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Parker KA, Ribet S, Kimmel BR, Dos Reis R, Mrksich M, Dravid VP. Scanning Transmission Electron Microscopy in a Scanning Electron Microscope for the High-Throughput Imaging of Biological Assemblies. Biomacromolecules 2022; 23:3235-3242. [PMID: 35881504 DOI: 10.1021/acs.biomac.2c00323] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electron microscopy of soft and biological materials, or "soft electron microscopy", is essential to the characterization of macromolecules. Soft microscopy is governed by enhancing contrast while maintaining low electron doses, and sample preparation and imaging methodologies are driven by the length scale of features of interest. While cryo-electron microscopy offers the highest resolution, larger structures can be characterized efficiently and with high contrast using low-voltage electron microscopy by performing scanning transmission electron microscopy in a scanning electron microscope (STEM-in-SEM). Here, STEM-in-SEM is demonstrated for a four-lobed protein assembly where the arrangement of the proteins in the construct must be examined. STEM image simulations show the theoretical contrast enhancement at SEM-level voltages for unstained structures, and experimental images with multiple STEM modes exhibit the resolution possible for negative-stained proteins. This technique can be extended to complex protein assemblies, larger structures such as cell sections, and hybrid materials, making STEM-in-SEM a valuable high-throughput imaging method.
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Affiliation(s)
- Kelly A Parker
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Stephanie Ribet
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Blaise R Kimmel
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Roberto Dos Reis
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Milan Mrksich
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Vinayak P Dravid
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, Northwestern University, Evanston, Illinois 60208, United States
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2
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Gang GW, Shin J, Kim YH, Ha TH, Ogawa T. Visualization of unstained homo/heterogeneous DNA nanostructures by low-voltage scanning transmission electron microscopy. Sci Rep 2020; 10:4868. [PMID: 32184416 PMCID: PMC7078320 DOI: 10.1038/s41598-020-61751-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 02/26/2020] [Indexed: 11/28/2022] Open
Abstract
Three-dimensional (3D) homo/heterogeneous DNA nanostructures were studied with low-voltage scanning transmission electron microscopy (LV-STEM). Four types of 3D DNA nanostructures were designed and fabricated by the origami method including newly proposed protocols. The low-energy electron probe and optimized dark-field STEM detector enabled individual unstained DNA nanostructures to be clearly imaged by the single acquisition without the averaging process. For the vertically stacked double structures, assembled through modified single-stranded domains, and the structures containing a square opening (i.e., a hole) in the center, the LV-STEM successfully reveals the vertical information of these 3D structures as the contrast differences compared to the reference. For the heterogeneous structures, the LV-STEM visualized both regions of the functionalized gold nanoparticles and the DNA base structure with distinct contrasts. This study introduces a straightforward method to fabricate stackable DNA nanostructures or nanoparticles by replacing a relatively small number of incumbent DNA strands, which could realize the simple and sophisticated fabrication of higher-order 3D DNA homo/hetero nanostructures. Together with these design techniques of DNA nanostructures, this study has demonstrated that the LV-STEM is the swift and simple method for visualizing the 3D DNA nanostructures and certifying the fabricated products as the specified design, which is applicable to various research fields on soft materials including DNA nanotechnology.
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Affiliation(s)
- Geun Won Gang
- Advanced Instrumentation Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, Republic of Korea
- Department of Physics, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Jihoon Shin
- BioNanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, 34141, Republic of Korea
| | - Young Heon Kim
- Division of Industrial Metrology, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, Republic of Korea
- Graduate School of Analytical Science and Technology (GRAST), Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Tai Hwan Ha
- BioNanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, 34141, Republic of Korea.
| | - Takashi Ogawa
- Advanced Instrumentation Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, Republic of Korea.
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Skoupy R, Nebesarova J, Slouf M, Krzyzanek V. Quantitative STEM imaging of electron beam induced mass loss of epoxy resin sections. Ultramicroscopy 2019; 202:44-50. [PMID: 30953993 DOI: 10.1016/j.ultramic.2019.03.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 03/26/2019] [Accepted: 03/29/2019] [Indexed: 10/27/2022]
Abstract
In sample preparation of biological samples for electron microscopy, many types of embedding media are widely used. Unfortunately, none of them is perfectly resistant to beam induced damage. The article is focused on mass loss measuring of pure epoxy resin EMbed 812 that replaced Epon - the most widely used embedding resin for biological electron microscopy, in a form of ultrathin sections with thicknesses ranging from 30 to 100 nm. The STEM imaging was performed in a quantitative way which allowed us to estimate the mass loss directly up to the total dose of 3000 e-/nm2. For data acquisition we used SEM equipped with a commercial STEM detector working at a relatively low acceleration voltage of 30 kV. In this study we estimated the influence of various factors which can affect the endurance of the epoxy resin EMbed 812 ultrathin sections under an electron beam, such as the sample aging, differences between storing the samples in forms of ultrathin sections and whole blocks, ultrathin sections thicknesses, temperature of the sample, probe current, and one or two-sided carbon coating of ultrathin sections. The aim of this work is to investigate beam induced mass loss at electron energies of SEM and find out how to reduce the mass loss.
