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Sitarska E, Almeida SD, Beckwith MS, Stopp J, Czuchnowski J, Siggel M, Roessner R, Tschanz A, Ejsing C, Schwab Y, Kosinski J, Sixt M, Kreshuk A, Erzberger A, Diz-Muñoz A. Sensing their plasma membrane curvature allows migrating cells to circumvent obstacles. Nat Commun 2023; 14:5644. [PMID: 37704612 PMCID: PMC10499897 DOI: 10.1038/s41467-023-41173-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 08/22/2023] [Indexed: 09/15/2023] Open
Abstract
To navigate through diverse tissues, migrating cells must balance persistent self-propelled motion with adaptive behaviors to circumvent obstacles. We identify a curvature-sensing mechanism underlying obstacle evasion in immune-like cells. Specifically, we propose that actin polymerization at the advancing edge of migrating cells is inhibited by the curvature-sensitive BAR domain protein Snx33 in regions with inward plasma membrane curvature. The genetic perturbation of this machinery reduces the cells' capacity to evade obstructions combined with faster and more persistent cell migration in obstacle-free environments. Our results show how cells can read out their surface topography and utilize actin and plasma membrane biophysics to interpret their environment, allowing them to adaptively decide if they should move ahead or turn away. On the basis of our findings, we propose that the natural diversity of BAR domain proteins may allow cells to tune their curvature sensing machinery to match the shape characteristics in their environment.
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Affiliation(s)
- Ewa Sitarska
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, EMBL and Heidelberg University, Heidelberg, Germany
| | - Silvia Dias Almeida
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Division of Medical Image Computing, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany
| | | | - Julian Stopp
- Institute of Science and Technology Austria, 3400, Klosterneuburg, Austria
| | - Jakub Czuchnowski
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Marc Siggel
- EMBL Hamburg, European Molecular Biology Laboratory, 22607, Hamburg, Germany
- Centre for Structural Systems Biology, 22607, Hamburg, Germany
| | - Rita Roessner
- EMBL Hamburg, European Molecular Biology Laboratory, 22607, Hamburg, Germany
- Centre for Structural Systems Biology, 22607, Hamburg, Germany
| | - Aline Tschanz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, EMBL and Heidelberg University, Heidelberg, Germany
| | - Christer Ejsing
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Department of Biochemistry and Molecular Biology, Villum Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
| | - Yannick Schwab
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Jan Kosinski
- EMBL Hamburg, European Molecular Biology Laboratory, 22607, Hamburg, Germany
- Centre for Structural Systems Biology, 22607, Hamburg, Germany
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Michael Sixt
- Institute of Science and Technology Austria, 3400, Klosterneuburg, Austria
| | - Anna Kreshuk
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Anna Erzberger
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Alba Diz-Muñoz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany.
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2
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Sankaran J, Wohland T. Fluorescence strategies for mapping cell membrane dynamics and structures. APL Bioeng 2020; 4:020901. [PMID: 32478279 PMCID: PMC7228782 DOI: 10.1063/1.5143945] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 04/17/2020] [Indexed: 12/20/2022] Open
Abstract
Fluorescence spectroscopy has been a cornerstone of research in membrane dynamics and organization. Technological advances in fluorescence spectroscopy went hand in hand with discovery of various physicochemical properties of membranes at nanometric spatial and microsecond timescales. In this perspective, we discuss the various challenges associated with quantification of physicochemical properties of membranes and how various modes of fluorescence spectroscopy have overcome these challenges to shed light on the structure and organization of membranes. Finally, we discuss newer measurement strategies and data analysis tools to investigate the structure, dynamics, and organization of membranes.
