51
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Li M, Wang L, Putnis CV. Energetic Basis for Inhibition of Calcium Phosphate Biomineralization by Osteopontin. J Phys Chem B 2017; 121:5968-5976. [DOI: 10.1021/acs.jpcb.7b04163] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Meng Li
- College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Lijun Wang
- College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Christine V. Putnis
- Institut
für Mineralogie, University of Münster, 48149 Münster, Germany
- Department of Chemistry, Curtin University, Perth, Western Australia 6845, Australia
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52
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Pfreundschuh M, Harder D, Ucurum Z, Fotiadis D, Müller DJ. Detecting Ligand-Binding Events and Free Energy Landscape while Imaging Membrane Receptors at Subnanometer Resolution. NANO LETTERS 2017; 17:3261-3269. [PMID: 28361535 DOI: 10.1021/acs.nanolett.7b00941] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Force-distance curve-based atomic force microscopy has emerged into a sophisticated technique for imaging cellular membranes and for detecting specific ligand-binding events of native membrane receptors. However, so far the resolution achieved has been insufficient to structurally map ligand-binding sites onto membrane proteins. Here, we introduce experimental and theoretical approaches for overcoming this limitation. To establish a structurally and functionally well-defined reference sample, we engineer a ligand-binding site to the light-driven proton pump bacteriorhodopsin of purple membrane. Functionalizing the AFM stylus with an appropriate linker-system tethering the ligand and optimizing the AFM conditions allows for imaging the engineered bacteriorhodopsin at subnanometer resolution while structurally mapping the specific ligand-receptor binding events. Improved data analysis allows reconstructing the ligand-binding free energy landscape from the experimental data, thus providing thermodynamic and kinetic insight into the ligand-binding process. The nanoscopic method introduced is generally applicable for imaging receptors in native membranes at subnanometer resolution and for systematically mapping and quantifying the free energy landscape of ligand binding.
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Affiliation(s)
- Moritz Pfreundschuh
- Department of Biosystems Science and Engineering, ETH Zürich , 4058 Basel, Switzerland
| | - Daniel Harder
- Institute of Biochemistry and Molecular Medicine, University of Bern , 3012 Bern, Switzerland
| | - Zöhre Ucurum
- Institute of Biochemistry and Molecular Medicine, University of Bern , 3012 Bern, Switzerland
| | - Dimitrios Fotiadis
- Institute of Biochemistry and Molecular Medicine, University of Bern , 3012 Bern, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, ETH Zürich , 4058 Basel, Switzerland
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53
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Lee JH, Jung SH, Lee SS, Kwon KY, Sakurai K, Jaworski J, Jung JH. Ultraviolet Patterned Calixarene-Derived Supramolecular Gels and Films with Spatially Resolved Mechanical and Fluorescent Properties. ACS NANO 2017; 11:4155-4164. [PMID: 28358496 DOI: 10.1021/acsnano.7b00997] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Supramolecular assemblies have in the past been considered mechanically weak and in most cases unable to withstand their own weight. Calixarene-derived networks can, however, provide robust supramolecular gels. Incorporating a photoreactive stilbene moiety, we show that the aggregation state of the material can be tuned by heating and UV exposure in order to control the mechanical as well as the fluorescent properties. Regulating the extent of heating to control the proportion of H-aggregates and J-aggregates and further cross-linking of H-aggregates by control over UV exposure allows for adjustable photopatterning of the fluorescence as well as the material stiffness in the range from ∼100 to 450 kPa. We expect this straightforward supramolecular system will be suitable for advanced prototyping in applications where modulus and shape are important design criteria.
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Affiliation(s)
- Ji Ha Lee
- Department of Chemistry and Research Institute of National Sciences, Gyeongsang National University , Jinju, Korea
- Department of Chemistry and Biochemistry, The University of Kitakyushu , Hibikino, Kitakyushu 808-0135, Japan
| | - Sung Ho Jung
- Department of Chemistry and Research Institute of National Sciences, Gyeongsang National University , Jinju, Korea
| | - Shim Sung Lee
- Department of Chemistry and Research Institute of National Sciences, Gyeongsang National University , Jinju, Korea
| | - Ki-Young Kwon
- Department of Chemistry and Research Institute of National Sciences, Gyeongsang National University , Jinju, Korea
| | - Kazuo Sakurai
- Department of Chemistry and Biochemistry, The University of Kitakyushu , Hibikino, Kitakyushu 808-0135, Japan
| | - Justyn Jaworski
- Department of Bioengineering, University of Texas, Arlington , Arlington, Texas 76010, United States
| | - Jong Hwa Jung
- Department of Chemistry and Research Institute of National Sciences, Gyeongsang National University , Jinju, Korea
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54
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Kim JS, Choi JS, Cho YW. Cell-Free Hydrogel System Based on a Tissue-Specific Extracellular Matrix for In Situ Adipose Tissue Regeneration. ACS APPLIED MATERIALS & INTERFACES 2017; 9:8581-8588. [PMID: 28233976 DOI: 10.1021/acsami.6b16783] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Well-designed scaffolds provide appropriate niches that can effectively recruit host cells and induce differentiation of recruited cells into the desired cell types, facilitating in situ tissue regeneration. Here we report a tissue-specific extracellular matrix (ECM) hydrogel composed of adipose-derived soluble ECM (sECM) and methylcellulose (MC) as a cell-free scaffold system for adipose tissue regeneration. The sECM-MC hydrogels showed a thermosensitive sol-gel phase transition and rapidly formed a soft hydrogel with a stiffness of 3.8 kPa at body temperature. An in vivo study showed that the sECM-MC hydrogel facilitated the infiltration of host cell populations, particularly adipose-derived stem cells (ASCs) and adipose tissue macrophages (ATMs) that directly contribute to the adipose tissue regeneration. Moreover, the hydrogel significantly enhanced host-derived adipogenesis and angiogenesis without exogenous cells or bioactive molecules. Our results indicate that the sECM-MC hydrogels provide mechanical and biochemical cues for host-derived adipose regeneration. Overall, the sECM-MC hydrogels are a highly promising cell-free therapeutic approach for in situ adipose tissue regeneration.
