1
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Bag S, Bhowmik S. Fluorescence Spectroscopy: A Useful Method to Explore the Interactions of Small Molecule Ligands with DNA Structures. Methods Mol Biol 2024; 2719:33-49. [PMID: 37803111 DOI: 10.1007/978-1-0716-3461-5_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/08/2023]
Abstract
Small molecule ligands-DNA interactions have recently received a lot of attention in the fields of life sciences, medicine, and chemical sciences. To decode these interactions, many strategies have been developed. DNA is the primary target for a wide range of drugs that may interact with DNA in particular or non-specific ways and impact its activities. Fluorescence spectroscopy is a highly advanced and non-invasive technology for measuring the concentrations of substrates and products or identifying characteristic processing states. Small molecule ligands-DNA interaction studies are beneficial not only in comprehending the method of interaction, but also in synthesizing DNA-targeted particular drugs. Several small compounds that bind to DNA are clinically established therapeutic medicines, while their specific mechanism of action is unknown. Figuring out their molecular recognizing patterns is the only way to construct innovative compounds that can target specific DNA sequences with strong affinities. This book chapter will mostly explore several fluorescence spectroscopic methodologies used to investigate interactions between small molecule ligands and DNA. In addition, we provide many approaches for determining a drug's binding mode with DNA. These strategies produce data that is both trustworthy and easy to comprehend. All of the knowledge gained by studying these fluorescence spectroscopies are supposed to lead to the development of more efficient new pharmaceuticals that might aid in the treatment of diseases.
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Affiliation(s)
- Sagar Bag
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, West Bengal, India
| | - Sudipta Bhowmik
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, West Bengal, India.
- Mahatma Gandhi Medical Advanced Research Institute (MGMARI), Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, India.
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2
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Wang Y, Chen J, Su G, Mei J, Li J. A Review of Single-Cell Microrobots: Classification, Driving Methods and Applications. MICROMACHINES 2023; 14:1710. [PMID: 37763873 PMCID: PMC10537272 DOI: 10.3390/mi14091710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/19/2023] [Accepted: 08/23/2023] [Indexed: 09/29/2023]
Abstract
Single-cell microrobots are new microartificial devices that use a combination of single cells and artificial devices, with the advantages of small size, easy degradation and ease of manufacture. With externally driven strategies such as light fields, sound fields and magnetic fields, microrobots are able to carry out precise micromanipulations and movements in complex microenvironments. Therefore, single-cell microrobots have received more and more attention and have been greatly developed in recent years. In this paper, we review the main classifications, control methods and recent advances in the field of single-cell microrobot applications. First, different types of robots, such as cell-based microrobots, bacteria-based microrobots, algae-based microrobots, etc., and their design strategies and fabrication processes are discussed separately. Next, three types of external field-driven technologies, optical, acoustic and magnetic, are presented and operations realized in vivo and in vitro by applying these three technologies are described. Subsequently, the results achieved by these robots in the fields of precise delivery, minimally invasive therapy are analyzed. Finally, a short summary is given and current challenges and future work on microbial-based robotics are discussed.
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Affiliation(s)
| | | | | | | | - Junyang Li
- School of Electronic Engineering, Ocean University of China, Qingdao 266000, China; (Y.W.); (J.C.); (G.S.); (J.M.)
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3
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Yang A, Lein FN, Weiler J, Drechsel J, Schumann V, Erichson F, Streek A, Börner R. Pressure-controlled microfluidics for automated single-molecule sample preparation. HARDWAREX 2023; 14:e00425. [PMID: 37424928 PMCID: PMC10329172 DOI: 10.1016/j.ohx.2023.e00425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 04/10/2023] [Accepted: 04/24/2023] [Indexed: 07/11/2023]
Abstract
Sample preparation is a crucial step in single-molecule experiments and involves passivating the microfluidic sample chamber, immobilizing the molecules, and setting experimental buffer conditions. The efficiency of the experiment depends on the quality and speed of sample preparation, which is often performed manually and relies on the experience of the experimenter. This can result in inefficient use of single-molecule samples and time, especially for high-throughput applications. To address this, a pressure-controlled microfluidic system is proposed to automate single-molecule sample preparation. The hardware is based on microfluidic components from ElveFlow and is designed to be cost-effective and adaptable to various microscopy applications. The system includes a reservoir pressure adapter and a reservoir holder designed for additive manufacturing. Two flow chamber designs Ibidi µ-slide and Grace Bio-Labs HybriWell chamber are characterized, and the flow characteristics of the liquid at different volume flow rates V˙ are simulated using CFD-simulations and compared to experimental and theoretical values. The goal of this work is to establish a straightforward and robust system for single-molecule sample preparation that can increase the efficiency of experiments and reduce the bottleneck of manual sample preparation, particularly for high-throughput applications.
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4
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Fontana M, Ivanovaitė Š, Lindhoud S, van der Wijk E, Mathwig K, Berg WVD, Weijers D, Hohlbein J. Probing DNA - Transcription Factor Interactions Using Single-Molecule Fluorescence Detection in Nanofluidic Devices. Adv Biol (Weinh) 2022; 6:e2100953. [PMID: 34472724 DOI: 10.1002/adbi.202100953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 07/16/2021] [Indexed: 01/27/2023]
Abstract
Single-molecule fluorescence detection offers powerful ways to study biomolecules and their complex interactions. Here, nanofluidic devices and camera-based, single-molecule Förster resonance energy transfer (smFRET) detection are combined to study the interactions between plant transcription factors of the auxin response factor (ARF) family and DNA oligonucleotides that contain target DNA response elements. In particular, it is shown that the binding of the unlabeled ARF DNA binding domain (ARF-DBD) to donor and acceptor labeled DNA oligonucleotides can be detected by changes in the FRET efficiency and changes in the diffusion coefficient of the DNA. In addition, this data on fluorescently labeled ARF-DBDs suggest that, at nanomolar concentrations, ARF-DBDs are exclusively present as monomers. In general, the fluidic framework of freely diffusing molecules minimizes potential surface-induced artifacts, enables high-throughput measurements, and proved to be instrumental in shedding more light on the interactions between ARF-DBDs monomers and between ARF-DBDs and their DNA response element.
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Affiliation(s)
- Mattia Fontana
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands.,Laboratory of Biochemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
| | - Šarunė Ivanovaitė
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
| | - Simon Lindhoud
- Laboratory of Biochemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
| | - Elmar van der Wijk
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands.,Laboratory of Biochemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
| | - Klaus Mathwig
- Groningen Research Institute of Pharmacy, Pharmaceutical Analysis, University of Groningen, P.O. Box 196, 9700 AD, Groningen, The Netherlands.,Stichting Imec Nederland within OnePlanet Research Center, Bronland 10, Wageningen, 6708 WH, The Netherlands
| | - Willy van den Berg
- Laboratory of Biochemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
| | - Dolf Weijers
- Laboratory of Biochemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
| | - Johannes Hohlbein
- Laboratory of Biochemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands.,Microspectroscopy Research Facility, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
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5
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Grytsyk N, Cianfarani D, Crégut O, Richert L, Boudier C, Humbert N, Didier P, Mély Y, Léonard J. Kinetics of protein-assisted nucleic acid interconversion monitored by transient time resolved fluorescence in microfluidic droplets. Nucleic Acids Res 2021; 49:e111. [PMID: 34450653 PMCID: PMC8565319 DOI: 10.1093/nar/gkab687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 06/29/2021] [Accepted: 08/24/2021] [Indexed: 11/25/2022] Open
Abstract
Interconversions between nucleic acid structures play an important role in transcriptional and translational regulation and also in repair and recombination. These interconversions are frequently promoted by nucleic acid chaperone proteins. To monitor their kinetics, Förster resonance energy transfer (FRET) is widely exploited using ensemble fluorescence intensity measurements in pre-steady-state stopped-flow experiments. Such experiments only provide a weighted average of the emission of all species in solution and consume large quantities of materials. Herein, we lift these limitations by combining time-resolved fluorescence (TRF) with droplet microfluidics (DmF). We validate the innovative TRF-DmF approach by investigating the well characterized annealing of the HIV-1 (+)/(–) Primer Binding Sequences (PBS) promoted by a HIV-1 nucleocapsid peptide. Upon rapid mixing of the FRET-labelled (–)PBS with its complementary (+)PBS sequence inside microdroplets, the TRF-DmF set-up enables resolving the time evolution of sub-populations of reacting species and reveals an early intermediate with a ∼50 ps donor fluorescence lifetime never identified so far. TRF-DmF also favorably compares with single molecule experiments, as it offers an accurate control of concentrations with no upper limit, no need to graft one partner on a surface and no photobleaching issues.