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3
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Oheim M, Salomon A, Weissman A, Brunstein M, Becherer U. Calibrating Evanescent-Wave Penetration Depths for Biological TIRF Microscopy. Biophys J 2019; 117:795-809. [PMID: 31439287 DOI: 10.1016/j.bpj.2019.07.048] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 07/08/2019] [Accepted: 07/23/2019] [Indexed: 11/28/2022] Open
Abstract
Roughly half of a cell's proteins are located at or near the plasma membrane. In this restricted space, the cell senses its environment, signals to its neighbors, and exchanges cargo through exo- and endocytotic mechanisms. Ligands bind to receptors, ions flow across channel pores, and transmitters and metabolites are transported against concentration gradients. Receptors, ion channels, pumps, and transporters are the molecular substrates of these biological processes, and they constitute important targets for drug discovery. Total internal reflection fluorescence (TIRF) microscopy suppresses the background from the cell's deeper layers and provides contrast for selectively imaging dynamic processes near the basal membrane of live cells. The optical sectioning of TIRF is based on the excitation confinement of the evanescent wave generated at the glass/cell interface. How deep the excitation light actually penetrates the sample is difficult to know, making the quantitative interpretation of TIRF data problematic. Nevertheless, many applications like superresolution microscopy, colocalization, Förster resonance energy transfer, near-membrane fluorescence recovery after photobleaching, uncaging or photoactivation/switching as well as single-particle tracking require the quantitative interpretation of evanescent-wave-excited images. Here, we review existing techniques for characterizing evanescent fields, and we provide a roadmap for comparing TIRF data across images, experiments, and laboratories.
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Affiliation(s)
- Martin Oheim
- Université de Paris, CNRS, Saints-Pères Paris Institute for the Neurosciences (SPPIN), Paris, France.
| | - Adi Salomon
- Department of Chemistry, Institute of Nanotechnology and Advanced Materials (BINA), Bar-Ilan University, Ramat Gan, Israel
| | - Adam Weissman
- Department of Chemistry, Institute of Nanotechnology and Advanced Materials (BINA), Bar-Ilan University, Ramat Gan, Israel
| | - Maia Brunstein
- Université de Paris, CNRS, Saints-Pères Paris Institute for the Neurosciences (SPPIN), Paris, France; Chaire d'Excellence Junior, Université Sorbonne Paris Cité, Paris, France
| | - Ute Becherer
- Saarland University, Department of Physiology, CIPMM, Homburg/Saar, Germany
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4
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Balleza D, Mescola A, Marín-Medina N, Ragazzini G, Pieruccini M, Facci P, Alessandrini A. Complex Phase Behavior of GUVs Containing Different Sphingomyelins. Biophys J 2019; 116:503-517. [PMID: 30665697 DOI: 10.1016/j.bpj.2018.12.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 11/28/2018] [Accepted: 12/20/2018] [Indexed: 01/06/2023] Open
Abstract
Understanding the lateral organization of biological membranes plays a key role on the road to fully appreciate the physiological functions of this fundamental barrier between the inside and outside regions of a cell. Ternary lipid bilayers composed of a high and a low melting temperature lipid and cholesterol represent a model system that mimics some of the important thermodynamical features of much more complex lipid mixtures such as those found in mammal membranes. The phase diagram of these ternary mixtures can be studied exploiting fluorescence microscopy in giant unilamellar vesicles, and it is typically expected to give rise, for specific combinations of composition and temperature, to regions of two-phase coexistence and a region with three-phase coexistence, namely, the liquid-ordered, liquid-disordered, and solid phases. Whereas the observation of two-phase coexistence is routinely possible using fluorescence microscopy, the three-phase region is more elusive to study. In this article, we show that particular lipid mixtures containing diphytanoyl-phosphatidylcholine and cholesterol plus different types of sphingomyelin (SM) are prone to produce bilayer regions with more than two levels of fluorescence intensity. We found that these intensity levels occur at low temperature and are linked to the copresence of long and asymmetric chains in SMs and diphytanoyl-phosphatidylcholine in the lipid mixtures. We discuss the possible interpretations for this observation in terms of bilayer phase organization in the presence of sphingolipids. Additionally, we also show that in some cases, liposomes in the three-phase coexistence state exhibit extreme sensitivity to lateral tension. We hypothesize that the appearance of the different phases is related to the asymmetric structure of SMs and to interdigitation effects.