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Affiliation(s)
- Radim Skoupy
- Institute of Scientific Instruments of the Czech Academy of Sciences, Kralovopolska 147, 612 64 Brno, Czech Republic
| | - Jana Nebesarova
- Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Branisovska 31, 370 05 Ceske Budejovice, Czech Republic; Faculty of Science, Charles University in Prague, Vinicna 7, 128 44 Prague 2, Czech Republic
| | - Miroslav Slouf
- Institute of Macromolecular Chemistry of the Czech Academy of Sciences, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic
| | - Vladislav Krzyzanek
- Institute of Scientific Instruments of the Czech Academy of Sciences, Kralovopolska 147, 612 64 Brno, Czech Republic.
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4
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Expanding horizons of cryo-tomography to larger volumes. Curr Opin Microbiol 2018; 43:155-161. [DOI: 10.1016/j.mib.2018.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/02/2018] [Accepted: 01/03/2018] [Indexed: 12/18/2022]
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Aleksis R, Oleskovs F, Jaudzems K, Pahnke J, Biverstål H. Structural studies of amyloid-β peptides: Unlocking the mechanism of aggregation and the associated toxicity. Biochimie 2017; 140:176-192. [PMID: 28751216 DOI: 10.1016/j.biochi.2017.07.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/21/2017] [Indexed: 12/31/2022]
Abstract
Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases worldwide. Formation of amyloid plaques consisting of amyloid-β peptides (Aβ) is one of the hallmarks of AD. Several lines of evidence have shown a correlation between the Aβ aggregation and the disease development. Extensive research has been conducted with the aim to reveal the structures of the neurotoxic Aβ aggregates. However, the exact structure of pathological aggregates and mechanism of the disease still remains elusive due to complexity of the occurring processes and instability of various disease-relevant Aβ species. In this article we review up-to-date structural knowledge about amyloid-β peptides, focusing on data acquired using solution and solid state NMR techniques. Furthermore, we discuss implications from these structural studies on the mechanisms of aggregation and neurotoxicity.
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Affiliation(s)
- Rihards Aleksis
- Department of Physical Organic Chemistry, Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, Latvia.
| | - Filips Oleskovs
- Department of Physical Organic Chemistry, Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, Latvia
| | - Kristaps Jaudzems
- Department of Physical Organic Chemistry, Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, Latvia
| | - Jens Pahnke
- Department of Neuro-/Pathology, Translational Neurodegeneration Research and Neuropathology Lab, University of Oslo (UiO) & Oslo University Hospital (OUS), Norway; LIED, University of Lübeck Uzl, Germany; Leibniz-Institute of Plant Biochemistry (IPB), Halle, Germany
| | - Henrik Biverstål
- Department of Physical Organic Chemistry, Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, Latvia; Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Karolinska Institutet, Stockholm, Sweden
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6
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Ogawa T, Gang GW, Thieu MT, Kwon H, Ahn SJ, Ha TH, Cho B. Graphene-supporting films and low-voltage STEM in SEM toward imaging nanobio materials without staining: Observation of insulin amyloid fibrils. Micron 2017; 96:65-71. [PMID: 28267641 DOI: 10.1016/j.micron.2016.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 12/16/2016] [Accepted: 12/17/2016] [Indexed: 11/30/2022]
Abstract
Utilization of graphene-supporting films and low-voltage scanning transmission electron microscopy (LV-STEM) in scanning electron microscopy (SEM) is shown to be an effective means of observing unstained nanobio materials. Insulin amyloid fibrils, which are implicated as a cause of type II diabetes, are formed in vitro and observed without staining at room temperature. An in-lens cold field-emission SEM, equipped with an additional homemade STEM detector, provides dark field (DF)-STEM images in the low energy range of 5-30keV, together with secondary electron (SE) images. Analysis based on Lenz's theory is used to interpret the experimental results. Graphene films, where the fibrils are deposited, reduce the background level of the STEM images compared with instances when conventional amorphous carbon films are used. Using 30keV, which is lower than that for conventional TEM (100-300keV), together with low detection angles (15-55mrad) enhances the signals from the fibrils. These factors improve image quality, which enables observation of thin fibrils with widths of 7-8nm. STEM imaging clearly reveals a twisted-ribbon structure of a fibril, and SE imaging shows an emphasized striped pattern of the fibril. The LV-STEM in SEM enables acquisition of two types of images of an identical fibril in a single instrument, which is useful for understanding the structure. This study expands the application of SEM to other systems of interest, which is beneficial to a large number of users. The method in this study can be applied to the observation of various nanobio materials and analysis of their native structures, thus contributing to research in materials and life sciences.
