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Jiang X, Xuan S, Zuckermann RN, Glaeser RM, Downing KH, Balsara NP. Minimizing Crinkling of Soft Specimens Using Holey Gold Films on Molybdenum Grids for Cryogenic Electron Microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2021; 27:767-775. [PMID: 34085628 DOI: 10.1017/s1431927621000520] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We introduce a novel composite holey gold support that prevents cryo-crinkling and reduces beam-induced motion of soft specimens, building on the previously introduced all-gold support. The composite holey gold support for high-resolution cryogenic electron microscopy of soft crystalline membranes was fabricated in two steps. In the first step, a holey gold film was transferred on top of a molybdenum grid. In the second step, a continuous thin carbon film was transferred onto the holey gold film. This support (Au/Mo grid) was used to image crystalline synthetic polymer membranes. The low thermal expansion of Mo is not only expected to avoid cryo-crinkling of the membrane when the grids are cooled to cryogenic temperatures, but it may also act to reduce whatever crinkling existed even before cooling. The Au/Mo grid exhibits excellent performance with specimens tilted to 45°. This is demonstrated by quantifying beam-induced motion and differences in local defocus values. In addition, images of specimens on the Au/Mo grids that are tilted at 45° show high-resolution information of the crystalline membranes that, after lattice-unbending, extends beyond 1.5 Å in the direction perpendicular to the tilt axis.
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Affiliation(s)
- Xi Jiang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
| | - Sunting Xuan
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
| | - Ronald N Zuckermann
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
| | - Robert M Glaeser
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
| | - Kenneth H Downing
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
| | - Nitash P Balsara
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA94720, USA
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Sample Preparation and Data Collection for Electron Crystallographic Studies on Membrane Protein Structures and Lipid-Protein Interaction. Methods Mol Biol 2020. [PMID: 33368007 DOI: 10.1007/978-1-0716-0966-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Electron crystallography is a unique tool to study membrane protein structures and lipid-protein interactions in their native-like environments. Two-dimensional (2D) protein crystallization enables the lipids immobilized by the proteins, and the generated high-resolution density map allows us to model the atomic coordinates of the surrounding lipids to study lipid-protein interaction. This protocol describes the sample preparation for electron crystallographic studies, including back-injection method and carbon sandwich method. The protocols of data collection for electron crystallography, including electron imaging and diffraction, of the 2D membrane crystal will be followed.
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Chiu PL, Li X, Li Z, Beckett B, Brilot AF, Grigorieff N, Agard DA, Cheng Y, Walz T. Evaluation of super-resolution performance of the K2 electron-counting camera using 2D crystals of aquaporin-0. J Struct Biol 2015; 192:163-73. [PMID: 26318383 DOI: 10.1016/j.jsb.2015.08.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 08/21/2015] [Accepted: 08/25/2015] [Indexed: 02/07/2023]
Abstract
The K2 Summit camera was initially the only commercially available direct electron detection camera that was optimized for high-speed counting of primary electrons and was also the only one that implemented centroiding so that the resolution of the camera can be extended beyond the Nyquist limit set by the physical pixel size. In this study, we used well-characterized two-dimensional crystals of the membrane protein aquaporin-0 to characterize the performance of the camera below and beyond the physical Nyquist limit and to measure the influence of electron dose rate on image amplitudes and phases.
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Affiliation(s)
- Po-Lin Chiu
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Xueming Li
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA
| | - Zongli Li
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; The Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Brian Beckett
- Department of Biochemistry, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | - Axel F Brilot
- Department of Biochemistry, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | | | - David A Agard
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA; The Howard Hughes Medical Institute, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA
| | - Yifan Cheng
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA.
| | - Thomas Walz
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; The Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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Stahlberg H, Biyani N, Engel A. 3D reconstruction of two-dimensional crystals. Arch Biochem Biophys 2015; 581:68-77. [PMID: 26093179 DOI: 10.1016/j.abb.2015.06.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 06/08/2015] [Accepted: 06/11/2015] [Indexed: 02/02/2023]
Abstract
Electron crystallography of two-dimensional (2D) crystals determines the structure of membrane proteins in the lipid bilayer by imaging with cryo-electron microscopy and image processing. Membrane proteins can be packed in regular 2D arrays by their reconstitution in the presence of lipids at low lipid to protein weight-to-weight ratio. The crystal quality depends on the protein purity and homogeneity, its stability, and on the crystallization conditions. A 2D crystal presents the membrane protein in a functional and fully lipidated state. Electron crystallography determines the 3D structure even of small membrane proteins up to atomic resolution, but 3D density maps have a better resolution in the membrane plane than in the vertical direction. This problem can be partly eliminated by applying an iterative algorithm that exploits additional known constraints about the 2D crystal. 2D electron crystallography is particularly attractive for the structural analysis of membrane proteins that are too small for single particle analyses and too unstable to form 3D crystals. With the recent introduction of direct electron detector cameras, the routine determination of the atomic 3D structure of membrane-embedded membrane proteins is in reach.
