201
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Galburt EA, Tomko EJ, Stump WT, Ruiz Manzano A. Force-dependent melting of supercoiled DNA at thermophilic temperatures. Biophys Chem 2014; 187-188:23-8. [PMID: 24486433 DOI: 10.1016/j.bpc.2014.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 01/07/2014] [Accepted: 01/07/2014] [Indexed: 11/28/2022]
Abstract
Local DNA opening plays an important role in DNA metabolism as the double-helix must be melted before the information contained within may be accessed. Cells finely tune the torsional state of their genomes to strike a balance between stability and accessibility. For example, while mesophilic life forms maintain negatively superhelical genomes, thermophilic life forms use unique mechanisms to maintain relaxed or even positively supercoiled genomes. Here, we use a single-molecule magnetic tweezers approach to quantify the force-dependent equilibrium between DNA melting and supercoiling at high temperatures populated by Thermophiles. We show that negatively supercoiled DNA denatures at 0.5 pN lower tension at thermophilic vs. mesophilic temperatures. This work demonstrates the ability to monitor DNA supercoiling at high temperature and opens the possibility to perform magnetic tweezers assays on thermophilic systems. The data allow for an estimation of the relative energies of base-pairing and DNA bending as a function of temperature and support speculation as to different general mechanisms of DNA opening in different environments. Lastly, our results imply that average in vivo DNA tensions range between 0.3 and 1.1 pN.
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Affiliation(s)
- E A Galburt
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - E J Tomko
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - W T Stump
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - A Ruiz Manzano
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
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202
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Chowdhury D. Modeling stochastic kinetics of molecular machines at multiple levels: from molecules to modules. Biophys J 2014; 104:2331-41. [PMID: 23746505 DOI: 10.1016/j.bpj.2013.04.042] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 04/16/2013] [Accepted: 04/17/2013] [Indexed: 01/14/2023] Open
Abstract
A molecular machine is either a single macromolecule or a macromolecular complex. In spite of the striking superficial similarities between these natural nanomachines and their man-made macroscopic counterparts, there are crucial differences. Molecular machines in a living cell operate stochastically in an isothermal environment far from thermodynamic equilibrium. In this mini-review we present a catalog of the molecular machines and an inventory of the essential toolbox for theoretically modeling these machines. The tool kits include 1), nonequilibrium statistical-physics techniques for modeling machines and machine-driven processes; and 2), statistical-inference methods for reverse engineering a functional machine from the empirical data. The cell is often likened to a microfactory in which the machineries are organized in modular fashion; each module consists of strongly coupled multiple machines, but different modules interact weakly with each other. This microfactory has its own automated supply chain and delivery system. Buoyed by the success achieved in modeling individual molecular machines, we advocate integration of these models in the near future to develop models of functional modules. A system-level description of the cell from the perspective of molecular machinery (the mechanome) is likely to emerge from further integrations that we envisage here.
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203
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Swoboda M, Grieb MS, Hahn S, Schlierf M. Measuring two at the same time: combining magnetic tweezers with single-molecule FRET. EXPERIENTIA SUPPLEMENTUM (2012) 2014; 105:253-76. [PMID: 25095999 DOI: 10.1007/978-3-0348-0856-9_12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Molecular machines are the workhorses of the cell that efficiently convert chemical energy into mechanical motion through conformational changes. They can be considered powerful machines, exerting forces and torque on the molecular level of several piconewtons and piconewton-nanometer, respectively. For studying translocation and conformational changes of these machines, fluorescence methods, like FRET, as well as "mechanical" methods, like optical and magnetic tweezers, have proven well suited over the past decades. One of the current challenges in the field of molecular machines is gaining maximal information from single-molecule experiments by simultaneously measuring translocation, conformational changes, and forces exerted by these machines. In this chapter, we describe the combination of magnetic tweezers with single-molecule FRET for orthogonal simultaneous readout to maximize the information gained in single-molecule experiments.