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Affiliation(s)
- Jun Sung Kim
- Department of Chemical Engineering, Hanyang University , Ansan, Gyeonggi-do 426-791, Republic of Korea
| | - Ji Suk Choi
- Department of Chemical Engineering, Hanyang University , Ansan, Gyeonggi-do 426-791, Republic of Korea
| | - Yong Woo Cho
- Department of Chemical Engineering, Hanyang University , Ansan, Gyeonggi-do 426-791, Republic of Korea
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55
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Alsteens D, Newton R, Schubert R, Martinez-Martin D, Delguste M, Roska B, Müller DJ. Nanomechanical mapping of first binding steps of a virus to animal cells. NATURE NANOTECHNOLOGY 2017; 12:177-183. [PMID: 27798607 DOI: 10.1038/nnano.2016.228] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 09/18/2016] [Indexed: 05/23/2023]
Abstract
Viral infection is initiated when a virus binds to cell surface receptors. Because the cell membrane is dynamic and heterogeneous, imaging living cells and simultaneously quantifying the first viral binding events is difficult. Here, we show an atomic force and confocal microscopy set-up that allows the surface receptor landscape of cells to be imaged and the virus binding events within the first millisecond of contact with the cell to be mapped at high resolution (<50 nm). We present theoretical approaches to contour the free-energy landscape of early binding events between an engineered virus and cell surface receptors. We find that the first bond formed between the viral glycoprotein and its cognate cell surface receptor has relatively low lifetime and free energy, but this increases as additional bonds form rapidly (≤1 ms). The formation of additional bonds occurs with positive allosteric modulation and the three binding sites of the viral glycoprotein are quickly occupied. Our quantitative approach can be readily applied to study the binding of other viruses to animal cells.
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Affiliation(s)
- David Alsteens
- ETH Zürich, Department of Biosystems Science and Engineering, 4058 Basel, Switzerland
- Université Catholique de Louvain, Institute of Life Sciences, 1348 Louvain-La-Neuve, Belgium
| | - Richard Newton
- ETH Zürich, Department of Biosystems Science and Engineering, 4058 Basel, Switzerland
| | - Rajib Schubert
- ETH Zürich, Department of Biosystems Science and Engineering, 4058 Basel, Switzerland
| | - David Martinez-Martin
- ETH Zürich, Department of Biosystems Science and Engineering, 4058 Basel, Switzerland
| | - Martin Delguste
- Université Catholique de Louvain, Institute of Life Sciences, 1348 Louvain-La-Neuve, Belgium
| | - Botond Roska
- Friedrich Miescher Institute (FMI), 4058 Basel, Switzerland
- Department of Ophthalmology, University of Basel, 4056 Basel, Switzerland
| | - Daniel J Müller
- ETH Zürich, Department of Biosystems Science and Engineering, 4058 Basel, Switzerland
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56
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Imaging and Force Recognition of Single Molecular Behaviors Using Atomic Force Microscopy. SENSORS 2017; 17:s17010200. [PMID: 28117741 PMCID: PMC5298773 DOI: 10.3390/s17010200] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 01/12/2017] [Accepted: 01/16/2017] [Indexed: 12/23/2022]
Abstract
The advent of atomic force microscopy (AFM) has provided a powerful tool for investigating the behaviors of single native biological molecules under physiological conditions. AFM can not only image the conformational changes of single biological molecules at work with sub-nanometer resolution, but also sense the specific interactions of individual molecular pair with piconewton force sensitivity. In the past decade, the performance of AFM has been greatly improved, which makes it widely used in biology to address diverse biomedical issues. Characterizing the behaviors of single molecules by AFM provides considerable novel insights into the underlying mechanisms guiding life activities, contributing much to cell and molecular biology. In this article, we review the recent developments of AFM studies in single-molecule assay. The related techniques involved in AFM single-molecule assay were firstly presented, and then the progress in several aspects (including molecular imaging, molecular mechanics, molecular recognition, and molecular activities on cell surface) was summarized. The challenges and future directions were also discussed.
