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Yadav S, Vinothkumar KR. Factors affecting macromolecule orientations in thin films formed in cryo-EM. Acta Crystallogr D Struct Biol 2024; 80:535-550. [PMID: 38935342 PMCID: PMC11220838 DOI: 10.1107/s2059798324005229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 06/01/2024] [Indexed: 06/28/2024] Open
Abstract
The formation of a vitrified thin film embedded with randomly oriented macromolecules is an essential prerequisite for cryogenic sample electron microscopy. Most commonly, this is achieved using the plunge-freeze method first described nearly 40 years ago. Although this is a robust method, the behaviour of different macromolecules shows great variation upon freezing and often needs to be optimized to obtain an isotropic, high-resolution reconstruction. For a macromolecule in such a film, the probability of encountering the air-water interface in the time between blotting and freezing and adopting preferred orientations is very high. 3D reconstruction using preferentially oriented particles often leads to anisotropic and uninterpretable maps. Currently, there are no general solutions to this prevalent issue, but several approaches largely focusing on sample preparation with the use of additives and novel grid modifications have been attempted. In this study, the effect of physical and chemical factors on the orientations of macromolecules was investigated through an analysis of selected well studied macromolecules, and important parameters that determine the behaviour of proteins on cryo-EM grids were revealed. These insights highlight the nature of the interactions that cause preferred orientations and can be utilized to systematically address orientation bias for any given macromolecule and to provide a framework to design small-molecule additives to enhance sample stability and behaviour.
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Affiliation(s)
- Swati Yadav
- National Centre for Biological SciencesTata Institute of Fundamental ResearchGKVK Post, Bellary RoadBengaluru560 065India
| | - Kutti R. Vinothkumar
- National Centre for Biological SciencesTata Institute of Fundamental ResearchGKVK Post, Bellary RoadBengaluru560 065India
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2
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Han BG, Avila-Sakar A, Remis J, Glaeser RM. Challenges in making ideal cryo-EM samples. Curr Opin Struct Biol 2023; 81:102646. [PMID: 37392555 DOI: 10.1016/j.sbi.2023.102646] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 06/02/2023] [Accepted: 06/02/2023] [Indexed: 07/03/2023]
Abstract
Recognizing that interaction with the air-water interface (AWI) is a major challenge for cryo-EM, we first review current approaches designed to avoid it. Of these, immobilizing particles on affinity grids is arguably the most promising. In addition, we review efforts to gain more reliable control of the sample thicknesses, not the least important reason being to prevent immobilized particles from coming in contact with the AWI of the remaining buffer. It is emphasized that avoiding such a contact is as important for cryo-ET as for single-particle cryo-EM. Finally, looking to the future, it is proposed that immobilized samples might be used to perform time-resolved biochemical experiments directly on EM grids rather than just in test tubes or cuvettes.
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Affiliation(s)
- Bong-Gyoon Han
- Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA
| | - Agustin Avila-Sakar
- Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA
| | - Jonathan Remis
- Department of Physics, University of California, Berkeley, CA 94720, USA
| | - Robert M Glaeser
- Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA.
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3
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Liu N, Wang HW. Better Cryo-EM Specimen Preparation: How to Deal with the Air-Water Interface? J Mol Biol 2022; 435:167926. [PMID: 36563741 DOI: 10.1016/j.jmb.2022.167926] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/08/2022] [Accepted: 12/14/2022] [Indexed: 12/24/2022]
Abstract
Cryogenic electron microscopy (cryo-EM) is now one of the most powerful and widely used methods to determine high-resolution structures of macromolecules. A major bottleneck of cryo-EM is to prepare high-quality vitrified specimen, which still faces many practical challenges. During the conventional vitrification process, macromolecules tend to adsorb at the air-water interface (AWI), which is known unfriendly to biological samples. In this review, we outline the nature of AWI and the problems caused by it, such as unpredictable or uneven particle distribution, protein denaturation, dissociation of complex and preferential orientation. We review and discuss the approaches and underlying mechanisms to deal with AWI: 1) Additives, exemplified by detergents, forming a protective layer at AWI and thus preserving the native folds of target macromolecules. 2) Fast vitrification devices based on the idea to freeze in-solution macromolecules before their touching of AWI. 3) Thin layer of continuous supporting films to adsorb macromolecules, and when functionalized with affinity ligands, to specifically anchor the target particles away from the AWI. Among these supporting films, graphene, together with its derivatives, with negligible background noise and mechanical robustness, has emerged as a new generation of support. These strategies have been proven successful in various cases and enable us a better handling of the problems caused by the AWI in cryo-EM specimen preparation.
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Affiliation(s)
- Nan Liu
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structures, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structures, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China.
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4
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Bromberg R, Cai K, Guo Y, Plymire D, Emde T, Puzio M, Borek D, Otwinowski Z. The His-tag as a decoy modulating preferred orientation in cryoEM. Front Mol Biosci 2022; 9:912072. [PMID: 36325274 PMCID: PMC9619061 DOI: 10.3389/fmolb.2022.912072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 08/19/2022] [Indexed: 12/02/2022] Open
Abstract
The His-tag is a widely used affinity tag that facilitates purification by means of affinity chromatography of recombinant proteins for functional and structural studies. We show here that His-tag presence affects how coproheme decarboxylase interacts with the air-water interface during grid preparation for cryoEM. Depending on His-tag presence or absence, we observe significant changes in patterns of preferred orientation. Our analysis of particle orientations suggests that His-tag presence can mask the hydrophobic and hydrophilic patches on a protein’s surface that mediate the interactions with the air-water interface, while the hydrophobic linker between a His-tag and the coding sequence of the protein may enhance other interactions with the air-water interface. Our observations suggest that tagging, including rational design of the linkers between an affinity tag and a protein of interest, offer a promising approach to modulating interactions with the air-water interface.
