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Tanaka Y, Fujimoto K. Dual-Arm Visuo-Haptic Optical Tweezers for Bimanual Cooperative Micromanipulation of Nonspherical Objects. MICROMACHINES 2022; 13:1830. [PMID: 36363851 PMCID: PMC9695214 DOI: 10.3390/mi13111830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/19/2022] [Accepted: 10/23/2022] [Indexed: 06/16/2023]
Abstract
Cooperative manipulation through dual-arm robots is widely implemented to perform precise and dexterous tasks to ensure automation; however, the implementation of cooperative micromanipulation through dual-arm optical tweezers is relatively rare in biomedical laboratories. To enable the bimanual and dexterous cooperative handling of a nonspherical object in microscopic workspaces, we present a dual-arm visuo-haptic optical tweezer system with two trapped microspheres, which are commercially available end-effectors, to realize indirect micromanipulation. By combining the precise correction technique of distortions in scanning optical tweezers and computer vision techniques, our dual-arm system allows a user to perceive the real contact forces during the cooperative manipulation of an object. The system enhances the dexterity of bimanual micromanipulation by employing the real-time representation of the forces and their directions. As a proof of concept, we demonstrate the cooperative indirect micromanipulation of single nonspherical objects, specifically, a glass fragment and a large diatom. Moreover, the precise correction method of the scanning optical tweezers is described. The unique capabilities offered by the proposed dual-arm visuo-haptic system can facilitate research on biomedical materials and single-cells under an optical microscope.
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2
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Optical tweezers integrated surface plasmon resonance holographic microscopy for characterizing cell-substrate interactions under noninvasive optical force stimuli. Biosens Bioelectron 2022; 206:114131. [DOI: 10.1016/j.bios.2022.114131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 02/10/2022] [Accepted: 02/22/2022] [Indexed: 11/23/2022]
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3
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Askari M, Kirkpatrick BC, Čižmár T, Di Falco A. All-optical manipulation of photonic membranes. OPTICS EXPRESS 2021; 29:14260-14268. [PMID: 33985149 DOI: 10.1364/oe.420364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 04/17/2021] [Indexed: 06/12/2023]
Abstract
We demonstrate the all-optical manipulation of polymeric membranes in microfluidic environments. The membranes are decorated with handles for their use in holographic optical tweezers systems. Our results show that due to their form factor the membranes present a substantial increase in their mechanical stability, respect to micrometric dielectric particles. This intrinsic superior stability is expected to improve profoundly a wide range of bio-photonic applications that rely on the optical manipulation of micrometric objects.
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4
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Morshed A, Karawdeniya BI, Bandara Y, Kim MJ, Dutta P. Mechanical characterization of vesicles and cells: A review. Electrophoresis 2020; 41:449-470. [PMID: 31967658 PMCID: PMC7567447 DOI: 10.1002/elps.201900362] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 12/05/2019] [Accepted: 12/08/2019] [Indexed: 12/30/2022]
Abstract
Vesicles perform many essential functions in all living organisms. They respond like a transducer to mechanical stress in converting the applied force into mechanical and biological responses. At the same time, both biochemical and biophysical signals influence the vesicular response in bearing mechanical loads. In recent years, liposomes, artificial lipid vesicles, have gained substantial attention from the pharmaceutical industry as a prospective drug carrier which can also serve as an artificial cell-mimetic system. The ability of these vesicles to enter through pores of even smaller size makes them ideal candidates for therapeutic agents to reach the infected sites effectively. Engineering of vesicles with desired mechanical properties that can encapsulate drugs and release as required is the prime challenge in this field. This requirement has led to the modifications of the composition of the bilayer membrane by adding cholesterol, sphingomyelin, etc. In this article, we review the manufacturing and characterization techniques of various artificial/synthetic vesicles. We particularly focus on the electric field-driven characterization techniques to determine different properties of vesicle and its membranes, such as bending rigidity, viscosity, capacitance, conductance, etc., which are indicators of their content and mobility. Similarities and differences between artificial vesicles, natural vesicles, and cells are highlighted throughout the manuscript since most of these artificial vesicles are intended for cell mimetic functions.
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Affiliation(s)
- Adnan Morshed
- School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
| | - Buddini Iroshika Karawdeniya
- Department of Mechanical Engineering, Lyle School of Engineering, Southern Methodist University, Dallas, Texas, USA
| | - Y.M.NuwanD.Y. Bandara
- Department of Mechanical Engineering, Lyle School of Engineering, Southern Methodist University, Dallas, Texas, USA
| | - Min Jun Kim
- Department of Mechanical Engineering, Lyle School of Engineering, Southern Methodist University, Dallas, Texas, USA
| | - Prashanta Dutta
- School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
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5
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Ungai-Salánki R, Peter B, Gerecsei T, Orgovan N, Horvath R, Szabó B. A practical review on the measurement tools for cellular adhesion force. Adv Colloid Interface Sci 2019; 269:309-333. [PMID: 31128462 DOI: 10.1016/j.cis.2019.05.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 05/05/2019] [Accepted: 05/06/2019] [Indexed: 01/03/2023]
Abstract
Cell-cell and cell-matrix adhesions are fundamental in all multicellular organisms. They play a key role in cellular growth, differentiation, pattern formation and migration. Cell-cell adhesion is substantial in the immune response, pathogen-host interactions, and tumor development. The success of tissue engineering and stem cell implantations strongly depends on the fine control of live cell adhesion on the surface of natural or biomimetic scaffolds. Therefore, the quantitative and precise measurement of the adhesion strength of living cells is critical, not only in basic research but in modern technologies, too. Several techniques have been developed or are under development to quantify cell adhesion. All of them have their pros and cons, which has to be carefully considered before the experiments and interpretation of the recorded data. Current review provides a guide to choose the appropriate technique to answer a specific biological question or to complete a biomedical test by measuring cell adhesion.