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57
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Garate H, Bianchi M, Pietrasanta LI, Goyanes S, D'Accorso NB. High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates. ACS APPLIED MATERIALS & INTERFACES 2017; 9:930-943. [PMID: 28004915 DOI: 10.1021/acsami.6b13212] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Hierarchical assembly of hard/soft nanoparticles holds great potential as reinforcements for polymer nanocomposites with tailored properties. Here, we present a facile strategy to integrate polystyrene-grafted carbon nanotubes (PSgCNT) (0.05-0.3 wt %) and poly(styrene-b-[isoprene-ran-epoxyisoprene]-b-styrene) block copolymer (10 wt %) into epoxy coatings using an ultrasound-assisted noncovalent functionalization process. The method leads to cured nanocomposites with core-shell block copolymer (BCP) nanodomains which are associated with carbon nanotubes (CNT) giving rise to CNT-BCP hybrid structures. Nanocomposite energy dissipation and reduced Young's Modulus (E*) is determined from force-distance curves by atomic force microscopy operating in the PeakForce QNM imaging mode and compared to thermosets modified with BCP and purified carbon nanotubes (pCNT). Remarkably, nanocomposites bearing PSgCNT-BCP conjugates display an increase in energy dissipation of up to 7.1-fold with respect to neat epoxy and 53% more than materials prepared with pCNT and BCP at the same CNT load (0.3 wt %), while reduced Young's Modulus shows no significant change with CNT type and increases up to 25% compared to neat epoxy E* at a CNT load of 0.3 wt %. The energy dissipation performance of nanocomposites is also reflected by the lower wear coefficients of materials with PSgCNT and BCP compared to those with pCNT and BCP, as determined by abrasion tests. Furthermore, scanning electron microscopy (SEM) images taken on wear surfaces show that materials incorporating PSgCNT and BCP exhibit much more surface deformation under shear forces in agreement with their higher ability to dissipate more energy before particle release. We propose that the synergistic effect observed in energy dissipation arises from hierarchical assembly of PSgCNT and BCP within the epoxy matrix and provides clues that the CNT-BCP interface has a significant role in the mechanisms of energy dissipation of epoxy coating modified by CNT-BCP conjugates. These findings provide a means to design epoxy-based coatings with high-energy dissipation performance.
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Affiliation(s)
- Hernan Garate
- CIHIDECAR-CONICET, Departamento de Química Orgánica, FCEyN-UBA, §Centro de Microscopías Avanzadas, FCEyN-UBA, ⊥LP&MC, and ‡IFIBA-CONICET, Departamento de Física, FCEyN-UBA, Ciudad Universitaria , 1428, Ciudad Autónoma de Buenos Aires, Argentina
| | - Micaela Bianchi
- CIHIDECAR-CONICET, Departamento de Química Orgánica, FCEyN-UBA, §Centro de Microscopías Avanzadas, FCEyN-UBA, ⊥LP&MC, and ‡IFIBA-CONICET, Departamento de Física, FCEyN-UBA, Ciudad Universitaria , 1428, Ciudad Autónoma de Buenos Aires, Argentina
| | - Lía I Pietrasanta
- CIHIDECAR-CONICET, Departamento de Química Orgánica, FCEyN-UBA, §Centro de Microscopías Avanzadas, FCEyN-UBA, ⊥LP&MC, and ‡IFIBA-CONICET, Departamento de Física, FCEyN-UBA, Ciudad Universitaria , 1428, Ciudad Autónoma de Buenos Aires, Argentina
| | - Silvia Goyanes
- CIHIDECAR-CONICET, Departamento de Química Orgánica, FCEyN-UBA, §Centro de Microscopías Avanzadas, FCEyN-UBA, ⊥LP&MC, and ‡IFIBA-CONICET, Departamento de Física, FCEyN-UBA, Ciudad Universitaria , 1428, Ciudad Autónoma de Buenos Aires, Argentina
| | - Norma B D'Accorso
- CIHIDECAR-CONICET, Departamento de Química Orgánica, FCEyN-UBA, §Centro de Microscopías Avanzadas, FCEyN-UBA, ⊥LP&MC, and ‡IFIBA-CONICET, Departamento de Física, FCEyN-UBA, Ciudad Universitaria , 1428, Ciudad Autónoma de Buenos Aires, Argentina
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58
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Godon C, Teulon JM, Odorico M, Basset C, Meillan M, Vellutini L, Chen SWW, Pellequer JL. Conditions to minimize soft single biomolecule deformation when imaging with atomic force microscopy. J Struct Biol 2016; 197:322-329. [PMID: 28017791 DOI: 10.1016/j.jsb.2016.12.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 12/06/2016] [Accepted: 12/21/2016] [Indexed: 11/24/2022]
Abstract
A recurrent interrogation when imaging soft biomolecules using atomic force microscopy (AFM) is the putative deformation of molecules leading to a bias in recording true topographical surfaces. Deformation of biomolecules comes from three sources: sample instability, adsorption to the imaging substrate, and crushing under tip pressure. To disentangle these causes, we measured the maximum height of a well-known biomolecule, the tobacco mosaic virus (TMV), under eight different experimental conditions positing that the maximum height value is a specific indicator of sample deformations. Six basic AFM experimental factors were tested: imaging in air (AIR) versus in liquid (LIQ), imaging with flat minerals (MICA) versus flat organic surfaces (self-assembled monolayers, SAM), and imaging forces with oscillating tapping mode (TAP) versus PeakForce tapping (PFT). The results show that the most critical parameter in accurately measuring the height of TMV in air is the substrate. In a liquid environment, regardless of the substrate, the most critical parameter is the imaging mode. Most importantly, the expected TMV height values were obtained with both imaging with the PeakForce tapping mode either in liquid or in air at the condition of using self-assembled monolayers as substrate. This study unambiguously explains previous poor results of imaging biomolecules on mica in air and suggests alternative methodologies for depositing soft biomolecules on well organized self-assembled monolayers.
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Affiliation(s)
| | - Jean-Marie Teulon
- Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France
| | - Michael Odorico
- ICSM-UMR5257 CEA/CNRS/UM2/ENSCM, F-30207 Bagnols sur Cèze, France
| | | | - Matthieu Meillan
- Univ. Bordeaux, ISM, UMR 5255, F-33400 Talence, France; CNRS, ISM, UMR 5255, F-33400 Talence, France
| | - Luc Vellutini
- Univ. Bordeaux, ISM, UMR 5255, F-33400 Talence, France; CNRS, ISM, UMR 5255, F-33400 Talence, France
| | | | - Jean-Luc Pellequer
- Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France.
