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Livne G, Gat S, Armon S, Bernheim-Groswasser A. Self-assembled active actomyosin gels spontaneously curve and wrinkle similar to biological cells and tissues. Proc Natl Acad Sci U S A 2024; 121:e2309125121. [PMID: 38175871 PMCID: PMC10786314 DOI: 10.1073/pnas.2309125121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 11/28/2023] [Indexed: 01/06/2024] Open
Abstract
Living systems adopt a diversity of curved and highly dynamic shapes. These diverse morphologies appear on many length scales, from cells to tissues and organismal scales. The common driving force for these dynamic shape changes are contractile stresses generated by myosin motors in the cell cytoskeleton, that converts chemical energy into mechanical work. A good understanding of how contractile stresses in the cytoskeleton arise into different three-dimensional (3D) shapes and what are the shape selection rules that determine their final configurations is still lacking. To obtain insight into the relevant physical mechanisms, we recreate the actomyosin cytoskeleton in vitro, with precisely controlled composition and initial geometry. A set of actomyosin gel discs, intrinsically identical but of variable initial geometry, dynamically self-organize into a family of 3D shapes, such as domes and wrinkled shapes, without the need for specific preprogramming or additional regulation. Shape deformation is driven by the spontaneous emergence of stress gradients driven by myosin and is encoded in the initial disc radius to thickness aspect ratio, which may indicate shaping scalability. Our results suggest that while the dynamical pathways may depend on the detailed interactions between the different microscopic components within the gel, the final selected shapes obey the general theory of elastic deformations of thin sheets. Altogether, our results emphasize the importance for the emergence of active stress gradients for buckling-driven shape deformations and provide insights on the mechanically induced spontaneous shape transitions in contractile active matter, revealing potential shared mechanisms with living systems across scales.
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Affiliation(s)
- Gefen Livne
- Department of Chemical Engineering, Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer-Sheva84105, Israel
| | - Shachar Gat
- Department of Chemical Engineering, Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer-Sheva84105, Israel
| | - Shahaf Armon
- Department of Physics, Weizmann Institute of Science, Rehovot76100, Israel
| | - Anne Bernheim-Groswasser
- Department of Chemical Engineering, Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer-Sheva84105, Israel
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2
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Ušaj M, Moretto L, Vemula V, Salhotra A, Månsson A. Single molecule turnover of fluorescent ATP by myosin and actomyosin unveil elusive enzymatic mechanisms. Commun Biol 2021; 4:64. [PMID: 33441912 PMCID: PMC7806905 DOI: 10.1038/s42003-020-01574-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 12/04/2020] [Indexed: 01/10/2023] Open
Abstract
Benefits of single molecule studies of biomolecules include the need for minimal amounts of material and the potential to reveal phenomena hidden in ensembles. However, results from recent single molecule studies of fluorescent ATP turnover by myosin are difficult to reconcile with ensemble studies. We found that key reasons are complexities due to dye photophysics and fluorescent contaminants. After eliminating these, through surface cleaning and use of triple state quenchers and redox agents, the distributions of ATP binding dwell times on myosin are best described by 2 to 3 exponential processes, with and without actin, and with and without the inhibitor para-aminoblebbistatin. Two processes are attributable to ATP turnover by myosin and actomyosin respectively, whereas the remaining process (rate constant 0.2–0.5 s−1) is consistent with non-specific ATP binding to myosin, possibly accelerating ATP transport to the active site. Finally, our study of actin-activated myosin ATP turnover without sliding between actin and myosin reveals heterogeneity in the ATP turnover kinetics consistent with models of isometric contraction. With fluorescence based-TIRF microspectroscopy, Ušaj et al. unveil mechanistic details about the ATP turnover rates by myosin and actomyosin with enzymatic reaction pathways that were not possible to obtain from ensemble studies. This study could be important to the field of molecular motors.
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Affiliation(s)
- Marko Ušaj
- Department of Chemistry and Biomedical Sciences, Linnaeus University, SE391 82, Kalmar, Sweden.
| | - Luisa Moretto
- Department of Chemistry and Biomedical Sciences, Linnaeus University, SE391 82, Kalmar, Sweden
| | - Venukumar Vemula
- Department of Chemistry and Biomedical Sciences, Linnaeus University, SE391 82, Kalmar, Sweden
| | - Aseem Salhotra
- Department of Chemistry and Biomedical Sciences, Linnaeus University, SE391 82, Kalmar, Sweden
| | - Alf Månsson
- Department of Chemistry and Biomedical Sciences, Linnaeus University, SE391 82, Kalmar, Sweden.
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3
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Stokes polarimetry-based second harmonic generation microscopy for collagen and skeletal muscle fiber characterization. Lasers Med Sci 2020; 36:1161-1167. [PMID: 32945997 PMCID: PMC8282547 DOI: 10.1007/s10103-020-03144-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 09/10/2020] [Indexed: 12/04/2022]
Abstract
The complete polarization state of second harmonic (SH) light was measured and characterized by collagen type I and skeletal muscle fiber using a Stokes vector-based SHG microscope. The polarization states of the SH signal are analyzed in a pixel-by-pixel manner and displayed through two dimensional (2D) Stokes vector images. Various polarization parameters are reconstructed using Stokes values to quantify the polarization properties of SH light. Also, the measurements are extended for different input polarization states to investigate the molecular structure of second harmonic generation (SHG) active molecules such as collagen type I and myosin.