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Affiliation(s)
- Raquel Bromberg
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Ligo Analytics, Dallas, TX, United States
| | - Kai Cai
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Yirui Guo
- Ligo Analytics, Dallas, TX, United States
| | - Daniel Plymire
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Ligo Analytics, Dallas, TX, United States
| | - Tabitha Emde
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Maciej Puzio
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Dominika Borek
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Center for Structural Genomics of Infectious Diseases, Dallas, TX, United States
- *Correspondence: Dominika Borek, ; Zbyszek Otwinowski,
| | - Zbyszek Otwinowski
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Center for Structural Genomics of Infectious Diseases, Dallas, TX, United States
- *Correspondence: Dominika Borek, ; Zbyszek Otwinowski,
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5
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Han BG, Armstrong M, Fletcher DA, Glaeser RM. Perspective: Biochemical and Physical Constraints Associated With Preparing Thin Specimens for Single-Particle Cryo-EM. Front Mol Biosci 2022; 9:864829. [PMID: 35573724 PMCID: PMC9100935 DOI: 10.3389/fmolb.2022.864829] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
While many aspects of single-particle electron cryo-microscopy (cryo-EM) of biological macromolecules have reached a sophisticated level of development, this is not yet the case when it comes to preparing thin samples on specimen grids. As a result, there currently is considerable interest in achieving better control of both the sample thickness and the amount of area that is useful, but this is only one aspect in which improvement is needed. This Perspective addresses the further need to prevent the macromolecular particles from making contact with the air-water interface, something that can result in preferential orientation and even structural disruption of macromolecular particles. This unwanted contact can occur either as the result of free diffusion of particles during the interval between application, thinning and vitrification of the remaining buffer, or-when particles have been immobilized-by the film of buffer becoming too thin prior to vitrification. An opportunity now exists to apply theoretical and practical insights from the fields of thin-film physical chemistry and interfacial science, in an effort to bring cryo-EM sample preparation to a level of sophistication that is comparable to that of current data collection and analysis.
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Affiliation(s)
- Bong-Gyoon Han
- Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States
| | - Max Armstrong
- Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States,Department of Bioengineering, University of California, Berkeley, Berkeley, CA, United States
| | - Daniel A. Fletcher
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, United States,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States,Chan Zuckerberg Biohub, San Francisco, CA, United States
| | - Robert M. Glaeser
- Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States,*Correspondence: Robert M. Glaeser,
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Han BG, Glaeser RM. Simple assay for adsorption of proteins to the air-water interface. J Struct Biol 2021; 213:107798. [PMID: 34534654 DOI: 10.1016/j.jsb.2021.107798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 09/05/2021] [Accepted: 09/09/2021] [Indexed: 11/27/2022]
Abstract
A rapid assay is described, based upon the Marangoni effect, which detects the formation of a denatured-protein film at the air-water interface (AWI) of aqueous samples. This assay requires no more than a 20 µL aliquot of sample, at a protein concentration of no more than1 mg/ml, and it can be performed with any buffer that is used to prepare grids for electron cryo-microscopy (cryo-EM). In addition, this assay provides an easy way to estimate the rate at which a given protein forms such a film at the AWI. Use of this assay is suggested as a way to pre-screen the effect of various additives and chemical modifications that one might use to optimize the preparation of grids, although the final proof of optimization still requires further screening of grids in the electron microscope. In those cases when the assay establishes that a given protein does form a sacrificial, denatured-protein monolayer, it is suggested that subsequent optimization strategies might focus on discovering how to improve the adsorption of native proteins onto that monolayer, rather than to prevent its formation. A second alternative might be to bind such proteins to the surface of rationally designed affinity grids, in order to prevent their diffusion to, and unwanted interaction with, the AWI.
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Affiliation(s)
- Bong-Gyoon Han
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA, United States
| | - Robert M Glaeser
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA, United States.
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7
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Glaeser RM. Preparing Better Samples for Cryo-Electron Microscopy: Biochemical Challenges Do Not End with Isolation and Purification. Annu Rev Biochem 2021; 90:451-474. [PMID: 33556280 DOI: 10.1146/annurev-biochem-072020-020231] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The preparation of extremely thin samples, which are required for high-resolution electron microscopy, poses extreme risk of damaging biological macromolecules due to interactions with the air-water interface. Although the rapid increase in the number of published structures initially gave little indication that this was a problem, the search for methods that substantially mitigate this hazard is now intensifying. The two main approaches under investigation are (a) immobilizing particles onto structure-friendly support films and (b) reducing the length of time during which such interactions may occur. While there is little possibility of outrunning diffusion to the interface, intentional passivation of the interface may slow the process of adsorption and denaturation. In addition, growing attention is being given to gaining more effective control of the thickness of the sample prior to vitrification.
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Affiliation(s)
- Robert M Glaeser
- Department of Molecular and Cell Biology and Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA;
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8
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Franken LE, Grünewald K, Boekema EJ, Stuart MCA. A Technical Introduction to Transmission Electron Microscopy for Soft-Matter: Imaging, Possibilities, Choices, and Technical Developments. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1906198. [PMID: 32130784 DOI: 10.1002/smll.201906198] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/30/2019] [Indexed: 05/24/2023]
Abstract
With a significant role in material sciences, physics, (soft matter) chemistry, and biology, the transmission electron microscope is one of the most widely applied structural analysis tool to date. It has the power to visualize almost everything from the micrometer to the angstrom scale. Technical developments keep opening doors to new fields of research by improving aspects such as sample preservation, detector performance, computational power, and workflow automation. For more than half a century, and continuing into the future, electron microscopy has been, and is, a cornerstone methodology in science. Herein, the technical considerations of imaging with electrons in terms of optics, technology, samples and processing, and targeted soft materials are summarized. Furthermore, recent advances and their potential for application to soft matter chemistry are highlighted.