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59
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van Pee K, Mulvihill E, Müller DJ, Yildiz Ö. Unraveling the Pore-Forming Steps of Pneumolysin from Streptococcus pneumoniae. NANO LETTERS 2016; 16:7915-7924. [PMID: 27796097 DOI: 10.1021/acs.nanolett.6b04219] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Pneumolysin (PLY) is the main virulence factor of Streptococcus pneumoniae that causes pneumonia, meningitis, and invasive pneumococcal infection. PLY is produced as monomers, which bind to cholesterol-containing membranes, where they oligomerize into large pores. To investigate the pore-forming mechanism, we determined the crystal structure of PLY at 2.4 Å and used it to design mutants on the surface of monomers. Electron microscopy of liposomes incubated with PLY mutants revealed that several mutations interfered with ring formation. Mutants that formed incomplete rings or linear arrays had strongly reduced hemolytic activity. By high-resolution time-lapse atomic force microscopy of wild-type PLY, we observed two different ring-shaped complexes. Most of the complexes protruded ∼8 nm above the membrane surface, while a smaller number protruded ∼11 nm or more. The lower complexes were identified as pores or prepores by the presence or absence of a lipid bilayer in their center. The taller complexes were side-by-side assemblies of monomers of soluble PLY that represent an early form of the prepore. Our observations suggest a four-step mechanism of membrane attachment and pore formation by PLY, which is discussed in the context of recent structural models. The functional separation of these steps is necessary for the understanding how cholesterol-dependent cytolysins form pores and lyse cells.
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Affiliation(s)
- Katharina van Pee
- Department of Structural Biology, Max PIanck Institute of Biophysics , Max von Laue Strasse 3, 60438 Frankfurt am Main, Germany
| | - Estefania Mulvihill
- Department of Biosystems Science and Engineering, ETH Zurich , Mattenstrasse 26, 4058 Basel, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, ETH Zurich , Mattenstrasse 26, 4058 Basel, Switzerland
| | - Özkan Yildiz
- Department of Structural Biology, Max PIanck Institute of Biophysics , Max von Laue Strasse 3, 60438 Frankfurt am Main, Germany
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60
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Lee M, Park C, Lee H, Kim H, Kim SY, In I, Kim B. Remarkably enhanced adhesion of coherently aligned catechol-terminated molecules on ultraclean ultraflat gold nanoplates. NANOTECHNOLOGY 2016; 27:475705. [PMID: 27779130 DOI: 10.1088/0957-4484/27/47/475705] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report the characterization and formation of catechol-terminated molecules immobilized on gold nanoplates (Au NPLs) using N-(3,4-dihydroxyphenethyl)-2-mercaptoacetamide (Cat-EAA-SH). Single-crystalline Au NPLs, synthesized using a one-step chemical vapor transport method, have ultraclean and ultraflat surfaces that make Cat-EAA-SH molecules aligned into a well-ordered network of a large-scale. Topographic study of the catechol-terminated molecules on Au NPLs using atomic force microscopy showed more orderly orientation and higher density, leading to significantly higher adhesion as observed from local force-distance curves than those on other Au surfaces. These coherently aligned catechol-terminated molecules on the atomically smooth gold surface led to significanty more reproducible and thus more physico-chemically meaningful measurements than was possible before by employing rough gold surfaces.
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Affiliation(s)
- Miyeon Lee
- Department of Chemistry, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
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61
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Wu H, Feng X, Kieviet BD, Zhang K, Zandvliet HJ, Canters GW, Schön PM, Vancso GJ. Electrochemical atomic force microscopy reveals potential stimulated height changes of redox responsive Cu-azurin on gold. Eur Polym J 2016. [DOI: 10.1016/j.eurpolymj.2015.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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62
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Kreplak L. Introduction to Atomic Force Microscopy (AFM) in Biology. ACTA ACUST UNITED AC 2016; 85:17.7.1-17.7.21. [PMID: 27479503 DOI: 10.1002/cpps.14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The atomic force microscope (AFM) has the unique capability of imaging biological samples with molecular resolution in buffer solution over a wide range of time scales from milliseconds to hours. In addition to providing topographical images of surfaces with nanometer- to angstrom-scale resolution, forces between single molecules and mechanical properties of biological samples can be investigated from the nano-scale to the micro-scale. Importantly, the measurements are made in buffer solutions, allowing biological samples to "stay alive" within a physiological-like environment while temporal changes in structure are measured-e.g., before and after addition of chemical reagents. These qualities distinguish AFM from conventional imaging techniques of comparable resolution, e.g., electron microscopy (EM). This unit provides an introduction to AFM on biological systems and describes specific examples of AFM on proteins, cells, and tissues. The physical principles of the technique and methodological aspects of its practical use and applications are also described. © 2016 by John Wiley & Sons, Inc.
