Making the Most of 3D Electron Diffraction: Best Practices to Handle a New Tool
Khai‐Nghi Truong, Shô Itô, Jakub Wojciechowski, Christian R. Göb, Christian J. Schürmann, Akihito Yamano, Mark Del Campo, Eiji Okunishi, Yoshitaka Aoyama, Tomohiro Mihira, Naoki Hosogi, Jordi Benet‐Buchholz, Eduardo C. Escudero‐Adán, Fraser White, Joseph D. Ferrara, Robert Bücker
Abstract
Along with the adoption of three-dimensional electron diffraction (3D ED/MicroED) as a mainstream tool for structure determination from sub-micron single crystals, questions about best practices regarding each step along the workflow, from data collection to structure solutions, arise. In this paper, we discuss three particular aspects of a 3D ED/MicroED experiment which, after hundreds of structures solved in Rigaku’s laboratories, we have found to be important to consider carefully. First, for a representative model system of a hydrated compound (trehalose dihydrate), we show that cryo-transfer of the sample into the diffractometer is an effective means to prevent dehydration, while cooling of the sample without cryo-transfer yields a marginal improvement only. Next, we demonstrate for a small (tyrosine) and a large (clarithromycin) organic compound, how a simplified and fast workflow for dynamical diffraction calculations can determine absolute crystal structures with high confidence. Finally, we discuss considerations and trade-offs for choosing an optimal effective crystal-to-detector distance; while a long distance is mandatory for a protein (thaumatin) example, even a small molecule with difficult diffraction behavior (cystine) yields superior results at longer distances than the one used by default.