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cryoSPARC: algorithms for rapid unsupervised cryo-EM structure determination

Nature Methods volume 14, pages 290296 (2017) | Download Citation


Single-particle electron cryomicroscopy (cryo-EM) is a powerful method for determining the structures of biological macromolecules. With automated microscopes, cryo-EM data can often be obtained in a few days. However, processing cryo-EM image data to reveal heterogeneity in the protein structure and to refine 3D maps to high resolution frequently becomes a severe bottleneck, requiring expert intervention, prior structural knowledge, and weeks of calculations on expensive computer clusters. Here we show that stochastic gradient descent (SGD) and branch-and-bound maximum likelihood optimization algorithms permit the major steps in cryo-EM structure determination to be performed in hours or minutes on an inexpensive desktop computer. Furthermore, SGD with Bayesian marginalization allows ab initio 3D classification, enabling automated analysis and discovery of unexpected structures without bias from a reference map. These algorithms are combined in a user-friendly computer program named cryoSPARC (

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We thank S. Dawood for construction of the GUI front end and members of the Rubinstein laboratory for testing cryoSPARC. A.P. was supported by a scholarship from the Natural Sciences and Engineering Research Council (NSERC), J.L.R. was supported by the Canada Research Chairs program, and D.J.F. was supported in part by the Learning in Machines and Brains program of the Canadian Institute for Advanced Research. This research was also supported by NSERC Discovery Grants (RGPIN 2015-05630 (D.J.F.) and 401724-12 (J.L.R.)) and an NVIDIA Academic Hardware Grant (M.A.B. and A.P.). Part of this work was performed while M.A.B. was a postdoctoral fellow at the University of Toronto.

Author information


  1. Department of Computer Science, The University of Toronto, Toronto, Ontario, Canada.

    • Ali Punjani
  2. Molecular Structure and Function Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.

    • John L Rubinstein
  3. Department of Biochemistry, The University of Toronto, Toronto, Ontario, Canada.

    • John L Rubinstein
  4. Department of Medical Biophysics, The University of Toronto, Toronto, Ontario, Canada.

    • John L Rubinstein
  5. Department of Computer Science, The University of Toronto, Toronto, Ontario, Canada.

    • David J Fleet
  6. Department of Electrical Engineering and Computer Science, York University, Toronto, Ontario, Canada.

    • Marcus A Brubaker


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A.P. and M.A.B. designed algorithms and implemented software. A.P., M.A.B. and J.L.R. performed experimental work. J.L.R., D.J.F., and M.A.B. contributed expertise and supervision. All authors contributed to manuscript preparation.

Competing interests

All authors are engaged in a venture to commercially support cryoSPARC for industrial use through Structura Biotechnology Inc.

Corresponding authors

Correspondence to Ali Punjani or Marcus A Brubaker.

Supplementary information

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    Supplementary Text and Figures

    Supplementary Notes 1–2

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    Supplementary Text and Figures

    Supplementary Protocol 1

Zip files

  1. 1.

    Supplementary Data 1

    3-D Maps from CryoSPARC Refinement

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    Supplementary Data 2

    3-D Maps from CryoSPARC Refinement

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    Supplementary Data 3

    3-D Maps from CryoSPARC Refinement

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    Supplementary Data 4

    3-D Maps from CryoSPARC Refinement


  1. 1.

    CryoSPARC Software and Interface

    CryoSPARC (cryo-EM single particle ab initio reconstruction and classification) is a software package implementing the algorithms described in this work, along with a user-friendly web browser based interface that can be used over the internet or through local installation of the software. CryoSPARC uses graphics processing using (GPU) acceleration with self-compiling code and automatic dependency management, so the package is very simple to install. The cryoSPARC web interface can be accessed from any computer on the same network as the computer running cryoSPARC, meaning that a single desktop computer or rackmount server can provide reconstruction and classification service for an entire group of cryo-EM users who each access the software from their own computers. Remote access is also simple, for instance, using a VPN or SSH. This video shows a brief overview of the cryoSPARC web interface, demonstrating example use of the program on a real dataset, along with the dataset and experiment organization functions. Parameters are set automatically or have prepopulated defaults in the program, meaning that a user can simply select their dataset and begin a reconstruction experiment with no expertise and minimal training.

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