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Affiliation(s)
- Laurent Kreplak
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Canada
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63
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Sborgi L, Rühl S, Mulvihill E, Pipercevic J, Heilig R, Stahlberg H, Farady CJ, Müller DJ, Broz P, Hiller S. GSDMD membrane pore formation constitutes the mechanism of pyroptotic cell death. EMBO J 2016; 35:1766-78. [PMID: 27418190 PMCID: PMC5010048 DOI: 10.15252/embj.201694696] [Citation(s) in RCA: 809] [Impact Index Per Article: 101.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 06/28/2016] [Indexed: 12/18/2022] Open
Abstract
Pyroptosis is a lytic type of cell death that is initiated by inflammatory caspases. These caspases are activated within multi‐protein inflammasome complexes that assemble in response to pathogens and endogenous danger signals. Pyroptotic cell death has been proposed to proceed via the formation of a plasma membrane pore, but the underlying molecular mechanism has remained unclear. Recently, gasdermin D (GSDMD), a member of the ill‐characterized gasdermin protein family, was identified as a caspase substrate and an essential mediator of pyroptosis. GSDMD is thus a candidate for pyroptotic pore formation. Here, we characterize GSDMD function in live cells and in vitro. We show that the N‐terminal fragment of caspase‐1‐cleaved GSDMD rapidly targets the membrane fraction of macrophages and that it induces the formation of a plasma membrane pore. In vitro, the N‐terminal fragment of caspase‐1‐cleaved recombinant GSDMD tightly binds liposomes and forms large permeability pores. Visualization of liposome‐inserted GSDMD at nanometer resolution by cryo‐electron and atomic force microscopy shows circular pores with variable ring diameters around 20 nm. Overall, these data demonstrate that GSDMD is the direct and final executor of pyroptotic cell death.
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Affiliation(s)
| | | | - Estefania Mulvihill
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, Basel, Switzerland
| | | | | | | | | | - Daniel J Müller
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, Basel, Switzerland
| | - Petr Broz
- Biozentrum, University of Basel, Basel, Switzerland
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64
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Gudzenko T, Franz CM. Studying early stages of fibronectin fibrillogenesis in living cells by atomic force microscopy. Mol Biol Cell 2016; 26:3190-204. [PMID: 26371081 PMCID: PMC4569311 DOI: 10.1091/mbc.e15-06-0421] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Time-lapse atomic force microscopy imaging is used to visualize the initial stages of fibronectin fibrillogenesis directly in living cells with high resolution. This approach provides new structural and mechanistic details, such as a stepwise extension mechanism and an accelerating effect of extracellular Mn2+ on early FN fibrillogenesis. Fibronectin (FN) is an extracellular matrix protein that can be assembled by cells into large fibrillar networks, but the dynamics of FN remodeling and the transition through intermediate fibrillar stages are incompletely understood. Here we used a combination of fluorescence microscopy and time-lapse atomic force microscopy (AFM) to visualize initial stages of FN fibrillogenesis in living fibroblasts at high resolution. Initial FN nanofibrils form within <5 min of cell–matrix contact and subsequently extend at a rate of 0.25 μm/min at sites of cell membrane retraction. FN nanofibrils display a complex linear array of globular features spaced at varying distances, indicating the coexistence of different conformational states within the fibril. In some cases, initial fibrils extended in discrete increments of ∼800 nm during a series of cyclical membrane retractions, indicating a stepwise fibrillar extension mechanism. In presence of Mn2+, a known activator of integrin adhesion to FN, fibrillogenesis was accelerated almost threefold to 0.68 μm/min and fibrillar dimensions were increased, underlining the importance of integrin activation for early FN fibrillogenesis. FN fibrillogenesis visualized by time-lapse AFM thus provides new structural and mechanistic insight into initial steps of cell-driven FN fibrillogenesis.
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Affiliation(s)
- Tetyana Gudzenko
- DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Clemens M Franz
- DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany )
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65
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Rapid recognition and functional analysis of membrane proteins on human cancer cells using atomic force microscopy. J Immunol Methods 2016; 436:41-9. [PMID: 27374866 DOI: 10.1016/j.jim.2016.06.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/27/2016] [Indexed: 11/23/2022]
Abstract
Understanding the physicochemical properties of cell surface signalling molecules is important for us to uncover the underlying mechanisms that guide the cellular behaviors. Atomic force microscopy (AFM) has become a powerful tool for detecting the molecular interactions on individual cells with nanometer resolution. In this paper, AFM peak force tapping (PFT) imaging mode was applied to rapidly locate and visually map the CD20 molecules on human lymphoma cells using biochemically sensitive tips. First, avidin-biotin system was used to test the effectiveness of using PFT imaging mode to probe the specific molecular interactions. The adhesion images obtained on avidin-coated mica using biotin-tethered tips obviously showed the recognition spots which corresponded to the avidins in the simultaneously obtained topography images. The experiments confirmed the specificity and reproducibility of the recognition results. Then, the established procedure was applied to visualize the nanoscale organization of CD20s on the surface of human lymphoma Raji cells using rituximab (a monoclonal anti-CD20 antibody)-tethered tips. The experiments showed that the recognition spots in the adhesion images corresponded to the specific CD20-rituximab interactions. The cluster sizes of CD20s on lymphoma Raji cells were quantitatively analyzed from the recognition images. Finally, under the guidance of fluorescence recognition, the established procedure was applied to cancer cells from a clinical lymphoma patient. The results showed that there were significant differences between the adhesion images obtained on cancer cells and on normal cells (red blood cell). The CD20 distributions on ten cancer cells from the patient were quantified according to the adhesion images. The experimental results demonstrate the capability of applying PFT imaging to rapidly investigate the nanoscale biophysical properties of native membrane proteins on the cell surface, which is of potential significance in developing novel biomarkers for cancer diagnosis and drug development.