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Affiliation(s)
- Natalia Grytsyk
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg & CNRS, 67034 Strasbourg, France.,Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France
| | - Damien Cianfarani
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg & CNRS, 67034 Strasbourg, France
| | - Olivier Crégut
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg & CNRS, 67034 Strasbourg, France
| | - Ludovic Richert
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France
| | - Christian Boudier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France
| | - Nicolas Humbert
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France
| | - Pascal Didier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France
| | - Yves Mély
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France
| | - Jérémie Léonard
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg & CNRS, 67034 Strasbourg, France
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6
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Götz R, Panzer S, Trinks N, Eilts J, Wagener J, Turrà D, Di Pietro A, Sauer M, Terpitz U. Expansion Microscopy for Cell Biology Analysis in Fungi. Front Microbiol 2020; 11:574. [PMID: 32318047 PMCID: PMC7147297 DOI: 10.3389/fmicb.2020.00574] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 03/16/2020] [Indexed: 12/11/2022] Open
Abstract
Super-resolution microscopy has evolved as a powerful method for subdiffraction-resolution fluorescence imaging of cells and cellular organelles, but requires sophisticated and expensive installations. Expansion microscopy (ExM), which is based on the physical expansion of the cellular structure of interest, provides a cheap alternative to bypass the diffraction limit and enable super-resolution imaging on a conventional fluorescence microscope. While ExM has shown impressive results for the magnified visualization of proteins and RNAs in cells and tissues, it has not yet been applied in fungi, mainly due to their complex cell wall. Here we developed a method that enables reliable isotropic expansion of ascomycetes and basidiomycetes upon treatment with cell wall degrading enzymes. Confocal laser scanning microscopy (CLSM) and structured illumination microscopy (SIM) images of 4.5-fold expanded sporidia of Ustilago maydis expressing fluorescent fungal rhodopsins and hyphae of Fusarium oxysporum or Aspergillus fumigatus expressing either histone H1-mCherry together with Lifeact-sGFP or mRFP targeted to mitochondria, revealed details of subcellular structures with an estimated spatial resolution of around 30 nm. ExM is thus well suited for cell biology studies in fungi on conventional fluorescence microscopes.
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Affiliation(s)
- Ralph Götz
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Biocenter, Julius-Maximilian-University, Würzburg, Germany
| | - Sabine Panzer
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Biocenter, Julius-Maximilian-University, Würzburg, Germany
| | - Nora Trinks
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Biocenter, Julius-Maximilian-University, Würzburg, Germany
| | - Janna Eilts
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Biocenter, Julius-Maximilian-University, Würzburg, Germany
| | - Johannes Wagener
- Institut für Hygiene und Mikrobiologie, Julius-Maximilian-University, Würzburg, Germany
| | - David Turrà
- Departamento de Genética, Universidad de Córdoba, Córdoba, Spain
| | | | - Markus Sauer
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Biocenter, Julius-Maximilian-University, Würzburg, Germany
| | - Ulrich Terpitz
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Biocenter, Julius-Maximilian-University, Würzburg, Germany
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7
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Petrova D, Sharma DK, Vacha M, Bonn D, Brouwer AM, Weber B. Ageing of Polymer Frictional Interfaces: The Role of Quantity and Quality of Contact. ACS APPLIED MATERIALS & INTERFACES 2020; 12:9890-9895. [PMID: 32024365 PMCID: PMC7049987 DOI: 10.1021/acsami.9b19125] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Accepted: 02/04/2020] [Indexed: 05/06/2023]
Abstract
When two objects are in contact, the force necessary for one to start sliding over the other is larger than the force necessary to keep the sliding motion going. This difference between static and dynamic friction is thought to result from a reduction in the area of real contact upon the onset of slip. Here, we resolve the structure in the area of contact on the molecular scale by means of environment-sensitive molecular rotors using (super-resolution) fluorescence microscopy and fluorescence lifetime imaging. We demonstrate that the macroscopic friction force is not only controlled by the area of real contact but also controlled by the "quality" of that area of real contact, which determines the friction per unit contact area. We show that the latter is affected by the local density of the contacting surfaces, a parameter that can be expected to change in time at any interface that involves glassy, amorphous materials.
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Affiliation(s)
- D. Petrova
- van
‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
| | - D. K. Sharma
- Department
of Materials Science and Engineering, Tokyo
Institute of Technology, Ookayama 2-12-1-S8-44, Meguro-ku, 152-8552 Tokyo, Japan
| | - M. Vacha
- Department
of Materials Science and Engineering, Tokyo
Institute of Technology, Ookayama 2-12-1-S8-44, Meguro-ku, 152-8552 Tokyo, Japan
| | - D. Bonn
- Van
der Waals-Zeeman Institute, IoP, University
of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
| | - A. M. Brouwer
- van
‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
| | - B. Weber
- Van
der Waals-Zeeman Institute, IoP, University
of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
- Advanced
Research Center for Nanolithography (ARCNL), Science Park 110, 1098 XG Amsterdam, Netherlands
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8
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Baldering TN, Dietz MS, Gatterdam K, Karathanasis C, Wieneke R, Tampé R, Heilemann M. Synthetic and genetic dimers as quantification ruler for single-molecule counting with PALM. Mol Biol Cell 2019; 30:1369-1376. [PMID: 30969885 PMCID: PMC6724688 DOI: 10.1091/mbc.e18-10-0661] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
How membrane proteins oligomerize determines their function. Superresolution microscopy can report on protein clustering and extract quantitative molecular information. Here, we evaluate the blinking kinetics of four photoactivatable fluorescent proteins for quantitative single-molecule microscopy. We identified mEos3.2 and mMaple3 to be suitable for molecular quantification through blinking histogram analysis. We designed synthetic and genetic dimers of mEos3.2 as well as fusion proteins of monomeric and dimeric membrane proteins as reference structures, and we demonstrate their versatile use for quantitative superresolution imaging in vitro and in situ. We further found that the blinking behavior of mEos3.2 and mMaple3 is modified by a reducing agent, offering the possibility to adjust blinking parameters according to experimental needs.
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Affiliation(s)
- Tim N Baldering
- Single Molecule Biophysics, Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Marina S Dietz
- Single Molecule Biophysics, Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Karl Gatterdam
- Institute of Biochemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Christos Karathanasis
- Single Molecule Biophysics, Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Ralph Wieneke
- Institute of Biochemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Robert Tampé
- Institute of Biochemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Mike Heilemann
- Single Molecule Biophysics, Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
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9
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Choudhary D, Mossa A, Jadhav M, Cecconi C. Bio-Molecular Applications of Recent Developments in Optical Tweezers. Biomolecules 2019; 9:E23. [PMID: 30641944 PMCID: PMC6359149 DOI: 10.3390/biom9010023] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/02/2019] [Accepted: 01/02/2019] [Indexed: 12/17/2022] Open
Abstract
In the past three decades, the ability to optically manipulate biomolecules has spurred a new era of medical and biophysical research. Optical tweezers (OT) have enabled experimenters to trap, sort, and probe cells, as well as discern the structural dynamics of proteins and nucleic acids at single molecule level. The steady improvement in OT's resolving power has progressively pushed the envelope of their applications; there are, however, some inherent limitations that are prompting researchers to look for alternatives to the conventional techniques. To begin with, OT are restricted by their one-dimensional approach, which makes it difficult to conjure an exhaustive three-dimensional picture of biological systems. The high-intensity trapping laser can damage biological samples, a fact that restricts the feasibility of in vivo applications. Finally, direct manipulation of biological matter at nanometer scale remains a significant challenge for conventional OT. A significant amount of literature has been dedicated in the last 10 years to address the aforementioned shortcomings. Innovations in laser technology and advances in various other spheres of applied physics have been capitalized upon to evolve the next generation OT systems. In this review, we elucidate a few of these developments, with particular focus on their biological applications. The manipulation of nanoscopic objects has been achieved by means of plasmonic optical tweezers (POT), which utilize localized surface plasmons to generate optical traps with enhanced trapping potential, and photonic crystal optical tweezers (PhC OT), which attain the same goal by employing different photonic crystal geometries. Femtosecond optical tweezers (fs OT), constructed by replacing the continuous wave (cw) laser source with a femtosecond laser, promise to greatly reduce the damage to living samples. Finally, one way to transcend the one-dimensional nature of the data gained by OT is to couple them to the other large family of single molecule tools, i.e., fluorescence-based imaging techniques. We discuss the distinct advantages of the aforementioned techniques as well as the alternative experimental perspective they provide in comparison to conventional OT.