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Affiliation(s)
- Linda E Franken
- Department of Structural Cell Biology of Viruses, Heinrich-Pette Institute-Leibniz-Institute of Experimental Virology University of Hamburg, Centre for Structural Systems Biology, Notkestraße 85, 22607, Hamburg, Germany
| | - Kay Grünewald
- Department of Structural Cell Biology of Viruses, Heinrich-Pette Institute-Leibniz-Institute of Experimental Virology University of Hamburg, Centre for Structural Systems Biology, Notkestraße 85, 22607, Hamburg, Germany
| | - Egbert J Boekema
- Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
| | - Marc C A Stuart
- Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
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9
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Microscale Fluid Behavior during Cryo-EM Sample Blotting. Biophys J 2020; 118:708-719. [PMID: 31952802 PMCID: PMC7004840 DOI: 10.1016/j.bpj.2019.12.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/05/2019] [Accepted: 12/16/2019] [Indexed: 12/14/2022] Open
Abstract
Blotting has been the standard technique for preparing aqueous samples for single-particle electron cryo-microscopy for over three decades. This technique removes the excess solution from a transmission electron microscope grid by pressing absorbent filter paper against the specimen before vitrification. However, this standard technique produces vitreous ice with inconsistent thickness from specimen to specimen and from region to region within the same specimen, the reasons for which are not understood. Here, high-speed interference contrast microscopy is used to demonstrate that the irregular pattern of fibers in the filter paper imposes tortuous, highly variable boundaries during the removal of excess liquid from a flat, hydrophilic surface. As a result, aqueous films of nonuniform thickness are formed while the filter paper is pressed against the substrate. This pattern of nonuniform liquid thickness changes again after the filter paper is pulled away, but the thickness still does not become completely uniform. We suggest that similar topographical features of the liquid film are produced during the standard technique used to blot EM grids and that these manifest in nonuniform ice after vitrification. These observations suggest that alternative thinning techniques, which do not rely on direct contact between the filter paper and the grid, may result in more repeatable and uniform sample thicknesses.
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10
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Manipulating and monitoring nanoparticles in micellar thin film superstructures. Nat Commun 2018; 9:5207. [PMID: 30523264 PMCID: PMC6283865 DOI: 10.1038/s41467-018-07568-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 11/09/2018] [Indexed: 11/18/2022] Open
Abstract
Understanding the dynamics of discrete self-assembled structures under influence of external triggers is of interest to harvest the potential of nano- and mesoscale materials. In particular, controlling the hierarchical organization of (macro)molecular and nanoparticle building blocks in monolayer superstructures is of paramount importance for tuning properties and characteristics. Here we show how the electron beam in cryo-transmission electron microscopy can be exploited to induce and follow local migration of building blocks and global migration of micellar aggregates inside micrometer-sized superstructures. We employ stroboscopic exposure to heat up and convert the vitrified superstructure into a liquid-like thin film under cryogenic conditions, resulting in controlled evaporation of water that finally leads to rupture of the micelle-containing superstructure. Micelle-embedded nanoparticles prove a powerful tool to study the complex hierarchically built-up superstructures, and to visualize both global movement of individual dendrimicelles and local migration of nanoparticles inside the micellar core during the exposure series. Understanding how nanoparticle superstructures respond to external stimuli is of importance to their potential application. Here, the authors demonstrate the use of cryo-transmission electron microscopy for monitoring and manipulating movement within nanoparticle-loaded dendrimicelle superstructure thin films upon irradiation with an electron beam.
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11
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Noble AJ, Dandey VP, Wei H, Brasch J, Chase J, Acharya P, Tan YZ, Zhang Z, Kim LY, Scapin G, Rapp M, Eng ET, Rice WJ, Cheng A, Negro CJ, Shapiro L, Kwong PD, Jeruzalmi D, des Georges A, Potter CS, Carragher B. Routine single particle CryoEM sample and grid characterization by tomography. eLife 2018; 7:e34257. [PMID: 29809143 PMCID: PMC5999397 DOI: 10.7554/elife.34257] [Citation(s) in RCA: 172] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 05/17/2018] [Indexed: 12/11/2022] Open
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 1000 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.
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Affiliation(s)
- Alex J Noble
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Venkata P Dandey
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Hui Wei
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Julia Brasch
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Department of Biochemistry and Molecular BiophysicsColumbia UniversityNew YorkUnited States
| | - Jillian Chase
- Department of Chemistry and BiochemistryCity College of New YorkNew YorkUnited States
- Program in BiochemistryThe Graduate Center of the City University of New YorkNew YorkUnited States
| | - Priyamvada Acharya
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Vaccine Research CenterNational Institute of Allergy and Infectious Diseases, National Institutes of HealthMarylandUnited States
| | - Yong Zi Tan
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Department of Biochemistry and Molecular BiophysicsColumbia UniversityNew YorkUnited States
| | - Zhening Zhang
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Laura Y Kim
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Giovanna Scapin
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Department of Structural Chemistry and Chemical BiotechnologyMerck & Co., IncNew JerseyUnited States
| | - Micah Rapp
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Department of Biochemistry and Molecular BiophysicsColumbia UniversityNew YorkUnited States
| | - Edward T Eng
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - William J Rice
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Anchi Cheng
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Carl J Negro
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Lawrence Shapiro
- Department of Biochemistry and Molecular BiophysicsColumbia UniversityNew YorkUnited States
| | - Peter D Kwong
- Vaccine Research CenterNational Institute of Allergy and Infectious Diseases, National Institutes of HealthMarylandUnited States
| | - David Jeruzalmi
- Department of Chemistry and BiochemistryCity College of New YorkNew YorkUnited States
- Program in BiochemistryThe Graduate Center of the City University of New YorkNew YorkUnited States
- Program in BiologyThe Graduate Center of the City University of New YorkNew YorkUnited States
- Program in ChemistryThe Graduate Center of the City University of New YorkNew YorkUnited States
| | - Amedee des Georges
- Department of Chemistry and BiochemistryCity College of New YorkNew YorkUnited States
- Program in BiochemistryThe Graduate Center of the City University of New YorkNew YorkUnited States
- Program in ChemistryThe Graduate Center of the City University of New YorkNew YorkUnited States
- Advanced Science Research CenterThe Graduate Center of the City University of New YorkNew YorkUnited States
| | - Clinton S Potter
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Department of Biochemistry and Molecular BiophysicsColumbia UniversityNew YorkUnited States
| | - Bridget Carragher
- National Resource for Automated Molecular MicroscopySimons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
- Department of Biochemistry and Molecular BiophysicsColumbia UniversityNew YorkUnited States
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12
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Franken LE, Boekema EJ, Stuart MCA. Transmission Electron Microscopy as a Tool for the Characterization of Soft Materials: Application and Interpretation. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2017; 4:1600476. [PMID: 28546914 PMCID: PMC5441488 DOI: 10.1002/advs.201600476] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 12/02/2016] [Indexed: 05/22/2023]
Abstract
Transmission electron microscopy (TEM) provides direct structural information on nano-structured materials and is popular as a characterization tool in soft matter and supramolecular chemistry. However, technical aspects of sample preparation are overlooked and erroneous image interpretations are regularly encountered in the literature. There are three most commonly used TEM methods as we derived from literature: drying, staining and cryo-TEM, which are explained here with respect to their application, limitations and interpretation. Since soft matter chemistry relies on a lot of indirect evidence, the role of TEM for the correct evaluation of the nature of an assembly is very large. Mistakes in application and interpretation can therefore have enormous impact on the quality of present and future studies. We provide helpful background information of these three techniques, the information that can and cannot be derived from them and provide assistance in selecting the right technique for soft matter imaging. This essay warns against the use of drying and explains why. In general cryo-TEM is by far the best suited method and many mistakes and over-interpretations can be avoided by the use of this technique.