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Affiliation(s)
| | | | | | - Gregorio Ragazzini
- Istituto Nanoscienze CNR, S3, Modena, Italy; Dipartimento di Scienze Fisiche, Matematiche e Informatiche, Università di Modena e Reggio Emilia, Modena, Italy
| | | | | | - Andrea Alessandrini
- Istituto Nanoscienze CNR, S3, Modena, Italy; Dipartimento di Scienze Fisiche, Matematiche e Informatiche, Università di Modena e Reggio Emilia, Modena, Italy.
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5
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Niederauer C, Blumhardt P, Mücksch J, Heymann M, Lambacher A, Schwille P. Direct characterization of the evanescent field in objective-type total internal reflection fluorescence microscopy. OPTICS EXPRESS 2018; 26:20492-20506. [PMID: 30119359 DOI: 10.1364/oe.26.020492] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 07/08/2018] [Indexed: 05/22/2023]
Abstract
Total internal reflection fluorescence (TIRF) microscopy is a commonly used method for studying fluorescently labeled molecules in close proximity to a surface. Usually, the TIRF axial excitation profile is assumed to be single-exponential with a characteristic penetration depth, governed by the incident angle of the excitation laser beam towards the optical axis. However, in practice, the excitation profile does not only comprise the theoretically predicted single-exponential evanescent field, but also an additional non-evanescent contribution, supposedly caused by scattering within the optical path or optical aberrations. We developed a calibration slide to directly characterize the TIRF excitation field. Our slide features ten height steps ranging from 25 to 550 nanometers, fabricated from a polymer with a refractive index matching that of water. Fluorophores in aqueous solution above the polymer step layers sample the excitation profile at different heights. The obtained excitation profiles confirm the theoretically predicted exponential decay over increasing step heights as well as the presence of a non-evanescent contribution.
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6
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Bondia P, Casado S, Flors C. Correlative Super-Resolution Fluorescence Imaging and Atomic Force Microscopy for the Characterization of Biological Samples. Methods Mol Biol 2017; 1663:105-113. [PMID: 28924662 DOI: 10.1007/978-1-4939-7265-4_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Recent advances in imaging tools have greatly improved our ability to analyze the structure and molecular components of a wide range of biological systems at the nanoscale. High resolution imaging can be performed with a handful of techniques, each of them revealing particular features of the sample. A more comprehensive picture of a biological system can be achieved by combining the information provided by complementary imaging methods. Specifically, the correlation between super-resolution fluorescence imaging and atomic force microscopy (AFM) provides high resolution topography as well as specific chemical information, the latter with a spatial resolution that approaches that of AFM. We present a detailed protocol and discuss the requirements and challenges in terms of sample preparation, instrumentation, and image alignment to combine these two powerful techniques. This hybrid nanoscale imaging tool has the potential to provide robust validation for super-resolution methods as well as new insight into biological samples.
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Affiliation(s)
- Patricia Bondia
- Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanoscience) and Nanobiotechnology Unit Associated to the National Center for Biotechnology (CSIC), C/ Faraday 9, Madrid, 28049, Spain
| | - Santiago Casado
- Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanoscience) and Nanobiotechnology Unit Associated to the National Center for Biotechnology (CSIC), C/ Faraday 9, Madrid, 28049, Spain
| | - Cristina Flors
- Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanoscience) and Nanobiotechnology Unit Associated to the National Center for Biotechnology (CSIC), C/ Faraday 9, Madrid, 28049, Spain.
