Solving protein structure from sparse serial microcrystal diffraction data at a storage-ring synchrotron source
Category
Published on
Type
journal-article
Author
Ti-Yen Lan and Jennifer L. Wierman and Mark W. Tate and Hugh T. Philipp and Jose M. Martin-Garcia and Lan Zhu and David Kissick and Petra Fromme and Robert F. Fischetti and Wei Liu and Veit Elser and Sol M. Gruner
Citation
Lan, T.-Y. et al., 2018. Solving protein structure from sparse serial microcrystal diffraction data at a storage-ring synchrotron source. IUCrJ, 5(5). Available at: http://dx.doi.org/10.1107/s205225251800903x.
Abstract
In recent years, the success of serial femtosecond crystallography and the paucity of beamtime at X-ray free-electron lasers have motivated the development of serial microcrystallography experiments at storage-ring synchrotron sources. However, especially at storage-ring sources, if a crystal is too small it will have suffered significant radiation damage before diffracting a sufficient number of X-rays into Bragg peaks for peak-indexing software to determine the crystal orientation. As a consequence, the data frames of small crystals often cannot be indexed and are discarded. Introduced here is a method based on the expand–maximize–compress (EMC) algorithm to solve protein structures, specifically from data frames for which indexing methods fail because too few X-rays are diffracted into Bragg peaks. The method is demonstrated on a real serial microcrystallography data set whose signals are too weak to be indexed by conventional methods. In spite of the daunting background scatter from the sample-delivery medium, it was still possible to solve the protein structure at 2.1 Å resolution. The ability of the EMC algorithm to analyze weak data frames will help to reduce sample consumption. It will also allow serial microcrystallography to be performed with crystals that are otherwise too small to be feasibly analyzed at storage-ring sources.
DOI
Funding
NSF-STC Biology with X-ray Lasers (NSF-1231306)