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6
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Gerena E, Regnier S, Haliyo S. High-Bandwidth 3-D Multitrap Actuation Technique for 6-DoF Real-Time Control of Optical Robots. IEEE Robot Autom Lett 2019. [DOI: 10.1109/lra.2019.2892393] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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7
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Català F, Marsà F, Montes-Usategui M, Farré A, Martín-Badosa E. Influence of experimental parameters on the laser heating of an optical trap. Sci Rep 2017; 7:16052. [PMID: 29167481 PMCID: PMC5700206 DOI: 10.1038/s41598-017-15904-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 11/01/2017] [Indexed: 01/06/2023] Open
Abstract
In optical tweezers, heating of the sample due to absorption of the laser light is a major concern as temperature plays an important role at microscopic scale. A popular rule of thumb is to consider that, at the typical wavelength of 1064 nm, the focused laser induces a heating rate of B = 1 °C/100 mW. We analysed this effect under different routine experimental conditions and found a remarkable variability in the temperature increase. Importantly, we determined that temperature can easily rise by as much as 4 °C at a relatively low power of 100 mW, for dielectric, non-absorbing particles with certain sets of specific, but common, parameters. Heating was determined from measurements of light momentum changes under drag forces at different powers, which proved to provide precise and robust results in watery buffers. We contrasted the experiments with computer simulations and obtained good agreement. These results suggest that this remarkable heating could be responsible for changes in the sample under study and could lead to serious damage of live specimens. It is therefore advisable to determine the temperature increase in each specific experiment and avoid the use of a universal rule that could inadvertently lead to critical changes in the sample.
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Affiliation(s)
- Frederic Català
- Optical Trapping Lab - Grup de Biofotònica, Departament de Física Aplicada, Universitat de Barcelona, Martí i Franquès 1, Barcelona, 08028, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Martí i Franquès 1, Barcelona, 08028, Spain
| | - Ferran Marsà
- Institut de Nanociència i Nanotecnologia (IN2UB), Martí i Franquès 1, Barcelona, 08028, Spain
- Impetux Optics S. L., Trias i Giró 15 1-5, Barcelona, 08034, Spain
| | - Mario Montes-Usategui
- Optical Trapping Lab - Grup de Biofotònica, Departament de Física Aplicada, Universitat de Barcelona, Martí i Franquès 1, Barcelona, 08028, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Martí i Franquès 1, Barcelona, 08028, Spain
- Impetux Optics S. L., Trias i Giró 15 1-5, Barcelona, 08034, Spain
| | - Arnau Farré
- Institut de Nanociència i Nanotecnologia (IN2UB), Martí i Franquès 1, Barcelona, 08028, Spain
- Impetux Optics S. L., Trias i Giró 15 1-5, Barcelona, 08034, Spain
| | - Estela Martín-Badosa
- Optical Trapping Lab - Grup de Biofotònica, Departament de Física Aplicada, Universitat de Barcelona, Martí i Franquès 1, Barcelona, 08028, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Martí i Franquès 1, Barcelona, 08028, Spain.
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8
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Bezryadina A, Li J, Zhao J, Kothambawala A, Ponsetto J, Huang E, Wang J, Liu Z. Localized plasmonic structured illumination microscopy with an optically trapped microlens. NANOSCALE 2017; 9:14907-14912. [PMID: 28949360 DOI: 10.1039/c7nr03654j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Localized plasmonic structured illumination microscopy (LPSIM) is a recently developed super resolution technique that demonstrates immense potential via arrays of localized plasmonic antennas. Microlens microscopy represents another distinct approach for improving resolution by introducing a spherical lens with a large refractive index to boost the effective numerical aperture of the imaging system. In this paper, we bridge together the LPSIM and optically trapped spherical microlenses, for the first time, to demonstrate a new super resolution technique for surface imaging. By trapping and moving polystyrene and TiO2 microspheres with optical tweezers on top of a LPSIM substrate, the new imaging system has achieved a higher NA and improved resolution.
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Affiliation(s)
- Anna Bezryadina
- Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA.
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9
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Welte MA, Gould AP. Lipid droplet functions beyond energy storage. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1260-1272. [PMID: 28735096 PMCID: PMC5595650 DOI: 10.1016/j.bbalip.2017.07.006] [Citation(s) in RCA: 331] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/17/2017] [Accepted: 07/17/2017] [Indexed: 02/07/2023]
Abstract
Lipid droplets are cytoplasmic organelles that store neutral lipids and are critically important for energy metabolism. Their function in energy storage is firmly established and increasingly well characterized. However, emerging evidence indicates that lipid droplets also play important and diverse roles in the cellular handling of lipids and proteins that may not be directly related to energy homeostasis. Lipid handling roles of droplets include the storage of hydrophobic vitamin and signaling precursors, and the management of endoplasmic reticulum and oxidative stress. Roles of lipid droplets in protein handling encompass functions in the maturation, storage, and turnover of cellular and viral polypeptides. Other potential roles of lipid droplets may be connected with their intracellular motility and, in some cases, their nuclear localization. This diversity highlights that lipid droplets are very adaptable organelles, performing different functions in different biological contexts. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY, United States.
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10
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Extending calibration-free force measurements to optically-trapped rod-shaped samples. Sci Rep 2017; 7:42960. [PMID: 28220855 PMCID: PMC5318951 DOI: 10.1038/srep42960] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/17/2017] [Indexed: 12/14/2022] Open
Abstract
Optical trapping has become an optimal choice for biological research at the microscale due to its non-invasive performance and accessibility for quantitative studies, especially on the forces involved in biological processes. However, reliable force measurements depend on the calibration of the optical traps, which is different for each experiment and hence requires high control of the local variables, especially of the trapped object geometry. Many biological samples have an elongated, rod-like shape, such as chromosomes, intracellular organelles (e.g., peroxisomes), membrane tubules, certain microalgae, and a wide variety of bacteria and parasites. This type of samples often requires several optical traps to stabilize and orient them in the correct spatial direction, making it more difficult to determine the total force applied. Here, we manipulate glass microcylinders with holographic optical tweezers and show the accurate measurement of drag forces by calibration-free direct detection of beam momentum. The agreement between our results and slender-body hydrodynamic theoretical calculations indicates potential for this force-sensing method in studying protracted, rod-shaped specimens.