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4
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Arata T. Myosin and Other Energy-Transducing ATPases: Structural Dynamics Studied by Electron Paramagnetic Resonance. Int J Mol Sci 2020; 21:E672. [PMID: 31968570 PMCID: PMC7014194 DOI: 10.3390/ijms21020672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 01/05/2020] [Accepted: 01/06/2020] [Indexed: 02/07/2023] Open
Abstract
The objective of this article was to document the energy-transducing and regulatory interactions in supramolecular complexes such as motor, pump, and clock ATPases. The dynamics and structural features were characterized by motion and distance measurements using spin-labeling electron paramagnetic resonance (EPR) spectroscopy. In particular, we focused on myosin ATPase with actin-troponin-tropomyosin, neural kinesin ATPase with microtubule, P-type ion-motive ATPase, and cyanobacterial clock ATPase. Finally, we have described the relationships or common principles among the molecular mechanisms of various energy-transducing systems and how the large-scale thermal structural transition of flexible elements from one state to the other precedes the subsequent irreversible chemical reactions.
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Affiliation(s)
- Toshiaki Arata
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
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5
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Sugawa M, Masaike T, Mikami N, Yamaguchi S, Shibata K, Saito K, Fujii F, Toyoshima YY, Nishizaka T, Yajima J. Circular orientation fluorescence emitter imaging (COFEI) of rotational motion of motor proteins. Biochem Biophys Res Commun 2018; 504:709-714. [PMID: 30213631 DOI: 10.1016/j.bbrc.2018.08.178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Accepted: 08/28/2018] [Indexed: 10/28/2022]
Abstract
Single-molecule fluorescence polarization technique has been utilized to detect structural changes in biomolecules and intermolecular interactions. Here we developed a single-molecule fluorescence polarization measurement system, named circular orientation fluorescence emitter imaging (COFEI), in which a ring pattern of an acquired fluorescent image (COFEI image) represents an orientation of a polarization and a polarization factor. Rotation and pattern change of the COFEI image allow us to find changes in the polarization by eye and further values of the parameters of a polarization are determined by simple image analysis with high accuracy. We validated its potential applications of COFEI by three assays: 1) Detection of stepwise rotation of F1-ATPase via single quantum nanorod attached to the rotary shaft γ; 2) Visualization of binding of fluorescent ATP analog to the catalytic subunit in F1-ATPase; and 3) Association and dissociation of one head of dimeric kinesin-1 on the microtubule during its processive movement through single bifunctional fluorescent probes attached to the head. These results indicate that the COFEI provides us the advantages of the user-friendly measurement system and persuasive data presentations.
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Affiliation(s)
- Mitsuhiro Sugawa
- Graduate School of Arts & Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Tomoko Masaike
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda City, Chiba, 278-8510, Japan
| | - Nagisa Mikami
- Department of Physics, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
| | - Shin Yamaguchi
- Graduate School of Arts & Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Keitaro Shibata
- Graduate School of Arts & Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Kei Saito
- Graduate School of Arts & Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Fumihiko Fujii
- Immunology Frontier Research Center, Osaka University, 3-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yoko Y Toyoshima
- Graduate School of Arts & Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Takayuki Nishizaka
- Department of Physics, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
| | - Junichiro Yajima
- Graduate School of Arts & Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
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6
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Backer AS, Lee MY, Moerner WE. Enhanced DNA imaging using super-resolution microscopy and simultaneous single-molecule orientation measurements. OPTICA 2016; 3:3-6. [PMID: 27722186 PMCID: PMC5050005 DOI: 10.1364/optica.3.000659] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Single-molecule orientation measurements provide unparalleled insight into a multitude of biological and polymeric systems. We report a simple, high-throughput technique for measuring the azimuthal orientation and rotational dynamics of single fluorescent molecules, which is compatible with localization microscopy. Our method involves modulating the polarization of an excitation laser, and analyzing the corresponding intensities emitted by single dye molecules and their modulation amplitudes. To demonstrate our approach, we use intercalating and groove-binding dyes to obtain super-resolved images of stretched DNA strands through binding-induced turn-on of fluorescence. By combining our image data with thousands of dye molecule orientation measurements, we develop a means of probing the structure of individual DNA strands, while also characterizing dye-DNA interactions. This approach may hold promise as a method for monitoring DNA conformation changes resulting from DNA-binding proteins.
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Affiliation(s)
- Adam S. Backer
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford CA 94305
- Institute for Computational and Mathematical Engineering, Stanford University, 475 Via Ortega, Stanford CA 94305
| | - Maurice Y. Lee
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford CA 94305
- Biophysics Program, Stanford University, Stanford CA 94305
| | - W. E. Moerner
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford CA 94305
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7
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Backer AS, Moerner WE. Determining the rotational mobility of a single molecule from a single image: a numerical study. OPTICS EXPRESS 2015; 23:4255-76. [PMID: 25836463 PMCID: PMC4394761 DOI: 10.1364/oe.23.004255] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 01/18/2015] [Accepted: 02/04/2015] [Indexed: 05/23/2023]
Abstract
Measurements of the orientational freedom with which a single molecule may rotate or 'wobble' about a fixed axis have provided researchers invaluable clues about the underlying behavior of a variety of biological systems. In this paper, we propose a measurement and data analysis procedure based on a widefield fluorescence microscope image for quantitatively distinguishing individual molecules that exhibit varying degrees of rotational mobility. Our proposed technique is especially applicable to cases in which the molecule undergoes rotational motions on a timescale much faster than the framerate of the camera used to record fluorescence images. Unlike currently available methods, sophisticated hardware for modulating the polarization of light illuminating the sample is not required. Additional polarization optics may be inserted in the microscope's imaging pathway to achieve superior measurement precision, but are not essential. We present a theoretical analysis, and benchmark our technique with numerical simulations using typical experimental parameters for single-molecule imaging.