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Affiliation(s)
- Linda E. Franken
- Electron Microscopy GroupGroningen Biomolecular Sciences and Biotechnology InstituteUniversity of GroningenNijenborgh 79747AGGroningenThe Netherlands
| | - Egbert J. Boekema
- Electron Microscopy GroupGroningen Biomolecular Sciences and Biotechnology InstituteUniversity of GroningenNijenborgh 79747AGGroningenThe Netherlands
| | - Marc C. A. Stuart
- Electron Microscopy GroupGroningen Biomolecular Sciences and Biotechnology InstituteUniversity of GroningenNijenborgh 79747AGGroningenThe Netherlands
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 79747AGGroningenThe Netherlands
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13
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Glaeser RM, Han BG. Opinion: hazards faced by macromolecules when confined to thin aqueous films. BIOPHYSICS REPORTS 2016; 3:1-7. [PMID: 28781996 PMCID: PMC5516009 DOI: 10.1007/s41048-016-0026-3] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 05/16/2016] [Indexed: 11/29/2022] Open
Abstract
Samples prepared for single-particle electron cryo-microscopy (cryo-EM) necessarily have a very high surface-to-volume ratio during the short period of time between thinning and vitrification. During this time, there is an obvious risk that macromolecules of interest may adsorb to the air–water interface with a preferred orientation, or that they may even become partially or fully unfolded at the interface. In addition, adsorption of macromolecules to an air–water interface may occur even before thinning. This paper addresses the question whether currently used methods of sample preparation might be improved if one could avoid such interfacial interactions. One possible way to do so might be to preemptively form a surfactant monolayer over the air–water interfaces, to serve as a structure-friendly slide and coverslip. An alternative is to immobilize particles of interest by binding them to some type of support film, which—to continue using the analogy—thus serves as a slide. In this case, the goal is not only to prevent the particles of interest from diffusing into contact with the air–water interface but also to increase the number of particles seen in each image. In this direction, it is natural to think of developing various types of affinity grids as structure-friendly alternatives to thin carbon films. Perhaps ironically, if precautions are not taken against adsorption of particles to air–water interfaces, sacrificial monolayers of denatured protein may take the roles of slide, coverslip, or even both.
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Affiliation(s)
- Robert M Glaeser
- Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 USA
| | - Bong-Gyoon Han
- Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 USA
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14
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Pretzel J, Mohring F, Rahlfs S, Becker K. Antiparasitic peptides. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2016; 135:157-92. [PMID: 23615879 DOI: 10.1007/10_2013_191] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
: The most important parasitic diseases, malaria, leishmaniasis, trypanosomiasis, and schistosomiasis, are a great burden to mankind, threatening the life of millions of people worldwide and mostly affecting the poorest. Because drug resistance is increasing and vaccines are rarely available, novel chemotherapeutic compounds are necessary in order to treat these devastating diseases. Insects serve as vectors of many human parasitic diseases and have been shown to express a huge variety of antimicrobial peptides (AMPs). Therefore, research activity on insect-derived AMPs has been increasing in the last 40 years. This chapter summarizes the current state of research on the possible role of AMPs as potential chemotherapeutic compounds against human parasitic diseases. As a representative antimicrobial peptide with antiparasitic activity, the structure of insect defensin A is shown [PDB accession code: 1ICA]. The molecule is surrounded by schematic representations of the human pathogenic parasites Plasmodium, Leishmania and Trypanosoma.
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Affiliation(s)
- Jette Pretzel
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
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15
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Glaeser RM, Han BG, Csencsits R, Killilea A, Pulk A, Cate JHD. Factors that Influence the Formation and Stability of Thin, Cryo-EM Specimens. Biophys J 2015; 110:749-55. [PMID: 26386606 DOI: 10.1016/j.bpj.2015.07.050] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/20/2015] [Accepted: 07/21/2015] [Indexed: 11/27/2022] Open
Abstract
Poor consistency of the ice thickness from one area of a cryo-electron microscope (cryo-EM) specimen grid to another, from one grid to the next, and from one type of specimen to another, motivates a reconsideration of how to best prepare suitably thin specimens. Here we first review the three related topics of wetting, thinning, and stability against dewetting of aqueous films spread over a hydrophilic substrate. We then suggest that the importance of there being a surfactant monolayer at the air-water interface of thin, cryo-EM specimens has been largely underappreciated. In fact, a surfactant layer (of uncontrolled composition and surface pressure) can hardly be avoided during standard cryo-EM specimen preparation. We thus suggest that better control over the composition and properties of the surfactant layer may result in more reliable production of cryo-EM specimens with the desired thickness.
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Affiliation(s)
- Robert M Glaeser
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California.
| | - Bong-Gyoon Han
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California
| | - Roseann Csencsits
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California
| | - Alison Killilea
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California
| | - Arto Pulk
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California; Department of Molecular and Cell Biology and California Institute of Quantitative Biosciences, University of California, Berkeley, Berkeley, California
| | - Jamie H D Cate
- Department of Molecular and Cell Biology and California Institute of Quantitative Biosciences, University of California, Berkeley, Berkeley, California; Department of Chemistry, University of California, Berkeley, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California
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Vale N, Aguiar L, Gomes P. Antimicrobial peptides: a new class of antimalarial drugs? Front Pharmacol 2014; 5:275. [PMID: 25566072 PMCID: PMC4271771 DOI: 10.3389/fphar.2014.00275] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 11/26/2014] [Indexed: 12/12/2022] Open
Abstract
A range of antimicrobial peptides (AMP) exhibit activity on malaria parasites, Plasmodium spp., in their blood or mosquito stages, or both. These peptides include a diverse array of both natural and synthetic molecules varying greatly in size, charge, hydrophobicity, and secondary structure features. Along with an overview of relevant literature reports regarding AMP that display antiplasmodial activity, this review makes a few considerations about those molecules as a potential new class of antimalarial drugs.