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66
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Evaluation of β1-integrin expression on chondrogenically differentiating human adipose-derived stem cells using atomic force microscopy. Biointerphases 2016; 11:021005. [PMID: 27106564 DOI: 10.1116/1.4947049] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The expression of β1-integrin on human adipose-derived stem cells, differentiating toward a chondrogenic lineage, is hypothesized to decrease when cells are grown under in vivo-like environments due to sufficient extracellular matrix (ECM) buildup in the engineered tissues. The opposite is true when cells are grown in static cultures such as in pellet or micromass. To probe β1-integrin distribution on cellular surfaces, atomic force microscopy cantilevers modified with anti-β1-integrin antibodies were used. Specific antibody-antigen adhesion forces were identified and indicated the locations of β1-integrins on cells. ECM properties were assessed by estimating the Young's modulus of the matrix. Specific single antibody-antigen interactions averaged 78 ± 10 pN with multiple bindings occurring at approximate multiples of 78 pN. The author's results show that upregulated β1-integrin expression coincided with a less robust ECM as assessed by mechanical properties of tissues. In micromass and pellet cultures, transforming growth factor β3(TGF-β3) elicited a decrease in Young's modulus by 3.7- and 4.4-fold while eliciting an increase in β1-integrin count by 1.1- and 1.3-fold, respectively. β1-integrin counts on cells grown in the presence of TGF-β3 with oscillating hydrostatic pressure decreased by a 1.1-fold while the Young's modulus increased by a 1.9-fold. Collectively, our results suggest that cells in insufficiently robust ECM express more integrin perhaps to facilitate cell-ECM adhesion and compensate for a looser less robust ECM.
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67
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Schön P. Imaging and force probing RNA by atomic force microscopy. Methods 2016; 103:25-33. [PMID: 27222101 DOI: 10.1016/j.ymeth.2016.05.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/19/2016] [Accepted: 05/20/2016] [Indexed: 12/12/2022] Open
Abstract
In the past 30years, the atomic force microscope (AFM) has become a true enabling platform in the life sciences opening entire novel avenues for structural and dynamic studies of biological systems. It enables visualization, probing and manipulation across the length scales, from single molecules to living cells in buffer solution under physiological conditions without the need for labeling or staining of the specimen. In particular, for structural studies of nucleic acids and assemblies thereof, the AFM has matured into a routinely used tool providing nanometer spatial resolution. This includes ssRNA, dsRNA and nucleoprotein complexes thereof, as well as RNA aggregates and 2D RNA assemblies. By AFM unique information can be obtained on RNA based assemblies which are becoming increasingly important as novel unique building blocks in the emerging field of RNA nanotechnology. In addition, the AFM is of fundamental relevance to study biological relevant RNA interactions and dynamics. In this short review first the basic functioning principles of commonly used AFM modes including AFM based force spectroscopy will be briefly described. Next a brief overview will be given on structural studies that have been done related to AFM topographic imaging of RNA, RNA assemblies and aggregates. Finally, an overview on AFM beyond imaging will be provided. This includes force spectroscopy of RNA under physiological conditions in aqueous buffer to probe RNA interaction with proteins and ligands as well as other AFM tip based RNA probing. The main intention of this short review to give the reader a flavor of what AFM contributes to RNA research and engineering.
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Affiliation(s)
- Peter Schön
- NanoBioInterface Chair, Research Center Design and Technology, Saxion University of Applied Sciences, 7500 KB Enschede, The Netherlands; Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
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68
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Dong C, Hu X, Dinu CZ. Current status and perspectives in atomic force microscopy-based identification of cellular transformation. Int J Nanomedicine 2016; 11:2107-18. [PMID: 27274238 PMCID: PMC4876801 DOI: 10.2147/ijn.s103501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Understanding the complex interplay between cells and their biomechanics and how the interplay is influenced by the extracellular microenvironment, as well as how the transforming potential of a tissue from a benign to a cancerous one is related to the dynamics of both the cell and its surroundings, holds promise for the development of targeted translational therapies. This review provides a comprehensive overview of atomic force microscopy-based technology and its applications for identification of cellular progression to a cancerous phenotype. The review also offers insights into the advancements that are required for the next user-controlled tool to allow for the identification of early cell transformation and thus potentially lead to improved therapeutic outcomes.
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Affiliation(s)
- Chenbo Dong
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV, USA
| | - Xiao Hu
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV, USA
| | - Cerasela Zoica Dinu
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV, USA
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69
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Hilbert M, Noga A, Frey D, Hamel V, Guichard P, Kraatz SHW, Pfreundschuh M, Hosner S, Flückiger I, Jaussi R, Wieser MM, Thieltges KM, Deupi X, Müller DJ, Kammerer RA, Gönczy P, Hirono M, Steinmetz MO. SAS-6 engineering reveals interdependence between cartwheel and microtubules in determining centriole architecture. Nat Cell Biol 2016; 18:393-403. [DOI: 10.1038/ncb3329] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 02/10/2016] [Indexed: 01/09/2023]
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70
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Gavara N. Combined strategies for optimal detection of the contact point in AFM force-indentation curves obtained on thin samples and adherent cells. Sci Rep 2016; 6:21267. [PMID: 26891762 PMCID: PMC4759531 DOI: 10.1038/srep21267] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 01/20/2016] [Indexed: 11/13/2022] Open
Abstract
Atomic Force Microscopy (AFM) is a widely used tool to study cell mechanics. Current AFM setups perform high-throughput probing of living cells, generating large amounts of force-indentations curves that are subsequently analysed using a contact-mechanics model. Here we present several algorithms to detect the contact point in force-indentation curves, a crucial step to achieve fully-automated analysis of AFM-generated data. We quantify and rank the performance of our algorithms by analysing a thousand force-indentation curves obtained on thin soft homogeneous hydrogels, which mimic the stiffness and topographical profile of adherent cells. We take advantage of the fact that all the proposed algorithms are based on sequential search strategies, and show that a combination of them yields the most accurate and unbiased results. Finally, we also observe improved performance when force-indentation curves obtained on adherent cells are analysed using our combined strategy, as compared to the classical algorithm used in the majority of previous cell mechanics studies.