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Affiliation(s)
- Takashi Ogawa
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea.
| | - Geun Won Gang
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea; Chungnam National University, Daejeon 34134, Republic of Korea
| | - Minh Thu Thieu
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea; Korea University of Science & Technology, Daejeon 34113, Republic of Korea
| | - Hyuksang Kwon
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
| | - Sang Jung Ahn
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea; Korea University of Science & Technology, Daejeon 34113, Republic of Korea
| | - Tai Hwan Ha
- Korea University of Science & Technology, Daejeon 34113, Republic of Korea; Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Republic of Korea
| | - Boklae Cho
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
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7
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Mitchell DR, Nancarrow MJ. Probe current determination in analytical TEM/STEM and its application to the characterization of large area EDS detectors. Microsc Res Tech 2015; 78:886-93. [DOI: 10.1002/jemt.22551] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 07/05/2015] [Indexed: 11/09/2022]
Affiliation(s)
- David R.G. Mitchell
- Electron Microscopy Centre, Innovation Campus, University of Wollongong; Squires Way North Wollongong New South Wales 2500 Australia
| | - Mitchell J.B. Nancarrow
- Electron Microscopy Centre, Innovation Campus, University of Wollongong; Squires Way North Wollongong New South Wales 2500 Australia
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8
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Mass mapping of amyloid fibrils in the electron microscope using STEM imaging. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2013; 950:195-207. [PMID: 23086877 DOI: 10.1007/978-1-62703-137-0_12] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Scanning transmission electron microscopy (STEM) in the dark-field mode of operation is a technique regularly used to record high-contrast images from isolated macromolecular assemblies at nanometer resolution. Dark-field STEM images are unique in that they can be readily quantified to provide information on the mass of individual molecular complexes. Importantly, because STEM images contain simultaneous mass and overall molecular shape information, the concept of "mass mapping" can be realized to provide distinctive measurements of the mass per area of planar assemblies or the mass per length of filamentous structures. In this chapter we describe how the STEM technique can be applied to generate characteristic measurements of mass per length from isolated Alzheimer's amyloid fibrils.
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Sousa AA, Leapman RD. Development and application of STEM for the biological sciences. Ultramicroscopy 2012; 123:38-49. [PMID: 22749213 PMCID: PMC3500455 DOI: 10.1016/j.ultramic.2012.04.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 04/06/2012] [Accepted: 04/13/2012] [Indexed: 01/06/2023]
Abstract
The design of the scanning transmission electron microscope (STEM), as conceived originally by Crewe and coworkers, enables the highly efficient and flexible collection of different elastic and inelastic signals resulting from the interaction of a focused probe of incident electrons with a specimen. In the present paper we provide a brief review for how the STEM today can be applied towards a range of different problems in the biological sciences, emphasizing four main areas of application. (1) For three decades, the most widely used STEM technique has been the mass determination of proteins and other macromolecular assemblies. Such measurements can be performed at low electron dose by collecting the high-angle dark-field signal using an annular detector. STEM mass mapping has proven valuable for characterizing large protein assemblies such as filamentous proteins with a well-defined mass per length. (2) The annular dark-field signal can also be used to image ultrasmall, functionalized nanoparticles of heavy atoms for labeling specific amino-acid sequences in protein assemblies. (3) By acquiring electron energy loss spectra (EELS) at each pixel in a hyperspectral image, it is possible to map the distributions of specific bound elements like phosphorus, calcium and iron in isolated macromolecular assemblies or in compartments within sectioned cells. Near single atom sensitivity is feasible provided that the specimen can tolerate a very high incident electron dose. (4) Electron tomography is a new application of STEM that enables three-dimensional reconstruction of micrometer-thick sections of cells. In this technique a probe of small convergence angle gives a large depth of field throughout the thickness of the specimen while maintaining a probe diameter of <2 nm; and the use of an on-axis bright-field detector reduces the effects of beam broadening and thus improves the spatial resolution compared to that attainable by STEM dark-field tomography.