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Affiliation(s)
- Marko Swoboda
- BCUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstraße 18, 01307, Dresden, Germany,
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204
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Jacobs MJ, Blank K. Joining forces: integrating the mechanical and optical single molecule toolkits. Chem Sci 2014. [DOI: 10.1039/c3sc52502c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Combining single molecule force measurements with fluorescence detection opens up exciting new possibilities for the characterization of mechanoresponsive molecules in Biology and Materials Science.
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Affiliation(s)
- Monique J. Jacobs
- Radboud University Nijmegen
- Institute for Molecules and Materials
- Department of Molecular Materials
- 6525 AJ Nijmegen, The Netherlands
| | - Kerstin Blank
- Radboud University Nijmegen
- Institute for Molecules and Materials
- Department of Molecular Materials
- 6525 AJ Nijmegen, The Netherlands
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205
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Scholl ZN, Li Q, Marszalek PE. Single molecule mechanical manipulation for studying biological properties of proteins,
DNA
, and sugars. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2013; 6:211-29. [DOI: 10.1002/wnan.1253] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 10/10/2013] [Accepted: 10/17/2013] [Indexed: 11/07/2022]
Affiliation(s)
- Zackary N. Scholl
- Department of Computational Biology and Bioinformatics Duke University Durham NC USA
| | - Qing Li
- Department of Mechanical Engineering and Materials Science Duke University Durham NC USA
| | - Piotr E. Marszalek
- Department of Mechanical Engineering and Materials Science, Center for Biologically Inspired Materials and Material Systems Duke University Durham NC USA
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206
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Richly MU, Türkcan S, Le Gall A, Fiszman N, Masson JB, Westbrook N, Perronet K, Alexandrou A. Calibrating optical tweezers with Bayesian inference. OPTICS EXPRESS 2013; 21:31578-31590. [PMID: 24514731 DOI: 10.1364/oe.21.031578] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present a new method for calibrating an optical-tweezer setup that does not depend on input parameters and is less affected by systematic errors like drift of the setup. It is based on an inference approach that uses Bayesian probability to infer the diffusion coefficient and the potential felt by a bead trapped in an optical or magnetic trap. It exploits a much larger amount of the information stored in the recorded bead trajectory than standard calibration approaches. We demonstrate that this method outperforms the equipartition method and the power-spectrum method in input information required (bead radius and trajectory length) and in output accuracy.
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207
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Affiliation(s)
- Sanghwa Lee
- Department
of Physics and Astronomy, Department of Biophysics and Chemical Biology,
and National Center for Creative Research Initiatives, Seoul National University, Seoul 151-747, Korea
| | - Sungchul Hohng
- Department
of Physics and Astronomy, Department of Biophysics and Chemical Biology,
and National Center for Creative Research Initiatives, Seoul National University, Seoul 151-747, Korea
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208
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Rajendran A, Endo M, Sugiyama H. State-of-the-Art High-Speed Atomic Force Microscopy for Investigation of Single-Molecular Dynamics of Proteins. Chem Rev 2013; 114:1493-520. [DOI: 10.1021/cr300253x] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Arivazhagan Rajendran
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho
Sakyo-ku, Kyoto 606-8502, Japan
| | - Masayuki Endo
- Institute
for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-ushinomiyacho,
Sakyo-ku, Kyoto 606-8501, Japan
- CREST, Japan Science and Technology Corporation (JST), Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan
| | - Hiroshi Sugiyama
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho
Sakyo-ku, Kyoto 606-8502, Japan
- Institute
for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-ushinomiyacho,
Sakyo-ku, Kyoto 606-8501, Japan
- CREST, Japan Science and Technology Corporation (JST), Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan
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209
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Mechanical unzipping and rezipping of a single SNARE complex reveals hysteresis as a force-generating mechanism. Nat Commun 2013; 4:1705. [PMID: 23591872 PMCID: PMC3644077 DOI: 10.1038/ncomms2692] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 03/01/2013] [Indexed: 01/15/2023] Open
Abstract
Formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex provides mechanical thrust for membrane fusion, but its molecular mechanism is still unclear. Here using magnetic tweezers, we observe mechanical responses of a single neuronal SNARE complex under constant pulling force. Single SNARE complexes may be unzipped with 34 pN force. When rezipping is induced by lowering the force to 11 pN, only a partially assembled state results, with the C-terminal half of the SNARE complex remaining disassembled. Reassembly of the C-terminal half occurs only when the force is further lowered below 11 pN. Thus, mechanical hysteresis, characterized by the unzipping and rezipping cycle of a single SNARE complex, produces the partially assembled state. In this metastable state, unzipping toward the N-terminus is suppressed while zippering toward the C-terminus is initiated as a steep function of force. This ensures the directionality of SNARE-complex formation, making the SNARE complex a robust force-generating machine. Interactions between (SNARE) proteins on vesicle and target membranes provide the force necessary to drive membrane fusion. By applying piconewton forces to single SNARE complexes, the authors identify a partially assembled intermediate state that reveals how force is generated in a consistent direction.
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210
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Affiliation(s)
- Jens Michaelis
- Biophysics
Institute, Faculty of Natural Sciences, Ulm University, Albert-Einstein-Allee
11, 89081 Ulm, Germany
- Center
for Integrated Protein Science Munich (CIPSM), Department
of Chemistry and Biochemistry, Munich University, Butenandtstrasse 5-13, 81377 München, Germany
| | - Barbara Treutlein
- Department
of Bioengineering, Stanford University, James H. Clark Center, E-300, 318
Campus Drive, Stanford, California 94305-5432, United States
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211
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Abstract
All organisms need homologous recombination (HR) to repair DNA double-strand breaks. Defects in recombination are linked to genetic instability and to elevated risks in developing cancers. The central catalyst of HR is a nucleoprotein filament, consisting of recombinase proteins (human RAD51 or bacterial RecA) bound around single-stranded DNA. Over the last two decades, single-molecule techniques have provided substantial new insights into the dynamics of homologous recombination. Here, we survey important recent developments in this field of research and provide an outlook on future developments.
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212
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Zhang L, Dong WF, Sun HB. Multifunctional superparamagnetic iron oxide nanoparticles: design, synthesis and biomedical photonic applications. NANOSCALE 2013; 5:7664-7684. [PMID: 23877222 DOI: 10.1039/c3nr01616a] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) have shown great promise in biomedical applications. In this review, we summarize the recent advances in the design and fabrication of core-shell and hetero-structured SPIONs and further outline some exciting developments and progresses of these multifunctional SPIONs for diagnosis, multimodality imaging, therapy, and biophotonics.
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Affiliation(s)
- Lu Zhang
- State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China
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213
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Nyberg L, Persson F, Akerman B, Westerlund F. Heterogeneous staining: a tool for studies of how fluorescent dyes affect the physical properties of DNA. Nucleic Acids Res 2013; 41:e184. [PMID: 23975199 PMCID: PMC3799460 DOI: 10.1093/nar/gkt755] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The commonly used fluorescent dye YOYO-1 (YOYO) has, using bulk techniques, been demonstrated to stain DNA heterogeneously at substoichiometric concentrations. We here, using nanofluidic channels and fluorescence microscopy, investigate the heterogeneous staining on the single DNA molecule level and demonstrate that the dye distribution is continuous. The equilibration of YOYO on DNA is extremely slow but can be accelerated by increasing the ionic strength and/or the temperature. Furthermore, we demonstrate how to use the heterogeneous staining as a tool for detailed and time-efficient studies of how fluorescent dyes affect the physical properties of DNA. We show that the relative increase in extension of DNA with increasing amount of YOYO bound is higher at low ionic strengths and also extrapolate the extension of native DNA. Our study reveals important information on how YOYO affects the physical properties of DNA, but it also has broader applications. First, it reveals how cationic intercalators, such as potential DNA drugs, affect DNA under strong confinement. Second, the strategy of using heterogeneous staining is of general use for single molecule studies of DNA interacting with proteins or ligands.