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Affiliation(s)
- Dhawal Choudhary
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, 41125 Modena, Italy.
- Center S3, CNR Institute Nanoscience, Via Campi 213/A, 41125 Modena, Italy.
| | - Alessandro Mossa
- Istituto Statale di Istruzione Superiore "Leonardo da Vinci", Via del Terzolle 91, 50127 Firenze, Italy.
- Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, Via Giovanni Sansone 1, 50019 Sesto Fiorentino, Italy.
| | - Milind Jadhav
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, 41125 Modena, Italy.
| | - Ciro Cecconi
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, 41125 Modena, Italy.
- Center S3, CNR Institute Nanoscience, Via Campi 213/A, 41125 Modena, Italy.
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10
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Fontana M, Fijen C, Lemay SG, Mathwig K, Hohlbein J. High-throughput, non-equilibrium studies of single biomolecules using glass-made nanofluidic devices. LAB ON A CHIP 2018; 19:79-86. [PMID: 30468446 DOI: 10.1039/c8lc01175c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Single-molecule detection schemes offer powerful means to overcome static and dynamic heterogeneity inherent to complex samples. However, probing biomolecular interactions and reactions with high throughput and time resolution remains challenging, often requiring surface-immobilized entities. Here, we introduce glass-made nanofluidic devices for the high-throughput detection of freely-diffusing single biomolecules by camera-based fluorescence microscopy. Nanochannels of 200 nm height and a width of several micrometers confine the movement of biomolecules. Using pressure-driven flow through an array of parallel nanochannels and by tracking the movement of fluorescently labelled DNA oligonucleotides, we observe conformational changes with high throughput. In a device geometry featuring a T-shaped junction of nanochannels, we drive steady-state non-equilibrium conditions by continuously mixing reactants and triggering chemical reactions. We use the device to probe the conformational equilibrium of a DNA hairpin as well as to continuously observe DNA synthesis in real time. Our platform offers a straightforward and robust method for studying reaction kinetics at the single-molecule level.
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Affiliation(s)
- Mattia Fontana
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, Wageningen, 6708 WE, The Netherlands
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11
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Site-Specific Labelling of Multidomain Proteins by Amber Codon Suppression. Sci Rep 2018; 8:14864. [PMID: 30291265 PMCID: PMC6173736 DOI: 10.1038/s41598-018-33115-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 09/18/2018] [Indexed: 01/30/2023] Open
Abstract
The access to information on the dynamic behaviour of large proteins is usually hindered as spectroscopic methods require the site-specific attachment of biophysical probes. A powerful emerging tool to tackle this issue is amber codon suppression. Till date, its application on large and complex multidomain proteins of MDa size has not been reported. Herein, we systematically investigate the feasibility to introduce different non-canonical amino acids into a 540 kDa homodimeric fatty acid synthase type I by genetic code expansion with subsequent fluorescent labelling. Our approach relies on a microplate-based reporter assay of low complexity using a GFP fusion protein to quickly screen for sufficient suppression conditions. Once identified, these findings were successfully utilized to upscale both the expression scale and the protein size to full-length constructs. These fluorescently labelled samples of fatty acid synthase were subjected to initial biophysical experiments, including HPLC analysis, activity assays and fluorescence spectroscopy. Successful introduction of such probes into a molecular machine such as fatty acid synthases may pave the way to understand the conformational variability, which is a primary intrinsic property required for efficient interplay of all catalytic functionalities, and to engineer them.
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12
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Zhang T, Li S, Du Y, He T, Shen Y, Bai C, Huang Y, Zhou X. Revealing the Activity Distribution of a Single Nanocatalyst by Locating Single Nanobubbles with Super-Resolution Microscopy. J Phys Chem Lett 2018; 9:5630-5635. [PMID: 30188127 DOI: 10.1021/acs.jpclett.8b02302] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
It is challenging to uncover the catalytic activity at different locations of a single nanocatalyst for gas-generating reactions in real time. This research uses super-resolution microscopy to localize the center of single nanobubbles and reveal the local activity distribution at several to tens of nanometers accuracy. The distances between the centers of the nanobubbles and the center of the nanoplate usually distribute in a certain range from 0 to 500 nm, with the maximum population exhibiting at ∼200 nm. This research also shows that more nanobubbles appear near the tips of the Pd-Ag nanoplate compared with the edges, which indicates higher activity at the tips. In addition, the relationship between the location, lifetime, and turnover rate of the nanobubbles was also carefully studied. This work presents an effective, high-resolution method to localize the activity distribution of nanocatalysts during gas-generating reactions, such as photocatalytic water splitting, dehydrogenation, and electro-oxidation.
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Affiliation(s)
- Ting Zhang
- Faculty of Materials Science and Chemistry , China University of Geosciences , Wuhan 430074 , China
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
| | - Shuping Li
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
| | - Ying Du
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
| | - Ting He
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
| | - Yangbin Shen
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
| | - Chuang Bai
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
| | - Yunjie Huang
- Faculty of Materials Science and Chemistry , China University of Geosciences , Wuhan 430074 , China
| | - Xiaochun Zhou
- Division of Advanced Nanomaterials , Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
- Key Lab of Nanodevices and Applications , Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS) , Suzhou 215123 , China
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13
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Hadzic MCAS, Börner R, König SLB, Kowerko D, Sigel RKO. Reliable State Identification and State Transition Detection in Fluorescence Intensity-Based Single-Molecule Förster Resonance Energy-Transfer Data. J Phys Chem B 2018; 122:6134-6147. [PMID: 29737844 DOI: 10.1021/acs.jpcb.7b12483] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a powerful technique to probe biomolecular structure and dynamics. A popular implementation of smFRET consists of recording fluorescence intensity time traces of surface-immobilized, chromophore-tagged molecules. This approach generates large and complex data sets, the analysis of which is to date not standardized. Here, we address a key challenge in smFRET data analysis: the generation of thermodynamic and kinetic models that describe with statistical rigor the behavior of FRET trajectories recorded from surface-tethered biomolecules in terms of the number of FRET states, the corresponding mean FRET values, and the kinetic rates at which they interconvert. For this purpose, we first perform Monte Carlo simulations to generate smFRET trajectories, in which a relevant space of experimental parameters is explored. Then, we provide an account on current strategies to achieve such model selection, as well as a quantitative assessment of their performances. Specifically, we evaluate the performance of each algorithm (change-point analysis, STaSI, HaMMy, vbFRET, and ebFRET) with respect to accuracy, reproducibility, and computing time, which yields a range of algorithm-specific referential benchmarks for various data qualities. Data simulation and analysis were performed with our MATLAB-based multifunctional analysis software for handling smFRET data (MASH-FRET).