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Affiliation(s)
- Alioscka A. Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - Richard D. Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
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10
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Norlin N, Hellberg M, Filippov A, Sousa AA, Gröbner G, Leapman RD, Almqvist N, Antzutkin ON. Aggregation and fibril morphology of the Arctic mutation of Alzheimer's Aβ peptide by CD, TEM, STEM and in situ AFM. J Struct Biol 2012; 180:174-89. [PMID: 22750418 PMCID: PMC3466396 DOI: 10.1016/j.jsb.2012.06.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 06/10/2012] [Accepted: 06/14/2012] [Indexed: 10/28/2022]
Abstract
Morphology of aggregation intermediates, polymorphism of amyloid fibrils and aggregation kinetics of the "Arctic" mutant of the Alzheimer's amyloid β-peptide, Aβ((1-40))(E22G), in a physiologically relevant Tris buffer (pH 7.4) were thoroughly explored in comparison with the human wild type Alzheimer's amyloid peptide, wt-Aβ((1-40)), using both in situ atomic force and electron microscopy, circular dichroism and thioflavin T fluorescence assays. For arc-Aβ((1-40)) at the end of the 'lag'-period of fibrillization an abrupt appearance of ≈ 3 nm size 'spherical aggregates' with a homogeneous morphology, was identified. Then, the aggregation proceeds with a rapid growth of amyloid fibrils with a variety of morphologies, while the spherical aggregates eventually disappeared during in situ measurements. Arc-Aβ((1-40)) was also shown to form fibrils at much lower concentrations than wt-Aβ((1-40)): ≤ 2.5 μM and 12.5 μM, respectively. Moreover, at the same concentration, 50 μM, the aggregation process proceeds more rapidly for arc-Aβ((1-40)): the first amyloid fibrils were observed after c.a. 72 h from the onset of incubation as compared to approximately 7 days for wt-Aβ((1-40)). Amyloid fibrils of arc-Aβ((1-40)) exhibit a large variety of polymorphs, at least five, both coiled and non-coiled distinct fibril structures were recognized by AFM, while at least four types of arc-Aβ((1-40)) fibrils were identified by TEM and STEM and their mass-per-length statistics were collected suggesting supramolecular structures with two, four and six β-sheet laminae. Our results suggest a pathway of fibrillogenesis for full-length Alzheimer's peptides with small and structurally ordered transient spherical aggregates as on-pathway immediate precursors of amyloid fibrils.
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Affiliation(s)
- Nils Norlin
- Chemistry of Interfaces, Luleå University of Technology, SE-971 87 Luleå, Sweden
| | - Magnus Hellberg
- Division of Physics, Luleå University of Technology, SE-971 87 Luleå, Sweden
| | - Andrei Filippov
- Chemistry of Interfaces, Luleå University of Technology, SE-971 87 Luleå, Sweden
- Department of Physics, Kazan State University, 420008, Kazan, Russia
| | - Alioscka A. Sousa
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892-5766, USA
| | - Gerhard Gröbner
- Department of Biological Chemistry, Institute of Chemistry, Umeå University, SE-90187, Umeå, Sweden
| | - Richard D. Leapman
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892-5766, USA
| | - Nils Almqvist
- Division of Physics, Luleå University of Technology, SE-971 87 Luleå, Sweden
| | - Oleg N. Antzutkin
- Chemistry of Interfaces, Luleå University of Technology, SE-971 87 Luleå, Sweden
- Department of Physics, Warwick University, Coventry, CV4 7AL, United Kingdom
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Dolashka P, Zal F, Dolashki A, Molin L, Traldi P, Salvato B. ESI-MS and MALLS analysis of quaternary structure of molluscan hemocyanins. JOURNAL OF MASS SPECTROMETRY : JMS 2012; 47:940-947. [PMID: 22791262 DOI: 10.1002/jms.2967] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The understanding of the function of macromolecular complexes is mainly related to a precise knowledge of their structure. Recently, the development of suitable mass spectrometric techniques (electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI)) and multi-angle laser light scattering has enabled mass determination of native complexes and of their subunits. By these techniques, the structure and association/dissociation behavior of huge molecules of molluscan Octopus vulgaris, Sepia officinalis and Rapana venosa have been characterized. Molecular masses of the native and dissociated molecule of cephalopodan Hcs O. vulgaris (3545 and 359.3 kDa, respectively) and S. officinalis (4134 and 443.8 kDa, respectively) revealed that only one type subunit organizes their molecules, while the presence of two isoforms with different masses (422.8 and 400.0 kDa) has been determined for gastropodan R. venosa Hc, aggregated into didecamers. The difference of their structural subunits was also established after limited proteolysis with TPCK-trypsin. Eight functional units (FUs) with masses of ~ 50 kDa were isolated from both subunits of RvH and isoform of Sepia officinalis, while seven FUs were purified from OvH. Further characterization of proteins by ESI-mass spectrometry (MS) and MALDI-MS, methods gave insights into post-translational modifications such as glycosylation. Glycosylation of O. vulgaris and S. officinalis Hcs was suggested based on the differences (11.6 and 40.0 kDa, respectively) between the masses measured by ESI-MS and those calculated by their gene sequences.
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Affiliation(s)
- Pavlina Dolashka
- Institute of Organic Chemistry, Bulgarian Academy of Sciences, G. Bonchev 9, Sofia 1113, Bulgaria.