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Affiliation(s)
- Adam S. Backer
- Institute for Computational and Mathematical Engineering, Stanford University, 475 Via Ortega, Stanford, CA 94305,
USA
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305,
USA
| | - W. E. Moerner
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305,
USA
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8
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Hoang DT, Paeng K, Park H, Leone LM, Kaufman LJ. Extraction of Rotational Correlation Times from Noisy Single Molecule Fluorescence Trajectories. Anal Chem 2014; 86:9322-9. [PMID: 25151855 DOI: 10.1021/ac502575k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Dat Tien Hoang
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Keewook Paeng
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Heungman Park
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Lindsay M. Leone
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Laura J. Kaufman
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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9
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Mazumder N, Hu CW, Qiu J, Foreman MR, Romero CM, Török P, Kao FJ. Revealing molecular structure and orientation with Stokes vector resolved second harmonic generation microscopy. Methods 2014; 66:237-45. [DOI: 10.1016/j.ymeth.2013.07.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 07/05/2013] [Accepted: 07/12/2013] [Indexed: 10/26/2022] Open
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10
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Duggal D, Nagwekar J, Rich R, Midde K, Fudala R, Gryczynski I, Borejdo J. Phosphorylation of myosin regulatory light chain has minimal effect on kinetics and distribution of orientations of cross bridges of rabbit skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2013; 306:R222-33. [PMID: 24285364 DOI: 10.1152/ajpregu.00382.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Force production in muscle results from ATP-driven cyclic interactions of myosin with actin. A myosin cross bridge consists of a globular head domain, containing actin and ATP-binding sites, and a neck domain with the associated light chain 1 (LC1) and the regulatory light chain (RLC). The actin polymer serves as a "rail" over which myosin translates. Phosphorylation of the RLC is thought to play a significant role in the regulation of muscle relaxation by increasing the degree of skeletal cross-bridge disorder and increasing muscle ATPase activity. The effect of phosphorylation on skeletal cross-bridge kinetics and the distribution of orientations during steady-state contraction of rabbit muscle is investigated here. Because the kinetics and orientation of an assembly of cross bridges (XBs) can only be studied when an individual XB makes a significant contribution to the overall signal, the number of observed XBs was minimized to ∼20 by limiting the detection volume and concentration of fluorescent XBs. The autofluorescence and photobleaching from an ex vivo sample was reduced by choosing a dye that was excited in the red and observed in the far red. The interference from scattering was eliminated by gating the signal. These techniques decrease large uncertainties associated with determination of the effect of phosphorylation on a few molecules ex vivo with millisecond time resolution. In spite of the remaining uncertainties, we conclude that the state of phosphorylation of RLC had no effect on the rate of dissociation of cross bridges from thin filaments, on the rate of myosin head binding to thin filaments, and on the rate of power stroke. On the other hand, phosphorylation slightly increased the degree of disorder of active cross bridges.
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Affiliation(s)
- Divya Duggal
- Department of Molecular Biology and Immunology and Center for Commercialization of Fluorescence Technologies, University of North Texas, Health Science Center, Fort Worth, Texas
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11
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Berger CL. Breaking the millisecond barrier: single molecule motors wobble to find their next binding sites. Biophys J 2013; 104:1219-20. [PMID: 23528080 DOI: 10.1016/j.bpj.2013.02.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 02/12/2013] [Indexed: 11/17/2022] Open
Affiliation(s)
- Christopher L Berger
- Department of Molecular Physiology & Biophysics, University of Vermont, Burlington, VT, USA.
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12
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Tilting and wobble of myosin V by high-speed single-molecule polarized fluorescence microscopy. Biophys J 2013; 104:1263-73. [PMID: 23528086 DOI: 10.1016/j.bpj.2013.01.057] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 12/23/2012] [Accepted: 01/28/2013] [Indexed: 01/07/2023] Open
Abstract
Myosin V is biomolecular motor with two actin-binding domains (heads) that take multiple steps along actin by a hand-over-hand mechanism. We used high-speed polarized total internal reflection fluorescence (polTIRF) microscopy to study the structural dynamics of single myosin V molecules that had been labeled with bifunctional rhodamine linked to one of the calmodulins along the lever arm. With the use of time-correlated single-photon counting technology, the temporal resolution of the polTIRF microscope was improved ~50-fold relative to earlier studies, and a maximum-likelihood, multitrace change-point algorithm was used to objectively determine the times when structural changes occurred. Short-lived substeps that displayed an abrupt increase in rotational mobility were detected during stepping, likely corresponding to random thermal fluctuations of the stepping head while it searched for its next actin-binding site. Thus, myosin V harnesses its fluctuating environment to extend its reach. Additional, less frequent angle changes, probably not directly associated with steps, were detected in both leading and trailing heads. The high-speed polTIRF method and change-point analysis may be applicable to single-molecule studies of other biological systems.
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13
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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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14
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Abstract
D166V point mutation in the ventricular myosin regulatory light chain (RLC) is one of the causes of familial hypertrophic cardiomyopathy (FHC). We show here that the rates of cross-bridge attachment and dissociation are significantly different in isometrically contracting cardiac myofibrils from right ventricle of WT and Tg-D166V mice. To avoid averaging over ensembles of molecules composing muscle fibers, the data was collected from a single molecule. Kinetics were derived by tracking the orientation of a single actin molecule by fluorescence anisotropy. Orientation oscillated between two states, corresponding to the actin-bound and actin-free states of the myosin cross-bridge. The cross-bridge in a wild-type (healthy) heart stayed attached and detached from thin filament on average for 0.7 and 2.7 s, respectively. In FHC heart, these numbers increased to 2.5 and 5.8 s, respectively. These findings suggest that alterations in myosin cross-bridge kinetics associated with D166V mutation of RLC ultimately affect the ability of a heart to efficiently pump the blood.
