difficult to monitor with high-speed atomic force microscopy (HS-AFM) due to the non-negligible tip–sample interaction forces involved in current methods. We have developed a HS-AFM technique, photothermal off-resonance tapping (PORT), which is gentle enough to monitor self-assembly reactions driven by weak interactions. We apply PORT to dissect the self-assembly reaction of SAS-6 proteins, which form a nine-fold radially symmetric ring-containing structure that seeds the formation of the centriole organelle. Our analysis reveals the kinetics of SAS-6 ring formation and demonstrates that distinct biogenesis routes can be followed to assemble a nine-fold symmetrical structure.

蛋白质复合物的自组装是许多基本生物过程¹的核心，从细胞骨架元素的聚合，如微管²，到病毒衣壳形成和细胞器组装³. 为了全面了解自组装的潜在机制，必须获得高空间和时间分辨率。由于需要在测量过程中不干扰反应，这很复杂。由于自组装通常受弱相互作用的控制，由于当前方法中涉及的尖端-样品相互作用力不可忽略，因此它们特别难以用高速原子力显微镜 (HS-AFM) 进行监测。我们开发了一种 HS-AFM 技术，即光热偏共振攻丝 (PORT)，它足够温和，可以监测由弱相互作用驱动的自组装反应。我们应用 PORT 来剖析 SAS-6 蛋白的自组装反应，这些反应形成了一个九重径向对称的含环结构，为中心粒细胞器的形成提供了种子。