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Affiliation(s)
- Núria Gavara
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, E1 3NS, London, UK
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71
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Bartkowiak D, Merk V, Reiter-Scherer V, Gernert U, Rabe JP, Kneipp J, Kemnitz E. Porous MgF2-over-gold nanoparticles (MON) as plasmonic substrate for analytical applications. RSC Adv 2016. [DOI: 10.1039/c6ra10501g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Porous MgF2-over-nanoparticles (MON) surfaces are fabricated from immobilized gold nanoparticles of different sizes on a glass surface by coating them with a magnesium fluoride layer, resulting in favorable optical and mechanical properties.
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Affiliation(s)
- D. Bartkowiak
- Humboldt-Universität zu Berlin
- Department of Chemistry
- 12489 Berlin
- Germany
- Humboldt-Universität zu Berlin
| | - V. Merk
- Humboldt-Universität zu Berlin
- Department of Chemistry
- 12489 Berlin
- Germany
- Humboldt-Universität zu Berlin
| | - V. Reiter-Scherer
- Humboldt-Universität zu Berlin
- Department of Physics & IRIS Adlershof
- 12489 Berlin
- Germany
| | - U. Gernert
- Technische Universität Berlin
- Center for Electron Microscopy (ZELMI)
- Berlin
- Germany
| | - J. P. Rabe
- Humboldt-Universität zu Berlin
- Department of Physics & IRIS Adlershof
- 12489 Berlin
- Germany
| | - J. Kneipp
- Humboldt-Universität zu Berlin
- Department of Chemistry
- 12489 Berlin
- Germany
| | - E. Kemnitz
- Humboldt-Universität zu Berlin
- Department of Chemistry
- 12489 Berlin
- Germany
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72
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Mulvihill E, van Pee K, Mari SA, Müller DJ, Yildiz Ö. Directly Observing the Lipid-Dependent Self-Assembly and Pore-Forming Mechanism of the Cytolytic Toxin Listeriolysin O. NANO LETTERS 2015; 15:6965-6973. [PMID: 26302195 DOI: 10.1021/acs.nanolett.5b02963] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Listeriolysin O (LLO) is the major virulence factor of Listeria monocytogenes and a member of the cholesterol-dependent cytolysin (CDC) family. Gram-positive pathogenic bacteria produce water-soluble CDC monomers that bind cholesterol-dependent to the lipid membrane of the attacked cell or of the phagosome, oligomerize into prepores, and insert into the membrane to form transmembrane pores. However, the mechanisms guiding LLO toward pore formation are poorly understood. Using electron microscopy and time-lapse atomic force microscopy, we show that wild-type LLO binds to membranes, depending on the presence of cholesterol and other lipids. LLO oligomerizes into arc- or slit-shaped assemblies, which merge into complete rings. All three oligomeric assemblies can form transmembrane pores, and their efficiency to form pores depends on the cholesterol and the phospholipid composition of the membrane. Furthermore, the dynamic fusion of arcs, slits, and rings into larger rings and their formation of transmembrane pores does not involve a height difference between prepore and pore. Our results reveal new insights into the pore-forming mechanism and introduce a dynamic model of pore formation by LLO and other CDC pore-forming toxins.
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Affiliation(s)
- Estefania Mulvihill
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich , Mattenstrasse 26, 4058 Basel, Switzerland
| | - Katharina van Pee
- Department of Structural Biology, Max-Planck-Institute of Biophysics , Max von Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Stefania A Mari
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich , Mattenstrasse 26, 4058 Basel, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich , Mattenstrasse 26, 4058 Basel, Switzerland
| | - Özkan Yildiz
- Department of Structural Biology, Max-Planck-Institute of Biophysics , Max von Laue Str. 3, 60438 Frankfurt am Main, Germany
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73
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Gudzenko T, Franz CM. Studying early stages of fibronectin fibrillogenesis in living cells by atomic force microscopy. Mol Biol Cell 2015. [DOI: 10.1091/mbc.e14-05-1026] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Fibronectin (FN) is an extracellular matrix protein that can be assembled by cells into large fibrillar networks, but the dynamics of FN remodeling and the transition through intermediate fibrillar stages are incompletely understood. Here we used a combination of fluorescence microscopy and time-lapse atomic force microscopy (AFM) to visualize initial stages of FN fibrillogenesis in living fibroblasts at high resolution. Initial FN nanofibrils form within <5 min of cell–matrix contact and subsequently extend at a rate of 0.25 μm/min at sites of cell membrane retraction. FN nanofibrils display a complex linear array of globular features spaced at varying distances, indicating the coexistence of different conformational states within the fibril. In some cases, initial fibrils extended in discrete increments of ∼800 nm during a series of cyclical membrane retractions, indicating a stepwise fibrillar extension mechanism. In presence of Mn2+, a known activator of integrin adhesion to FN, fibrillogenesis was accelerated almost threefold to 0.68 μm/min and fibrillar dimensions were increased, underlining the importance of integrin activation for early FN fibrillogenesis. FN fibrillogenesis visualized by time-lapse AFM thus provides new structural and mechanistic insight into initial steps of cell-driven FN fibrillogenesis.