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15
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Beausang JF, Sun Y, Quinlan ME, Forkey JN, Goldman YE. Orientation and rotational motions of single molecules by polarized total internal reflection fluorescence microscopy (polTIRFM). Cold Spring Harb Protoc 2012; 2012:2012/5/pdb.top069344. [PMID: 22550303 DOI: 10.1101/pdb.top069344] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In this article, we describe methods to detect the spatial orientation and rotational dynamics of single molecules using polarized total internal reflection fluorescence microscopy (polTIRFM). polTIRFM determines the three-dimensional angular orientation and the extent of wobble of a fluorescent probe bound to the macromolecule of interest. We discuss single-molecule versus ensemble measurements, as well as single-molecule techniques for orientation and rotation, and fluorescent probes for orientation studies. Using calmodulin (CaM) as an example of a target protein, we describe a method for labeling CaM with bifunctional rhodamine (BR). We also describe the physical principles and experimental setup of polTIRFM. We conclude with a brief introduction to assays using polTIRFM to assess the interaction of actin and myosin.
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16
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Mesoscopic analysis of motion and conformation of cross-bridges. Biophys Rev 2012; 4:299-311. [PMID: 28510208 DOI: 10.1007/s12551-012-0074-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 03/15/2012] [Indexed: 01/03/2023] Open
Abstract
The orientation of a cross-bridge is widely used as a parameter in determining the state of muscle. The conventional measurements of orientation, such as that made by wide-field fluorescence microscopy, electron paramagnetic resonance (EPR) or X-ray diffraction or scattering, report the average orientation of 1012-109 myosin cross-bridges. Under conditions where all the cross-bridges are immobile and assume the same orientation, for example in normal skeletal muscle in rigor, it is possible to determine the average orientation from such global measurements. But in actively contracting muscle, where a parameter indicating orientation fluctuates in time, the measurements of the average value provide no information about cross-bridge kinetics. To avoid problems associated with averaging information from trillions of cross-bridges, it is necessary to decrease the number of observed cross-bridges to a mesoscopic value (i.e. the value affected by fluctuations around the average). In such mesoscopic regimes, the averaging of the signal is minimal and dynamic behavior can be examined in great detail. Examples of mesoscopic analysis on skeletal and cardiac muscle are provided.
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17
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Ellis-Davies GCR, Pugh EN. The 64th Symposium of the Society for General Physiologists: optogenetics and superresolution microscopy take center stage. ACTA ACUST UNITED AC 2011; 138:1-11. [PMID: 21708951 PMCID: PMC3135327 DOI: 10.1085/jgp.201110673] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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18
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Pfeffer CP, Olsen BR, Ganikhanov F, Légaré F. Imaging skeletal muscle using second harmonic generation and coherent anti-Stokes Raman scattering microscopy. BIOMEDICAL OPTICS EXPRESS 2011; 2:1366-76. [PMID: 21559148 PMCID: PMC3087593 DOI: 10.1364/boe.2.001366] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 04/11/2011] [Accepted: 04/18/2011] [Indexed: 05/23/2023]
Abstract
We describe experimental results on label free imaging of striated skeletal muscle using second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) microscopy. The complementarity of the SHG and CARS data makes it possible to clearly identify the main sarcomere sub-structures such as actin, myosin, acto-myosin, and the intact T-tubular system as it emanates from the sarcolemma. Owing to sub-micron spatial resolution and the high sensitivity of the CARS microscopy technique we were able to resolve individual myofibrils. In addition, key organelles such as mitochondria, cell nuclei and their structural constituents were observed revealing the entire structure of the muscle functional units. There is a noticeable difference in the CARS response of the muscle structure within actin, myosin and t-tubule areas with respect to laser polarization. We attribute this to a preferential alignment of the probed molecular bonds along certain directions. The combined CARS and SHG microscopy approach yields more extensive and complementary information and has a potential to become an indispensable method for live skeletal muscle characterization.
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Affiliation(s)
| | - Bjorn R. Olsen
- Harvard School of Dental Medicine, 188 Longwood Avenue, Boston, MA 02115, USA
| | - Feruz Ganikhanov
- Department of Physics, PO BOX 6315, West Virginia University, Morgantown, WV 2650, USA
| | - François Légaré
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
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19
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Abstract
The experimental study of individual macromolecules has opened a door to determining the details of their mechanochemical operation. Motor enzymes such as the myosin family have been particularly attractive targets for such study, in part because some of them are highly processive and their "product" is spatial motion. But single-molecule resolution comes with its own costs and limitations. Often, the observations rest on single fluorescent dye molecules, which emit a limited number of photons before photobleaching and are subject to complex internal dynamics. Thus, it is important to develop methods that extract the maximum useful information from a finite set of detected photons. We have extended an experimental technique, multiple polarization illumination in total internal reflection fluorescence microscopy (polTIRF), to record the arrival time and polarization state of each individual detected photon. We also extended an analysis technique, previously applied to FRET experiments, that optimally determines times of changes in photon emission rates. Combining these improvements allows us to identify the structural dynamics of a molecular motor (myosin V) with unprecedented detail and temporal resolution.
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20
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Bharill S, Chen C, Stevens B, Kaur J, Smilansky Z, Mandecki W, Gryczynski I, Gryczynski Z, Cooperman BS, Goldman YE. Enhancement of single-molecule fluorescence signals by colloidal silver nanoparticles in studies of protein translation. ACS NANO 2011; 5:399-407. [PMID: 21158483 PMCID: PMC3049198 DOI: 10.1021/nn101839t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Metal-enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold, respectively. Fluorescence intensity fluctuations above shot noise, at 0.1-5 Hz, were greater on silver particles. Overall signal-to-noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G.