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Komatsu H, Feingold-Link E, Sharp KA, Rastogi T, Axelsen PH. Intrinsic linear heterogeneity of amyloid β protein fibrils revealed by higher resolution mass-per-length determinations. J Biol Chem 2010; 285:41843-51. [PMID: 20940298 PMCID: PMC3009912 DOI: 10.1074/jbc.m110.165068] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 10/01/2010] [Indexed: 11/06/2022] Open
Abstract
Amyloid β proteins spontaneously form fibrils in vitro that vary in their thermodynamic stability and in morphological characteristics such as length, width, shape, longitudinal twist, and the number of component filaments. It is vitally important to determine which variant best represents the type of fibril that accumulates in Alzheimer disease. In the present study, the nature of morphological variation was examined by dark-field and transmission electron microscopy in a preparation of seeded amyloid β protein fibrils that formed at relatively low protein concentrations and exhibited remarkably high thermodynamic stability. The number of filaments comprising these fibrils changed frequently from two to six along their length, and these changes only became apparent when mass-per-length (MPL) determinations are made with sufficient resolution. The MPL results could be reproduced by a simple stochastic model with a single adjustable parameter. The presence of more than two primary filaments could not be discerned by transmission electron microscopy, and they had no apparent relationship to the longitudinal twist of the fibrils. However, the pitch of the twist was strongly affected by the pH of the negative stain. We conclude that highly stable amyloid fibrils may form in which a surprising amount of intrinsic linear heterogeneity may be obscured by MPL measurements of insufficient resolution, and by the negative stains used for imaging fibrils by electron microscopy.
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Affiliation(s)
| | | | | | | | - Paul H. Axelsen
- From the Departments of Pharmacology
- Biochemistry and Biophysics, and
- Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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Jackson JJ, Puretzky AA, More KL, Rouleau CM, Eres G, Geohegan DB. Pulsed growth of vertically aligned nanotube arrays with variable density. ACS NANO 2010; 4:7573-7581. [PMID: 21128670 DOI: 10.1021/nn102029y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The density of vertically aligned carbon nanotube arrays is shown to vary significantly during normal growth by chemical vapor deposition and respond rapidly to changes in feedstock flux. Pulsing the feedstock gas to repeatedly stop and start nanotube growth is shown to induce density variations up to a factor of 1.6 within ca. 1-2 μm long layers, allowing the synthesis of new array architectures with distinct regions of controllable length and density variation. Z-Contrast scanning transmission electron microscopy of corresponding sections of the arrays is used to provide unambiguous measurements of these density variations. Time-resolved optical reflectivity measurements of the height and optical extinction coefficient of the growing arrays are shown to provide a real-time diagnostic of both array density and growth kinetics.
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Affiliation(s)
- Jeremy J Jackson
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6488, USA
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14
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Wang F, Zhang HB, Cao M, Nishi R, Takaoka A. Determination of the linear attenuation range of electron transmission through film specimens. Micron 2010; 41:769-74. [PMID: 20558075 DOI: 10.1016/j.micron.2010.05.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 05/19/2010] [Accepted: 05/22/2010] [Indexed: 11/26/2022]
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15
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Bhirde AA, Sousa AA, Patel V, Azari AA, Gutkind JS, Leapman RD, Rusling JF. Imaging the distribution of individual platinum-based anticancer drug molecules attached to single-wall carbon nanotubes. Nanomedicine (Lond) 2010; 4:763-72. [PMID: 19839812 DOI: 10.2217/nnm.09.56] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
AIMS To image the distribution of drug molecules attached to single-wall carbon nanotubes (SWNTs). MATERIALS & METHODS Herein we report the use of scanning transmission electron microscopy (STEM) for atomic scale visualization and quantitation of single platinum-based drug molecules attached to SWNTs designed for targeted drug delivery. Fourier transform infrared spectroscopy and energy-dispersive x-ray spectroscopy were used for characterization of the SWNT drug conjugates. RESULTS Z-contrast STEM imaging enabled visualization of the first-line anticancer drug cisplatin on the nanotubes at single molecule level. The identity and presence of cisplatin on the nanotubes was confirmed using energy-dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy. STEM tomography was also used to provide additional insights concerning the nanotube conjugates. Finally, our observations provide a rationale for exploring the use of SWNT bioconjugates to selectively target and kill squamous cancer cells. CONCLUSION Z-contrast STEM imaging provides a means for direct visualization of heavy metal containing molecules (i.e., cisplatin) attached to surfaces of carbon SWNTs along with distribution and quantitation.
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Sousa AA, Aronova MA, Wu H, Sarin H, Griffiths GL, Leapman RD. Determining molecular mass distributions and compositions of functionalized dendrimer nanoparticles. Nanomedicine (Lond) 2009; 4:391-9. [PMID: 19505242 DOI: 10.2217/nnm.09.14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This study demonstrates that a combination of unconventional electron microscopy techniques provides a quantitative means of assessing the degree of monodispersity of gadolinium (Gd) diethylenetriamine pentaacetic acid-conjugated polyamidoamine (PAMAM) dendrimers, which are designed for diagnostic imaging and delivering chemotherapeutics. Specifically, analysis of images acquired in the scanning transmission electron microscopy mode yields the distribution of molecular weights of individual dendrimers, whereas analysis of images acquired in the energy-filtering transmission electron microscopy mode yields the distribution of Gd atoms bound to the dendrimer nanoparticles. Measured compositions of Gd-conjugated G7 and G8 PAMAM dendrimers were consistent with the known synthetic chemistry. The G7 dendrimers had a mass of 330 +/- 4 kDa and 266 +/- 4 Gd atoms (+/- standard error of the mean). The G8 dendrimers had a mass of 600 +/- 8 kDa and 350 +/- 5 Gd atoms (+/- standard error of the mean). This approach will be particularly attractive for assessing the mass, composition and homogeneity of metal-containing organic nanoparticles used in nanomedicine.