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11
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Asbury CL. Anaphase A: Disassembling Microtubules Move Chromosomes toward Spindle Poles. BIOLOGY 2017; 6:E15. [PMID: 28218660 PMCID: PMC5372008 DOI: 10.3390/biology6010015] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/04/2017] [Accepted: 02/10/2017] [Indexed: 11/16/2022]
Abstract
The separation of sister chromatids during anaphase is the culmination of mitosis and one of the most strikingly beautiful examples of cellular movement. It consists of two distinct processes: Anaphase A, the movement of chromosomes toward spindle poles via shortening of the connecting fibers, and anaphase B, separation of the two poles from one another via spindle elongation. I focus here on anaphase A chromosome-to-pole movement. The chapter begins by summarizing classical observations of chromosome movements, which support the current understanding of anaphase mechanisms. Live cell fluorescence microscopy studies showed that poleward chromosome movement is associated with disassembly of the kinetochore-attached microtubule fibers that link chromosomes to poles. Microtubule-marking techniques established that kinetochore-fiber disassembly often occurs through loss of tubulin subunits from the kinetochore-attached plus ends. In addition, kinetochore-fiber disassembly in many cells occurs partly through 'flux', where the microtubules flow continuously toward the poles and tubulin subunits are lost from minus ends. Molecular mechanistic models for how load-bearing attachments are maintained to disassembling microtubule ends, and how the forces are generated to drive these disassembly-coupled movements, are discussed.
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Affiliation(s)
- Charles L Asbury
- Department of Physiology & Biophysics, University of Washington, Seattle, WA 98195, USA.
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12
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Liu X, Huang J, Zhang Y, Li B. Optical regulation of cell chain. Sci Rep 2015; 5:11578. [PMID: 26098707 PMCID: PMC4476432 DOI: 10.1038/srep11578] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/29/2015] [Indexed: 01/09/2023] Open
Abstract
Formation of cell chains is a straightforward and efficient method to study the cell interaction. By regulating the contact sequence and interaction distance, the influence of different extracellular cues on the cell interaction can be investigated. However, it faces great challenges in stable retaining and precise regulation of cell chain, especially in cell culture with relatively low cell concentration. Here we demonstrated an optical method to realize the precise regulation of cell chain, including removing or adding a single cell, adjusting interaction distance, and changing cell contact sequence. After injecting a 980-nm wavelength laser beam into a tapered optical fiber probe (FP), a cell chain of Escherichia colis (E. colis) is formed under the optical gradient force. By manipulating another FP close to the cell chain, a targeted E. coli cell can be trapped by the FP and removed from the chain. Further, the targeted cell can be added back to the chain at different positions to change the cell contact sequence. The experiments were interpreted by numerical simulations and the impact of cell sizes and shapes on this method was analyzed.
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Affiliation(s)
- Xiaoshuai Liu
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Jianbin Huang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Yao Zhang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Baojun Li
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
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13
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14
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Li Y, Xin H, Liu X, Li B. Non-contact intracellular binding of chloroplasts in vivo. Sci Rep 2015; 5:10925. [PMID: 26043396 PMCID: PMC4455249 DOI: 10.1038/srep10925] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 05/08/2015] [Indexed: 12/12/2022] Open
Abstract
Non-contact intracellular binding and controllable manipulation of chloroplasts in vivo was demonstrated using an optical fiber probe. Launching a 980-nm laser beam into a fiber, which was placed about 3 μm above the surface of a living plant (Hydrilla verticillata) leaf, enabled stable binding of different numbers of chloroplasts, as well as their arrangement into one-dimensional chains and two-dimensional arrays inside the leaf without damaging the chloroplasts. Additionally, the formed chloroplast chains were controllably transported inside the living cells. The optical force exerted on the chloroplasts was calculated to explain the experimental results. This method provides a flexible method for studying intracellular organelle interaction with highly organized organelle-organelle contact in vivo in a non-contact manner.
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Affiliation(s)
- Yuchao Li
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Hongbao Xin
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xiaoshuai Liu
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Baojun Li
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
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15
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Welte MA. As the fat flies: The dynamic lipid droplets of Drosophila embryos. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1156-85. [PMID: 25882628 DOI: 10.1016/j.bbalip.2015.04.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/31/2015] [Accepted: 04/06/2015] [Indexed: 01/09/2023]
Abstract
Research into lipid droplets is rapidly expanding, and new cellular and organismal roles for these lipid-storage organelles are continually being discovered. The early Drosophila embryo is particularly well suited for addressing certain questions in lipid-droplet biology and combines technical advantages with unique biological phenomena. This review summarizes key features of this experimental system and the techniques available to study it, in order to make it accessible to researchers outside this field. It then describes the two topics most heavily studied in this system, lipid-droplet motility and protein sequestration on droplets, discusses what is known about the molecular players involved, points to open questions, and compares the results from Drosophila embryo studies to what it is known about lipid droplets in other systems.
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Affiliation(s)
- Michael A Welte
- Department of Biology University of Rochester, RC Box 270211, 317 Hutchison Hall, Rochester, NY 14627, USA.
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16
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Calibration of optical tweezers for in vivo force measurements: how do different approaches compare? Biophys J 2015; 107:1474-84. [PMID: 25229154 DOI: 10.1016/j.bpj.2014.07.033] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 07/07/2014] [Accepted: 07/15/2014] [Indexed: 12/29/2022] Open
Abstract
There is significant interest in quantifying force production inside cells, but since conditions in vivo are less well controlled than those in vitro, in vivo measurements are challenging. In particular, the in vivo environment may vary locally as far as its optical properties, and the organelles manipulated by the optical trap frequently vary in size and shape. Several methods have been proposed to overcome these difficulties. We evaluate the relative merits of these methods and directly compare two of them, a refractive index matching method, and a light-momentum-change method. Since in vivo forces are frequently relatively high (e.g., can exceed 15 pN for lipid droplets), a high-power laser is employed. We discover that this high-powered trap induces local temperature changes, and we develop an approach to compensate for uncertainties in the magnitude of applied force due to such temperature variations.
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17
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Stellamanns E, Uppaluri S, Hochstetter A, Heddergott N, Engstler M, Pfohl T. Optical trapping reveals propulsion forces, power generation and motility efficiency of the unicellular parasites Trypanosoma brucei brucei. Sci Rep 2014; 4:6515. [PMID: 25269514 PMCID: PMC4180810 DOI: 10.1038/srep06515] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 09/12/2014] [Indexed: 12/01/2022] Open
Abstract
Unicellular parasites have developed sophisticated swimming mechanisms to survive in a wide range of environments. Cell motility of African trypanosomes, parasites responsible for fatal illness in humans and animals, is crucial both in the insect vector and the mammalian host. Using millisecond-scale imaging in a microfluidics platform along with a custom made optical trap, we are able to confine single cells to study trypanosome motility. From the trapping characteristics of the cells, we determine the propulsion force generated by cells with a single flagellum as well as of dividing trypanosomes with two fully developed flagella. Estimates of the dissipative energy and the power generation of single cells obtained from the motility patterns of the trypanosomes within the optical trap indicate that specific motility characteristics, in addition to locomotion, may be required for antibody clearance. Introducing a steerable second optical trap we could further measure the force, which is generated at the flagellar tip. Differences in the cellular structure of the trypanosomes are correlated with the trapping and motility characteristics and in consequence with their propulsion force, dissipative energy and power generation.