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Affiliation(s)
- Shashank Bharill
- Department of Molecular Biology and Immunology, UNTHSC, Fort Worth, TX, USA
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA, USA
| | - Chunlai Chen
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA, USA
| | - Benjamin Stevens
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA, USA
- Anima Cell Metrology, Inc., Bernardsville, NJ, USA
| | - Jaskiran Kaur
- Anima Cell Metrology, Inc., Bernardsville, NJ, USA
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Wlodek Mandecki
- Department of Microbiology and Molecular Genetics, UMDNJ, Newark, NJ, USA
| | - Ignacy Gryczynski
- Department of Molecular Biology and Immunology, UNTHSC, Fort Worth, TX, USA
| | - Zygmunt Gryczynski
- Department of Molecular Biology and Immunology, UNTHSC, Fort Worth, TX, USA
| | - Barry S. Cooperman
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | - Yale E. Goldman
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA, USA
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21
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Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Borejdo J. Observing cycling of a few cross-bridges during isometric contraction of skeletal muscle. Cytoskeleton (Hoboken) 2010; 67:400-11. [PMID: 20517927 DOI: 10.1002/cm.20453] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
During muscle contraction a myosin cross-bridge imparts periodic force impulses to actin. It is possible to visualize those impulses by observing a few molecules of actin or myosin. We have followed the time course of orientation change of a few actin molecules during isometric contraction by measuring parallel polarized intensity of its fluorescence. The orientation of actin reflects local bending of a thin filament and is different when a cross-bridge binds to, or is detached from, F-actin. The changes in orientation were characterized by periods of activity during which myosin cross-bridges interacted normally with actin, interspersed with periods of inactivity during which actin and myosin were unable to interact. The periods of activity lasted on average 1.2 +/- 0.4 s and were separated on average by 2.3 +/- 1.0 s. During active period, actin orientation oscillated between the two extreme values with the ON and OFF times of 0.4 +/- 0.2 and 0.7 +/- 0.4 s, respectively. When the contraction was induced by a low concentration of ATP both active and inactive times were longer and approximately equal. These results imply that cross-bridges interact with actin in bursts and suggest that during active period, on average 36% of cross-bridges are involved in force generation.
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Affiliation(s)
- P Mettikolla
- Department of Molecular Biology & Immunology, Center for Commercialization of Fluorescence Technology, University of North Texas HSC, Fort Worth, Texas 76107, USA
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22
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Abstract
Macromolecules drive the complex behavior of neurons. For example, channels and transporters control the movements of ions across membranes, SNAREs direct the fusion of vesicles at the synapse, and motors move cargo throughout the cell. Understanding the structure, assembly, and conformational movements of these and other neuronal proteins is essential to understanding the brain. Developments in fluorescence have allowed the architecture and dynamics of proteins to be studied in real time and in a cellular context with great accuracy. In this review, we cover classic and recent methods for studying protein structure, assembly, and dynamics with fluorescence. These methods include fluorescence and luminescence resonance energy transfer, single-molecule bleaching analysis, intensity measurements, colocalization microscopy, electron transfer, and bimolecular complementation analysis. We present the principles of these methods, highlight recent work that uses the methods, and discuss a framework for interpreting results as they apply to molecular neurobiology.
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23
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Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Borejdo J. Kinetics of a single cross-bridge in familial hypertrophic cardiomyopathy heart muscle measured by reverse Kretschmann fluorescence. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:017011. [PMID: 20210485 PMCID: PMC2847936 DOI: 10.1117/1.3324871] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 01/04/2010] [Accepted: 01/06/2010] [Indexed: 05/28/2023]
Abstract
Familial hypertrophic cardiomyopathy (FHC) is a serious heart disease that often leads to a sudden cardiac death of young athletes. It is believed that the alteration of the kinetics of interaction between actin and myosin causes FHC by making the heart to pump blood inefficiently. We set out to check this hypothesis ex vivo. During contraction of heart muscle, a myosin cross-bridge imparts periodic force impulses to actin. The impulses are analyzed by fluorescence correlation spectroscopy (FCS) of fluorescently labeled actin. To minimize observation volume and background fluorescence, we carry out FCS measurements in surface plasmon coupled emission mode in a reverse Kretschmann configuration. Fluorescence is a result of near-field coupling of fluorophores excited in the vicinity of the metal-coated surface of a coverslip with the surface plasmons propagating in the metal. Surface plasmons decouple on opposite sides of the metal film and emit in a directional manner as far-field p-polarized radiation. We show that the rate of changes of orientation is significantly faster in contracting cardiac myofibrils of transgenic mice than wild type. These results are consistent with the fact that mutated heart muscle myosin translates actin faster in in vitro motility assays.
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Affiliation(s)
- Prasad Mettikolla
- University of North Texas Health Science Center, Department of Molecular Biology and Immunology, Fort Worth, Texas 76107, USA
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24
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Muthu P, Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Szczesna-Cordary D, Borejdo J. Single molecule kinetics in the familial hypertrophic cardiomyopathy D166V mutant mouse heart. J Mol Cell Cardiol 2009; 48:989-98. [PMID: 19914255 DOI: 10.1016/j.yjmcc.2009.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 10/21/2009] [Accepted: 11/06/2009] [Indexed: 11/26/2022]
Abstract
One of the sarcomeric mutations associated with a malignant phenotype of familial hypertrophic cardiomyopathy (FHC) is the D166V point mutation in the ventricular myosin regulatory light chain (RLC) encoded by the MYL2 gene. In this report we show that the rates of myosin cross-bridge attachment and dissociation are significantly different in isometrically contracting cardiac myofibrils from right ventricles of transgenic (Tg)-D166V and Tg-WT mice. We have derived the myosin cross-bridge kinetic rates by tracking the orientation of a fluorescently labeled single actin molecule. Orientation (measured by polarized fluorescence) oscillated between two states, corresponding to the actin-bound and actin-free states of the myosin cross-bridge. The rate of cross-bridge attachment during isometric contraction decreased from 3 s(-1) in myofibrils from Tg-WT to 1.4 s(-1) in myofibrils from Tg-D166V. The rate of detachment decreased from 1.3 s(-1) (Tg-WT) to 1.2 s(-1) (Tg-D166V). We also showed that the level of RLC phosphorylation was largely decreased in Tg-D166V myofibrils compared to Tg-WT. Our findings suggest that alterations in the myosin cross-bridge kinetics brought about by the D166V mutation in RLC might be responsible for the compromised function of the mutated hearts and lead to their inability to efficiently pump blood.
