Epr Spectral Fitting - The Fourier Deconvolution Distance Calculation Methods And Software, And

Distance measurement between functional domains in protein is essential for the study of relationship between structure and function of protein. Electron Paramagnetic Resonance (EPR) combined with site-directed spin labeling (SDSL) has been an important method to determine distance between selected points in protein. Since the introduction of this technology,EPR distance measurement method has been widely applied in protein structure, function and dynamics.Fourier Deconvolution Distance Measurement (FDDM) method has been widely used for its several advantages. But high deviation of distance calculation may occur by this method under some special experimental conditions. In addition, some crucial parameters need to be set up manually in calculation process, therefore subjective errors may be increased. To solve these problems, a new distance calculation method, the Spectrum Simulation-Fourier Deconvolution Distance Measurement (SS-FDDM) method is developed.First, EPR spectra simulation and distance measurement software was developed based on the principle of SS-FDDM. The software consists of two main modules–the spectrum simulation module and the distance calculation module. The spectrum simulation module can be used to fit fast motion spectrum, slow motion spectrum, powder spectrum and complex spectrum with two components. By changing values of line width, supper hyperfine couple tensor A and some other parameters, the effect of spectrum broadening was successfully simulated. This is essential for implementing the SS-FDDM method.Distance calculation module is the combination of spectral simulation module and FDDM method. It can be used to calculate distance between 0.8nm to 2.5 nm, using SS-FDDM method or FDDM method. All operations of this software can be done in a graphical user interface, so it's easy to use. Because it was developed in Matlab environment, it also has many advantages such as easy maintenance, scalability and so on.Comparisons on practicability, anti-noise and field shifting correction effect between SS-FDDM and FDDM were carried out by using this software. The results show that SS-FDDM can substantially improve the calculation errors induced from spectrum center shift and high noise, which will result in a more reasonable distance result. A group of experiment models of free radical frozen solution were constructed to simulate different distances by changing the concentration. The applicability of SS-FDDM was tested on this model. The calculated distances are consistent with theoretical. Despite the practicability has been initially confirmed, SS-FDDM still need to be test on real bimolecular.