Imaging of Self‐Assembled Structures: Interpretation of TEM and Cryo‐TEM Images

Friedrich, Heiner; Frederik, PM Peter; Sommerdijk, Nico A. J. M.

doi:10.1002/anie.201001493

Cited by 214 publications

(181 citation statements)

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“…Imaging contrast was optimized by applying a nominal defocus of −0.5 μm. This defocus value resulted in a CTF that allowed the direct interpretation of dark contrast objects ≥0.9 nm (25).…”

Section: Methodsmentioning

confidence: 99%

A classical view on nonclassical nucleation

Smeets

Finney

Habraken

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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217

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Understanding and controlling nucleation is important for many crystallization applications. Calcium carbonate (CaCO 3 ) is often used as a model system to investigate nucleation mechanisms. Despite its great importance in geology, biology, and many industrial applications, CaCO 3 nucleation is still a topic of intense discussion, with new pathways for its growth from ions in solution proposed in recent years. These new pathways include the socalled nonclassical nucleation mechanism via the assembly of thermodynamically stable prenucleation clusters, as well as the formation of a dense liquid precursor phase via liquid-liquid phase separation. Here, we present results from a combined experimental and computational investigation on the precipitation of CaCO 3 in dilute aqueous solutions. We propose that a dense liquid phase (containing 4-7 H 2 O per CaCO 3 unit) forms in supersaturated solutions through the association of ions and ion pairs without significant participation of larger ion clusters. This liquid acts as the precursor for the formation of solid CaCO 3 in the form of vaterite, which grows via a net transfer of ions from solution according to z Ca 2+ + z CO 3 2− → z CaCO 3 . The results show that all steps in this process can be explained according to classical concepts of crystal nucleation and growth, and that long-standing physical concepts of nucleation can describe multistep, multiphase growth mechanisms.calcium carbonate | nucleation | crystal growth | cryo-electron microscopy | molecular simulation I n the process of forming a solid phase from a supersaturated solution, nucleation is the key step governing the timescale of the transition. Controlling nucleation is an essential aspect in many crystallization processes, where distinct crystal polymorphism, size, morphology, and other characteristics are required. It is, therefore, important to obtain a fundamental understanding of nucleation mechanisms.More than 150 years ago, a basic theoretical framework, classical nucleation theory (CNT) (1, 2), was developed to describe such nucleation events. CNT describes the formation of nuclei from the dynamic and stochastic association of monomeric units (e.g., ions, atoms, or molecules) that overcome a free-energy barrier at a critical nucleus size and grow out to a mature bulk phase. Calcium carbonate (CaCO 3 ) is a frequently used model system to study nucleation (3-5); however, despite the many years of effort, there are still phenomena associated with CaCO 3 crystal formation where the applicability of classical nucleation concepts have been questioned (6). These include certain microstructures and habits of biominerals formed by organisms (7), or geological mineral deposits with unusual mineralogical and textural patterns (8).Three anhydrous crystalline polymorphs of CaCO 3 are observed in nature: vaterite, aragonite, and calcite in order of increasing thermodynamic stability. In many cases, the precipitation of CaCO 3 from solution is described as a multistep process, with amorphous phases first pr...

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Section: Methodsmentioning

confidence: 99%

A classical view on nonclassical nucleation

Smeets

Finney

Habraken

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

217

212

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“…As both drying and the interaction with staining agents may affect the structure of the specimens under investigation, cryoTEM -which involves the vitrication of $100-200 nm thin volumes of liquid -has evolved as an important technique for the visualization of nanostructures in their near native dispersed state. [7][8][9][10] However, to prevent radiation damage to the delicate specimens, cryoTEM is generally performed under low-dose conditions, which together with the oen weak scattering of electrons in the vitried solvent lm, limits the resolution of the technique to the nanometer level. However, in a few cases high resolution images with sub-nanometer details 11,12 or even lattice resolution have been reported.…”