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Affiliation(s)
- Eric Stellamanns
- 1] Department of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen, Germany [2]
| | - Sravanti Uppaluri
- 1] Department of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen, Germany [2]
| | - Axel Hochstetter
- Department of Chemistry, University of Basel, 4056 Basel, Switzerland
| | - Niko Heddergott
- Department of Cell and Developmental Biology, Biocentre, University of Würzburg, 97074 Würzburg, Germany
| | - Markus Engstler
- Department of Cell and Developmental Biology, Biocentre, University of Würzburg, 97074 Würzburg, Germany
| | - Thomas Pfohl
- 1] Department of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen, Germany [2] Department of Chemistry, University of Basel, 4056 Basel, Switzerland
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18
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Pang Y, Song H, Kim JH, Hou X, Cheng W. Optical trapping of individual human immunodeficiency viruses in culture fluid reveals heterogeneity with single-molecule resolution. NATURE NANOTECHNOLOGY 2014; 9:624-30. [PMID: 25038779 PMCID: PMC4125448 DOI: 10.1038/nnano.2014.140] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 06/12/2014] [Indexed: 05/22/2023]
Abstract
Optical tweezers use the momentum of photons to trap and manipulate microscopic objects, contact-free, in three dimensions. Although this technique has been widely used in biology and nanotechnology to study molecular motors, biopolymers and nanostructures, its application to study viruses has been very limited, largely due to their small size. Here, using optical tweezers that can simultaneously resolve two-photon fluorescence at the single-molecule level, we show that individual HIV-1 viruses can be optically trapped and manipulated, allowing multi-parameter analysis of single virions in culture fluid under native conditions. We show that individual HIV-1 differs in the numbers of envelope glycoproteins by more than one order of magnitude, which implies substantial heterogeneity of these virions in transmission and infection at the single-particle level. Analogous to flow cytometry for cells, this fluid-based technique may allow ultrasensitive detection, multi-parameter analysis and sorting of viruses and other nanoparticles in biological fluid with single-molecule resolution.
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Affiliation(s)
| | | | | | | | - Wei Cheng
- Corresponding author: University of Michigan, 428 Church Street, Ann Arbor, MI 48109-1065, Tel: (734) 763-3709, Fax: (734) 615-6162,
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López-Quesada C, Fontaine AS, Farré A, Joseph M, Selva J, Egea G, Ludevid MD, Martín-Badosa E, Montes-Usategui M. Artificially-induced organelles are optimal targets for optical trapping experiments in living cells. BIOMEDICAL OPTICS EXPRESS 2014; 5:1993-2008. [PMID: 25071944 PMCID: PMC4102344 DOI: 10.1364/boe.5.001993] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 05/24/2014] [Accepted: 05/25/2014] [Indexed: 05/24/2023]
Abstract
Optical trapping supplies information on the structural, kinetic or rheological properties of inner constituents of the cell. However, the application of significant forces to intracellular objects is notoriously difficult due to a combination of factors, such as the small difference between the refractive indices of the target structures and the cytoplasm. Here we discuss the possibility of artificially inducing the formation of spherical organelles in the endoplasmic reticulum, which would contain densely packed engineered proteins, to be used as optimized targets for optical trapping experiments. The high index of refraction and large size of our organelles provide a firm grip for optical trapping and thereby allow us to exert large forces easily within safe irradiation limits. This has clear advantages over alternative probes, such as subcellular organelles or internalized synthetic beads.
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Affiliation(s)
- C. López-Quesada
- Optical Trapping Lab – Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - A.-S. Fontaine
- Optical Trapping Lab – Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - A. Farré
- Optical Trapping Lab – Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - M. Joseph
- Department of Molecular Genetics, Center for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), 08193 Barcelona, Spain
| | - J. Selva
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Facultat de Medicina, Universitat de Barcelona and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), U. de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - G. Egea
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Facultat de Medicina, Universitat de Barcelona and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), U. de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - M. D. Ludevid
- Department of Molecular Genetics, Center for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), 08193 Barcelona, Spain
| | - E. Martín-Badosa
- Optical Trapping Lab – Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), U. de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - M. Montes-Usategui
- Optical Trapping Lab – Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), U. de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
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20
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Lipid droplets purified from Drosophila embryos as an endogenous handle for precise motor transport measurements. Biophys J 2014; 105:1182-91. [PMID: 24010661 DOI: 10.1016/j.bpj.2013.07.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 07/09/2013] [Accepted: 07/11/2013] [Indexed: 12/26/2022] Open
Abstract
Molecular motor proteins are responsible for long-range transport of vesicles and organelles. Recent works have elucidated the richness of the transport complex, with multiple teams of similar and dissimilar motors and their cofactors attached to individual cargoes. The interaction among these different proteins, and with the microtubules along which they translocate, results in the intricate patterns of cargo transport observed in cells. High-precision and high-bandwidth measurements are required to capture the dynamics of these interactions, yet the crowdedness in the cell necessitates performing such measurements in vitro. Here, we show that endogenous cargoes, lipid droplets purified from Drosophila embryos, can be used to perform high-precision and high-bandwidth optical trapping experiments to study motor regulation in vitro. Purified droplets have constituents of the endogenous transport complex attached to them and exhibit long-range motility. A novel method to determine the quality of the droplets for high-resolution measurements in an optical trap showed that they compare well with plastic beads in terms of roundness, homogeneity, position sensitivity, and trapping stiffness. Using high-resolution and high-bandwidth position measurements, we demonstrate that we can follow the series of binding and unbinding events that lead to the onset of active transport.