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Affiliation(s)
- Nuno Vale
- Department of Chemistry and Biochemistry, Faculty of Sciences, Centro de Investigação em Química, University of Porto Porto, Portugal
| | - Luísa Aguiar
- Department of Chemistry and Biochemistry, Faculty of Sciences, Centro de Investigação em Química, University of Porto Porto, Portugal
| | - Paula Gomes
- Department of Chemistry and Biochemistry, Faculty of Sciences, Centro de Investigação em Química, University of Porto Porto, Portugal
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Burrows ND, Penn RL. Cryogenic transmission electron microscopy: aqueous suspensions of nanoscale objects. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2013; 19:1542-1553. [PMID: 24001937 DOI: 10.1017/s1431927613013354] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Direct imaging of nanoscale objects suspended in liquid media can be accomplished using cryogenic transmission electron microscopy (cryo-TEM). Cryo-TEM has been used with particular success in microbiology and other biological fields. Samples are prepared by plunging a thin film of sample into an appropriate cryogen, which essentially produces a snapshot of the suspended objects in their liquid medium. With successful sample preparation, cryo-TEM images can facilitate elucidation of aggregation and self-assembly, as well as provide detailed information about cells and viruses. This work provides an explanation of sample preparation, detailed examples of the many artifacts found in cryo-TEM of aqueous samples, and other key considerations for successful cryo-TEM imaging.
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Affiliation(s)
- Nathan D Burrows
- Department of Chemistry, University of Minnesota - Twin Cities 207 Pleasant St. SE, Minneapolis, MN 55455, USA
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Friedrich H, Frederik PM, de With G, Sommerdijk NAJM. Imaging of Self-Assembled Structures: Interpretation of TEM and Cryo-TEM Images. Angew Chem Int Ed Engl 2010; 49:7850-8. [DOI: 10.1002/anie.201001493] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Abbildung selbstorganisierter Strukturen: Interpretation von TEM- und Kryo-TEM-Aufnahmen. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201001493] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Ultradeformable cationic liposomes for delivery of small interfering RNA (siRNA) into human primary melanocytes. J Control Release 2008; 133:214-20. [PMID: 18973779 DOI: 10.1016/j.jconrel.2008.10.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 09/26/2008] [Accepted: 10/02/2008] [Indexed: 11/24/2022]
Abstract
The aim of this work was to develop a system that can deliver siRNA into cells present in the human epidermis. More specifically, we wanted to block the expression of a specific Myosin Va exon F containing isoform that is physiologically involved in melanosome transport in human melanocytes. Therefore, we prepared and investigated the capacity of ultradeformable cationic liposomes (UCLs) to deliver siRNA in hard-to-transfect human primary melanocytes. UCLs were formulated from different w:w ratios (6:1, 8:1 and 10:1) of the cationic lipid 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and the edge activator sodium cholate. Subsequently, UCL/siRNA complexes were prepared and their particle size, surface charge, deformability, cytotoxicity, transfection efficiency and long-term stability were tested. The best results were obtained with UCLs composed of a DOTAP/NaChol ratio of 6:1 (w:w) which are promising for future in vivo experiments.
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Vos MR, Bomans PH, Frederik PM, Sommerdijk NA. The development of a glove-box/Vitrobot combination: Air–water interface events visualized by cryo-TEM. Ultramicroscopy 2008; 108:1478-83. [DOI: 10.1016/j.ultramic.2008.03.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 03/28/2008] [Indexed: 11/25/2022]
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Stuart MCA, Boekema EJ. Two distinct mechanisms of vesicle-to-micelle and micelle-to-vesicle transition are mediated by the packing parameter of phospholipid-detergent systems. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2681-9. [PMID: 17714686 DOI: 10.1016/j.bbamem.2007.06.024] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Revised: 05/21/2007] [Accepted: 06/21/2007] [Indexed: 10/23/2022]
Abstract
The detergent solubilization and reformation of phospholipid vesicles was studied for various detergents. Two distinct mechanisms of vesicle-to-micelle and micelle-to-vesicle transition were observed by turbidimetry and cryo-electron microscopy. The first mechanism involves fast solubilization of phospholipids and occurs via open vesicular intermediates. The reverse process, micelle-to-vesicle transition, mimics the vesicle-to-micelle transition. In the second mechanism the solubilization is a slow process that proceeds via micelles that pinch off from closed vesicles. During vesicle reformation, the micelle-to-vesicle transition, a large number of densely packed multilamellar vesicles are formed. The route used, for solubilization and reformation, by a given detergent-phospholipid combination is critically dependent on the overall packing parameter of the detergent-saturated phospholipid membranes. By a change of the overall packing parameter the solubilization and or reformation mechanism could be changed. All five detergents tested fit within the proposed model. With two detergents the mechanism could be changed by changing the phospholipid composition or the medium conditions.
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Affiliation(s)
- Marc C A Stuart
- Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
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Saveyn P, Cocquyt J, Bomans P, Frederik P, De Cuyper M, Van der Meeren P. Osmotically induced morphological changes of extruded dioctadecyldimethylammonium chloride (DODAC) dispersions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:4775-81. [PMID: 17388615 DOI: 10.1021/la063468+] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Extruded vesicles, which are often used as models for living cells, can change their morphology when they are diluted into a hyperosmotic medium. Different morphological changes were observed with extruded dioctadecyldimethylammonium chloride (DODAC) vesicles after dilution with a nonionic (sucrose) and ionic (CaCl2) osmotic agent above and below the gel-to-liquid crystalline transition temperature. By means of turbidimetry, dynamic light scattering, and cryo-transmission electron microscopy, it was seen that the vesicles only deflated when they were in the gel state, whereas in the liquid crystalline state, an ionic osmotic agent could induce twinning of the vesicles, reminiscent to endocytosis. The latter could occur as a result of the combined effects of reduced repulsion, local dehydration, and reduced bending rigidity induced by the ionic agent.