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Affiliation(s)
- Priya Muthu
- Department of Molecular Biology and Immunology and Center for Commercialization of Fluorescence Technologies, University of North Texas, Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA
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25
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Thomas DD, Kast D, Korman VL. Site-directed spectroscopic probes of actomyosin structural dynamics. Annu Rev Biophys 2009; 38:347-69. [PMID: 19416073 DOI: 10.1146/annurev.biophys.35.040405.102118] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Spectroscopy of myosin and actin has entered a golden age. High-resolution crystal structures of isolated actin and myosin have been used to construct detailed models for the dynamic actomyosin interactions that move muscle. Improved protein mutagenesis and expression technologies have facilitated site-directed labeling with fluorescent and spin probes. Spectroscopic instrumentation has achieved impressive advances in sensitivity and resolution. Here we highlight the contributions of site-directed spectroscopic probes to understanding the structural dynamics of myosin II and its actin complexes in solution and muscle fibers. We emphasize studies that probe directly the movements of structural elements within the myosin catalytic and light-chain domains, and changes in the dynamics of both actin and myosin due to their alternating strong and weak interactions in the ATPase cycle. A moving picture emerges in which single biochemical states produce multiple structural states, and transitions between states of order and dynamic disorder power the actomyosin engine.
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Affiliation(s)
- David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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26
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Greenberg MJ, Mealy TR, Watt JD, Jones M, Szczesna-Cordary D, Moore JR. The molecular effects of skeletal muscle myosin regulatory light chain phosphorylation. Am J Physiol Regul Integr Comp Physiol 2009; 297:R265-74. [PMID: 19458282 DOI: 10.1152/ajpregu.00171.2009] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phosphorylation of the myosin regulatory light chain (RLC) in skeletal muscle has been proposed to act as a molecular memory of recent activation by increasing the rate of force development, ATPase activity, and isometric force at submaximal activation in fibers. It has been proposed that these effects stem from phosphorylation-induced movement of myosin heads away from the thick filament backbone. In this study, we examined the molecular effects of skeletal muscle myosin RLC phosphorylation using in vitro motility assays. We showed that, independently of the thick filament backbone, the velocity of skeletal muscle myosin is decreased upon phosphorylation due to an increase in the myosin duty cycle. Furthermore, we did not observe a phosphorylation-dependent shift in calcium sensitivity in the absence of the myosin thick filament. These data suggest that phosphorylation-induced movement of myosin heads away from the thick filament backbone explains only part of the observed phosphorylation-induced changes in myosin mechanics. Last, we showed that the duty cycle of skeletal muscle myosin is strain dependent, consistent with the notion that strain slows the rate of ADP release in striated muscle.
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Affiliation(s)
- Michael J Greenberg
- Dept. of Physiology and Biophysics, Boston Univ. School of Medicine, 72 E. Concord St., Boston, MA 02118, USA
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27
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Beausang JF, Schroeder HW, Nelson PC, Goldman YE. Twirling of actin by myosins II and V observed via polarized TIRF in a modified gliding assay. Biophys J 2008; 95:5820-31. [PMID: 18931255 PMCID: PMC2599829 DOI: 10.1529/biophysj.108.140319] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 09/12/2008] [Indexed: 11/18/2022] Open
Abstract
The force generated between actin and myosin acts predominantly along the direction of the actin filament, resulting in relative sliding of the thick and thin filaments in muscle or transport of myosin cargos along actin tracks. Previous studies have also detected lateral forces or torques that are generated between actin and myosin, but the origin and biological role of these sideways forces is not known. Here we adapt an actin gliding filament assay to measure the rotation of an actin filament about its axis ("twirling") as it is translocated by myosin. We quantify the rotation by determining the orientation of sparsely incorporated rhodamine-labeled actin monomers, using polarized total internal reflection microscopy. To determine the handedness of the filament rotation, linear incident polarizations in between the standard s- and p-polarizations were generated, decreasing the ambiguity of our probe orientation measurement fourfold. We found that whole myosin II and myosin V both twirl actin with a relatively long (approximately 1 microm), left-handed pitch that is insensitive to myosin concentration, filament length, and filament velocity.
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Affiliation(s)
- John F Beausang
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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28
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Oreopoulos J, Yip CM. Combined scanning probe and total internal reflection fluorescence microscopy. Methods 2008; 46:2-10. [PMID: 18602010 DOI: 10.1016/j.ymeth.2008.05.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Accepted: 05/22/2008] [Indexed: 11/19/2022] Open
Abstract
Combining scanning probe and optical microscopy represents a powerful approach for investigating structure-function relationships and dynamics of biomolecules and biomolecular assemblies, often in situ and in real-time. This platform technology allows us to obtain three-dimensional images of individual molecules with nanometer resolution, while simultaneously characterizing their structure and interactions though complementary techniques such as optical microscopy and spectroscopy. We describe herein the practical strategies for the coupling of scanning probe and total internal reflection fluorescence microscopy along with challenges and the potential applications of such platforms, with a particular focus on their application to the study of biomolecular interactions at membrane surfaces.