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21
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Nicholas MP, Rao L, Gennerich A. An improved optical tweezers assay for measuring the force generation of single kinesin molecules. Methods Mol Biol 2014; 1136:171-246. [PMID: 24633799 PMCID: PMC4254714 DOI: 10.1007/978-1-4939-0329-0_10] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Numerous microtubule-associated molecular motors, including several kinesins and cytoplasmic dynein, produce opposing forces that regulate spindle and chromosome positioning during mitosis. The motility and force generation of these motors are therefore critical to normal cell division, and dysfunction of these processes may contribute to human disease. Optical tweezers provide a powerful method for studying the nanometer motility and piconewton force generation of single motor proteins in vitro. Using kinesin-1 as a prototype, we present a set of step-by-step, optimized protocols for expressing a kinesin construct (K560-GFP) in Escherichia coli, purifying it, and studying its force generation in an optical tweezers microscope. We also provide detailed instructions on proper alignment and calibration of an optical trapping microscope. These methods provide a foundation for a variety of similar experiments.
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Affiliation(s)
- Matthew P Nicholas
- Department of Anatomy and Structural Biology, Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10461, USA
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22
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Teamwork in microtubule motors. Trends Cell Biol 2013; 23:575-82. [PMID: 23877011 DOI: 10.1016/j.tcb.2013.06.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 06/11/2013] [Accepted: 06/17/2013] [Indexed: 01/10/2023]
Abstract
Diverse cellular processes are driven by the collective force from multiple motor proteins. Disease-causing mutations cause aberrant function of motors, but the impact is observed at a cellular level and beyond, therefore necessitating an understanding of cell mechanics at the level of motor molecules. One way to do this is by measuring the force generated by ensembles of motors in vivo at single-motor resolution. This has been possible for microtubule motor teams that transport intracellular organelles, revealing unexpected differences between collective and single-molecule function. Here we review how the biophysical properties of single motors, and differences therein, may translate into collective motor function during organelle transport and perhaps in other processes outside transport.
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23
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Mas J, Richardson AC, Reihani SNS, Oddershede LB, Berg-Sørensen K. Quantitative determination of optical trapping strength and viscoelastic moduli inside living cells. Phys Biol 2013; 10:046006. [PMID: 23820071 DOI: 10.1088/1478-3975/10/4/046006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
With the success of in vitro single-molecule force measurements obtained in recent years, the next step is to perform quantitative force measurements inside a living cell. Optical traps have proven excellent tools for manipulation, also in vivo, where they can be essentially non-invasive under correct wavelength and exposure conditions. It is a pre-requisite for in vivo quantitative force measurements that a precise and reliable force calibration of the tweezers is performed. There are well-established calibration protocols in purely viscous environments; however, as the cellular cytoplasm is viscoelastic, it would be incorrect to use a calibration procedure relying on a viscous environment. Here we demonstrate a method to perform a correct force calibration inside a living cell. This method (theoretically proposed in Fischer and Berg-Sørensen (2007 J. Opt. A: Pure Appl. Opt. 9 S239)) takes into account the viscoelastic properties of the cytoplasm and relies on a combination of active and passive recordings of the motion of the cytoplasmic object of interest. The calibration procedure allows us to extract absolute values for the viscoelastic moduli of the living cell cytoplasm as well as the force constant describing the optical trap, thus paving the way for quantitative force measurements inside the living cell. Here, we determine both the spring constant of the optical trap and the elastic contribution from the cytoplasm, influencing the motion of naturally occurring tracer particles. The viscoelastic moduli that we find are of the same order of magnitude as moduli found in other cell types by alternative methods.
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Affiliation(s)
- Josep Mas
- Department of Physics, Technical University of Denmark, Kgs Lyngby, Denmark
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24
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Haro-González P, Ramsay WT, Martinez Maestro L, del Rosal B, Santacruz-Gomez K, Iglesias-de la Cruz MDC, Sanz-Rodríguez F, Chooi JY, Rodriguez Sevilla P, Bettinelli M, Choudhury D, Kar AK, Solé JG, Jaque D, Paterson L. Quantum dot-based thermal spectroscopy and imaging of optically trapped microspheres and single cells. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:2162-70. [PMID: 23401166 DOI: 10.1002/smll.201201740] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 11/15/2012] [Indexed: 05/24/2023]
Abstract
Laser-induced thermal effects in optically trapped microspheres and single cells are investigated by quantum dot luminescence thermometry. Thermal spectroscopy has revealed a non-localized temperature distribution around the trap that extends over tens of micrometers, in agreement with previous theoretical models besides identifying water absorption as the most important heating source. The experimental results of thermal loading at a variety of wavelengths reveal that an optimum trapping wavelength exists for biological applications close to 820 nm. This is corroborated by a simultaneous analysis of the spectral dependence of cellular heating and damage in human lymphocytes during optical trapping. This quantum dot luminescence thermometry demonstrates that optical trapping with 820 nm laser radiation produces minimum intracellular heating, well below the cytotoxic level (43 °C), thus, avoiding cell damage.
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Affiliation(s)
- Patricia Haro-González
- Laboratorio di Chimica dello Stato Solido, DB, Università di Verona and INSTM, UdR Verona, Ca' Vignal, Strada Le Grazie 15, I-37134 Verona, Italy
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25
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Molecular adaptations allow dynein to generate large collective forces inside cells. Cell 2013; 152:172-82. [PMID: 23332753 DOI: 10.1016/j.cell.2012.11.044] [Citation(s) in RCA: 194] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 09/06/2012] [Accepted: 11/08/2012] [Indexed: 12/22/2022]
Abstract
Many cellular processes require large forces that are generated collectively by multiple cytoskeletal motor proteins. Understanding how motors generate force as a team is therefore fundamentally important but is poorly understood. Here, we demonstrate optical trapping at single-molecule resolution inside cells to quantify force generation by motor teams driving single phagosomes. In remarkable paradox, strong kinesins fail to work collectively, whereas weak and detachment-prone dyneins team up to generate large forces that tune linearly in strength and persistence with dynein number. Based on experimental evidence, we propose that leading dyneins in a load-carrying team take short steps, whereas trailing dyneins take larger steps. Dyneins in such a team bunch close together and therefore share load better to overcome low/intermediate loads. Up against higher load, dyneins "catch bond" tenaciously to the microtubule, but kinesins detach rapidly. Dynein therefore appears uniquely adapted to work in large teams, which may explain how this motor executes bewilderingly diverse cellular processes.