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7
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Two-dimensional slither swimming of sperm within a micrometre of a surface. Nat Commun 2015; 6:8703. [PMID: 26555792 PMCID: PMC4667638 DOI: 10.1038/ncomms9703] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Accepted: 09/22/2015] [Indexed: 11/13/2022] Open
Abstract
Sperm motion near surfaces plays a crucial role in fertilization, but the nature of this motion has not been resolved. Using total internal reflection fluorescence microscopy, we selectively imaged motile human and bull sperm located within one micron of a surface, revealing a distinct two-dimensional (2D) ‘slither' swimming mode whereby the full cell length (50–80 μm) is confined within 1 μm of a surface. This behaviour is distinct from bulk and near-wall swimming modes where the flagellar wave is helical and the head continuously rotates. The slither mode is intermittent (∼1 s, ∼70 μm), and in human sperm, is observed only for viscosities over 20 mPa·s. Bull sperm are slower in this surface-confined swimming mode, owing to a decrease in their flagellar wave amplitude. In contrast, human sperm are ∼50% faster—suggesting a strategy that is well suited to the highly viscous and confined lumen within the human fallopian tube. Sperm motion near surfaces plays a key role in fertilization, but a description of how this motion differs from bulk swimming is lacking. Here, Nosrati et al. visualize sperm swimming within 1 μm of a glass surface and describe a ‘slither' swimming mode which differs from bulk helical swimming, and increases the velocity of human sperm.
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8
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The proapoptotic protein tBid forms both superficially bound and membrane-inserted oligomers. Biophys J 2014; 106:2085-95. [PMID: 24853737 DOI: 10.1016/j.bpj.2014.03.049] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 03/13/2014] [Accepted: 03/31/2014] [Indexed: 11/22/2022] Open
Abstract
Bid is a proapopotic activator protein of the Bcl-2 family that plays a pivotal role in controlling mitochondrial outer membrane permeabilization during apoptosis. Here, we characterized the interaction of fluorescently labeled truncated Bid (tBid) with a mitochondria-like supported lipid bilayer at the single-molecule level. The proteins observed at the membrane exhibited a very wide range of mobility. Confocal images of the membrane displayed both diffraction-limited Gaussian spots and horizontal streaks, corresponding to immobile and mobile tBid species, respectively. We observed 1), fast-diffusing proteins corresponding to a loosely, probably electrostatically bound state; 2), slowly diffusing proteins, likely corresponding to a superficially inserted state; and 3), fully immobilized proteins, suggesting a fully inserted state. The stoichiometry of these proteins was determined by normalizing their fluorescence intensity by the brightness of a tBid monomer, measured separately using fluorescence fluctuation techniques. Strikingly, the immobile species were found to be mainly tetramers and higher, whereas the mobile species had on average a significantly lower stoichiometry. Taken together, these results show that as soluble Bid progresses toward a membrane-inserted state, it undergoes an oligomerization process similar to that observed for Bax.
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9
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Matysik A, Kraut RS. Preparation of mica supported lipid bilayers for high resolution optical microscopy imaging. J Vis Exp 2014. [PMID: 24961277 DOI: 10.3791/52054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Supported lipid bilayers (SLBs) are widely used as a model for studying membrane properties (phase separation, clustering, dynamics) and its interaction with other compounds, such as drugs or peptides. However SLB characteristics differ depending on the support used. Commonly used techniques for SLB imaging and measurements are single molecule fluorescence microscopy, FCS and atomic force microscopy (AFM). Because most optical imaging studies are carried out on a glass support, while AFM requires an extremely flat surface (generally mica), results from these techniques cannot be compared directly, since the charge and smoothness properties of these materials strongly influence diffusion. Unfortunately, the high level of manual dexterity required for the cutting and gluing thin slices of mica to the glass slide presents a hurdle to routine use of mica for SLB preparation. Although this would be the method of choice, such prepared mica surfaces often end up being uneven (wavy) and difficult to image, especially with small working distance, high numerical aperture lenses. Here we present a simple and reproducible method for preparing thin, flat mica surfaces for lipid vesicle deposition and SLB preparation. Additionally, our custom made chamber requires only very small volumes of vesicles for SLB formation. The overall procedure results in the efficient, simple and inexpensive production of high quality lipid bilayer surfaces that are directly comparable to those used in AFM studies.