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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, 160 College St, Toronto, Ont., Canada M5S 3E1
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29
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Borejdo J, Muthu P, Talent J, Gryczynski Z, Calander N, Akopova I, Shtoyko T, Gryczynski I. Reduction of photobleaching and photodamage in single molecule detection: observing single actin monomer in skeletal myofibrils. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:034021. [PMID: 18601566 DOI: 10.1117/1.2938689] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Recent advances in detector technology make it possible to achieve single molecule detection (SMD) in a cell. SMD avoids complications associated with averaging signals from large assemblies and with diluting and disorganizing proteins. However, it requires that cells be illuminated with an intense laser beam, which causes photobleaching and cell damage. To reduce these effects, we study cells on coverslips coated with silver nanoparticle monolayers (NML). Muscle is used as an example. Actin is labeled with a low concentration of fluorescent phalloidin to assure that less than a single molecule in a sarcomere is fluorescent. On a glass substrate, the fluorescence of actin decays in a step-wise fashion, establishing a single molecule detection regime. Single molecules of actin in living muscle are visualized for the first time. NML coating decreases the fluorescence lifetime 17 times and enhances intensity ten times. As a result, fluorescence of muscle bleaches four to five times slower than on glass. Monolayers decrease photobleaching because they shorten the fluorescence lifetime, thus decreasing the time that a fluorophore spends in the excited state when it is vulnerable to oxygen attack. They decrease damage to cells because they enhance the electric field near the fluorophore, making it possible to illuminate samples with weaker light.
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Affiliation(s)
- Julian Borejdo
- University of North Texas Health Science Center, Department of Molecular Biology and Immunology, Fort Worth, Texas 76107, USA.
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30
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Muthu P, Talent JM, Gryczynski I, Borejdo J. Cross-bridge duty cycle in isometric contraction of skeletal myofibrils. Biochemistry 2008; 47:5657-67. [PMID: 18426224 DOI: 10.1021/bi7023223] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During interaction of actin with myosin, cross-bridges impart mechanical impulses to thin filaments resulting in rotations of actin monomers. Impulses are delivered on the average every tc seconds. A cross-bridge spends a fraction of this time (ts) strongly attached to actin, during which it generates force. The "duty cycle" (DC), defined as the fraction of the total cross-bridge cycle that myosin spends attached to actin in a force generating state (ts/ tc), is small for cross-bridges acting against zero load, like freely shortening muscle, and increases as the load rises. Here we report, for the first time, an attempt to measure DC of a single cross-bridge in muscle. A single actin molecule in a half-sarcomere was labeled with fluorescent phalloidin. Its orientation was measured by monitoring intensity of the polarized TIRF images. Actin changed orientation when a cross-bridge bound to it. During isometric contraction, but not during rigor, actin orientation oscillated between two values, corresponding to the actin-bound and actin-free state of the cross-bridge. The average ts and tc were 3.4 and 6 s, respectively. These results suggest that, in isometrically working muscle, cross-bridges spend about half of the cycle time attached to actin. The fact that 1/ tc was much smaller than the ATPase rate suggests that the bulk of the energy of ATP hydrolysis is used for purposes other than performance of mechanical work.
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Affiliation(s)
- P Muthu
- Department of Molecular Biology & Immunology and Center for Commercialization of Fluorescence Technology, the University of North Texas HSC, Fort Worth, Texas 76107, USA
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31
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Sun Y, Schroeder HW, Beausang JF, Homma K, Ikebe M, Goldman YE. Myosin VI walks "wiggly" on actin with large and variable tilting. Mol Cell 2008; 28:954-64. [PMID: 18158894 DOI: 10.1016/j.molcel.2007.10.029] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Revised: 08/18/2007] [Accepted: 10/15/2007] [Indexed: 10/21/2022]
Abstract
Myosin VI is an unconventional motor protein with unusual motility properties such as its direction of motion and path on actin and a large stride relative to its short lever arms. To understand these features, the rotational dynamics of the lever arm were studied by single-molecule polarized total internal reflection fluorescence (polTIRF) microscopy during processive motility of myosin VI along actin. The axial angle is distributed in two peaks, consistent with the hand-over-hand model. The changes in lever arm angles during discrete steps suggest that it exhibits large and variable tilting in the plane of actin and to the sides. These motions imply that, in addition to the previously suggested flexible tail domain, there is a compliant region between the motor domain and lever arm that allows myosin VI to accommodate the helical position of binding sites while taking variable step sizes along the actin filament.
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Affiliation(s)
- Yujie Sun
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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32
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Hong F, Root DD. Downscaling functional bioassays by single-molecule techniques. Drug Discov Today 2007; 11:640-5. [PMID: 16793533 DOI: 10.1016/j.drudis.2006.05.003] [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] [Received: 01/10/2006] [Revised: 04/07/2006] [Accepted: 05/11/2006] [Indexed: 11/17/2022]
Abstract
In this short review we examine the potential of single-molecule assays in drug development and in basic research to provide new types of information at the smallest assay scales. A key advantage of many single-molecule assays is the requirement for conservative amounts of precious sample compared to conventional assays. In addition, they measure processes that are not observed directly in molecular ensembles. These advantages are balanced currently by difficulties in assay setup, preparation and equipment expense. However, future developments will ameliorate these drawbacks with the production of simpler, less expensive experimental systems for single-molecule assays.
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Affiliation(s)
- Feng Hong
- Department of Biological Sciences, Division of Biochemistry and Molecular Biology, University of North Texas, Denton, TX 76203-5220, USA
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33
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Abstract
The "conventional" isoform of myosin that polymerizes into filaments (myosin II) is the molecular motor powering contraction in all three types of muscle. Considerable attention has been paid to the developmental progression, isoform distribution, and mutations that affect myocardial development, function, and adaptation. Optical trap (laser tweezer) experiments and various types of high-resolution fluorescence microscopy, capable of interrogating individual protein motors, are revealing novel and detailed information about their functionally relevant nanometer motions and pico-Newton forces. Single-molecule laser tweezer studies of cardiac myosin isoforms and their mutants have helped to elucidate the pathogenesis of familial hypertrophic cardiomyopathies. Surprisingly, some disease mutations seem to enhance myosin function. More broadly, the myosin superfamily includes more than 20 nonfilamentous members with myriad cellular functions, including targeted organelle transport, endocytosis, chemotaxis, cytokinesis, modulation of sensory systems, and signal transduction. Widely varying genetic, developmental and functional disorders of the nervous, pigmentation, and immune systems have been described in accordance with these many roles. Compared to the collective nature of myosin II, some myosin family members operate with only a few partners or even alone. Individual myosin V and VI molecules can carry cellular vesicular cargoes much farther distances than their own size. Laser tweezer mechanics, single-molecule fluorescence polarization, and imaging with nanometer precision have elucidated the very different mechano-chemical properties of these isoforms. Critical contributions of nonsarcomeric myosins to myocardial development and adaptation are likely to be discovered in future studies, so these techniques and concepts may become important in cardiovascular research.