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26
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Schwingel M, Bastmeyer M. Force mapping during the formation and maturation of cell adhesion sites with multiple optical tweezers. PLoS One 2013; 8:e54850. [PMID: 23372781 PMCID: PMC3556026 DOI: 10.1371/journal.pone.0054850] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 12/17/2012] [Indexed: 01/19/2023] Open
Abstract
Focal contacts act as mechanosensors allowing cells to respond to their biomechanical environment. Force transmission through newly formed contact sites is a highly dynamic process requiring a stable link between the intracellular cytoskeleton and the extracellular environment. To simultaneously investigate cellular traction forces in several individual maturing adhesion sites within the same cell, we established a custom-built multiple trap optical tweezers setup. Beads functionalized with fibronectin or RGD-peptides were placed onto the apical surface of a cell and trapped with a maximum force of 160 pN. Cells form adhesion contacts around the beads as demonstrated by vinculin accumulation and start to apply traction forces after 30 seconds. Force transmission was found to strongly depend on bead size, surface density of integrin ligands and bead location on the cell surface. Highest traction forces were measured for beads positioned on the leading edge. For mouse embryonic fibroblasts, traction forces acting on single beads are in the range of 80 pN after 5 minutes. If two beads were positioned parallel to the leading edge and with a center-to-center distance less than 10 µm, traction forces acting on single beads were reduced by 40%. This indicates a spatial and temporal coordination of force development in closely related adhesion sites. We also used our setup to compare traction forces, retrograde transport velocities, and migration velocities between two cell lines (mouse melanoma and fibroblasts) and primary chick fibroblasts. We find that maximal force development differs considerably between the three cell types with the primary cells being the strongest. In addition, we observe a linear relation between force and retrograde transport velocity: a high retrograde transport velocity is associated with strong cellular traction forces. In contrast, migration velocity is inversely related to traction forces and retrograde transport velocity.
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Affiliation(s)
- Melanie Schwingel
- Karlsruhe Institute of Technology (KIT), Zoological Institute, Cell- and Neurobiology, Karlsruhe, Germany
- DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Martin Bastmeyer
- Karlsruhe Institute of Technology (KIT), Zoological Institute, Cell- and Neurobiology, Karlsruhe, Germany
- DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- * E-mail:
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27
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Leidel C, Longoria RA, Gutierrez FM, Shubeita GT. Measuring molecular motor forces in vivo: implications for tug-of-war models of bidirectional transport. Biophys J 2013; 103:492-500. [PMID: 22947865 DOI: 10.1016/j.bpj.2012.06.038] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 06/03/2012] [Accepted: 06/20/2012] [Indexed: 12/27/2022] Open
Abstract
Molecular motor proteins use the energy released from ATP hydrolysis to generate force and haul cargoes along cytoskeletal filaments. Thus, measuring the force motors generate amounts to directly probing their function. We report on optical trapping methodology capable of making precise in vivo stall-force measurements of individual cargoes hauled by molecular motors in their native environment. Despite routine measurement of motor forces in vitro, performing and calibrating such measurements in vivo has been challenging. We describe the methodology recently developed to overcome these difficulties, and used to measure stall forces of both kinesin-1 and cytoplasmic dynein-driven lipid droplets in Drosophila embryos. Critically, by measuring the cargo dynamics in the optical trap, we find that there is memory: it is more likely for a cargo to resume motion in the same direction-rather than reverse direction-after the motors transporting it detach from the microtubule under the force of the optical trap. This suggests that only motors of one polarity are active on the cargo at any instant in time and is not consistent with the tug-of-war models of bidirectional transport where both polarity motors can bind the microtubules at all times. We further use the optical trap to measure in vivo the detachment rates from microtubules of kinesin-1 and dynein-driven lipid droplets. Unlike what is commonly assumed, we find that dynein's but not kinesin's detachment time in vivo increases with opposing load. This suggests that dynein's interaction with microtubules behaves like a catch bond.
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Affiliation(s)
- Christina Leidel
- Center for Nonlinear Dynamics and Department of Physics, The University of Texas at Austin, Austin, Texas
| | - Rafael A Longoria
- Center for Nonlinear Dynamics and Department of Physics, The University of Texas at Austin, Austin, Texas
| | - Franciso Marquez Gutierrez
- Center for Nonlinear Dynamics and Department of Physics, The University of Texas at Austin, Austin, Texas
| | - George T Shubeita
- Center for Nonlinear Dynamics and Department of Physics, The University of Texas at Austin, Austin, Texas; Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas.
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28
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Farré A, Marsà F, Montes-Usategui M. Optimized back-focal-plane interferometry directly measures forces of optically trapped particles. OPTICS EXPRESS 2012; 20:12270-91. [PMID: 22714216 DOI: 10.1364/oe.20.012270] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Back-focal-plane interferometry is used to measure displacements of optically trapped samples with very high spatial and temporal resolution. However, the technique is closely related to a method that measures the rate of change in light momentum. It has long been known that displacements of the interference pattern at the back focal plane may be used to track the optical force directly, provided that a considerable fraction of the light is effectively monitored. Nonetheless, the practical application of this idea has been limited to counter-propagating, low-aperture beams where the accurate momentum measurements are possible. Here, we experimentally show that the connection can be extended to single-beam optical traps. In particular, we show that, in a gradient trap, the calibration product κ · β (where κ is the trap stiffness and 1/β is the position sensitivity) corresponds to the factor that converts detector signals into momentum changes; this factor is uniquely determined by three construction features of the detection instrument and does not depend, therefore, on the specific conditions of the experiment. Then, we find that force measurements obtained from back-focal-plane displacements are in practice not restricted to a linear relationship with position and hence they can be extended outside that regime. Finally, and more importantly, we show that these properties are still recognizable even when the system is not fully optimized for light collection. These results should enable a more general use of back-focal-plane interferometry whenever the ultimate goal is the measurement of the forces exerted by an optical trap.