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Affiliation(s)
- Artur Matysik
- School of Biological Sciences, Nanyang Technological University;
| | - Rachel S Kraut
- School of Biological Sciences, Nanyang Technological University
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10
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Monserrate A, Casado S, Flors C. Correlative Atomic Force Microscopy and Localization-Based Super-Resolution Microscopy: Revealing Labelling and Image Reconstruction Artefacts. Chemphyschem 2013; 15:647-50. [DOI: 10.1002/cphc.201300853] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Indexed: 11/10/2022]
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11
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Ramachandran S, Cohen DA, Quist AP, Lal R. High performance, LED powered, waveguide based total internal reflection microscopy. Sci Rep 2013; 3:2133. [PMID: 23823601 PMCID: PMC3701166 DOI: 10.1038/srep02133] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 06/13/2013] [Indexed: 11/16/2022] Open
Abstract
Total internal reflection fluorescence (TIRF) microscopy is a rapidly expanding optical technique with excellent surface sensitivity and limited background fluorescence. Commercially available TIRF systems are either objective based that employ expensive special high numerical aperture (NA) objectives or prism based that restrict integrating other modalities of investigation for structure-function analysis. Both techniques result in uneven illumination of the field of view and require training and experience in optics. Here we describe a novel, inexpensive, LED powered, waveguide based TIRF system that could be used as an add-on module to any standard fluorescence microscope even with low NA objectives. This system requires no alignment, illuminates the entire field evenly, and allows switching between epifluorescence/TIRF/bright field modes without adjustments or objective replacements. The simple design allows integration with other imaging systems, including atomic force microscopy (AFM), for probing complex biological systems at their native nanoscale regimes.
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Affiliation(s)
- Srinivasan Ramachandran
- University of California San Diego, Department of Mechanical and Aerospace Engineering, La Jolla, CA 92093, USA.
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12
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Yip CM. Correlative optical and scanning probe microscopies for mapping interactions at membranes. Methods Mol Biol 2013; 950:439-56. [PMID: 23086889 DOI: 10.1007/978-1-62703-137-0_24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Innovative approaches for real-time imaging on molecular-length scales are providing researchers with powerful strategies for characterizing molecular and cellular structures and dynamics. Combinatorial techniques that integrate two or more distinct imaging modalities are particularly compelling as they provide a means for overcoming the limitations of the individual modalities and, when applied simultaneously, enable the collection of rich multi-modal datasets. Almost since its inception, scanning probe microscopy has closely associated with optical microscopy. This is particularly evident in the fields of cellular and molecular biophysics where researchers are taking full advantage of these real-time, in situ, tools to acquire three-dimensional molecular-scale topographical images with nanometer resolution, while simultaneously characterizing their structure and interactions though conventional optical microscopy. The ability to apply mechanical or optical stimuli provides an additional experimental dimension that has shown tremendous promise for examining dynamic events on sub-cellular length scales. In this chapter, we describe recent efforts in developing these integrated platforms, the methodology for, and inherent challenges in, performing coupled imaging experiments, and the potential and future opportunities of these research tools for the fields of molecular and cellular biophysics with a specific emphasis on the application of these coupled approaches for the characterization of interactions occurring at membrane interfaces.
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Affiliation(s)
- Christopher M Yip
- Department of Chemical Engineering and Applied Chemistry, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada.
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13
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Last JA, Russell P, Nealey PF, Murphy CJ. The applications of atomic force microscopy to vision science. Invest Ophthalmol Vis Sci 2011; 51:6083-94. [PMID: 21123767 DOI: 10.1167/iovs.10-5470] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The atomic force microscope (AFM) is widely used in materials science and has found many applications in biological sciences but has been limited in use in vision science. The AFM can be used to image the topography of soft biological materials in their native environments. It can also be used to probe the mechanical properties of cells and extracellular matrices, including their intrinsic elastic modulus and receptor-ligand interactions. In this review, the operation of the AFM is described along with a review of how it has been thus far used in vision science. It is hoped that this review will serve to stimulate vision scientists to consider incorporating AFM as part of their research toolkit.