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Affiliation(s)
- Lena Nyberg
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden and Department for Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
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214
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Zhao Y, Chen D, Yue H, French JB, Rufo J, Benkovic SJ, Huang TJ. Lab-on-a-chip technologies for single-molecule studies. LAB ON A CHIP 2013; 13:2183-98. [PMID: 23670195 PMCID: PMC3955889 DOI: 10.1039/c3lc90042h] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Recent developments on various lab-on-a-chip techniques allow miniaturized and integrated devices to perform on-chip single-molecule studies. Fluidic-based platforms that utilize unique microscale fluidic behavior are capable of conducting single-molecule experiments with high sensitivities and throughputs, while biomolecular systems can be studied on-chip using techniques such as DNA curtains, magnetic tweezers, and solid-state nanopores. The advances of these on-chip single-molecule techniques lead to next-generation lab-on-a-chip devices, such as DNA transistors, and single-molecule real-time (SMRT) technology for rapid and low-cost whole genome DNA sequencing. In this Focus article, we will discuss some recent successes in the development of lab-on-a-chip techniques for single-molecule studies and expound our thoughts on the near future of on-chip single-molecule studies.
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Affiliation(s)
- Yanhui Zhao
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802 USA
| | - Danqi Chen
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802 USA
| | - Hongjun Yue
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802 USA
| | - Jarrod B. French
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802 USA
| | - Joey Rufo
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802 USA
| | - Stephen J. Benkovic
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802 USA
| | - Tony Jun Huang
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802 USA
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215
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van Loenhout MTJ, De Vlaminck I, Flebus B, den Blanken JF, Zweifel LP, Hooning KM, Kerssemakers JWJ, Dekker C. Scanning a DNA molecule for bound proteins using hybrid magnetic and optical tweezers. PLoS One 2013; 8:e65329. [PMID: 23755219 PMCID: PMC3670887 DOI: 10.1371/journal.pone.0065329] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 04/24/2013] [Indexed: 11/25/2022] Open
Abstract
The functional state of the genome is determined by its interactions with proteins that bind, modify, and move along the DNA. To determine the positions and binding strength of proteins localized on DNA we have developed a combined magnetic and optical tweezers apparatus that allows for both sensitive and label-free detection. A DNA loop, that acts as a scanning probe, is created by looping an optically trapped DNA tether around a DNA molecule that is held with magnetic tweezers. Upon scanning the loop along the λ-DNA molecule, EcoRI proteins were detected with ∼17 nm spatial resolution. An offset of 33±5 nm for the detected protein positions was found between back and forwards scans, corresponding to the size of the DNA loop and in agreement with theoretical estimates. At higher applied stretching forces, the scanning loop was able to remove bound proteins from the DNA, showing that the method is in principle also capable of measuring the binding strength of proteins to DNA with a force resolution of 0.1 pN/. The use of magnetic tweezers in this assay allows the facile preparation of many single-molecule tethers, which can be scanned one after the other, while it also allows for direct control of the supercoiling state of the DNA molecule, making it uniquely suitable to address the effects of torque on protein-DNA interactions.
