【学术报告】Direct phasing of protein crystals

报告人：何洪兴  博士

时　间：2019年9月2日（周一）下午15:00

地　点：长江路校区理工北楼204会议室

主　办：物理与电子电气工程学院

江苏省现代检测技术与智能系统重点建设实验室

淮安市物理学会

报告内容：The structure of a protein is built from its electron density mapwhich could be calculated by a Fourier transform. The magnitudes of the Fouriercoefficients are recorded by the X-ray diffraction pattern of the proteincrystal. The phases of the Fourier coefficients are lost. Solving the phaseproblem is crucial for building the model of a protein structure.

An iterative transformmethod is proposed for solving the phase problem in protein crystallography. Ineach iteration, a weighted average electron-density map is constructed todefine an estimated protein mask. Density modifications are then imposed throughthe histogram matching technique in the protein region, and the hybridinput–output algorithm in the solvent region. Starting from random initialphases, after thousands of iterations the calculated protein mask evolves intothe correct shape and the phases converge to the correct values with an averageerror of for high-resolution data forseveral protein crystals with high solvent content. With the use of non-crystallographicsymmetry and other density constraints, the method has been extended to phaseprotein crystals with less than 50% solvent fraction. The new phasing algorithmcan supplement and enhance the traditional refinement tools.

References:

1. Hongxing He, M. Jiang& W.-P. Su, “Direct phasing of protein crystals with non-crystallographicsymmetry”, Crystals, 9, 55, 2019.

2. Hongxing He & W.-P. Su, “Improvingthe convergence rate of a hybrid-input-output phasing algorithm by varying thereflection data weight”, Acta Crystallographica A: Foundations and Advances,74, 36-43, 2018.

3. Hongxing He, H. Fang, M. D. Miller, G.N. Phillips, Jr., & W.-P. Su, “Improving the efficiency of molecularreplacement by utilizing a new iterative transform phasing algorithm”, ActaCrystallographica A: Foundations and Advances, 72, 539-547, 2016.

4. Hongxing He & W.-P. Su, “Direct phasing of protein crystals withhigh solvent content”, Acta Crystallographica A: Foundations and Advances 71,92-98, 2015.

报告人简介：何洪兴博士主要致力于开发结构生物学的计算算法。2006年南京大学物理系物理学专业毕业，同年就读于南京大学物理系理论物理专业（硕士），2009年赴美国休斯敦大学物理系攻读博士学位，2015年6月—2018年8月于美国休斯敦大学物理系从事博士后研究。