Solving protein structure from sparse serial microcrystal diffraction data at a storage-ring synchrotron source
Ti-Yen Lan,
Jennifer L. Wierman,
Mark W. Tate,
Hugh T. Philipp,
Jose M. Martin-Garcia,
Lan Zhu,
David Kissick,
Petra Fromme,
Robert F. Fischetti,
Wei Liu,
Veit Elser,
Sol M. Gruner
Affiliations
Ti-Yen Lan
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
Jennifer L. Wierman
Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853, USA
Mark W. Tate
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
Hugh T. Philipp
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
Jose M. Martin-Garcia
School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
Lan Zhu
School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
David Kissick
Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
Petra Fromme
School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
Robert F. Fischetti
Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
Wei Liu
School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
Veit Elser
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
Sol M. Gruner
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
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.
