State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University , Beijing 100871, People's Republic of China.
Graduate School of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8522, Japan.
ACS Nano. 2017 Jun 27;11(6):5706-5716. doi: 10.1021/acsnano.7b01212. Epub 2017 May 9.
Proteins are structurally dynamic macromolecules, and it is challenging to quantify the conformational properties of their native state in solution. Nanopores can be efficient tools to study proteins in a solution environment. In this method, an electric field induces electrophoretic and/or electro-osmotic transport of protein molecules through a nanopore slightly larger than the protein molecule. High-bandwidth ion current measurement is used to detect the transit of each protein molecule. First, our measurements reveal a correlation between the mean current blockade amplitude and the radius of gyration for each protein. Next, we find a correlation between the shape of the current signal amplitude distributions and the protein fluctuation as obtained from molecular dynamics simulations. Further, the magnitude of the structural fluctuations, as probed by experiments and simulations, correlates with the ratio of α-helix to β-sheet content. We highlight the resolution of our measurements by resolving two states of calmodulin, a canonical protein that undergoes a conformational change in response to calcium binding.
蛋白质是结构动态的大分子，定量描述其在溶液中的天然构象特性极具挑战性。纳米孔可以成为在溶液环境中研究蛋白质的有效工具。在这种方法中，电场通过稍大于蛋白质分子的纳米孔诱导蛋白质分子的电泳和/或电动传输。高带宽离子电流测量用于检测每个蛋白质分子的传输。首先，我们的测量结果揭示了每个蛋白质的平均电流阻断幅度与回转半径之间的相关性。接下来，我们发现电流信号幅度分布的形状与从分子动力学模拟获得的蛋白质波动之间存在相关性。此外，实验和模拟探测到的结构波动幅度与α-螺旋与β-折叠含量的比值相关。我们通过解析钙调蛋白的两种状态来突出我们测量的分辨率，钙调蛋白是一种经典的蛋白质，它会在钙结合时发生构象变化。
