Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195.
Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352.
Proc Natl Acad Sci U S A. 2022 Apr 19;119(16):e2020242119. doi: 10.1073/pnas.2020242119. Epub 2022 Apr 11.
Assembly of biomolecules at solid–water interfaces requires molecules to traverse complex orientation-dependent energy landscapes through processes that are poorly understood, largely due to the dearth of in situ single-molecule measurements and statistical analyses of the rotational dynamics that define directional selection. Emerging capabilities in high-speed atomic force microscopy and machine learning have allowed us to directly determine the orientational energy landscape and observe and quantify the rotational dynamics for protein nanorods on the surface of muscovite mica under a variety of conditions. Comparisons with kinetic Monte Carlo simulations show that the transition rates between adjacent orientation-specific energetic minima can largely be understood through traditional models of in-plane Brownian rotation across a biased energy landscape, with resulting transition rates that are exponential in the energy barriers between states. However, transitions between more distant angular states are decoupled from barrier height, with jump-size distributions showing a power law decay that is characteristic of a nonclassical Levy-flight random walk, indicating that large jumps are enabled by alternative modes of motion via activated states. The findings provide insights into the dynamics of biomolecules at solid–liquid interfaces that lead to self-assembly, epitaxial matching, and other orientationally anisotropic outcomes and define a general procedure for exploring such dynamics with implications for hybrid biomolecular–inorganic materials design.
生物分子在固-液界面上的组装需要分子通过复杂的、依赖于取向的能量景观，这些过程的机制尚未被充分理解，主要是因为缺乏原位单分子测量和对确定定向选择的旋转动力学的统计分析。高速原子力显微镜和机器学习方面的新进展使我们能够直接确定蛋白质纳米棒在云母表面的取向能景观，并在各种条件下观察和量化其旋转动力学。与动力学蒙特卡罗模拟的比较表明，相邻特定取向的能量最小之间的跃迁速率可以通过传统的平面内布朗旋转跨越偏置能量景观的模型来很好地理解，得到的跃迁速率在状态之间的能量势垒中呈指数形式。然而，更远的角状态之间的跃迁与势垒高度解耦，跳跃大小分布呈幂律衰减，这是一种非经典的 Lévy 飞行随机游动的特征，表明通过激活态可以实现大跳跃的替代运动模式。这些发现为生物分子在导致自组装、外延匹配和其他各向异性结果的固-液界面上的动力学提供了深入了解，并定义了一种探索此类动力学的通用方法，对混合生物分子-无机材料的设计具有重要意义。