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Affiliation(s)
- Julie A Last
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
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14
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Oreopoulos J, Epand RF, Epand RM, Yip CM. Peptide-induced domain formation in supported lipid bilayers: direct evidence by combined atomic force and polarized total internal reflection fluorescence microscopy. Biophys J 2010; 98:815-23. [PMID: 20197035 DOI: 10.1016/j.bpj.2009.12.4327] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 11/25/2009] [Accepted: 12/09/2009] [Indexed: 12/01/2022] Open
Abstract
Direct visualization of the mechanism(s) by which peptides induce localized changes to the structure of membranes has high potential for enabling understanding of the structure-function relationship in antimicrobial and cell-penetrating peptides. We have applied a combined imaging strategy to track the interaction of a model antimicrobial peptide, PFWRIRIRR-amide, with bacterial membrane-mimetic supported phospholipid bilayers comprised of POPE/TOCL. Our in situ studies revealed rapid reorganization of the POPE/TOCL membrane into localized TOCL-rich domains with a concomitant change in the organization of the membranes themselves, as reflected by changes in fluorescent-membrane-probe order parameter, upon introduction of the peptide.
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Affiliation(s)
- John Oreopoulos
- Institute of Biomaterials and Biomedical Engineering, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Ontario, Canada
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15
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Abstract
Atomic force microscopy (AFM) is a powerful tool for microbiological investigation. This versatile technique cannot only image cellular surfaces at high resolution, but also measure many forms of fundamental interactions over scales ranging from molecules to cells. In this work, we review the recent development of AFM applications in the microbial area. We discuss several approaches for using AFM scanning images to investigate morphological characteristics of microbes and the use of force-distance curves to investigate interaction of microbial samples at the nanometer and cellular levels. Complementary techniques used in combination with AFM for study of microbes are also discussed.
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Affiliation(s)
- Shaoyang Liu
- Biosystems Engineering Department, Auburn University, Auburn, Alabama 36849-5417, USA
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16
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Single-photon atomic force microscopy. Anal Bioanal Chem 2010; 397:987-90. [PMID: 20066528 DOI: 10.1007/s00216-009-3426-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2009] [Revised: 12/16/2009] [Accepted: 12/17/2009] [Indexed: 10/20/2022]
Abstract
In the last few years, an array of novel technologies, especially the big family of scanning probe microscopy, now often integrated with other powerful imaging tools such as laser confocal microscopy and total internal reflection fluorescence microscopy, have been widely applied in the investigation of biomolecular interactions and dynamics. But it is still a great challenge to directly monitor the dynamics of biomolecular interactions with high spatial and temporal resolution in living cells. An innovative method termed "single-photon atomic force microscopy" (SP-AFM), superior to existing techniques in tracing biomolecular interactions and dynamics in vivo, was proposed on the basis of the combination of atomic force microscopy with the technologies of carbon nanotubes and single-photon detection. As a unique tool, SP-AFM, capable of simultaneous topography imaging and molecular identification at the subnanometer level by synchronous acquisitions and analyses of the surface topography and fluorescent optical signals while scanning the sample, could play a very important role in exploring biomolecular interactions and dynamics in living cells or in a complicated biomolecular background.
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17
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Oreopoulos J, Yip CM. Combinatorial microscopy for the study of protein–membrane interactions in supported lipid bilayers: Order parameter measurements by combined polarized TIRFM/AFM. J Struct Biol 2009; 168:21-36. [DOI: 10.1016/j.jsb.2009.02.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 02/23/2009] [Accepted: 02/24/2009] [Indexed: 02/06/2023]
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