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Affiliation(s)
- Pieter Saveyn
- Ghent University, Faculty of Bioscience Engineering, Particle and Interfacial Technology Group, Coupure Links 653, B-9000 Gent, Belgium
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Crucifix C, Uhring M, Schultz P. Immobilization of biotinylated DNA on 2-D streptavidin crystals. J Struct Biol 2005; 146:441-51. [PMID: 15099585 DOI: 10.1016/j.jsb.2004.02.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 02/03/2004] [Indexed: 01/22/2023]
Abstract
The structural study of transient nucleoprotein complexes by electron microscopy is hampered by the coexistence of multiple interaction states leading to an heterogeneous image population. To tackle this problem, we have investigated the controlled immobilization of double stranded DNA molecules and of nucleoprotein complexes onto a support suitable for cryo-electron microscopy observation. The DNA was end-labeled with a biotin moiety in order to decorate, or to be incorporated into, two-dimensional streptavidin crystals formed in contact of a biotinylated lipid layer. The binding specificity and efficiency were examined by radioactively labeled oligonucleotides and by direct visualization of unstained and hydrated nucleic acid molecules in cryo-electron microscopy. By using RNA polymerase we further show that, once immobilized, femtomolar amounts of DNA template are suitable to interact with the enzyme. The image analysis of the RNA polymerase-DNA complexes showed that a three-dimensional model can be retrieved from such samples.
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Affiliation(s)
- Corinne Crucifix
- Institut de Génétique et de Biologie Moléculaire et Cellulaire CNRS/INSERM/ULP 1, rue Laurent Fries, BP10142 67404 Illkirch, France
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Abstract
A thin aqueous film of suspended lipid vesicles?micelles is the object of choice for vitrification and subsequent study by cryoelectron microscopy. Just prior to vitrification, a thin film (compare with a soap film) is vulnerable to heat and mass exchange. Preparation of thin films in a temperature- and humidity-controlled environment is essential to prevent osmotic and temperature-induced alterations of the lipid structure, as will be explained in this chapter. Further automation of the preparative procedure by automatic blotting and PC control over the timing of critical steps (including vitrification) may further assist in the reproducible throughput of high-quality specimens. By cryotomography, taking a tilt series under low-dose conditions, a three-dimensional reconstruction of the specimen can be analyzed.
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Nishikawa H, Morita T, Sugiyama J, Kimura S. Formation of gold nanoparticles in microreactor composed of helical peptide assembly in water. J Colloid Interface Sci 2004; 280:506-10. [PMID: 15533423 DOI: 10.1016/j.jcis.2004.08.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2004] [Accepted: 08/04/2004] [Indexed: 10/26/2022]
Abstract
A novel microreactor was prepared by self-assembly of an amphiphilic block copolymer composed of a hydrophobic helical peptide unit with a naphthyl group at the C terminal and a hydrophilic poly(ethylene glycol) unit. The copolymer formed a self-assembly in water, taking a vesicular structure. Noticeably, when the copolymer was dispersed in an Au(3+) aqueous solution, gold nanoparticles were formed without addition of any reducing reagent. The naphthyl groups, which are located at the inner surface of the vesicular assembly, promoted the reduction of Au(3+) ions with accompanying pH decrease.
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Affiliation(s)
- Hiroyuki Nishikawa
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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Affiliation(s)
- Olivier Lambert
- Institut Curie, Section de Recherche, UMR-CNRS 168 et LRC-CEA 8, 11 rue Pierre et Marie Curie, 75231 Paris, France
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28
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Schmidtgen, Drechsler, Lasch, Schubert. Energy‐filtered cryotransmission electron microscopy of liposomes prepared from human stratum corneum lipids. J Microsc 2002. [DOI: 10.1046/j.1365-2818.1998.00369.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Schmidtgen
- Department of Pharmaceutical Technology, Albert‐Ludwigs‐University, Hermann‐Herder‐Str. 9, D‐79104 Freiburg, Germany,
| | - Drechsler
- Cardiological Research Laboratory of the Charité, Humboldt‐University, Ziegelstr. 5‐9, D‐10117 Berlin, Germany,
| | - Lasch
- Institute of Physiological Chemistry, Martin‐Luther‐University, Hollystr. 1, D‐06114 Halle, Germany
| | - Schubert
- Department of Pharmaceutical Technology, Albert‐Ludwigs‐University, Hermann‐Herder‐Str. 9, D‐79104 Freiburg, Germany,
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Burger KNJ, Staffhorst RWHM, de Vijlder HC, Velinova MJ, Bomans PH, Frederik PM, de Kruijff B. Nanocapsules: lipid-coated aggregates of cisplatin with high cytotoxicity. Nat Med 2002; 8:81-4. [PMID: 11786911 DOI: 10.1038/nm0102-81] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cisplatin is one of the most widely used agents in the treatment of solid tumors, but its clinical utility is limited by toxicity. The development of less toxic, liposomal formulations of cisplatin has been hampered by the low water solubility and low lipophilicity of cisplatin, resulting in very low encapsulation efficiencies. We describe a novel method allowing the efficient encapsulation of cisplatin in a lipid formulation; it is based on repeated freezing and thawing of a concentrated solution of cisplatin in the presence of negatively charged phospholipids. The method is unique in that it generates nanocapsules, which are small aggregates of cisplatin covered by a single lipid bilayer. The nanocapsules have an unprecedented drug-to-lipid ratio and an in vitro cytotoxicity up to 1000-fold higher than the free drug. Analysis of the mechanism of nanocapsule formation suggests that the method may be generalized to other drugs showing low water solubility and lipophilicity.
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Affiliation(s)
- Koert N J Burger
- Department Biochemistry of Membranes, Center for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands.