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Affiliation(s)
- Arnau Farré
- Optical Trapping Lab–Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, Barcelona 08028, Spain
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29
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Brenner MD, Zhou R, Ha T. Forcing a connection: impacts of single-molecule force spectroscopy on in vivo tension sensing. Biopolymers 2011; 95:332-44. [PMID: 21267988 PMCID: PMC3097292 DOI: 10.1002/bip.21587] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 12/21/2010] [Accepted: 12/22/2010] [Indexed: 01/01/2023]
Abstract
Mechanical tension plays a large role in cell development ranging from morphology to gene expression. On the molecular level, the effects of tension can be seen in the dynamic arrangement of membrane proteins as well as the recruitment and activation of intracellular proteins. Forces applied to biopolymers during in vitro force measurements offer greater understanding of the effects of tension on molecules in live cells, and experimental techniques involving test tubes and live cells can often overlap. Indeed, when forces exerted on cellular components can be calibrated ex vivo with force spectroscopy, a powerful tool is available for researchers in probing cellular mechanotransduction on the molecular scale. This review will discuss the techniques used in measuring both cellular traction forces and single-molecule force spectroscopy. Emphasis will be placed on the use of fluorescence reporter systems for the development of in vivo tension sensors that can be used for calibration with single molecule force methods.
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Affiliation(s)
- Michael D Brenner
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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30
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Straub A, Durst ME, Xu C. High speed multiphoton axial scanning through an optical fiber in a remotely scanned temporal focusing setup. BIOMEDICAL OPTICS EXPRESS 2010; 2:80-8. [PMID: 21326638 PMCID: PMC3028501 DOI: 10.1364/boe.2.000080] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 11/07/2010] [Accepted: 12/02/2010] [Indexed: 05/09/2023]
Abstract
Simultaneous spatial and temporal focusing is used to acquire high speed (200Hz), chemically specific axial scans of mouse skin through a single-mode fiber. The temporal focus is remotely scanned by modulating the group delay dispersion (GDD) at the proximal end of the fiber. No moving parts or electronics are required at the distal end. A novel GDD modulation technique is implemented using a piezo bimorph mirror in a folded grating pair to achieve a large GDD tuning range at high speed.
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31
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Characterization of photoactivated singlet oxygen damage in single-molecule optical trap experiments. Biophys J 2010; 97:2128-36. [PMID: 19843445 DOI: 10.1016/j.bpj.2009.07.048] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 07/20/2009] [Accepted: 07/23/2009] [Indexed: 11/20/2022] Open
Abstract
Optical traps or "tweezers" use high-power, near-infrared laser beams to manipulate and apply forces to biological systems, ranging from individual molecules to cells. Although previous studies have established that optical tweezers induce photodamage in live cells, the effects of trap irradiation have yet to be examined in vitro, at the single-molecule level. In this study, we investigate trap-induced damage in a simple system consisting of DNA molecules tethered between optically trapped polystyrene microspheres. We show that exposure to the trapping light affects the lifetime of the tethers, the efficiency with which they can be formed, and their structure. Moreover, we establish that these irreversible effects are caused by oxidative damage from singlet oxygen. This reactive state of molecular oxygen is generated locally by the optical traps in the presence of a sensitizer, which we identify as the trapped polystyrene microspheres. Trap-induced oxidative damage can be reduced greatly by working under anaerobic conditions, using additives that quench singlet oxygen, or trapping microspheres lacking the sensitizers necessary for singlet state photoexcitation. Our findings are relevant to a broad range of trap-based single-molecule experiments-the most common biological application of optical tweezers-and may guide the development of more robust experimental protocols.
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32
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Lee J, Teh SY, Lee A, Kim HH, Lee C, Shung KK. Transverse acoustic trapping using a gaussian focused ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:350-5. [PMID: 20045590 PMCID: PMC2815109 DOI: 10.1016/j.ultrasmedbio.2009.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/16/2009] [Accepted: 10/06/2009] [Indexed: 05/03/2023]
Abstract
The optical tweezer has become a popular device to manipulate particles in nanometer scales and to study the underlying principles of many cellular or molecular interactions. Theoretical analysis was previously carried out at the authors' laboratory, to show that similar acoustic trapping of microparticles may be possible with a single beam ultrasound. This article experimentally presents the transverse trapping of 125 microm lipid droplets under an acoustically transparent mylar film, which is an intermediate step toward achieving acoustic tweezers in three-dimension. Despite the lack of axial trapping capability in the current experimental arrangement, it was found that a 30 MHz focused beam could be used to laterally direct the droplets toward the focus. The spatial range within which acoustic traps may guide droplet motion was in the range of hundreds of micrometers, much greater than that of optical traps. This suggests that this acoustic device may offer an alternative for manipulating microparticles in a wider spatial range.
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Affiliation(s)
- Jungwoo Lee
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
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33
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Sims PA, Xie XS. Probing dynein and kinesin stepping with mechanical manipulation in a living cell. Chemphyschem 2009; 10:1511-6. [PMID: 19504528 DOI: 10.1002/cphc.200900113] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We report a label-free assay for simultaneous optical manipulation and tracking of endogenous lipid droplets as actively transported cargoes in a living mammalian cell with sub-millisecond time resolution. Using an EM-CCD camera as a highly sensitive quadrant detector, we can detect steps of dynein- and kinesin-driven cargoes under known force loads. We can distinguish single and multiple motor-driven cargoes and show that the stall forces for inward and outward transported cargoes are similar. By combining the stall force observable with the ability to detect individual steps, we can characterize kinesin- and dynein-driven active transport in different force regimes.
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Affiliation(s)
- Peter A Sims
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
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34
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Blakely JT, Gordon R, Sinton D. Flow-dependent optofluidic particle trapping and circulation. LAB ON A CHIP 2008; 8:1350-6. [PMID: 18651078 DOI: 10.1039/b805318a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Microfluidics and fiber optics are integrated in-plane to achieve several flow-dependent particle trapping mechanisms on-chip. Each mechanism results from a combination of fluid drag and optical scattering forces. Parallel and offset fibers, orthogonally oriented to the flow, show cyclic cross-stream particle transit with flow-dependent particle trajectories and loss. Upstream-angled fibers with flow result in circulatory particle trajectories. Asymmetric angled fibers result in continuous particle circulation whereas symmetry with respect to the flow axis enables both stable trapping and circulation modes. Stable trapping of single particles, self-guided multi-particle arrays and particle assemblies are demonstrated with a single upstream-oriented fiber. Size tuning of trapped multiple particle assemblies is also presented. The planar interaction of fluid drag and optical forces results in novel possibilities for cost-effective on-chip diagnostics, mixing, flow rate monitoring, and cell analysis.
