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Xue H, Zhang M, Liu J, Wang J, Ren G. Cryo-electron tomography related radiation-damage parameters for individual-molecule 3D structure determination. Front Chem 2022; 10:889203. [PMID: 36110139 PMCID: PMC9468540 DOI: 10.3389/fchem.2022.889203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 07/13/2022] [Indexed: 11/28/2022] Open
Abstract
To understand the dynamic structure-function relationship of soft- and biomolecules, the determination of the three-dimensional (3D) structure of each individual molecule (nonaveraged structure) in its native state is sought-after. Cryo-electron tomography (cryo-ET) is a unique tool for imaging an individual object from a series of tilted views. However, due to radiation damage from the incident electron beam, the tolerable electron dose limits image contrast and the signal-to-noise ratio (SNR) of the data, preventing the 3D structure determination of individual molecules, especially at high-resolution. Although recently developed technologies and techniques, such as the direct electron detector, phase plate, and computational algorithms, can partially improve image contrast/SNR at the same electron dose, the high-resolution structure, such as tertiary structure of individual molecules, has not yet been resolved. Here, we review the cryo-electron microscopy (cryo-EM) and cryo-ET experimental parameters to discuss how these parameters affect the extent of radiation damage. This discussion can guide us in optimizing the experimental strategy to increase the imaging dose or improve image SNR without increasing the radiation damage. With a higher dose, a higher image contrast/SNR can be achieved, which is crucial for individual-molecule 3D structure. With 3D structures determined from an ensemble of individual molecules in different conformations, the molecular mechanism through their biochemical reactions, such as self-folding or synthesis, can be elucidated in a straightforward manner.
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Affiliation(s)
- Han Xue
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Meng Zhang
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Jianfang Liu
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Jianjun Wang
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Gang Ren
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
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S'ari M, Blade H, Cosgrove S, Drummond-Brydson R, Hondow N, Hughes LP, Brown A. Characterization of Amorphous Solid Dispersions and Identification of Low Levels of Crystallinity by Transmission Electron Microscopy. Mol Pharm 2021; 18:1905-1919. [PMID: 33797925 DOI: 10.1021/acs.molpharmaceut.0c00918] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Amorphous solid dispersions (ASDs) are used to increase the solubility of oral medicines by kinetically stabilizing the more soluble amorphous phase of an active pharmaceutical ingredient with a suitable amorphous polymer. Low levels of a crystalline material in an ASD can negatively impact the desired dissolution properties of the drug. Characterization techniques such as powder X-ray diffraction (pXRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) are often used to detect and measure any crystallinity within ASDs. These techniques are unable to detect or quantify very low levels because they have limits of detection typically in the order of 1-5%. Herein, an ASD of felodipine (FEL) and polyvinylpyrrolidone/vinyl acetate copolymer (PVP/VA) prepared via a hot melt extrusion (HME) in a mass ratio of 30:70 was characterized using a range of techniques. No signs of residual crystallinity were found by pXRD, DSC, or FTIR. However, transmission electron microscopy (TEM) did identify two areas containing crystals at the edges of milled particles from a total of 55 examined. Both crystalline areas contained Cl Kα X-ray peaks when measured by energy-dispersive X-ray spectroscopy, confirming the presence of FEL (due to the presence of Cl atoms in FEL and not in PVP/VA). Further analysis was carried out by TEM using conical dark field (DF) imaging of a HME ASD of 50:50 FEL-PVP/VA to provide insights into the recrystallization process that occurs at the edges of particles during accelerated ageing conditions in an atmosphere of 75% relative humidity. Multiple metastable polymorphs of recrystallized FEL could be identified by selected area electron diffraction (SAED), predominately form II and the more stable form I. Conical DF imaging was also successful in spatially resolving and sizing crystals. This work highlights the potential for TEM-based techniques to improve the limit of detection of crystallinity in ASDs, while also providing insights into transformation pathways by identifying the location, size, and form of any crystallization that might occur on storage. This opens up the possibility of providing an enhanced understanding of a drug product's stability and performance.