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Affiliation(s)
| | | | | | - Danny Kowerko
- Department of Computer Science , Chemnitz University of Technology , 09111 Chemnitz , Germany
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14
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Börner R, Kowerko D, Hadzic MCAS, König SLB, Ritter M, Sigel RKO. Simulations of camera-based single-molecule fluorescence experiments. PLoS One 2018; 13:e0195277. [PMID: 29652886 PMCID: PMC5898730 DOI: 10.1371/journal.pone.0195277] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 03/19/2018] [Indexed: 01/23/2023] Open
Abstract
Single-molecule microscopy has become a widely used technique in (bio)physics and (bio)chemistry. A popular implementation is single-molecule Förster Resonance Energy Transfer (smFRET), for which total internal reflection fluorescence microscopy is frequently combined with camera-based detection of surface-immobilized molecules. Camera-based smFRET experiments generate large and complex datasets and several methods for video processing and analysis have been reported. As these algorithms often address similar aspects in video analysis, there is a growing need for standardized comparison. Here, we present a Matlab-based software (MASH-FRET) that allows for the simulation of camera-based smFRET videos, yielding standardized data sets suitable for benchmarking video processing algorithms. The software permits to vary parameters that are relevant in cameras-based smFRET, such as video quality, and the properties of the system under study. Experimental noise is modeled taking into account photon statistics and camera noise. Finally, we survey how video test sets should be designed to evaluate currently available data analysis strategies in camera-based sm fluorescence experiments. We complement our study by pre-optimizing and evaluating spot detection algorithms using our simulated video test sets.
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Affiliation(s)
- Richard Börner
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Danny Kowerko
- Department of Computer Science, Chemnitz University of Technology, Chemnitz, Germany
| | | | - Sebastian L. B. König
- Department of Chemistry, University of Zurich, Zurich, Switzerland
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Marc Ritter
- Department of Applied Computer and Biosciences, Mittweida University of Applied Sciences, Mittweida, Germany
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15
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Steffen FD, Sigel RKO, Börner R. An atomistic view on carbocyanine photophysics in the realm of RNA. Phys Chem Chem Phys 2018; 18:29045-29055. [PMID: 27783069 DOI: 10.1039/c6cp04277e] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Carbocyanine dyes have a long-standing tradition in fluorescence imaging and spectroscopy, due to their photostability and large spectral separation between individual dye species. Herein, we explore the versatility of cyanine dyes to probe the dynamics of nucleic acids and we report on the interrelation of fluorophores, RNA, and metal ions, namely K+ and Mg2+. Photophysical parameters including the fluorescence lifetime, quantum yield and dynamic anisotropy are monitored as a function of the nucleic acid composition, conformation, and metal ion abundance. Occasional excursions to a non-fluorescent cis-state hint at the remarkable sensitivity of carbocyanines to their local environment. Comparison of time-correlated single photon experiments with all-atom molecular dynamics simulations demonstrate that the propensity of photoisomerization is dictated by sterical constraints imposed on the fluorophore. Structural features in the vicinity of the dye play a crucial role in RNA recognition and have far-reaching implications on the mobility of the fluorescent probe. An atomic level description of the mutual interactions will ultimately benefit the quantitative interpretation of single-molecule FRET measurements on large RNA systems.
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Affiliation(s)
- Fabio D Steffen
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Roland K O Sigel
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Richard Börner
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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16
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Stracy M, Kapanidis AN. Single-molecule and super-resolution imaging of transcription in living bacteria. Methods 2017; 120:103-114. [PMID: 28414097 PMCID: PMC5670121 DOI: 10.1016/j.ymeth.2017.04.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/21/2017] [Accepted: 04/05/2017] [Indexed: 12/20/2022] Open
Abstract
In vivo single-molecule and super-resolution techniques are transforming our ability to study transcription as it takes place in its native environment in living cells. This review will detail the methods for imaging single molecules in cells, and the data-analysis tools which can be used to extract quantitative information on the spatial organization, mobility, and kinetics of the transcription machinery from these experiments. Furthermore, we will highlight studies which have applied these techniques to shed new light on bacterial transcription.
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Affiliation(s)
- Mathew Stracy
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
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17
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Börner R, Kowerko D, Miserachs HG, Schaffer MF, Sigel RK. Metal ion induced heterogeneity in RNA folding studied by smFRET. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2016.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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18
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Hohlbein J, Kapanidis AN. Probing the Conformational Landscape of DNA Polymerases Using Diffusion-Based Single-Molecule FRET. Methods Enzymol 2016; 581:353-378. [PMID: 27793286 DOI: 10.1016/bs.mie.2016.08.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Monitoring conformational changes in DNA polymerases using single-molecule Förster resonance energy transfer (smFRET) has provided new tools for studying fidelity-related mechanisms that promote the rejection of incorrect nucleotides before DNA synthesis. In addition to the previously known open and closed conformations of DNA polymerases, our smFRET assays utilizing doubly labeled variants of Escherichia coli DNA polymerase I were pivotal in identifying and characterizing a partially closed conformation as a primary checkpoint for nucleotide selection. Here, we provide a comprehensive overview of the methods we used for the conformational analysis of wild-type DNA polymerase and some of its low-fidelity derivatives; these methods include strategies for protein labeling and our procedures for solution-based single-molecule fluorescence data acquisition and data analysis. We also discuss alternative single-molecule fluorescence strategies for analyzing the conformations of DNA polymerases in vitro and in vivo.
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Affiliation(s)
- J Hohlbein
- Laboratory of Biophysics, Wageningen University and Research, Wageningen, The Netherlands; Microspectroscopy Centre, Wageningen University and Research, Wageningen, The Netherlands.
| | - A N Kapanidis
- Clarendon Laboratory, University of Oxford, Oxford, United Kingdom.
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19
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Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers. Sci Rep 2016; 6:33257. [PMID: 27641327 PMCID: PMC5027553 DOI: 10.1038/srep33257] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 08/24/2016] [Indexed: 01/24/2023] Open
Abstract
Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble.
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20
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Egloff D, Oleinich IA, Zhao M, König SLB, Sigel RKO, Freisinger E. Sequence-Specific Post-Synthetic Oligonucleotide Labeling for Single-Molecule Fluorescence Applications. ACS Chem Biol 2016; 11:2558-67. [PMID: 27409145 DOI: 10.1021/acschembio.6b00343] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The sequence-specific fluorescence labeling of nucleic acids is a prerequisite for various methods including single-molecule Förster resonance energy transfer (smFRET) for the detailed study of nucleic acid folding and function. Such nucleic acid derivatives are commonly obtained by solid-phase methods; however, yields decrease rapidly with increasing length and restrict the practicability of this approach for long strands. Here, we report a new labeling strategy for the postsynthetic incorporation of a bioorthogonal group into single stranded regions of both DNA and RNA of unrestricted length. A 12-alkyne-etheno-adenine modification is sequence-selectively formed using DNA-templated synthesis, followed by conjugation of the fluorophore Cy3 via a copper-catalyzed azide-alkyne cycloaddition (CuAAC). Evaluation of the labeled strands in smFRET measurements shows that the strategy developed here has the potential to be used for the study of long functional nucleic acids by (single-molecule) fluorescence or other methods. To prove the universal use of the method, its application was successfully extended to the labeling of a short RNA single strand. As a proof-of-concept, also the labeling of a large RNA molecule in form of a 633 nucleotide long construct derived from the Saccharomyces cerevisiae group II intron Sc.ai5γ was performed, and covalent attachment of the Cy3 fluorophore was shown with gel electrophoresis.
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Affiliation(s)
- David Egloff
- Department of Chemistry, University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
| | - Igor A. Oleinich
- Department of Chemistry, University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
| | - Meng Zhao
- Department of Chemistry, University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
| | - Sebastian L. B. König
- Department of Chemistry, University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
| | - Roland K. O. Sigel
- Department of Chemistry, University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
| | - Eva Freisinger
- Department of Chemistry, University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
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21
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Farooq S, Hohlbein J. Camera-based single-molecule FRET detection with improved time resolution. Phys Chem Chem Phys 2016; 17:27862-72. [PMID: 26439729 DOI: 10.1039/c5cp04137f] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The achievable time resolution of camera-based single-molecule detection is often limited by the frame rate of the camera. Especially in experiments utilizing single-molecule Förster resonance energy transfer (smFRET) to probe conformational dynamics of biomolecules, increasing the frame rate by either pixel-binning or cropping the field of view decreases the number of molecules that can be monitored simultaneously. Here, we present a generalised excitation scheme termed stroboscopic alternating-laser excitation (sALEX) that significantly improves the time resolution without sacrificing highly parallelised detection in total internal reflection fluorescence (TIRF) microscopy. In addition, we adapt a technique known from diffusion-based confocal microscopy to analyse the complex shape of FRET efficiency histograms. We apply both sALEX and dynamic probability distribution analysis (dPDA) to resolve conformational dynamics of interconverting DNA hairpins in the millisecond time range.