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Affiliation(s)
- A A Sousa
- National Institute of Biomedical Imaging & Bioengineering, National Institutes of Health, Bldg. 13, Rm 3N17, 13 South Drive, Bethesda, MD 20892-5766, USA
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Measurement of amyloid fibril mass-per-length by tilted-beam transmission electron microscopy. Proc Natl Acad Sci U S A 2009; 106:14339-44. [PMID: 19706519 DOI: 10.1073/pnas.0907821106] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We demonstrate that accurate values of mass-per-length (MPL), which serve as strong constraints on molecular structure, can be determined for amyloid fibrils by quantification of intensities in dark-field electron microscope images obtained in the tilted-beam mode of a transmission electron microscope. MPL values for fibrils formed by residues 218-289 of the HET-s fungal prion protein, for 2-fold- and 3-fold-symmetric fibrils formed by the 40-residue beta-amyloid peptide, and for fibrils formed by the yeast prion protein Sup35NM are in good agreement with previous results from scanning transmission electron microscopy. Results for fibrils formed by the yeast prion protein Rnq1, for which the MPL value has not been previously reported, support an in-register parallel beta-sheet structure, with one Rnq1 molecule per 0.47-nm beta-sheet repeat spacing. Since tilted-beam dark-field images can be obtained on many transmission electron microscopes, this work should facilitate MPL determination by a large number of research groups engaged in studies of amyloid fibrils and similar supramolecular assemblies.
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Sarin H, Kanevsky AS, Wu H, Sousa AA, Wilson CM, Aronova MA, Griffiths GL, Leapman RD, Vo HQ. Physiologic upper limit of pore size in the blood-tumor barrier of malignant solid tumors. J Transl Med 2009; 7:51. [PMID: 19549317 PMCID: PMC2706803 DOI: 10.1186/1479-5876-7-51] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 06/23/2009] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND The existence of large pores in the blood-tumor barrier (BTB) of malignant solid tumor microvasculature makes the blood-tumor barrier more permeable to macromolecules than the endothelial barrier of most normal tissue microvasculature. The BTB of malignant solid tumors growing outside the brain, in peripheral tissues, is more permeable than that of similar tumors growing inside the brain. This has been previously attributed to the larger anatomic sizes of the pores within the BTB of peripheral tumors. Since in the physiological state in vivo a fibrous glycocalyx layer coats the pores of the BTB, it is possible that the effective physiologic pore size in the BTB of brain tumors and peripheral tumors is similar. If this were the case, then the higher permeability of the BTB of peripheral tumor would be attributable to the presence of a greater number of pores in the BTB of peripheral tumors. In this study, we probed in vivo the upper limit of pore size in the BTB of rodent malignant gliomas grown inside the brain, the orthotopic site, as well as outside the brain in temporalis skeletal muscle, the ectopic site. METHODS Generation 5 (G5) through generation 8 (G8) polyamidoamine dendrimers were labeled with gadolinium (Gd)-diethyltriaminepentaacetic acid, an anionic MRI contrast agent. The respective Gd-dendrimer generations were visualized in vitro by scanning transmission electron microscopy. Following intravenous infusion of the respective Gd-dendrimer generations (Gd-G5, N = 6; Gd-G6, N = 6; Gd-G7, N = 5; Gd-G8, N = 5) the blood and tumor tissue pharmacokinetics of the Gd-dendrimer generations were visualized in vivo over 600 to 700 minutes by dynamic contrast-enhanced MRI. One additional animal was imaged in each Gd-dendrimer generation group for 175 minutes under continuous anesthesia for the creation of voxel-by-voxel Gd concentration maps. RESULTS The estimated diameters of Gd-G7 dendrimers were 11 +/- 1 nm and those of Gd-G8 dendrimers were 13 +/- 1 nm. The BTB of ectopic RG-2 gliomas was more permeable than the BTB of orthotopic RG-2 gliomas to all Gd-dendrimer generations except for Gd-G8. The BTB of both ectopic RG-2 gliomas and orthotopic RG-2 gliomas was not permeable to Gd-G8 dendrimers. CONCLUSION The physiologic upper limit of pore size in the BTB of malignant solid tumor microvasculature is approximately 12 nanometers. In the physiologic state in vivo the luminal fibrous glycocalyx of the BTB of malignant brain tumor and peripheral tumors is the primary impediment to the effective transvascular transport of particles across the BTB of malignant solid tumor microvasculature independent of tumor host site. The higher permeability of malignant peripheral tumor microvasculature to macromolecules smaller than approximately 12 nm in diameter is attributable to the presence of a greater number of pores underlying the glycocalyx of the BTB of malignant peripheral tumor microvasculature.
