Development of Advanced Diffracted X-Ray Tracking for Single Molecule Intra- Dynamics with Low Dose and Wide Angular Dynamic Range

Abstract

Diffracted X-ray Tracking (DXT) is one of single molecule techniques for investigating internal motion of protein at single molecule level. In DXT, a gold nanocrystal is used as motion probe and its motion is investigated by trajectory of diffraction spot in time resolved diffraction images. It can detect atomic-scale dynamic motion of the protein with several tens of microseconds time resolution. Although DXT is expected as a powerful tool, the narrow dynamic angular range (about one degree in BL40XU/SPring-8), and the X-ray radiation damage for the sample are big issues. The wider energy width of incident X-ray enhances the dynamic angular range of the method; however, such incident X-ray has serious radiation damage for the sample. In this presentation we report the following developing methods which we have been working on to solve problems described above. [A] Sample Angular Scanning type DXT: Recording time resolved diffraction images with high-speed sample angular scanning, and motions of diffraction spots are reconstructed by angular position information of the sample and its diffraction images (angular dynamic range broadened) [B] Diffraction Intensity Correlation Spectroscopic DXT: Analyzes self and cross correlation of diffraction intensity and derives motion of diffraction spots (incident X-ray with broad energy width is not necessarily required) [C] Time of Arrival (ToA) imaging DXT: Using ToA function of TimePix detector, acquires diffracted photon information and derives diffraction spot motion. These methods were applied for motion analysis of AChBP (acetylcholine binding protein) upon agonist biding, and angular motion enhancement were detected. We expect those methods to be able to trace a wide range of angle changes while minimizing damage to the sample.