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Affiliation(s)
- Shazia Farooq
- Laboratory of Biophysics, Wageningen UR, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
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22
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Gül OT, Pugliese KM, Choi Y, Sims PC, Pan D, Rajapakse AJ, Weiss GA, Collins PG. Single Molecule Bioelectronics and Their Application to Amplification-Free Measurement of DNA Lengths. BIOSENSORS-BASEL 2016; 6:bios6030029. [PMID: 27348011 PMCID: PMC5039648 DOI: 10.3390/bios6030029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/08/2016] [Accepted: 06/15/2016] [Indexed: 01/17/2023]
Abstract
As biosensing devices shrink smaller and smaller, they approach a scale in which single molecule electronic sensing becomes possible. Here, we review the operation of single-enzyme transistors made using single-walled carbon nanotubes. These novel hybrid devices transduce the motions and catalytic activity of a single protein into an electronic signal for real-time monitoring of the protein’s activity. Analysis of these electronic signals reveals new insights into enzyme function and proves the electronic technique to be complementary to other single-molecule methods based on fluorescence. As one example of the nanocircuit technique, we have studied the Klenow Fragment (KF) of DNA polymerase I as it catalytically processes single-stranded DNA templates. The fidelity of DNA polymerases makes them a key component in many DNA sequencing techniques, and here we demonstrate that KF nanocircuits readily resolve DNA polymerization with single-base sensitivity. Consequently, template lengths can be directly counted from electronic recordings of KF’s base-by-base activity. After measuring as few as 20 copies, the template length can be determined with <1 base pair resolution, and different template lengths can be identified and enumerated in solutions containing template mixtures.
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Affiliation(s)
- O Tolga Gül
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA
- Department of Physics, Polatlı Faculty of Science and Arts, Gazi University, Polatlı 06900, Turkey
| | - Kaitlin M Pugliese
- Department of Chemistry, University of California at Irvine, Irvine, CA 92697, USA
| | - Yongki Choi
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA
- Department of Physics, North Dakota State University, Fargo, ND 58108, USA
| | - Patrick C Sims
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA
| | - Deng Pan
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA
| | - Arith J Rajapakse
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA
| | - Gregory A Weiss
- Department of Chemistry, University of California at Irvine, Irvine, CA 92697, USA.
- Department of Molecular Biology and Biochemistry, University of California at Irvine, Irvine, CA 92697, USA.
| | - Philip G Collins
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA.
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23
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Weber’s Red-Edge Effect that Changed the Paradigm in Photophysics and Photochemistry. ACTA ACUST UNITED AC 2016. [DOI: 10.1007/4243_2016_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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24
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Börner R, Ehrlich N, Hohlbein J, Hübner CG. Single Molecule 3D Orientation in Time and Space: A 6D Dynamic Study on Fluorescently Labeled Lipid Membranes. J Fluoresc 2016; 26:963-75. [DOI: 10.1007/s10895-016-1784-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Accepted: 03/02/2016] [Indexed: 10/22/2022]
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25
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Characterizing 3D RNA structure by single molecule FRET. Methods 2016; 103:57-67. [PMID: 26853327 DOI: 10.1016/j.ymeth.2016.02.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 02/02/2016] [Accepted: 02/03/2016] [Indexed: 12/26/2022] Open
Abstract
The importance of elucidating the three dimensional structures of RNA molecules is becoming increasingly clear. However, traditional protein structural techniques such as NMR and X-ray crystallography have several important drawbacks when probing long RNA molecules. Single molecule Förster resonance energy transfer (smFRET) has emerged as a useful alternative as it allows native sequences to be probed in physiological conditions and allows multiple conformations to be probed simultaneously. This review serves to describe the method of generating a three dimensional RNA structure from smFRET data from the biochemical probing of the secondary structure to the computational refinement of the final model.
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26
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Bourouina N, de Kort DW, Hoeben FJM, Janssen HM, Van As H, Hohlbein J, van Duynhoven JPM, Kleijn JM. Complex Coacervate Core Micelles with Spectroscopic Labels for Diffusometric Probing of Biopolymer Networks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12635-43. [PMID: 26535962 DOI: 10.1021/acs.langmuir.5b03496] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We present the design, preparation, and characterization of two types of complex coacervate core micelles (C3Ms) with cross-linked cores and spectroscopic labels and demonstrate their use as diffusional probes to investigate the microstructure of percolating biopolymer networks. The first type consists of poly(allylamine hydrochloride) (PAH) and poly(ethylene oxide)-poly(methacrylic acid) (PEO-b-PMAA), labeled with ATTO 488 fluorescent dyes. We show that the size of these probes can be tuned by choosing the length of the PEO-PMAA chains. ATTO 488-labeled PEO113-PMAA15 micelles are very bright with 18 dye molecules incorporated into their cores. The second type is a (19)F-labeled micelle, for which we used PAH and a (19)F-labeled diblock copolymer tailor-made from poly(ethylene oxide)-poly(acrylic acid) (mPEO79-b-PAA14). These micelles contain approximately 4 wt % of (19)F and can be detected by (19)F NMR. The (19)F labels are placed at the end of a small spacer to allow for the necessary rotational mobility. We used these ATTO- and (19)F-labeled micelles to probe the microstructures of a transient gel (xanthan gum) and a cross-linked, heterogeneous gel (κ-carrageenan). For the transient gel, sensitive optical diffusometry methods, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, and super-resolution single nanoparticle tracking, allowed us to measure the diffusion coefficient in networks with increasing density. From these measurements, we determined the diameters of the constituent xanthan fibers. In the heterogeneous κ-carrageenan gels, bimodal nanoparticle diffusion was observed, which is a signpost of microstructural heterogeneity of the network.
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Affiliation(s)
- Nadia Bourouina
- Physical Chemistry and Soft Matter, Wageningen University , P.O. Box 8038, 6700 EK Wageningen, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Daan W de Kort
- Laboratory of Biophysics, Wageningen University , P.O. Box 8128, 6700 ET Wageningen, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Freek J M Hoeben
- SyMO-Chem B.V., Het Kraneveld 4, 5612 AZ Eindhoven, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Henk M Janssen
- SyMO-Chem B.V., Het Kraneveld 4, 5612 AZ Eindhoven, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Henk Van As
- Laboratory of Biophysics, Wageningen University , P.O. Box 8128, 6700 ET Wageningen, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Johannes Hohlbein
- Laboratory of Biophysics, Wageningen University , P.O. Box 8128, 6700 ET Wageningen, The Netherlands
| | - John P M van Duynhoven
- Laboratory of Biophysics, Wageningen University , P.O. Box 8128, 6700 ET Wageningen, The Netherlands
- Unilever R&D, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - J Mieke Kleijn
- Physical Chemistry and Soft Matter, Wageningen University , P.O. Box 8038, 6700 EK Wageningen, The Netherlands
- TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands
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27
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McGinn S, Bauer D, Brefort T, Dong L, El-Sagheer A, Elsharawy A, Evans G, Falk-Sörqvist E, Forster M, Fredriksson S, Freeman P, Freitag C, Fritzsche J, Gibson S, Gullberg M, Gut M, Heath S, Heath-Brun I, Heron AJ, Hohlbein J, Ke R, Lancaster O, Le Reste L, Maglia G, Marie R, Mauger F, Mertes F, Mignardi M, Moens L, Oostmeijer J, Out R, Pedersen JN, Persson F, Picaud V, Rotem D, Schracke N, Sengenes J, Stähler PF, Stade B, Stoddart D, Teng X, Veal CD, Zahra N, Bayley H, Beier M, Brown T, Dekker C, Ekström B, Flyvbjerg H, Franke A, Guenther S, Kapanidis AN, Kaye J, Kristensen A, Lehrach H, Mangion J, Sauer S, Schyns E, Tost J, van Helvoort JMLM, van der Zaag PJ, Tegenfeldt JO, Brookes AJ, Mir K, Nilsson M, Willcocks JP, Gut IG. New technologies for DNA analysis--a review of the READNA Project. N Biotechnol 2015; 33:311-30. [PMID: 26514324 DOI: 10.1016/j.nbt.2015.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 10/17/2015] [Indexed: 01/09/2023]
Abstract
The REvolutionary Approaches and Devices for Nucleic Acid analysis (READNA) project received funding from the European Commission for 41/2 years. The objectives of the project revolved around technological developments in nucleic acid analysis. The project partners have discovered, created and developed a huge body of insights into nucleic acid analysis, ranging from improvements and implementation of current technologies to the most promising sequencing technologies that constitute a 3(rd) and 4(th) generation of sequencing methods with nanopores and in situ sequencing, respectively.