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Kimura S, Muraji Y, Sugiyama J, Fujita K, Imanishi Y. Spontaneous Vesicle Formation by Helical Glycopeptides in Water. J Colloid Interface Sci 2000; 222:265-267. [PMID: 10662522 DOI: 10.1006/jcis.1999.6643] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hydrophobic helical peptide molecules with a lactose unit at the C terminal, Nap-(Ala-Aib)(n)-NHCH(2)CH(2)NH-Lac (Nap, Aib, and Lac represent 2-naphthylacetic acid group, 2-aminoisobutyric acid, and lactobionic acid group, respectively, n=4, 6, 8), were synthesized and their formation of self-assemblies in water was investigated. Nap-(Ala-Aib)(4)-NHCH(2)CH(2)NH-Lac was spontaneously dispersed in water and formed aggregates of 70 nm diameter, shown by dynamic light scattering measurement. Cryo-TEM observation revealed that the aggregates took on a vesicular structure with a single membrane. The membrane is suggested to be composed of helical peptide molecules with an interdigitated antiparallel packing on the basis of circular dichroism and fluorescence measurements. On the other hand, the dodecapeptide formed a fibrous assembly, and the hexadecapeptide could not be dispersed in water. Copyright 2000 Academic Press.
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Affiliation(s)
- S Kimura
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto, 606-8501, Japan
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Gantz DL, Wang DQ, Carey MC, Small DM. Cryoelectron microscopy of a nucleating model bile in vitreous ice: formation of primordial vesicles. Biophys J 1999; 76:1436-51. [PMID: 10049325 PMCID: PMC1300121 DOI: 10.1016/s0006-3495(99)77304-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Because gallstones form so frequently in human bile, pathophysiologically relevant supersaturated model biles are commonly employed to study cholesterol crystal formation. We used cryo-transmission electron microscopy, complemented by polarizing light microscopy, to investigate early stages of cholesterol nucleation in model bile. In the system studied, the proposed microscopic sequence involves the evolution of small unilamellar to multilamellar vesicles to lamellar liquid crystals and finally to cholesterol crystals. Small aliquots of a concentrated (total lipid concentration = 29.2 g/dl) model bile containing 8.5% cholesterol, 22.9% egg yolk lecithin, and 68.6% taurocholate (all mole %) were vitrified at 2 min to 20 days after fourfold dilution to induce supersaturation. Mixed micelles together with a category of vesicles denoted primordial, small unilamellar vesicles of two distinct morphologies (sphere/ellipsoid and cylinder/arachoid), large unilamellar vesicles, multilamellar vesicles, and cholesterol monohydrate crystals were imaged. No evidence of aggregation/fusion of small unilamellar vesicles to form multilamellar vesicles was detected. Low numbers of multilamellar vesicles were present, some of which were sufficiently large to be identified as liquid crystals by polarizing light microscopy. Dimensions, surface areas, and volumes of spherical/ellipsoidal and cylindrical/arachoidal vesicles were quantified. Early stages in the separation of vesicles from micelles, referred to as primordial vesicles, were imaged 23-31 min after dilution. Observed structures such as enlarged micelles in primordial vesicle interiors, segments of bilayer, and faceted edges at primordial vesicle peripheries are probably early stages of small unilamellar vesicle assembly. A decrease in the mean surface area of spherical/ellipsoidal vesicles was correlated with the increased production of cholesterol crystals at 10-20 days after supersaturation by dilution, supporting the role of small unilamellar vesicles as key players in cholesterol nucleation and as cholesterol donors to crystals. This is the first visualization of an intermediate structure that has been temporally linked to the development of small unilamellar vesicles in the separation of vesicles from micelles in a model bile and suggests a time-resolved system for further investigation.
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Affiliation(s)
- D L Gantz
- Department of Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
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Skalko N, Bouwstra J, Spies F, Stuart M, Frederik PM, Gregoriadis G. Morphological observations on liposomes bearing covalently bound protein: studies with freeze-fracture and cryo electron microscopy and small angle X-ray scattering techniques. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1370:151-60. [PMID: 9518587 DOI: 10.1016/s0005-2736(97)00256-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The appearance of protein bound to the surface of intact and microfluidized liposomes and its possible influence on their morphology was examined by freeze-fracture electron microscopy, cryo electron microscopy and small angle X-ray scattering (SAXS) techniques. Results obtained by the two microscopy techniques were in agreement with one another in terms of vesicle size and localization of protein (tetanus toxoid or immunoglobulin G) on the surface of vesicles. Surface-bound protein was observed as particles (10-12 nm diameter) by freeze-fracture electron microscopy and was confirmed by immunogold cryo microscopy. SAXS was shown to be a suitable means to further characterize liposomes with, or without bound protein.
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Affiliation(s)
- N Skalko
- Centre for Drug Delivery Research, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, UK
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Denkov ND, Yoshimura H, Nagayama K. Method for controlled formation of vitrified films for cryo-electron microscopy. Ultramicroscopy 1996. [DOI: 10.1016/s0304-3991(96)00065-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Zijlstra AI, Van de Heijning BJ, van Overveld M, Groen AK. A novel vesicular assay to study factors affecting cholesterol crystallization in vitro. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)37585-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Dierksen K, Typke D, Hegerl R, Walz J, Sackmann E, Baumeister W. Three-dimensional structure of lipid vesicles embedded in vitreous ice and investigated by automated electron tomography. Biophys J 1995; 68:1416-22. [PMID: 7787027 PMCID: PMC1282036 DOI: 10.1016/s0006-3495(95)80314-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Automated electron tomography is shown to be a suitable means to visualize the shape of phospholipid vesicles embedded in vitrified ice. With a slow-scan charge-coupled device camera as a recording device, the cumulative electron dose needed to record a data set of 60 projections at a magnification of 20,000X can be kept as low as 15 e-/A2 (or 1500 electrons/nm2). The membrane of the three-dimensionally reconstructed vesicles is clearly visible in two-dimensional sections through the three-dimensionally reconstructed volume. Some edges indicating a polygonal shape of the vesicles, frozen from the gel phase, are also clearly recognized. Because of the presently limited tilt angle range (+/- 60 degrees), the upper and lower "caps" of the vesicles (representing about 35% of the surface of the ellipsoidal particles) remain invisible in the three-dimensional reconstruction.
