EPR波谱拟合-傅里叶去卷积距离计算方法

An EPR Spectrum Simulation-Fourier Deconvolution Method for Distance Measurement in Proteins

在蛋白质结构与功能研究中经常需要测量和计算蛋白质分子功能基团间的距离.电子顺磁共振(Electron Paramagnetic Resonance,EPR)结合定点自旋标记(Site Directed Spin Labeling,SDSL)技术已成为测量蛋白质特殊位点间距离的重要方法.目前在计算距离中广泛使用的傅里叶去卷积距离计算方法(Fourier Deconvolution Distance Measurement,FDDM)在某些特殊实验条件下会产生计算误差较大或需要人为设置一些关键参数,从而影响计算结果的客观性等问题.本文在其基础上提出波谱拟合-傅里叶去卷积距离计算方法(Spectrum Simulation-Fourier Deconvolution Distance Measurement,SS-FDDM),比较了SS-FDDM与FDDM方法计算距离的实用性、抗噪能力和磁场偏移修正能力等.结果表明,SS-FDDM方法能一定程度地克服原方法存在的不足,减少由谱偏移和高噪声带来的误差,使计算结果更加准确客观.利用SS-FDDM方法,对不同浓度的自由基冰冻溶液模型样品进行了实际距离计算,验证了该方法是实际可行的.

Measuring distances among the functional domains of a protein is essential for understanding the structure-function relationship in the protein. Electron paramagnetic resonance （EPR） combined with site directed spin labeling （SDSL） is an important ap proach for deterraining the distances among selected points in a protein. With this approach, Fourier deconvolution distance measurement （FDDM） was often used to calculate the distances. The FDDM method, however, may show poor performance under special experimental conditions, such that some crucial parameters need to be set up manually, resulting in increased susceptibility to subjective errors. To solve this problem, a new distance calculation method, spectrum simulation-Fourier deconvolution distance measurement （SS-FDDM）, was developed in this study. The validity of the meth od was tested with an experimental model of frozen free radical solution. SS-FDDM was then compared to FDDM in terms of practicability, antinoise performance and susceptibility to field shifting. The results showed that, with SS-FDDM, calculation errors originated from spectrum center shift and high noise levels can be reduced substantially, thus giving more reliable results.