Theory of single molecule imaging by X-ray free-electron laser

X線自由電子レーザを用いた単分子イメージングの理論

徳久 淳師; 高 潤一郎; 河野 秀俊; 郷 信広*

Tokuhisa, Atsushi; Taka, Junichiro; Kono, Hidetoshi; Go, Nobuhiro*

New light sources of X-ray free-electron laser (XFEL) are under construction in Europe, USA and Japan. XFEL offers a new possibility in imaging single biological macromolecules. Our goal is to develop a computational method for the determination of molecule 3D structures from diffraction intensity data by XFEL. A straight forward procedure would be (1) to classify and average 2D diffraction patterns to improve the S/N ratio, (2) to obtain a 3D diffraction pattern by determining the relative positions of averaged-2D-images and (3) to retrieve the phases and construct the 3D structure using the over-sampling method. One of the big problems is the quantum noise resulting from the extremely weak intensity of elastically diffracted X-ray. Algorithms for structure determination must be developed to process the experimental data immersed in the quantum noise. In this meeting we report detailed procedures of analysis of experimental diffraction intensity data to be obtained 3D structure.