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Affiliation(s)
- J Thomas Blakely
- Department Electrical and Computer Engineering, University of Victoria, BC, CanadaV8W 3P6
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35
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Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy. Nat Methods 2008; 5:491-505. [PMID: 18511917 DOI: 10.1038/nmeth.1218] [Citation(s) in RCA: 1375] [Impact Index Per Article: 85.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.
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36
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Vieregg J, Cheng W, Bustamante C, Tinoco I. Measurement of the effect of monovalent cations on RNA hairpin stability. J Am Chem Soc 2007; 129:14966-73. [PMID: 17997555 DOI: 10.1021/ja074809o] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using optical tweezers, we have measured the effect of monovalent cation concentration and species on the folding free energy of five large (49-124 nt) RNA hairpins, including HIV-1 TAR and molecules approximating A.U and G.C homopolymers. RNA secondary structure thermodynamics are accurately described by a model consisting of nearest-neighbor interactions and additive loop and bulge terms. Melting of small (<15 bp) duplexes and hairpins in 1 M NaCl has been used to determine the parameters of this model, which is now used extensively to predict structure and folding dynamics. Few systematic measurements have been made in other ionic conditions or for larger structures. By applying mechanical force, we measured the work required to fold and unfold single hairpins at room temperature over a range of cation concentrations from 50 to 1000 mM. Free energies were then determined using the Crooks fluctuation theorem. We observed the following: (1) In most cases, the nearest-neighbor model accurately predicted the free energy of folding at 1 M NaCl. (2) Free energy was proportional to the logarithm of salt concentration. (3) Substituting potassium ions for sodium slightly decreased hairpin stability. The TAR hairpin also misfolded nearly twice as often in KCl, indicating a differential kinetic response. (4) Monovalent cation concentration affects RNA stability in a sequence-dependent manner. G.C helices were unaffected by changing salt concentration, A.U helices were modestly affected, and the hairpin loop was very sensitive. Surprisingly, the U.C.U bulge of TAR was found to be equally stable in all conditions tested. We also report a new estimate for the elastic parameters of single-stranded RNA.
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Affiliation(s)
- Jeffrey Vieregg
- Department of Physics, University of California, Berkeley, California 94720, USA.
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37
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Kyoung M, Karunwi K, Sheets ED. A versatile multimode microscope to probe and manipulate nanoparticles and biomolecules. J Microsc 2007; 225:137-46. [PMID: 17359248 DOI: 10.1111/j.1365-2818.2007.01725.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We describe a flexible, multifaceted optical setup that allows quantitative measurement and manipulation of biomolecules and nanoparticles in biomimetic and cellular systems. We have implemented integrated biophotonics techniques (i.e. differential interference contrast, wide-field fluorescence, prism- and objective-based total internal reflection excitation, single particle tracking, fluorescence correlation spectroscopy and dynamic holographic optical trapping) on a single platform. The adaptability of this versatile, custom-designed system allows us to simultaneously monitor cell morphology, while measuring lateral diffusion of biomolecules or controlling their cellular location or interaction partners.
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Affiliation(s)
- M Kyoung
- Department of Chemistry, Pennsylvania State University, University Park PA 16802, USA
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Tinoco I, Li PTX, Bustamante C. Determination of thermodynamics and kinetics of RNA reactions by force. Q Rev Biophys 2006; 39:325-60. [PMID: 17040613 PMCID: PMC2542947 DOI: 10.1017/s0033583506004446] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Single-molecule methods have made it possible to apply force to an individual RNA molecule. Two beads are attached to the RNA; one is on a micropipette, the other is in a laser trap. The force on the RNA and the distance between the beads are measured. Force can change the equilibrium and the rate of any reaction in which the product has a different extension from the reactant. This review describes use of laser tweezers to measure thermodynamics and kinetics of unfolding/refolding RNA. For a reversible reaction the work directly provides the free energy; for irreversible reactions the free energy is obtained from the distribution of work values. The rate constants for the folding and unfolding reactions can be measured by several methods. The effect of pulling rate on the distribution of force-unfolding values leads to rate constants for unfolding. Hopping of the RNA between folded and unfolded states at constant force provides both unfolding and folding rates. Force-jumps and force-drops, similar to the temperature jump method, provide direct measurement of reaction rates over a wide range of forces. The advantages of applying force and using single-molecule methods are discussed. These methods, for example, allow reactions to be studied in non-denaturing solvents at physiological temperatures; they also simplify analysis of kinetic mechanisms because only one intermediate at a time is present. Unfolding of RNA in biological cells by helicases, or ribosomes, has similarities to unfolding by force.
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Affiliation(s)
- Ignacio Tinoco
- Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
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Mao H, Arias-Gonzalez JR, Smith SB, Tinoco I, Bustamante C. Temperature control methods in a laser tweezers system. Biophys J 2005; 89:1308-16. [PMID: 15923237 PMCID: PMC1366615 DOI: 10.1529/biophysj.104.054536] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two methods of temperature control of a dual-beam optical-tweezers system are compared. In the first method, we used a 975 nm infrared laser to raise the temperature 5.6 degrees C/100 mW in a nonheating (830 nm) optical trap. The temperature increment logarithmically decreases toward the periphery of the heating beam, causing a fluid convection of 8 mum/s inside a 180 microm thick microchamber. In the second method, heating or cooling fluid was pumped through copper jackets that were placed on the water immersion objectives on both sides of the microchamber to control its temperature from 4.5 degrees C to 68 degrees C. The temperature controlled by the second method was both stable and homogeneous, inducing little fluid convection that would disturb single-molecule applications. An analysis of the power spectrum of the thermal force on a trapped bead showed no detectable vibration due to the liquid circulation. In both methods, force was measured directly by sensors of the momentum flux of light, independent of environmental disturbances including refractive index changes that vary with temperature. The utility of the second method was demonstrated in single-molecule experiments by measuring the mechanical stretch of a 41 kbp lambda double-stranded DNA at temperatures ranging from 8.4 degrees C to 45.6 degrees C.
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Affiliation(s)
- Hanbin Mao
- Lawrence Berkeley National Laboratory, California 94720, USA
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Abstract
Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on-and the measurement of nanometer-level displacements of-optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications.
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Affiliation(s)
- Keir C. Neuman
- Department of Biological Sciences, and Department of Applied Physics, Stanford University, Stanford, California 94305
| | - Steven M. Block
- Department of Biological Sciences, and Department of Applied Physics, Stanford University, Stanford, California 94305
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