Time-resolved cryo-EM using a combination of droplet microfluidics with on-demand jetting

Stefania Torino; Mugdha Dhurandhar; Annelore Stroobants; Raf Claessens; Rouslan G. Efremov

doi:10.1038/s41592-023-01967-z

Time-resolved cryo-EM using a combination of droplet microfluidics with on-demand jetting

Stefania Torino, Mugdha Dhurandhar, Annelore Stroobants, Raf Claessens, Rouslan G. Efremov

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Abstract

Single-particle cryogenic electron microscopy (cryo-EM) allows reconstruction of high-resolution structures of proteins in different conformations. Protein function often involves transient functional conformations, which can be resolved using time-resolved cryo-EM (trEM). In trEM, reactions are arrested after a defined delay time by rapid vitrification of protein solution on the EM grid. Despite the increasing interest in trEM among the cryo-EM community, making trEM samples with a time resolution below 100 ms remains challenging. Here we report the design and the realization of a time-resolved cryo-plunger that combines a droplet-based microfluidic mixer with a laser-induced generator of microjets that allows rapid reaction initiation and plunge-freezing of cryo-EM grids. Using this approach, a time resolution of 5 ms was achieved and the protein density map was reconstructed to a resolution of 2.1 Å. trEM experiments on GroEL:GroES chaperonin complex resolved the kinetics of the complex formation and visualized putative short-lived conformations of GroEL–ATP complex.

Original language	English
Pages (from-to)	1400-1408
Number of pages	9
Journal	Nature Methods
Volume	20
Issue number	9
DOIs	https://doi.org/10.1038/s41592-023-01967-z
Publication status	Published - Sep 2023

Bibliographical note

Funding Information:
We thank H. De Greve for designing primers used to clone the lacZ gene. We are indebted to A. Manz (KIST, Saarbrüken) for helpful discussions, B. Schied (ULB, Brussels) for a practical introduction to microfluidics and help with setting up microfabrication laboratory, and M. Fislage for assistance with cryo-EM data collection. We would like to acknowledge the funding provided by Vlaams Instituut Voor Biotechnologie, Fonds Wetenschappelijk Onderzoek (grant nos. G0H5916N, G054617N to R.G.E.), and by the European Research Council (grant no. 726436 to R.G.E.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
© 2023, The Author(s), under exclusive licence to Springer Nature America, Inc.

Copyright:
Copyright 2023 Elsevier B.V., All rights reserved.

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98631187Accepted author manuscript, 10.2 MBLicence: Other

Cite this

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title = "Time-resolved cryo-EM using a combination of droplet microfluidics with on-demand jetting",

abstract = "Single-particle cryogenic electron microscopy (cryo-EM) allows reconstruction of high-resolution structures of proteins in different conformations. Protein function often involves transient functional conformations, which can be resolved using time-resolved cryo-EM (trEM). In trEM, reactions are arrested after a defined delay time by rapid vitrification of protein solution on the EM grid. Despite the increasing interest in trEM among the cryo-EM community, making trEM samples with a time resolution below 100 ms remains challenging. Here we report the design and the realization of a time-resolved cryo-plunger that combines a droplet-based microfluidic mixer with a laser-induced generator of microjets that allows rapid reaction initiation and plunge-freezing of cryo-EM grids. Using this approach, a time resolution of 5 ms was achieved and the protein density map was reconstructed to a resolution of 2.1 {\AA}. trEM experiments on GroEL:GroES chaperonin complex resolved the kinetics of the complex formation and visualized putative short-lived conformations of GroEL–ATP complex.",

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note = "Funding Information: We thank H. De Greve for designing primers used to clone the lacZ gene. We are indebted to A. Manz (KIST, Saarbr{\"u}ken) for helpful discussions, B. Schied (ULB, Brussels) for a practical introduction to microfluidics and help with setting up microfabrication laboratory, and M. Fislage for assistance with cryo-EM data collection. We would like to acknowledge the funding provided by Vlaams Instituut Voor Biotechnologie, Fonds Wetenschappelijk Onderzoek (grant nos. G0H5916N, G054617N to R.G.E.), and by the European Research Council (grant no. 726436 to R.G.E.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Publisher Copyright: {\textcopyright} 2023, The Author(s), under exclusive licence to Springer Nature America, Inc. Copyright: Copyright 2023 Elsevier B.V., All rights reserved.",

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Time-resolved cryo-EM using a combination of droplet microfluidics with on-demand jetting

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