偶极取向动力学导致的 Förster 半径时间非均质性对单分子 FRET 实验的影响
Time-Heterogeneity of the Förster Radius from Dipole Orientational Dynamics Impacts Single-Molecule FRET Experiments
AI总结：
针对单分子 FRET 中的动态位移问题，本文建立含旋转动力学的染料连接子 Langevin 模型，证明位移主要源于偶极矩相互取向而非可及体积。
摘要：
Förster 共振能量转移（FRET）是一种量子力学现象，涉及耦合电偶极子之间的非辐射能量转移。由于 FRET 对偶极子之间距离具有强烈依赖性，它在生物学、化学和物理学中常被用作“分子尺”。具体做法是将称为染料的偶极分子放置在目标分子上。在时间分辨共聚焦单分子 FRET（smFRET）实验中，FRET 效率与供体荧光寿命的联合分布可通过偏离其理论 Förster 关系来揭示潜在的分子构象动力学。这种偏离被称为动态位移。量化由荧光染料运动引起的动态位移，对于解耦所研究分子与染料的动力学至关重要。我们基于第一性原理物理学和恰当的染料连接子化学，开发了用于染料连接子动力学（包括旋转动力学）的新型 Langevin 模型，以匹配分子动力学模拟预测的可及体积。通过模拟染料的随机平动和旋转动力学，我们表明观测到的动态位移在很大程度上可归因于与染料相关的电偶极矩的相互取向动力学，而非其可及体积。我们的模型提供了最新且最准确的 FRET 估计。
英文摘要：
Förster resonance energy transfer (FRET) is a quantum mechanical phenomenon involving the non-radiative transfer of energy between coupled electric dipoles. Due to the strong dependence of FRET on the distance between the dipoles, it is frequently used as a ``molecular ruler" in biology, chemistry, and physics. This is done by placing dipolar molecules called dyes on molecules of interest. In time-resolved confocal single-molecule FRET (smFRET) experiments, the joint distribution of the FRET efficiency and the donor fluorescence lifetime can reveal underlying molecular conformational dynamics via deviation from their theoretical Förster relationship. This deviation is referred to as a dynamic shift. Quantifying the dynamic shift caused by the motion of the fluorescent dyes is essential to decoupling the dynamics of the studied molecules and the dyes. We develop novel Langevin models for the dye linker dynamics, including rotational dynamics, based on first principle physics and proper dye linker chemistry to match accessible volumes predicted by molecular dynamics simulations. By simulating the dyes' stochastic translational and rotational dynamics, we show that the observed dynamic shift can largely be attributed to the mutual orientational dynamics of the electric dipole moments associated with the dyes, not their accessible volume. Our models provide the most up-to-date and accurate estimation of FRET.
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