Technology Of Soft X-Ray Diffraction And Sulfur Single-wavelength Anomalous Diffraction In Protein Crystallography

X-ray crystallography is an important method to solve three-dimensional structure of protein.The synchrotron radiation light source with its unique advantages is widely used in macromolecular crystallography.This paper according to the existing conditions of X-Ray Diffraction and Scattering(XRDS) Station in National Synchrotron Radiation Laboratory(NSRL) at University of Science and Technology of China(USTC) in Hefei,China,set up the experiment platform of Sulfur Singlewavelength Anomalous Diffraction(S-SAD) to solve the phase problem in protein crystallography.Also the decline of quality in S-SAD data caused by radiation damage effects was discussed.The main works are shown as follows:1.The platform of diffraction data collection and analysis for protein crystalAccording to the characteristics of Hefei Light Source(HLS),based on the XRDS Station in NSRL at USTC,the experiment platform was set up for measuring sulfur anomalous scattering signal with long-wavelength X-ray.The methodology research of using S-SAD signal to solve the phase problem in protein crystallography was carried out.The three-dimensional structures of lysozyme and Acutolysin-C proteins were obtained at this platform,verified the feasibility of researching the three-dimensional structure of protein crystals at HLS.2.Selection and optimization of experimental conditionsContrasting the data set collected with different X-ray wavelengths,2(?) is estimated as the optimization wavelength of X-ray for S-SAD at this platform.To improve the experimental conditions,the single-bounced capillary was used to enhance the brilliance of incidence X-ray,and the helium atmosphere was covered the whole workshop for reducing the air-absorption to enhance the flux of X-ray.3.The impact on data quality due to radiation damageEach set of lysozyme and acutolysin-C protein crystal diffraction data with 2.0(?) X-ray was divided into four groups by collection time sequence.Compared the statistical parameters(Completeness,Multiplicity,Signal-to-Noise,R_merge and volume of unit cell) of each group in data processing,the impact of radiation damage on data quality was discussed.Via the analysis of the correlation coefficient(CC) between the absolute anomalous amplitude difference |â–³F| and the heavy-atom structure-factor amplitude F_A,the impairment on anomalous atom due to the radiation damage was discussed.