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Affiliation(s)
- Henning Stahlberg
- Center for Cellular Imaging and NanoAnalytics, Biozentrum, University of Basel, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Nikhil Biyani
- Center for Cellular Imaging and NanoAnalytics, Biozentrum, University of Basel, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Andreas Engel
- Department of BioNanoscience, Delft University of Technology, Van der Waalsweg 8, 2628 CH Delft, The Netherlands; Department of Pharmacology, Case Western Reserve University, 10900 Euclid Avenue, Wood Bldg 321D, Cleveland, OH 44106-4965, USA.
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Hite RK, Chiu PL, Schuller JM, Walz T. Effect of lipid head groups on double-layered two-dimensional crystals formed by aquaporin-0. PLoS One 2015; 10:e0117371. [PMID: 25635393 PMCID: PMC4311914 DOI: 10.1371/journal.pone.0117371] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 12/23/2014] [Indexed: 11/18/2022] Open
Abstract
Aquaporin-0 (AQP0) is a lens-specific water channel that also forms membrane junctions. Reconstitution of AQP0 with dimyristoyl phosphatidylcholine (DMPC) and E. coli polar lipids (EPL) yielded well-ordered, double-layered two-dimensional (2D) crystals that allowed electron crystallographic structure determination of the AQP0-mediated membrane junction. The interacting tetramers in the two crystalline layers are exactly in register, resulting in crystals with p422 symmetry. The high-resolution density maps also allowed modeling of the annular lipids surrounding the tetramers. Comparison of the DMPC and EPL bilayers suggested that the lipid head groups do not play an important role in the interaction of annular lipids with AQP0. We now reconstituted AQP0 with the anionic lipid dimyristoyl phosphatidylglycerol (DMPG), which yielded a mixture of 2D crystals with different symmetries. The different crystal symmetries result from shifts between the two crystalline layers, suggesting that the negatively charged PG head group destabilizes the interaction between the extracellular AQP0 surfaces. Reconstitution of AQP0 with dimyristoyl phosphatidylserine (DMPS), another anionic lipid, yielded crystals that had the usual p422 symmetry, but the crystals showed a pH-dependent tendency to stack through their cytoplasmic surfaces. Finally, AQP0 failed to reconstitute into membranes that were composed of more than 40% dimyristoyl phosphatidic acid (DMPA). Hence, although DMPG, DMPS, and DMPA are all negatively charged lipids, they have very different effects on AQP0 2D crystals, illustrating the importance of the specific lipid head group chemistry beyond its mere charge.
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Affiliation(s)
- Richard Kevin Hite
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Po-Lin Chiu
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jan Michael Schuller
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Thomas Walz
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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Schenk AD, Philippsen A, Engel A, Walz T. A pipeline for comprehensive and automated processing of electron diffraction data in IPLT. J Struct Biol 2013; 182:173-85. [PMID: 23500887 DOI: 10.1016/j.jsb.2013.02.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 02/27/2013] [Indexed: 11/25/2022]
Abstract
Electron crystallography of two-dimensional crystals allows the structural study of membrane proteins in their native environment, the lipid bilayer. Determining the structure of a membrane protein at near-atomic resolution by electron crystallography remains, however, a very labor-intense and time-consuming task. To simplify and accelerate the data processing aspect of electron crystallography, we implemented a pipeline for the processing of electron diffraction data using the Image Processing Library and Toolbox (IPLT), which provides a modular, flexible, integrated, and extendable cross-platform, open-source framework for image processing. The diffraction data processing pipeline is organized as several independent modules implemented in Python. The modules can be accessed either from a graphical user interface or through a command line interface, thus meeting the needs of both novice and expert users. The low-level image processing algorithms are implemented in C++ to achieve optimal processing performance, and their interface is exported to Python using a wrapper. For enhanced performance, the Python processing modules are complemented with a central data managing facility that provides a caching infrastructure. The validity of our data processing algorithms was verified by processing a set of aquaporin-0 diffraction patterns with the IPLT pipeline and comparing the resulting merged data set with that obtained by processing the same diffraction patterns with the classical set of MRC programs.