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Affiliation(s)
- Steven McGinn
- CEA - Centre National de Génotypage, 2, rue Gaston Cremieux, 91057 Evry Cedex, France
| | - David Bauer
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Thomas Brefort
- Comprehensive Biomarker Center GmbH, Im Neuenheimer Feld 583, D-69120 Heidelberg, Germany
| | - Liqin Dong
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Afaf El-Sagheer
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK; Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK; Chemistry Branch, Department of Science and Mathematics, Faculty of Petroleum and Mining Engineering, Suez University, Suez 43721, Egypt
| | - Abdou Elsharawy
- Institute of Clinical Molecular Biology, Christian-Albrechts-University (CAU), Am Botanischen Garten 11, D-24118 Kiel, Germany; Faculty of Sciences, Division of Biochemistry, Chemistry Department, Damietta University, New Damietta City, Egypt
| | - Geraint Evans
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, Parks Road, Oxford OX1 3PU, UK
| | - Elin Falk-Sörqvist
- Department of Immunology, Genetics, and Pathology, Science for Life Laboratory, Uppsala University, Sweden
| | - Michael Forster
- Institute of Clinical Molecular Biology, Christian-Albrechts-University (CAU), Am Botanischen Garten 11, D-24118 Kiel, Germany
| | | | - Peter Freeman
- University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Camilla Freitag
- Department of Physics, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Joachim Fritzsche
- Department of Applied Physics, Chalmers University of Technology, Kemivägen 10, 412 96 Göteborg, Sweden
| | - Spencer Gibson
- University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Mats Gullberg
- Olink AB, Dag Hammarskjölds väg 52A, 752 37 Uppsala, Sweden
| | - Marta Gut
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, C/Baldiri Reixac 7, 08028 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Simon Heath
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, C/Baldiri Reixac 7, 08028 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Isabelle Heath-Brun
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, C/Baldiri Reixac 7, 08028 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Andrew J Heron
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, England, UK
| | - Johannes Hohlbein
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, Parks Road, Oxford OX1 3PU, UK
| | - Rongqin Ke
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Box 1031, Se-171 21 Solna, Sweden; Department of Immunology, Genetics, and Pathology, Science for Life Laboratory, Uppsala University, Sweden
| | - Owen Lancaster
- University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Ludovic Le Reste
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, Parks Road, Oxford OX1 3PU, UK
| | - Giovanni Maglia
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, England, UK
| | - Rodolphe Marie
- DTU Nanotech, Oerstedsplads Building 345 East, 2800, Kongens Lyngby, Denmark
| | - Florence Mauger
- CEA - Centre National de Génotypage, 2, rue Gaston Cremieux, 91057 Evry Cedex, France
| | - Florian Mertes
- Max Planck Institute for Molecular Genetics, Ihnestrasse 73, 14195 Berlin, Germany
| | - Marco Mignardi
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Box 1031, Se-171 21 Solna, Sweden; Department of Immunology, Genetics, and Pathology, Science for Life Laboratory, Uppsala University, Sweden
| | - Lotte Moens
- Department of Immunology, Genetics, and Pathology, Science for Life Laboratory, Uppsala University, Sweden
| | | | - Ruud Out
- FlexGen BV, Galileiweg 8, 2333 BD Leiden, The Netherlands
| | | | - Fredrik Persson
- Department of Physics, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Vincent Picaud
- CEA-Saclay, Bât DIGITEO 565 - Pt Courrier 192, 91191 Gif-sur-Yvette Cedex, France
| | - Dvir Rotem
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, England, UK
| | - Nadine Schracke
- Comprehensive Biomarker Center GmbH, Im Neuenheimer Feld 583, D-69120 Heidelberg, Germany
| | - Jennifer Sengenes
- CEA - Centre National de Génotypage, 2, rue Gaston Cremieux, 91057 Evry Cedex, France
| | - Peer F Stähler
- Comprehensive Biomarker Center GmbH, Im Neuenheimer Feld 583, D-69120 Heidelberg, Germany
| | - Björn Stade
- Institute of Clinical Molecular Biology, Christian-Albrechts-University (CAU), Am Botanischen Garten 11, D-24118 Kiel, Germany
| | - David Stoddart
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, England, UK
| | - Xia Teng
- FlexGen BV, Galileiweg 8, 2333 BD Leiden, The Netherlands
| | - Colin D Veal
- University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Nathalie Zahra
- University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Hagan Bayley
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, England, UK
| | - Markus Beier
- Comprehensive Biomarker Center GmbH, Im Neuenheimer Feld 583, D-69120 Heidelberg, Germany
| | - Tom Brown
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK; Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Björn Ekström
- Olink AB, Dag Hammarskjölds väg 52A, 752 37 Uppsala, Sweden
| | - Henrik Flyvbjerg
- DTU Nanotech, Oerstedsplads Building 345 East, 2800, Kongens Lyngby, Denmark
| | - Andre Franke
- Institute of Clinical Molecular Biology, Christian-Albrechts-University (CAU), Am Botanischen Garten 11, D-24118 Kiel, Germany
| | - Simone Guenther
- Thermo Fisher Scientific Frankfurter Straße 129B, 64293 Darmstadt, Germany
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, Parks Road, Oxford OX1 3PU, UK
| | - Jane Kaye
- HeLEX - Centre for Health, Law and Emerging Technologies, Nuffield Department of Population Health, University of Oxford, Old Road Campus, Oxford OX3 7LF, UK
| | - Anders Kristensen
- DTU Nanotech, Oerstedsplads Building 345 East, 2800, Kongens Lyngby, Denmark
| | - Hans Lehrach
- Max Planck Institute for Molecular Genetics, Ihnestrasse 73, 14195 Berlin, Germany
| | - Jonathan Mangion
- Thermo Fisher Scientific Frankfurter Straße 129B, 64293 Darmstadt, Germany
| | - Sascha Sauer
- Max Planck Institute for Molecular Genetics, Ihnestrasse 73, 14195 Berlin, Germany
| | - Emile Schyns
- PHOTONIS France S.A.S. Avenue Roger Roncier, 19100 Brive B.P. 520, 19106 BRIVE Cedex, France
| | - Jörg Tost
- CEA - Centre National de Génotypage, 2, rue Gaston Cremieux, 91057 Evry Cedex, France
| | | | - Pieter J van der Zaag
- Philips Research Laboratories, High Tech Campus 11, 5656 AE Eindhoven, The Netherlands
| | - Jonas O Tegenfeldt
- Division of Solid State Physics and NanoLund, Lund University, Box 118, 22100 Lund, Sweden
| | | | - Kalim Mir
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Mats Nilsson
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Box 1031, Se-171 21 Solna, Sweden; Department of Immunology, Genetics, and Pathology, Science for Life Laboratory, Uppsala University, Sweden
| | - James P Willcocks
- Oxford Nanopore Technologies, Edmund Cartwright House, 4 Robert Robinson Avenue, Oxford Science Park, Oxford OX4 4GA, UK
| | - Ivo G Gut
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, C/Baldiri Reixac 7, 08028 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain.