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Affiliation(s)
- Marijn T. J. van Loenhout
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Iwijn De Vlaminck
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Benedetta Flebus
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Johan F. den Blanken
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Ludovit P. Zweifel
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Koen M. Hooning
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Jacob W. J. Kerssemakers
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
- * E-mail:
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216
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Lansdorp BM, Tabrizi SJ, Dittmore A, Saleh OA. A high-speed magnetic tweezer beyond 10,000 frames per second. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:044301. [PMID: 23635212 DOI: 10.1063/1.4802678] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The magnetic tweezer is a single-molecule instrument that can apply a constant force to a biomolecule over a range of extensions, and is therefore an ideal tool to study biomolecules and their interactions. However, the video-based tracking inherent to most magnetic single-molecule instruments has traditionally limited the instrumental resolution to a few nanometers, above the length scale of single DNA base-pairs. Here we have introduced superluminescent diode illumination and high-speed camera detection to the magnetic tweezer, with graphics processing unit-accelerated particle tracking for high-speed analysis of video files. We have demonstrated the ability of the high-speed magnetic tweezer to resolve particle position to within 1 Å at 100 Hz, and to measure the extension of a 1566 bp DNA with 1 nm precision at 100 Hz in the presence of thermal noise.
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Affiliation(s)
- Bob M Lansdorp
- Materials Department, University of California Santa Barbara, Santa Barbara, California 93106, USA
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217
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Optical Methods to Study Protein-DNA Interactions in Vitro and in Living Cells at the Single-Molecule Level. Int J Mol Sci 2013; 14:3961-92. [PMID: 23429188 PMCID: PMC3588080 DOI: 10.3390/ijms14023961] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Revised: 01/13/2013] [Accepted: 02/04/2013] [Indexed: 12/13/2022] Open
Abstract
The maintenance of intact genetic information, as well as the deployment of transcription for specific sets of genes, critically rely on a family of proteins interacting with DNA and recognizing specific sequences or features. The mechanisms by which these proteins search for target DNA are the subject of intense investigations employing a variety of methods in biology. A large interest in these processes stems from the faster-than-diffusion association rates, explained in current models by a combination of 3D and 1D diffusion. Here, we present a review of the single-molecule approaches at the forefront of the study of protein-DNA interaction dynamics and target search in vitro and in vivo. Flow stretch, optical and magnetic manipulation, single fluorophore detection and localization as well as combinations of different methods are described and the results obtained with these techniques are discussed in the framework of the current facilitated diffusion model.
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218
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Yu Z, Mao H. Non-B DNA structures show diverse conformations and complex transition kinetics comparable to RNA or proteins--a perspective from mechanical unfolding and refolding experiments. CHEM REC 2013; 13:102-16. [PMID: 23389854 DOI: 10.1002/tcr.201200021] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Indexed: 01/03/2023]
Abstract
With the firm demonstration of the in vivo presence and biological functions of many non-B DNA structures, it is of great significance to understand their physiological roles from the perspective of structural conformation, stability, and transition kinetics. Although relatively simple in primary sequences compared to proteins, non-B DNA species show rather versatile conformations and dynamic transitions. As the most-studied non-B DNA species, the G-quadruplex displays a myriad of conformations that can interconvert between each other in different solutions. These features impose challenges for ensemble-average techniques, such as X-ray crystallography, NMR spectroscopy, and circular dichroism (CD), but leave room for single-molecular approaches to illustrate the structure, stability, and transition kinetics of individual non-B DNA species in a solution mixture. Deconvolution of the mixture can be further facilitated by statistical data treatment, such as iPoDNano (integrated population deconvolution with nanometer resolution), which resolves populations with subnanometer size differences. This Personal Account summarizes current mechanical unfolding and refolding methods to interrogate single non-B DNA species, with an emphasis on DNA G-quadruplexes and i-motifs. These single-molecule studies start to demonstrate that structures and transitions in non-B DNA species can approach the complexity of those in RNA or proteins, which provides solid justification for the biological functions carried out by non-B DNA species.