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Affiliation(s)
- Mark S'ari
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K
| | - Helen Blade
- Oral Product Development, Pharmaceutical Technology and Development Operations, AstraZeneca, Macclesfield SK10 2NA, U.K
| | - Stephen Cosgrove
- New Modalities and Parenterals Development, Pharmaceutical Technology and Development Operations, AstraZeneca, Macclesfield SK10 2NA, U.K
| | - Rik Drummond-Brydson
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K
| | - Nicole Hondow
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K
| | - Leslie P Hughes
- Oral Product Development, Pharmaceutical Technology and Development Operations, AstraZeneca, Macclesfield SK10 2NA, U.K
| | - Andy Brown
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K
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Paterson GW, Webster RWH, Ross A, Paton KA, Macgregor TA, McGrouther D, MacLaren I, Nord M. Fast Pixelated Detectors in Scanning Transmission Electron Microscopy. Part II: Post-Acquisition Data Processing, Visualization, and Structural Characterization. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2020; 26:944-963. [PMID: 32883393 DOI: 10.1017/s1431927620024307] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Fast pixelated detectors incorporating direct electron detection (DED) technology are increasingly being regarded as universal detectors for scanning transmission electron microscopy (STEM), capable of imaging under multiple modes of operation. However, several issues remain around the post-acquisition processing and visualization of the often very large multidimensional STEM datasets produced by them. We discuss these issues and present open source software libraries to enable efficient processing and visualization of such datasets. Throughout, we provide examples of the analysis methodologies presented, utilizing data from a 256 × 256 pixel Medipix3 hybrid DED detector, with a particular focus on the STEM characterization of the structural properties of materials. These include the techniques of virtual detector imaging; higher-order Laue zone analysis; nanobeam electron diffraction; and scanning precession electron diffraction. In the latter, we demonstrate a nanoscale lattice parameter mapping with a fractional precision ≤6 × 10−4 (0.06%).
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Affiliation(s)
- Gary W Paterson
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Robert W H Webster
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Andrew Ross
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Kirsty A Paton
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Thomas A Macgregor
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Damien McGrouther
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Ian MacLaren
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
| | - Magnus Nord
- SUPA, School of Physics and Astronomy, University of Glasgow, GlasgowG12 8QQ, UK
- EMAT, Department of Physics, University of Antwerp, Antwerp2000, Belgium
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Yang Y, Kim CS, Hobbs RG, Keathley PD, Berggren KK. Nanostructured-membrane electron phase plates. Ultramicroscopy 2020; 217:113053. [PMID: 32623205 DOI: 10.1016/j.ultramic.2020.113053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/15/2020] [Accepted: 06/21/2020] [Indexed: 10/24/2022]
Abstract
Electron beams can acquire designed phase modulations by passing through nanostructured material phase plates. These phase modulations enable electron wavefront shaping and benefit electron microscopy, spectroscopy, lithography, and interferometry. However, in the fabrication of electron phase plates, the typically used focused-ion-beam-milling method limits the fabrication throughput and hence the active area of the phase plates. Here, we fabricated large-area electron phase plates with electron-beam lithography and reactive-ion-etching. The phase plates are characterized by electron diffraction in transmission electron microscopes with various electron energies, as well as diffractive imaging in a scanning electron microscope. We found the phase plates could produce a null in the center of the bright-field based on coherent interference of diffractive beams. Our work adds capabilities to the fabrication of electron phase plates. The nullification of the direct beam and the tunable diffraction efficiency demonstrated here also paves the way towards novel dark-field electron-microscopy techniques.
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Affiliation(s)
- Yujia Yang
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
| | - Chung-Soo Kim
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Richard G Hobbs
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials Bio-Engineering Research Centre (AMBER), School of Chemistry, Trinity College Dublin, Dublin 2, Ireland
| | - Phillip D Keathley
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Karl K Berggren
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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