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Affiliation(s)
- Tetyana Gudzenko
- DFG–Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Clemens M. Franz
- DFG–Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
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74
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Seghezza S, Dante S, Diaspro A, Canale C. High resolution nanomechanical characterization of multi-domain model membranes by fast Force Volume. J Mol Recognit 2015. [DOI: 10.1002/jmr.2490] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Silvia Seghezza
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
| | - Silvia Dante
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
| | - Alberto Diaspro
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
- University of Genova; Department of Physics; Genova GE Italy
| | - Claudio Canale
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
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75
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Imaging G protein-coupled receptors while quantifying their ligand-binding free-energy landscape. Nat Methods 2015; 12:845-851. [PMID: 26167642 DOI: 10.1038/nmeth.3479] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 05/29/2015] [Indexed: 11/08/2022]
Abstract
Imaging native membrane receptors and testing how they interact with ligands is of fundamental interest in the life sciences but has proven remarkably difficult to accomplish. Here, we introduce an approach that uses force-distance curve-based atomic force microscopy to simultaneously image single native G protein-coupled receptors in membranes and quantify their dynamic binding strength to native and synthetic ligands. We measured kinetic and thermodynamic parameters for individual protease-activated receptor-1 (PAR1) molecules in the absence and presence of antagonists, and these measurements enabled us to describe PAR1's ligand-binding free-energy landscape with high accuracy. Our nanoscopic method opens an avenue to directly image and characterize ligand binding of native membrane receptors.
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76
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Stoichev S, Krumova SB, Andreeva T, Busto JV, Todinova S, Balashev K, Busheva M, Goñi FM, Taneva SG. Low pH modulates the macroorganization and thermal stability of PSII supercomplexes in grana membranes. Biophys J 2015; 108:844-853. [PMID: 25692589 PMCID: PMC4336371 DOI: 10.1016/j.bpj.2014.12.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/08/2014] [Accepted: 12/22/2014] [Indexed: 11/25/2022] Open
Abstract
Protonation of the lumen-exposed residues of some photosynthetic complexes in the grana membranes occurs under conditions of high light intensity and triggers a major photoprotection mechanism known as energy dependent nonphotochemical quenching. We have studied the role of protonation in the structural reorganization and thermal stability of isolated grana membranes. The macroorganization of granal membrane fragments in protonated and partly deprotonated state has been mapped by means of atomic force microscopy. The protonation of the photosynthetic complexes has been found to induce large-scale structural remodeling of grana membranes-formation of extensive domains of the major light-harvesting complex of photosystem II and clustering of trimmed photosystem II supercomplexes, thinning of the membrane, and reduction of its size. These events are accompanied by pronounced thermal destabilization of the photosynthetic complexes, as evidenced by circular dichroism spectroscopy and differential scanning calorimetry. Our data reveal a detailed nanoscopic picture of the initial steps of nonphotochemical quenching.
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Affiliation(s)
- Svetozar Stoichev
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Sashka B Krumova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Tonya Andreeva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Jon V Busto
- Unidad de Biofísica (CSIC, UPV-EHU) and Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain
| | - Svetla Todinova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Konstantin Balashev
- Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, Sofia University "St. Kliment Ohridski," Sofia, Bulgaria
| | - Mira Busheva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Félix M Goñi
- Unidad de Biofísica (CSIC, UPV-EHU) and Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain
| | - Stefka G Taneva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria; Unidad de Biofísica (CSIC, UPV-EHU) and Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain.
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77
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Kroeger ME, Sorenson BA, Thomas JS, Stojković EA, Tsonchev S, Nicholson KT. Atomic force microscopy of red-light photoreceptors using peakforce quantitative nanomechanical property mapping. J Vis Exp 2014:e52164. [PMID: 25407118 DOI: 10.3791/52164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or "tapping mode" AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials. The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials.
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78
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Pfreundschuh M, Alsteens D, Hilbert M, Steinmetz MO, Müller DJ. Localizing chemical groups while imaging single native proteins by high-resolution atomic force microscopy. NANO LETTERS 2014; 14:2957-2964. [PMID: 24766578 DOI: 10.1021/nl5012905] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Simultaneous high-resolution imaging and localization of chemical interaction sites on single native proteins is a pertinent biophysical, biochemical, and nanotechnological challenge. Such structural mapping and characterization of binding sites is of importance in understanding how proteins interact with their environment and in manipulating such interactions in a plethora of biotechnological applications. Thus far, this challenge remains to be tackled. Here, we introduce force-distance curve-based atomic force microscopy (FD-based AFM) for the high-resolution imaging of SAS-6, a protein that self-assembles into cartwheel-like structures. Using functionalized AFM tips bearing Ni(2+)-N-nitrilotriacetate groups, we locate specific interaction sites on SAS-6 at nanometer resolution and quantify the binding strength of the Ni(2+)-NTA groups to histidine residues. The FD-based AFM approach can readily be applied to image any other native protein and to locate and structurally map histidine residues. Moreover, the surface chemistry used to functionalize the AFM tip can be modified to map other chemical interaction sites.
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Affiliation(s)
- Moritz Pfreundschuh
- Department of Biosystems Science and Engineering, ETH Zurich , Mattenstrasse 26, 4058 Basel, Switzerland
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