Hillel Z, Wu C W
Biochemistry. 1976 May 18;15(10):2105-13. doi: 10.1021/bi00655a012.
A statistical method is presented for the interpretation of intramolecular distance measurements by the fluorescence energy transfer technique in systems for which the detailed geometries of the donor-acceptor pairs are unknown. This method enables calculation of the probability that a specified distance range corresponds to the actual distance to be measured. It makes use of the numerically calculated probability density function for the distance of interest. The two general systems considered are the single donor-acceptor pair and the multi-donor-single-acceptor transfer. In both systems, the statistical method incorporates the uncertainty in the orientation of the donor and acceptor dipoles. In addition, it can take into account the rotational mobility of the donor dipoles determined by time-dependent emission anisotropy measurements. When more than one donor is involved in the transfer process, the uncertainties associated with the number and location of individual donors and the size and shape of the donor distribution are also incorporated in calculating the distance ranges. Application of the method was demonstrated for a wide range of transfer efficiency and Ro values for the single donor-acceptor system. Specific examples are also presented for interpretation of both single donor-acceptor and multi-donor-single-acceptor energy transfer measurements performed in order to reveal the spatial relationship of the sigma subunit and the rifampicin binding site in the Escherichia coli RNA polymerase (see Wu, C.-W., Yarbrough, L. R., Wu, F. Y.-H., and Hillel, Z. (1976), Biochemistry, preceding paper in this issue). Analysis of these energy transfer data by methods which use average values of the unknown geometrical parameters of the system yielded results similar to those obtained by the statistical method. However, the statistical method represents a more realistic approach to the interpretation of energy transfer measurements since it provides information concerning the entire range of possible distances and their relative likelihood.
本文提出了一种统计方法，用于解释荧光能量转移技术在供体 - 受体对详细几何结构未知的系统中进行的分子内距离测量。该方法能够计算指定距离范围对应于待测量实际距离的概率。它利用了针对感兴趣距离的数值计算概率密度函数。所考虑的两种一般系统是单供体 - 受体对和多供体 - 单受体转移。在这两种系统中，统计方法都纳入了供体和受体偶极子取向的不确定性。此外，它还可以考虑通过时间相关发射各向异性测量确定的供体偶极子的旋转流动性。当转移过程涉及多个供体时，与单个供体的数量和位置以及供体分布的大小和形状相关的不确定性也被纳入距离范围的计算中。该方法在单供体 - 受体系统的广泛转移效率和Ro值范围内得到了验证。还给出了具体示例，用于解释为揭示大肠杆菌RNA聚合酶中σ亚基与利福平结合位点的空间关系而进行的单供体 - 受体和多供体 - 单受体能量转移测量（见Wu，C.-W.，Yarbrough，L.R.，Wu，F.Y.-H.和Hillel，Z.（1976年），《生物化学》，本期前文）。通过使用系统未知几何参数平均值的方法对这些能量转移数据进行分析，得到的结果与统计方法获得的结果相似。然而，统计方法代表了一种更现实的能量转移测量解释方法，因为它提供了有关所有可能距离范围及其相对可能性的信息。