Section: Introductionmentioning

confidence: 99%

Graphene oxide single sheets as substrates for high resolution cryoTEM

et al. 2015

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Link to publication• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. CryoTEM is an important tool in the analysis of soft matter, where generally defocus conditions are used to enhance the contrast in the images, but this is at the expense of the maximum resolution that can be obtained. Here, we demonstrate the use of graphene oxide single sheets as support for the formation of 10 nm thin films for high resolution cryoTEM imaging, using DNA as an example. With this procedure, the overlap of objects in the vitrified film is avoided. Moreover, in these thin films less background scattering occurs and as a direct result, an increased contrast can be observed in the images. Hence, imaging closer to focus as compared with conventional cryoTEM procedures is achieved, without losing contrast. In addition, we demonstrate an $1.8 fold increase in resolution, which is crucial for accurate size analysis of nanostructures.

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“…Materials characterization techniques are typically aimed at direct observations of the magnetite nucleation and growth at high spatial resolution. High resolution TEM is often used to observe formation of magnetosomes in magnetotactic bacteria via cryogenic TEM (cryo-TEM) 4,[22][23][24][25][26][27][28][29] . This technique provides vital information about organization of the cellular structures and development of the magnetosomes 20,27 .…”

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confidence: 99%

Correlative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging

et al. 2015

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Magnetotactic bacteria biomineralize ordered chains of uniform, membrane-bound magnetite or greigite nanocrystals that exhibit nearly perfect crystal structures and species-specific morphologies. Transmission electron microscopy (TEM) is a critical technique for providing information regarding the organization of cellular and magnetite structures in these microorganisms. However, conventional TEM can only be used to image air-dried or vitrified bacteria removed from their natural environment. Here we present a correlative scanning TEM (STEM) and fluorescence microscopy technique for imaging viable cells of Magnetospirillum magneticum strain AMB-1 in liquid using an in situ fluid cell TEM holder. Fluorescently labeled cells were immobilized on microchip window surfaces and visualized in a fluid cell with STEM, followed by correlative fluorescence imaging to verify their membrane integrity. Notably, the post-STEM fluorescence imaging indicated that the bacterial cell wall membrane did not sustain radiation damage during STEM imaging at low electron dose conditions. We investigated the effects of radiation damage and sample preparation on the bacteria viability and found that approximately 50% of the bacterial membranes remained intact after an hour in the fluid cell, decreasing to ,30% after two hours. These results represent a first step toward in vivo studies of magnetite biomineralization in magnetotactic bacteria.B iomineralization is a widespread biological phenomenon occurring in living organisms ranging from single cells to complex multicellular organisms. Biomineralization of inorganic materials in single cell organisms is an ideal system for studying fundamental mechanisms of biomineralization 1 . Model systems range from prokaryotic organisms, such as magnetite formation in magnetotactic bacteria 2-4 , to eukaryotic organisms, such as silica biomineralization in diatoms 5,6 . Understanding biomineralization in these organisms in terms of crystal nucleation and growth, as well as the involvement of biological macromolecules and cellular processes, is of fundamental interest to scientists as similar principles can be used to develop synthetic nanomaterials.Magnetite biomineralization by magnetotactic bacteria is a topic of great interest in nanotechnology 7-12 , functional materials [11][12][13][14][15][16] , and astrobiology 17 . Magnetotactic bacteria take up soluble iron species that they use to biomineralize chains of magnetite nanocrystals, known as magnetosomes, in intracellular membrane vesicles 2 . The nanocrystals have nearly perfect mineral crystal structures with consistent species-specific morphologies, leading to well-defined magnetic properties 2,3,9,12,18,19 . As a result, magnetotactic bacteria are one of the best model systems for investigating the molecular mechanisms of biomineralization. Magnetite biomineralization in these bacteria is a complex process involving a number of steps including cellular uptake and reduction of ferric ions, complexation of the iron with membrane proteins, an...

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Imaging of Self‐Assembled Structures: Interpretation of TEM and Cryo‐TEM Images

Cited by 214 publications

References 123 publications

A classical view on nonclassical nucleation

A classical view on nonclassical nucleation

Graphene oxide single sheets as substrates for high resolution cryoTEM

Correlative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging

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