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Affiliation(s)
- Hemant Sarin
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
- Radiology and Imaging Sciences Program, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Ariel S Kanevsky
- Radiology and Imaging Sciences Program, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Haitao Wu
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Alioscka A Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Colin M Wilson
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Maria A Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Gary L Griffiths
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Richard D Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Howard Q Vo
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
- Radiology and Imaging Sciences Program, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
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Sarin H, Kanevsky AS, Wu H, Brimacombe KR, Fung SH, Sousa AA, Auh S, Wilson CM, Sharma K, Aronova MA, Leapman RD, Griffiths GL, Hall MD. Effective transvascular delivery of nanoparticles across the blood-brain tumor barrier into malignant glioma cells. J Transl Med 2008; 6:80. [PMID: 19094226 PMCID: PMC2639552 DOI: 10.1186/1479-5876-6-80] [Citation(s) in RCA: 182] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Accepted: 12/18/2008] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Effective transvascular delivery of nanoparticle-based chemotherapeutics across the blood-brain tumor barrier of malignant gliomas remains a challenge. This is due to our limited understanding of nanoparticle properties in relation to the physiologic size of pores within the blood-brain tumor barrier. Polyamidoamine dendrimers are particularly small multigenerational nanoparticles with uniform sizes within each generation. Dendrimer sizes increase by only 1 to 2 nm with each successive generation. Using functionalized polyamidoamine dendrimer generations 1 through 8, we investigated how nanoparticle size influences particle accumulation within malignant glioma cells. METHODS Magnetic resonance and fluorescence imaging probes were conjugated to the dendrimer terminal amines. Functionalized dendrimers were administered intravenously to rodents with orthotopically grown malignant gliomas. Transvascular transport and accumulation of the nanoparticles in brain tumor tissue was measured in vivo with dynamic contrast-enhanced magnetic resonance imaging. Localization of the nanoparticles within glioma cells was confirmed ex vivo with fluorescence imaging. RESULTS We found that the intravenously administered functionalized dendrimers less than approximately 11.7 to 11.9 nm in diameter were able to traverse pores of the blood-brain tumor barrier of RG-2 malignant gliomas, while larger ones could not. Of the permeable functionalized dendrimer generations, those that possessed long blood half-lives could accumulate within glioma cells. CONCLUSION The therapeutically relevant upper limit of blood-brain tumor barrier pore size is approximately 11.7 to 11.9 nm. Therefore, effective transvascular drug delivery into malignant glioma cells can be accomplished by using nanoparticles that are smaller than 11.7 to 11.9 nm in diameter and possess long blood half-lives.
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Affiliation(s)
- Hemant Sarin
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
- Diagnostic Radiology Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Ariel S Kanevsky
- Diagnostic Radiology Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Haitao Wu
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kyle R Brimacombe
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Steve H Fung
- Neuroradiology Department, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Alioscka A Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sungyoung Auh
- Biostatistics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Colin M Wilson
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kamal Sharma
- Metabolism Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
- Division of Biologic Drug Products, Office of Oncology Products, Center for Drug Evaluation and Research, U.S. Food & Drug Administration, Silver Spring, Maryland 20993, USA
| | - Maria A Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Richard D Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Gary L Griffiths
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Matthew D Hall
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Krzyzánek V, Müller SA, Engel A, Reichelt R. MASDET-A fast and user-friendly multiplatform software for mass determination by dark-field electron microscopy. J Struct Biol 2008; 165:78-87. [PMID: 19041401 DOI: 10.1016/j.jsb.2008.10.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Revised: 10/10/2008] [Accepted: 10/16/2008] [Indexed: 11/28/2022]
Abstract
Electron microscopy has been used to measure the mass of biological nanoparticles since the early 60s, and is the only way to obtain the mass of large structures or parameters such as the mass-per-length of filaments. The ability of this method to sort heterogeneous samples both in terms of mass and shape promises to make it a key tool for proteomics down to the single cell level. A new multiplatform software package, MASDET, that can be run under MATLAB or as a standalone program is described. Based on a user-friendly graphical interface MASDET streamlines mass evaluation and greatly increases the speed of required optimisation procedures. Importantly, the immediate application of Monte-Carlo simulations to describe multiple scattering is possible, allowing the mass analysis of thicker samples and the generation of mass thickness maps.
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Affiliation(s)
- Vladislav Krzyzánek
- Institute of Medical Physics and Biophysics, Universitätsklinikum Münster, University of Münster, Germany.