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Affiliation(s)
- Zhongbo Yu
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, USA
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219
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Heidarsson PO, Naqvi MM, Sonar P, Valpapuram I, Cecconi C. Conformational Dynamics of Single Protein Molecules Studied by Direct Mechanical Manipulation. DYNAMICS OF PROTEINS AND NUCLEIC ACIDS 2013; 92:93-133. [DOI: 10.1016/b978-0-12-411636-8.00003-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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220
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Kim H, Ha T. Single-molecule nanometry for biological physics. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:016601. [PMID: 23249673 PMCID: PMC3549428 DOI: 10.1088/0034-4885/76/1/016601] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Precision measurement is a hallmark of physics but the small length scale (∼nanometer) of elementary biological components and thermal fluctuations surrounding them challenge our ability to visualize their action. Here, we highlight the recent developments in single-molecule nanometry where the position of a single fluorescent molecule can be determined with nanometer precision, reaching the limit imposed by the shot noise, and the relative motion between two molecules can be determined with ∼0.3 nm precision at ∼1 ms time resolution, as well as how these new tools are providing fundamental insights into how motor proteins move on cellular highways. We will also discuss how interactions between three and four fluorescent molecules can be used to measure three and six coordinates, respectively, allowing us to correlate the movements of multiple components. Finally, we will discuss recent progress in combining angstrom-precision optical tweezers with single-molecule fluorescent detection, opening new windows for multi-dimensional single-molecule nanometry for biological physics.
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Affiliation(s)
- Hajin Kim
- Howard Hughes Medical Institute, Urbana, IL 61801, USA
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221
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Abstract
DNA in cells exhibits a supercoiled state in which the double helix is additionally twisted to form extended intertwined loops called plectonemes. Although supercoiling is vital to many cellular processes, its dynamics remain elusive. In this work, we directly visualize the dynamics of individual plectonemes. We observe that multiple plectonemes can be present and that their number depends on applied stretching force and ionic strength. Plectonemes moved along DNA by diffusion or, unexpectedly, by a fast hopping process that facilitated very rapid (<20 milliseconds) long-range plectoneme displacement by nucleating a new plectoneme at a distant position. These observations directly reveal the dynamics of plectonemes and identify a mode of movement that allows long-distance reorganization of the conformation of the genome on a millisecond time scale.
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Affiliation(s)
- M T J van Loenhout
- Delft University of Technology, Department of Bionanoscience, Kavli Institute of Nanoscience, Lorentzweg 1, 2628CJ Delft, Netherlands
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222
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De Vlaminck I, Henighan T, van Loenhout MTJ, Burnham DR, Dekker C. Magnetic forces and DNA mechanics in multiplexed magnetic tweezers. PLoS One 2012; 7:e41432. [PMID: 22870220 PMCID: PMC3411724 DOI: 10.1371/journal.pone.0041432] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 06/26/2012] [Indexed: 12/02/2022] Open
Abstract
Magnetic tweezers (MT) are a powerful tool for the study of DNA-enzyme interactions. Both the magnet-based manipulation and the camera-based detection used in MT are well suited for multiplexed measurements. Here, we systematically address challenges related to scaling of multiplexed magnetic tweezers (MMT) towards high levels of parallelization where large numbers of molecules (say 103) are addressed in the same amount of time required by a single-molecule measurement. We apply offline analysis of recorded images and show that this approach provides a scalable solution for parallel tracking of the xyz-positions of many beads simultaneously. We employ a large field-of-view imaging system to address many DNA-bead tethers in parallel. We model the 3D magnetic field generated by the magnets and derive the magnetic force experienced by DNA-bead tethers across the large field of view from first principles. We furthermore experimentally demonstrate that a DNA-bead tether subject to a rotating magnetic field describes a bicircular, Limaçon rotation pattern and that an analysis of this pattern simultaneously yields information about the force angle and the position of attachment of the DNA on the bead. Finally, we apply MMT in the high-throughput investigation of the distribution of the induced magnetic moment, the position of attachment of DNA on the beads, and DNA flexibility. The methods described herein pave the way to kilo-molecule level magnetic tweezers experiments.
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Affiliation(s)
- Iwijn De Vlaminck
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Thomas Henighan
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | | | - Daniel R. Burnham
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Cees Dekker
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
- * E-mail:
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