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Affiliation(s)
- Jody A Dantzig
- University of Pennsylvania School of Medicine, Pennsylvania Muscle Institute, 3700 Hamilton Walk, D700 Richards Building, Philadelphia, PA 19104-6083, USA
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34
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Vanzi F, Capitanio M, Sacconi L, Stringari C, Cicchi R, Canepari M, Maffei M, Piroddi N, Poggesi C, Nucciotti V, Linari M, Piazzesi G, Tesi C, Antolini R, Lombardi V, Bottinelli R, Pavone FS. New techniques in linear and non-linear laser optics in muscle research. J Muscle Res Cell Motil 2006; 27:469-79. [PMID: 16933024 DOI: 10.1007/s10974-006-9084-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 06/26/2006] [Indexed: 11/26/2022]
Abstract
This review proposes a brief summary of two applications of lasers to muscle research. The first application (laser tweezers), is now a well-established technique in the field, adopted by several laboratories in the world and producing a constant stream of original data, fundamental for our improved understanding of muscle contraction at the level of detail that only single molecule measurements can provide. As an example of the power of this technique, here we focus on some recent results, revealing the performance of the working stroke in at least two distinct steps also in skeletal muscle myosin. A second laser-based technique described here is second-harmonic generation; the application of this technique to muscle research is very recent. We describe the main results obtained thus far in this area and the potentially remarkable impact that this technology may have in muscle research.
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Affiliation(s)
- F Vanzi
- LENS (European Laboratory for Non-linear Spectroscopy), University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Firenze, Italy
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35
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Fletcher KA, Fakayode SO, Lowry M, Tucker SA, Neal SL, Kimaru IW, McCarroll ME, Patonay G, Oldham PB, Rusin O, Strongin RM, Warner IM. Molecular fluorescence, phosphorescence, and chemiluminescence spectrometry. Anal Chem 2006; 78:4047-68. [PMID: 16771540 PMCID: PMC2662353 DOI: 10.1021/ac060683m] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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36
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Quinlan ME, Forkey JN, Goldman YE. Orientation of the myosin light chain region by single molecule total internal reflection fluorescence polarization microscopy. Biophys J 2005; 89:1132-42. [PMID: 15894631 PMCID: PMC1366598 DOI: 10.1529/biophysj.104.053496] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Accepted: 04/27/2005] [Indexed: 11/18/2022] Open
Abstract
To study the orientation and dynamics of myosin, we measured fluorescence polarization of single molecules and ensembles of myosin decorating actin filaments. Engineered chicken gizzard regulatory light chain (RLC), labeled with bisiodoacetamidorhodamine at cysteine residues 100 and 108 or 104 and 115, was exchanged for endogenous RLC in rabbit skeletal muscle HMM or S1. AEDANS-labeled actin, fully decorated with labeled myosin fragment or a ratio of approximately 1:1000 labeled:unlabeled myosin fragment, was adhered to a quartz slide. Eight polarized fluorescence intensities were combined with the actin orientation from the AEDANS fluorescence to determine the axial angle (relative to actin), the azimuthal angle (around actin), and RLC mobility on the <<10 ms timescale. Order parameters of the orientation distributions from heavily labeled filaments agree well with comparable measurements in muscle fibers, verifying the technique. Experiments with HMM provide sufficient angular resolution to detect two orientations corresponding to the two heads in rigor. Experiments with S1 show a single orientation intermediate to the two seen for HMM. The angles measured for HMM are consistent with heads bound on adjacent actin monomers of a filament, under strain, similar to predictions based on ensemble measurements made on muscle fibers with electron microscopy and spectroscopic experiments.
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Affiliation(s)
- Margot E Quinlan
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, 19104-6083, USA
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37
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Forkey JN, Quinlan ME, Goldman YE. Measurement of single macromolecule orientation by total internal reflection fluorescence polarization microscopy. Biophys J 2005; 89:1261-71. [PMID: 15894632 PMCID: PMC1366610 DOI: 10.1529/biophysj.104.053470] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A new approach is presented for measuring the three-dimensional orientation of individual macromolecules using single molecule fluorescence polarization (SMFP) microscopy. The technique uses the unique polarizations of evanescent waves generated by total internal reflection to excite the dipole moment of individual fluorophores. To evaluate the new SMFP technique, single molecule orientation measurements from sparsely labeled F-actin are compared to ensemble-averaged orientation data from similarly prepared densely labeled F-actin. Standard deviations of the SMFP measurements taken at 40 ms time intervals indicate that the uncertainty for individual measurements of axial and azimuthal angles is approximately 10 degrees at 40 ms time resolution. Comparison with ensemble data shows there are no substantial systematic errors associated with the single molecule measurements. In addition to evaluating the technique, the data also provide a new measurement of the torsional rigidity of F-actin. These measurements support the smaller of two values of the torsional rigidity of F-actin previously reported.
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Affiliation(s)
- Joseph N Forkey
- Pennsylvania Muscle Institute and Department of Physiology, University of Pennsylvania, Philadelphia, 19104-6083, USA
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