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Sousa AA, Aronova MA, Kim YC, Dorward LM, Zhang G, Leapman RD. Reprint of "On the feasibility of visualizing ultrasmall gold labels in biological specimens by STEM tomography" [J. Struct. Biol. 159 (2007) 507-522]. J Struct Biol 2008; 161:336-51. [PMID: 18342743 DOI: 10.1016/s1047-8477(08)00063-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2007] [Revised: 06/15/2007] [Accepted: 06/19/2007] [Indexed: 11/25/2022]
Abstract
Labeling with heavy atom clusters attached to antibody fragments is an attractive technique for determining the 3D distribution of specific proteins in cells using electron tomography. However, the small size of the labels makes them very difficult to detect by conventional bright-field electron tomography. Here, we evaluate quantitative scanning transmission electron microscopy (STEM) at a beam voltage of 300kV for detecting 11-gold atom clusters (Undecagold) and 1.4nm-diameter nanoparticles (Nanogold) for a variety of specimens and imaging conditions. STEM images as well as tomographic tilt series are simulated by means of the NIST Elastic-Scattering Cross-Section Database for gold clusters embedded in carbon. The simulations indicate that the visibility in 2D of Undecagold clusters in a homogeneous matrix is maximized for low inner collection semi-angles of the STEM annular dark-field detector (15-20mrad). Furthermore, our calculations show that the visibility of Undecagold in 3D reconstructions is significantly higher than in 2D images for an inhomogeneous matrix corresponding to fluctuations in local density. The measurements demonstrate that it is possible to detect Nanogold particles in plastic sections of tissue freeze-substituted in the presence of osmium. STEM tomography has the potential to localize specific proteins in permeabilized cells using antibody fragments tagged with small heavy atom clusters. Our quantitative analysis provides a framework for determining the detection limits and optimal experimental conditions for localizing these small clusters.
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Affiliation(s)
- A A Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Building 13, Room 3N17, 13 South Drive, Bethesda, MD 20892-5766, USA
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22
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Sousa AA, Hohmann-Marriott M, Aronova MA, Zhang G, Leapman RD. Determination of quantitative distributions of heavy-metal stain in biological specimens by annular dark-field STEM. J Struct Biol 2008; 162:14-28. [PMID: 18359249 PMCID: PMC2705981 DOI: 10.1016/j.jsb.2008.01.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 01/16/2008] [Accepted: 01/17/2008] [Indexed: 11/24/2022]
Abstract
It is shown that dark-field images collected in the scanning transmission electron microscope (STEM) at two different camera lengths yield quantitative distributions of both the heavy and light atoms in a stained biological specimen. Quantitative analysis of the paired STEM images requires knowledge of the elastic scattering cross sections, which are calculated from the NIST elastic scattering cross section database. The results reveal quantitative information about the distribution of fixative and stain within the biological matrix, and provide a basis for assessing detection limits for heavy-metal clusters used to label intracellular proteins. In sectioned cells that have been stained only with osmium tetroxide, we find an average of 1.2+/-0.1 Os atom per nm(3), corresponding to an atomic ratio of Os:C atoms of approximately 0.02, which indicates that small heavy atom clusters of Undecagold and Nanogold can be detected in lightly stained specimens.
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Affiliation(s)
- A. A. Sousa
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - M. Hohmann-Marriott
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - M. A. Aronova
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - G. Zhang
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - R. D. Leapman
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
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Sousa AA, Aronova MA, Kim YC, Dorward LM, Zhang G, Leapman RD. On the feasibility of visualizing ultrasmall gold labels in biological specimens by STEM tomography. J Struct Biol 2007; 159:507-22. [PMID: 17689263 PMCID: PMC2748118 DOI: 10.1016/j.jsb.2007.06.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2007] [Revised: 06/15/2007] [Accepted: 06/19/2007] [Indexed: 10/23/2022]
Abstract
Labeling with heavy atom clusters attached to antibody fragments is an attractive technique for determining the 3D distribution of specific proteins in cells using electron tomography. However, the small size of the labels makes them very difficult to detect by conventional bright-field electron tomography. Here, we evaluate quantitative scanning transmission electron microscopy (STEM) at a beam voltage of 300 kV for detecting 11-gold atom clusters (Undecagold) and 1.4 nm-diameter nanoparticles (Nanogold) for a variety of specimens and imaging conditions. STEM images as well as tomographic tilt series are simulated by means of the NIST Elastic-Scattering Cross-Section Database for gold clusters embedded in carbon. The simulations indicate that the visibility in 2D of Undecagold clusters in a homogeneous matrix is maximized for low inner collection semi-angles of the STEM annular dark-field detector (15-20 mrad). Furthermore, our calculations show that the visibility of Undecagold in 3D reconstructions is significantly higher than in 2D images for an inhomogeneous matrix corresponding to fluctuations in local density. The measurements demonstrate that it is possible to detect Nanogold particles in plastic sections of tissue freeze-substituted in the presence of osmium. STEM tomography has the potential to localize specific proteins in permeabilized cells using antibody fragments tagged with small heavy atom clusters. Our quantitative analysis provides a framework for determining the detection limits and optimal experimental conditions for localizing these small clusters.
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Affiliation(s)
- A. A. Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - M. A. Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - Y. C. Kim
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, MD 20892, USA
| | - L. M. Dorward
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - G. Zhang
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - R. D. Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
- Correspondence: Dr. Richard D. Leapman, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bldg. 13, Rm. 3N17, 13 South Drive, Bethesda, MD 20892-5766, Tel: 301-496-2599, Fax: 301-435-4699,
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