Localising elements in single-particle reconstructions by REEL-EM: Reconstructed Electron Energy-Loss - Elemental Mapping

• Published in: bioRxiv
• Main Authors: Pfeil-Gardiner, Olivia, Higor Vinicius Dias Rosa, Riedel, Dietmar, Chen, Yu Seby, Lorks, Dominique, Kukelhan, Pirmin, Linck, Martin, Muller, Heiko, Filip Van Petegem, Murphy, Bonnie J
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 18.01.2024
• Subjects: Image processing; Lipids; Macromolecules; Mapping; Metals; Spectroscopy
• DOI: 10.1101/2024.01.18.575858

For structures determined by single particle cryo-EM, no technique currently exists for mapping elements to defined locations, leading to errors in the assignment of metals and other ions, cofactors, substrates, inhibitors, and lipids that play essential roles in activity and regulation. Elemental mapping in the electron microscope is well established for dose-tolerant samples but is challenging for biological samples, especially in a cryo-preserved state. Here, we combine electron energy-loss spectroscopy (EELS) with single-particle image processing to allow elemental mapping in cryo-preserved macromolecular complexes. Proof-of-principle data show that our method, REEL-EM, allows 3D reconstruction of EELS data, such that a high total electron dose is accumulated across many copies of a complex. Working with two test samples, we demonstrate that we can reliably localise abundant elements. We discuss the current limitations of the method and potential future developments.Competing Interest StatementD.L. P.K., M.L., and H.M. are employed by CEOS GmbH, the manufacturer of the CEFID energy filter used in this work. The authors declare no further competing interests.