Abstract
Single particle cryo-electron microscopy (cryoEM) is often performed under the assumption that particles are not adsorbed to the air-water interfaces and in thin, vitreous ice. In this study, we performed fiducial-less tomography on over 50 different cryoEM grid/sample preparations to determine the particle distribution within the ice and the overall geometry of the ice in grid holes. Surprisingly, by studying particles in holes in 3D from over 1,000 tomograms, we have determined that the vast majority of particles (approximately 90%) are adsorbed to an air-water interface. The implications of this observation are wide-ranging, with potential ramifications regarding protein denaturation, conformational change, and preferred orientation. We also show that fiducial-less cryo-electron tomography on single particle grids may be used to determine ice thickness, optimal single particle collection areas and strategies, particle heterogeneity, and de novo models for template picking and single particle alignment.
Data availability
Several representative tilt-series from the datasets have been deposited to the Electron Microscopy Data Bank (EMDB) in the form of binned by 4 or 8 tomograms and to the Electron Microscopy Pilot Image Archive (EMPIAR) in the form of unaligned tilt-series images (one including super-resolution frames), Appion-Protomo tilt-series alignment runs, and aligned tilt-series stacks.Protomo estimations for the orientation of the local ice normal based on the tilt-series alignment of the particles in the ice, which includes potential systematic stage and beam axis error, are available in all deposited EMPIAR datasets as a plot located: protomo_alignments/tiltseries####/media/angle_refinement/series####_orientation.gifA Docker-based version of Appion-Protomo fiducial-less tilt-series alignment is available at http://github.com/nysbc/appion-protomo.
Article and author information
Author details
Funding
Simons Foundation (SF349247)
- Clinton S Potter
- Bridget Carragher
National Institutes of Health (R01 GM084162)
- David Jeruzalmi
New York State Foundation for Science, Technology and Innovation
- Clinton S Potter
- Bridget Carragher
National Institute of General Medical Sciences (GM103310)
- Clinton S Potter
- Bridget Carragher
Agouron Institute (F00316)
- Clinton S Potter
- Bridget Carragher
National Institutes of Health (S10 OD019994-01)
- Clinton S Potter
- Bridget Carragher
National Institute on Minority Health and Health Disparities (5G12MD007603-30)
- David Jeruzalmi
National Institute of Allergy and Infectious Diseases (Intramural Funding from the Vaccine Research Center)
- Peter D Kwong
Agency for Science, Technology and Research
- Yong Zi Tan
National Institutes of Health (R01-MH1148175)
- Lawrence Shapiro
The authors declare that the funders played no role in this work, including the experimental design, data collection, or data analysis.
Reviewing Editor
- Axel T Brunger, Stanford University Medical Center, United States
Publication history
- Received: December 12, 2017
- Accepted: May 17, 2018
- Accepted Manuscript published: May 29, 2018 (version 1)
- Version of Record published: June 13, 2018 (version 2)
Copyright
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
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