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Fricke F, Beaudouin J, Eils R, Heilemann M. One, two or three? Probing the stoichiometry of membrane proteins by single-molecule localization microscopy. Sci Rep 2015; 5:14072. [PMID: 26358640 PMCID: PMC4642553 DOI: 10.1038/srep14072] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/18/2015] [Indexed: 12/18/2022] Open
Abstract
Probing the oligomeric state of abundant molecules, such as membrane proteins in intact cells, is essential, but has not been straightforward. We address this challenge with a simple counting strategy that is capable of reporting the oligomeric state of dense, membrane-bound protein complexes. It is based on single-molecule localization microscopy to super-resolve protein structures in intact cells and basic quantitative evaluation. We validate our method with membrane-bound monomeric CD86 and dimeric cytotoxic T-lymphocyte-associated protein as model proteins and confirm their oligomeric states. We further detect oligomerization of CD80 and vesicular stomatitis virus glycoprotein and propose coexistence of monomers and dimers for CD80 and trimeric assembly of the viral protein at the cell membrane. This approach should prove valuable for researchers striving for reliable molecular counting in cells.
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Affiliation(s)
- Franziska Fricke
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
| | - Joel Beaudouin
- Department for Bioinformatics and Functional Genomics, Bioquant and Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, and Division of Theoretical Bioinformatics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Roland Eils
- Department for Bioinformatics and Functional Genomics, Bioquant and Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, and Division of Theoretical Bioinformatics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Mike Heilemann
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
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29
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Schulz S, Kramm K, Werner F, Grohmann D. Fluorescently labeled recombinant RNAP system to probe archaeal transcription initiation. Methods 2015; 86:10-8. [PMID: 25912642 DOI: 10.1016/j.ymeth.2015.04.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 04/14/2015] [Accepted: 04/16/2015] [Indexed: 10/24/2022] Open
Abstract
The transcriptional apparatus is one of the most complex cellular machineries and in order to fully appreciate the behavior of these protein-nucleic acid assemblies one has to understand the molecular details of the system. In addition to classical biochemical and structural studies, fluorescence-based techniques turned out as an important--and sometimes the critical--tool to obtain information about the molecular mechanisms of transcription. Fluorescence is not only a multi-modal parameter that can report on molecular interactions, environment and oligomerization status. Measured on the single-molecule level it also informs about the heterogeneity of the system and gives access to distances and distance changes in the molecular relevant nanometer regime. A pre-requisite for fluorescence-based measurements is the site-specific incorporation of one or multiple fluorescent dyes. In this respect, the archaeal transcription system is ideally suited as it is available in a fully recombinant form and thus allows for site-specific modification via sophisticated labeling schemes. The application of fluorescence based approaches to the archaeal transcription apparatus changed our understanding of the molecular mechanisms and dynamics that drive archaeal transcription and unraveled the architecture of transcriptional complexes not amenable to structural interrogation.
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Affiliation(s)
- Sarah Schulz
- Physikalische und Theoretische Chemie - NanoBioSciences, Technische Universität Braunschweig, Hans-Sommer-Straße 10, 38106 Braunschweig, Germany
| | - Kevin Kramm
- Physikalische und Theoretische Chemie - NanoBioSciences, Technische Universität Braunschweig, Hans-Sommer-Straße 10, 38106 Braunschweig, Germany
| | - Finn Werner
- RNAP Laboratory, University College London, Institute of Structural and Molecular Biology, Division of Biosciences, Gower St, London WC1E 6BT, UK
| | - Dina Grohmann
- Physikalische und Theoretische Chemie - NanoBioSciences, Technische Universität Braunschweig, Hans-Sommer-Straße 10, 38106 Braunschweig, Germany.
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30
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31
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Aigrain L, Sustarsic M, Crawford R, Plochowietz A, Kapanidis AN. Internalization and observation of fluorescent biomolecules in living microorganisms via electroporation. J Vis Exp 2015. [PMID: 25741968 PMCID: PMC4354625 DOI: 10.3791/52208] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The ability to study biomolecules in vivo is crucial for understanding their function in a biological context. One powerful approach involves fusing molecules of interest to fluorescent proteins such as GFP to study their expression, localization and function. However, GFP and its derivatives are significantly larger and less photostable than organic fluorophores generally used for in vitro experiments, and this can limit the scope of investigation. We recently introduced a straightforward, versatile and high-throughput method based on electroporation, allowing the internalization of biomolecules labeled with organic fluorophores into living microorganisms. Here we describe how to use electroporation to internalize labeled DNA fragments or proteins into Escherichia coli and Saccharomyces cerevisiæ, how to quantify the number of internalized molecules using fluorescence microscopy, and how to quantify the viability of electroporated cells. Data can be acquired at the single-cell or single-molecule level using fluorescence or FRET. The possibility of internalizing non-labeled molecules that trigger a physiological observable response in vivo is also presented. Finally, strategies of optimization of the protocol for specific biological systems are discussed.
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Affiliation(s)
- Louise Aigrain
- Clarendon Laboratory, Department of Physics, University of Oxford; Wellcome Trust Sanger Institute, Genome Center
| | - Marko Sustarsic
- Clarendon Laboratory, Department of Physics, University of Oxford
| | - Robert Crawford
- Clarendon Laboratory, Department of Physics, University of Oxford
| | - Anne Plochowietz
- Clarendon Laboratory, Department of Physics, University of Oxford
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32
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Hohlbein J, Craggs TD, Cordes T. Alternating-laser excitation: single-molecule FRET and beyond. Chem Soc Rev 2014; 43:1156-71. [PMID: 24037326 DOI: 10.1039/c3cs60233h] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The alternating-laser excitation (ALEX) scheme continues to expand the possibilities of fluorescence-based assays to study biological entities and interactions. Especially the combination of ALEX and single-molecule Förster Resonance Energy Transfer (smFRET) has been very successful as ALEX enables the sorting of fluorescently labelled species based on the number and type of fluorophores present. ALEX also provides a convenient way of accessing the correction factors necessary for determining accurate molecular distances. Here, we provide a comprehensive overview of the concept and current applications of ALEX and we explicitly discuss how to obtain fully corrected distance information across the entire FRET range. We also present new ideas for applications of ALEX which will push the limits of smFRET-based experiments in terms of temporal and spatial resolution for the study of complex biological systems.
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Affiliation(s)
- Johannes Hohlbein
- Laboratory of Biophysics, Wageningen UR, Wageningen, The Netherlands.
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33
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Crawford R, Torella JP, Aigrain L, Plochowietz A, Gryte K, Uphoff S, Kapanidis AN. Long-lived intracellular single-molecule fluorescence using electroporated molecules. Biophys J 2014; 105:2439-50. [PMID: 24314075 DOI: 10.1016/j.bpj.2013.09.057] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/12/2013] [Accepted: 09/06/2013] [Indexed: 11/28/2022] Open
Abstract
Studies of biomolecules in vivo are crucial to understand their function in a natural, biological context. One powerful approach involves fusing molecules of interest to fluorescent proteins to study their expression, localization, and action; however, the scope of such studies would be increased considerably by using organic fluorophores, which are smaller and more photostable than their fluorescent protein counterparts. Here, we describe a straightforward, versatile, and high-throughput method to internalize DNA fragments and proteins labeled with organic fluorophores into live Escherichia coli by employing electroporation. We studied the copy numbers, diffusion profiles, and structure of internalized molecules at the single-molecule level in vivo, and were able to extend single-molecule observation times by two orders of magnitude compared to green fluorescent protein, allowing continuous monitoring of molecular processes occurring from seconds to minutes. We also exploited the desirable properties of organic fluorophores to perform single-molecule Förster resonance energy transfer measurements in the cytoplasm of live bacteria, both for DNA and proteins. Finally, we demonstrate internalization of labeled proteins and DNA into yeast Saccharomyces cerevisiae, a model eukaryotic system. Our method should broaden the range of biological questions addressable in microbes by single-molecule fluorescence.