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Affiliation(s)
- Andreas D Schenk
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, USA.
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Avila-Sakar A, Li X, Zheng SQ, Cheng Y. Recording high-resolution images of two-dimensional crystals of membrane proteins. Methods Mol Biol 2013; 955:129-152. [PMID: 23132059 DOI: 10.1007/978-1-62703-176-9_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Principles underlying the recording of high-quality/resolution images of two-dimensional crystals of membrane proteins are discussed in the context of instrumental conditions and operational procedures. A detailed example of low-dose microscope settings is provided along with an overview of a program that implements a computer-aided data acquisition procedure.
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Affiliation(s)
- Agustin Avila-Sakar
- The WM Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
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Resch GP, Brandstetter M, Pickl-Herk AM, Königsmaier L, Wonesch VI, Urban E. Immersion freezing of biological specimens: rationale, principles, and instrumentation. Cold Spring Harb Protoc 2011; 2011:778-782. [PMID: 21724824 DOI: 10.1101/pdb.top118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
INTRODUCTIONCryo-transmission electron microscopy (cryo-TEM) allows the visualization of biological specimens within their native, hydrated environment at nanometer resolution. To prevent the formation of destructive ice crystals, an extremely high cooling rate has to be achieved in the freezing process. For samples that are inherently thin enough, ranging from macromolecules to peripheral parts of spread cells, this can be accomplished by plunging the sample into a cryogen. This approach, known as “immersion freezing,” is an essential preparation technique in structural, molecular, and cell biology. In this article, we discuss the advantages of cryo-EM, the scope of specimens that can be visualized using this technique, the method of immersion freezing, and the instrumentation available. In particular, we focus on the new semiautomatic immersion freezer by Leica Microsystems (“EM GP”).
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Affiliation(s)
- Guenter P Resch
- IMP-IMBA-GMI Electron Microscopy Facility, Institute of Molecular Biotechnology, 1030 Vienna, Austria.
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Chiu PL, Kelly DF, Walz T. The use of trehalose in the preparation of specimens for molecular electron microscopy. Micron 2011; 42:762-72. [PMID: 21752659 DOI: 10.1016/j.micron.2011.06.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/09/2011] [Accepted: 06/10/2011] [Indexed: 11/29/2022]
Abstract
Biological specimens have to be prepared for imaging in the electron microscope in a way that preserves their native structure. Two-dimensional (2D) protein crystals to be analyzed by electron crystallography are best preserved by sugar embedding. One of the sugars often used to embed 2D crystals is trehalose, a disaccharide used by many organisms for protection against stress conditions. Sugars such as trehalose can also be added to negative staining solutions used to prepare proteins and macromolecular complexes for structural studies by single-particle electron microscopy (EM). In this review, we describe trehalose and its characteristics that make it so well suited for preparation of EM specimens and we review specimen preparation methods with a focus on the use of trehalose.
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Affiliation(s)
- Po-Lin Chiu
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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Schenk AD, Hite RK, Engel A, Fujiyoshi Y, Walz T. Electron crystallography and aquaporins. Methods Enzymol 2010; 483:91-119. [PMID: 20888471 DOI: 10.1016/s0076-6879(10)83005-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Electron crystallography of two-dimensional (2D) crystals can provide information on the structure of membrane proteins at near-atomic resolution. Originally developed and used to determine the structure of bacteriorhodopsin (bR), electron crystallography has recently been applied to elucidate the structure of aquaporins (AQPs), a family of membrane proteins that form pores mostly for water but also other solutes. While electron crystallography has made major contributions to our understanding of the structure and function of AQPs, structural studies on AQPs, in turn, have fostered a number of technical developments in electron crystallography. In this contribution, we summarize the insights electron crystallography has provided into the biology of AQPs, and describe technical advancements in electron crystallography that were driven by structural studies on AQP 2D crystals. In addition, we discuss some of the lessons that were learned from electron crystallographic work on AQPs.
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Affiliation(s)
- Andreas D Schenk
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
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