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Affiliation(s)
- K Dierksen
- Max-Planck-Institut für Biochemie, Martinsried, Germany
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Giesen PL, Willems GM, Hemker HC, Stuart MC, Hermens WT. Monitoring of unbound protein in vesicle suspensions with off-null ellipsometry. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1147:125-31. [PMID: 8466922 DOI: 10.1016/0005-2736(93)90322-q] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In studies on the binding of proteins to small unilamellar phospholipid vesicles (SUV), the concentration of unbound protein usually remains unknown, because the vesicles cannot be separated from the bulk solution. In the present study, this limitation was overcome by addition of a supported planar phospholipid bilayer to the cuvette containing a vesicle suspension. Ellipsometric measurement of the protein adsorption velocities on this bilayer allowed determination of the concentrations of unbound protein. At high protein concentrations the adsorption is rapidly completed and the usual null-ellipsometry is too slow to obtain well-defined initial adsorption rates. Therefore, an off-null technique was developed, allowing measurement of the adsorbed protein mass at time intervals of 20 ms. Binding of prothrombin and coagulation factor Xa was measured in SUV suspensions prepared from a 20% dioleoylphosphatidylserine (DOPS) and 80% dioleoylphosphatidylcholine (DOPC) phospholipid mixture. For prothrombin, a dissociation constant Kd = 140 +/- 27 nM (mean +/- S.E.) and maximal surface concentration gamma max = (8.9 +/- 0.8) x 10(-3) mole of protein per mole of lipid, were obtained. For factor Xa, these values were Kd = 49.6 +/- 6.3 nM and gamma max = (23.0 +/- 1.4) x 10(-3) mole of protein per mole of lipid. These binding parameters are similar to those obtained earlier for planar bilayers. Apparently, the binding of factor Xa and prothrombin is not dependent on surface curvature.
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Affiliation(s)
- P L Giesen
- Cardiovascular Research Institute Maastricht, University of Limburg, The Netherlands
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Burger KN, Calder LJ, Frederik PM, Verkleij AJ. Electron microscopy of virus--liposome fusion. Methods Enzymol 1993; 220:362-79. [PMID: 8350762 DOI: 10.1016/0076-6879(93)20095-k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- K N Burger
- Department of Cell Biology, Medical School AZU, University of Utrecht, The Netherlands
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Frederik P, Bomans P, Stuart M. Matrix effects and the induction of mass loss or bubbling by the electron beam in vitrified hydrated specimens. Ultramicroscopy 1993. [DOI: 10.1016/0304-3991(93)90176-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Frederik PM, Burger KN, Stuart MC, Verkleij AJ. Lipid polymorphism as observed by cryo-electron microscopy. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1062:133-41. [PMID: 2004103 DOI: 10.1016/0005-2736(91)90384-k] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Lipid polymorphism was studied with the aim to gain more insight in bilayer to non-bilayer phase transitions, with particular emphasis on the development of cubic structures on one hand and inverted hexagonal structures on the other hand. Thin vitrified films prepared from aqueous lipid suspensions were used in this study. The entire hydrated contents of these films can be visualized in their two-dimensional projection by cryo-electron microscopy. As the starting material, unilamellar vesicles were prepared from mixtures of dioleoylphosphatidylethanolamine, dioleoylphosphatidylcholine and cholesterol. By heating of the suspension, vesicle fusion (Frederik et al. (1989) Biochim. Biophys. Acta 979, 275-278) and lipid polymorphism was induced. From these suspensions thin films were prepared at various temperatures, and vitrified for low temperature observation. In a parallel series of experiments samples were fast-frozen for freeze-fracture analysis. In vitrified thin films bilayer structures were often observed in coexistence with an inverted hexagonal structure. The bilayer areas were frequently of a complex structure because multiple contacts between stacked membranes were found. These contact points were variable in size and shape and usually had the form of a diabolo (when viewed side-on) giving the impression of a bilayer contact with an aqueous channel. This structure is compatible with the interlamellar attachment site (ILA) proposed by Siegel ((1986) Biophys. J. 49, 1155-1170). In some specimens ILA's seemed to merge into arrays. After thermal cycling of the suspension, arrays of packed globules were observed, which are likely the result of close packing of ILA's. The arrays probably represent a cubic structure. A comparison of freeze-fracture replicas and vitrified thin films indicated that both techniques may provide valuable structural information on lipid polymorphism. Most of the lipidic particles observed by freeze-fracturing probably correspond to the ILA's (fractured around their waist region) as observed in vitrified thin films. The results obtained with vitrified thin films were interpreted in relation to the principles of thin-film formation. Finally, we speculate that lipid structures occurring close to each other in space may represent a developmental series of structures occurring successively in time.
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Affiliation(s)
- P M Frederik
- Department of Pathology, University of Limburg, Maastricht, The Netherlands
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Frederik PM, Stuart MC, Bomans PH, Busing WM, Burger KN, Verkleij AJ. Perspective and limitations of cryo-electron microscopy. From model systems to biological specimens. J Microsc 1991; 161:253-62. [PMID: 2038033 DOI: 10.1111/j.1365-2818.1991.tb03088.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We investigated the possibility of vitrifying temperature-sensitive lipid phases as well as (small) biological specimens. From a suspension of unilamellar vesicles, prepared from dipalmitoyl-phosphatidylcholine (DPPC), thin aqueous films were formed at various temperatures. With cryo-electron microscopy vesicles were found to be smooth, rippled and faceted or faceted only, depending on the temperature of thin-film formation (318, 312 and 296 K respectively). The morphology and the electron diffraction patterns indicate that membranes can by physically fixed by vitrification in their high-temperature configuration and studied at low temperature by cryo-electron microscopy. This finding suggests that it may also be possible to preserve, in their original state, the more complex membrane systems found in living organisms by initiating rapid-cooling at a physiological temperature. This was explored by vitrification of thin films formed on specimen grids with (human) blood platelets adhering to collagen fibres. Low-temperature observation with an acceleration voltage of 120 kV revealed subcellular details, More details were observed when using higher accelerating voltages (200 and 300 kV) of the electron beam. The results presented in this paper illustrate the great potential of cryo-electron microscopy in the study of membrane dynamics, both in relatively simple model membrane systems and in more complex biological membrane systems.
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Affiliation(s)
- P M Frederik
- Department of Pathology, University of Limburg, Maastricht, The Netherlands
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Frederik PM, Stuart MCA, Bomans PHH, Berger KNJ, Verkleij AJ. Cryo - electronmicroscopy of membranes - from model systems to biological sepcimens. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0739-6260(91)90081-a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Jakubowski U, Baumeister W, Glaeser R. Evaporated carbon stabilizes thin, frozen-hydrated specimens. Ultramicroscopy 1989. [DOI: 10.1016/0304-3991(89)90333-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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