van der Meer B W, Raymer M A, Wagoner S L, Hackney R L, Beechem J M, Gratton E
Department of Physics and Astronomy, Western Kentucky University, Bowling Green 42101.
Biophys J. 1993 Apr;64(4):1243-63. doi: 10.1016/S0006-3495(93)81490-5.
A recipe is given for designing theoretical models for donor-acceptor systems in which fluorescence energy transfer and motion takes place simultaneously. This recipe is based on the idea that a system exhibiting both motion and fluorescence energy transfer can be modeled by specifying a number of "states" and the rates of transitions between them. A state in this context is a set of specific coordinates and conditions that describe the system at a certain moment in time. As time goes on, the coordinates and conditions for the system change, and this evolution can be described as a series of transitions from one state to the next. The recipe is applied to a number of example systems in which the donors and/or acceptors undergo either rotational or translational motion. In each example, fluorescence intensities and anisotropies for the donor and acceptor are calculated from solutions of eigensystems. The proposed method allows for analyzing time-resolved fluorescence energy transfer data without restrictive assumptions for motional averaging regimes and the orientation factor. It is shown that the fluorescence quantities depend on the size of the motional step (i.e., on the number of states), only if fluorescence energy transfer occurs. This finding indicates that fluorescence energy transfer studies may reveal whether the dynamics of a system (e.g., a protein) is better described in terms of transitions between a relatively small number of discrete states (jumping) or a large number of dense states (diffusion).
给出了一种用于设计供体 - 受体系统理论模型的方法，其中荧光能量转移和运动同时发生。该方法基于这样一种理念，即一个同时表现出运动和荧光能量转移的系统可以通过指定一些“状态”以及它们之间的跃迁速率来进行建模。在此背景下，一个状态是一组特定的坐标和条件，用于描述系统在某一时刻的状态。随着时间的推移，系统的坐标和条件会发生变化，这种演变可以描述为从一个状态到下一个状态的一系列跃迁。该方法应用于多个示例系统，其中供体和/或受体经历旋转或平移运动。在每个示例中，供体和受体的荧光强度和各向异性是根据本征系统的解来计算的。所提出的方法允许在不对运动平均机制和取向因子进行限制性假设的情况下分析时间分辨荧光能量转移数据。结果表明，只有当发生荧光能量转移时，荧光量才取决于运动步长的大小（即状态的数量）。这一发现表明，荧光能量转移研究可能揭示一个系统（例如蛋白质）的动力学是用相对较少的离散状态之间的跃迁（跳跃）还是大量密集状态（扩散）来更好地描述。