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Affiliation(s)
- Robert Crawford
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
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34
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Farooq S, Fijen C, Hohlbein J. Studying DNA-protein interactions with single-molecule Förster resonance energy transfer. PROTOPLASMA 2014; 251:317-32. [PMID: 24374460 DOI: 10.1007/s00709-013-0596-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 12/09/2013] [Indexed: 05/21/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) has emerged as a powerful tool for elucidating biological structure and mechanisms on the molecular level. Here, we focus on applications of smFRET to study interactions between DNA and enzymes such as DNA and RNA polymerases. SmFRET, used as a nanoscopic ruler, allows for the detection and precise characterisation of dynamic and rarely occurring events, which are otherwise averaged out in ensemble-based experiments. In this review, we will highlight some recent developments that provide new means of studying complex biological systems either by combining smFRET with force-based techniques or by using data obtained from smFRET experiments as constrains for computer-aided modelling.
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Affiliation(s)
- Shazia Farooq
- Laboratory of Biophysics, Wageningen UR, Wageningen, The Netherlands
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35
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Opportunities and challenges in single-molecule and single-particle fluorescence microscopy for mechanistic studies of chemical reactions. Nat Chem 2014; 5:993-9. [PMID: 24256861 DOI: 10.1038/nchem.1800] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 10/08/2013] [Indexed: 12/19/2022]
Abstract
In recent years, single-molecule and single-particle fluorescence microscopy has emerged as a tool to investigate chemical systems. After an initial lag of over a decade with respect to biophysical studies, this powerful imaging technique is now revealing mechanisms of 'classical' organic reactions, spatial distribution of chemical reactivity on surfaces and the phase of active catalysts. The recent advance into commercial imaging systems obviates the need for home-built laser systems and thus opens this technique to traditionally trained synthetic chemists. We discuss the requisite photophysical and chemical properties of fluorescent reporters and highlight the main challenges in applying single-molecule techniques to chemical questions. The goal of this Perspective is to provide a snapshot of an emerging multidisciplinary field and to encourage broader use of this young experimental approach that aids the observation of chemical reactions as depicted in many textbooks: molecule by molecule.
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Abstract
Single-molecule fluorescence studies of nucleic acids are revolutionizing our understanding of fundamental cellular processes related to DNA and RNA processing mechanisms. Detailed molecular insights into DNA repair, replication, transcription, and RNA folding and function are continuously being uncovered by using the full repertoire of single-molecule fluorescence techniques. The fundamental reason behind the stunning growth in the application of single-molecule techniques to study nucleic acid structure and dynamics is the unmatched ability of single-molecule fluorescence, and mostly single-molecule FRET, to resolve heterogeneous static and dynamic populations and identify transient and low-populated states without the need for sample synchronization. New advances in DNA and RNA synthesis, post-synthetic dye-labeling methods, immobilization and passivation strategies, improved dye photophysics, and standardized analysis methods have enabled the implementation of single-molecule techniques beyond specialized laboratories. In this chapter, we introduce the practical aspects of applying single-molecule techniques to investigate nucleic acid structure, dynamics, and function.
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Affiliation(s)
- Kaley McCluskey
- SUPA School of Physics and Astronomy, University of St. Andrews, St. Andrews, Scotland, UK
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37
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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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38
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Klehs K, Spahn C, Endesfelder U, Lee SF, Fürstenberg A, Heilemann M. Increasing the brightness of cyanine fluorophores for single-molecule and superresolution imaging. Chemphyschem 2013; 15:637-41. [PMID: 24376142 DOI: 10.1002/cphc.201300874] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Indexed: 01/12/2023]
Abstract
In spite of their relatively low fluorescence quantum yield, cyanine dyes such as Cy3, Cy5, or Cy7 are widely used in single-molecule fluorescence applications due to their high extinction coefficients and excellent photon yields. We show that the fluorescence quantum yield and lifetime of red-emitting cyanine dyes can be substantially increased in heavy water (D2 O) compared with water (H2 O). We find that the magnitude of the quantum yield increase in D2 O scales with the emission wavelength, reaching a particularly high value of 2.6-fold for the most red-emitting dye investigated, Cy7. We further demonstrate a higher photon yield in single-molecule superresolution experiments in D2 O compared to H2 O, which leads to an improved localization precision and hence better spatial resolution. This finding is especially beneficial for biological applications of fluorescence microscopy, which are typically carried out in aqueous media and which greatly profit from the red spectral range due to reduced cellular auto-fluorescence.
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Affiliation(s)
- Kathrin Klehs
- Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe-University, Max-von-Laue-Str. 7, 60438 Frankfurt (Germany)
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39
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DNA conformations in mismatch repair probed in solution by X-ray scattering from gold nanocrystals. Proc Natl Acad Sci U S A 2013; 110:17308-13. [PMID: 24101514 DOI: 10.1073/pnas.1308595110] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
DNA metabolism and processing frequently require transient or metastable DNA conformations that are biologically important but challenging to characterize. We use gold nanocrystal labels combined with small angle X-ray scattering to develop, test, and apply a method to follow DNA conformations acting in the Escherichia coli mismatch repair (MMR) system in solution. We developed a neutral PEG linker that allowed gold-labeled DNAs to be flash-cooled and stored without degradation in sample quality. The 1,000-fold increased gold nanocrystal scattering vs. DNA enabled investigations at much lower concentrations than otherwise possible to avoid concentration-dependent tetramerization of the MMR initiation enzyme MutS. We analyzed the correlation scattering functions for the nanocrystals to provide higher resolution interparticle distributions not convoluted by the intraparticle distribution. We determined that mispair-containing DNAs were bent more by MutS than complementary sequence DNA (csDNA), did not promote tetramer formation, and allowed MutS conversion to a sliding clamp conformation that eliminated the DNA bends. Addition of second protein responder MutL did not stabilize the MutS-bent forms of DNA. Thus, DNA distortion is only involved at the earliest mispair recognition steps of MMR: MutL does not trap bent DNA conformations, suggesting migrating MutL or MutS/MutL complexes as a conserved feature of MMR. The results promote a mechanism of mismatch DNA bending followed by straightening in initial MutS and MutL responses in MMR. We demonstrate that small angle X-ray scattering with gold labels is an enabling method to examine protein-induced DNA distortions key to the DNA repair, replication, transcription, and packaging.
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40
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Abstract
Single molecule bioelectronic circuits provide an opportunity to study chemical kinetics and kinetic variability with bond-by-bond resolution. To demonstrate this approach, we examined the catalytic activity of T4 lysozyme processing peptidoglycan substrates. Monitoring a single lysozyme molecule through changes in a circuit's conductance helped elucidate unexplored and previously invisible aspects of lysozyme's catalytic mechanism and demonstrated lysozyme to be a processive enzyme governed by 9 independent time constants. The variation of each time constant with pH or substrate crosslinking provided different insights into catalytic activity and dynamic disorder. Overall, ten lysozyme variants were synthesized and tested in single molecule circuits to dissect the transduction of chemical activity into electronic signals. Measurements show that a single amino acid with the appropriate properties is sufficient for good signal generation, proving that the single molecule circuit technique can be easily extended to other proteins.
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Affiliation(s)
- Yongki Choi
- Department of Physics and Astronomy, University of California at Irvine, Irvine, California 92697, United States
| | - Gregory A. Weiss
- Departments of Chemistry and Molecular Biology and Biochemistry, University of California at Irvine, Irvine, California 92697, United States
| | - Philip G. Collins
- Department of Physics and Astronomy, University of California at Irvine, Irvine, California 92697, United States
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41
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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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42
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Dietz MS, Haße D, Ferraris DM, Göhler A, Niemann HH, Heilemann M. Single-molecule photobleaching reveals increased MET receptor dimerization upon ligand binding in intact cells. BMC BIOPHYSICS 2013; 6:6. [PMID: 23731667 PMCID: PMC3674922 DOI: 10.1186/2046-1682-6-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/23/2013] [Indexed: 12/14/2022]
Abstract
Background The human receptor tyrosine kinase MET and its ligand hepatocyte growth factor/scatter factor are essential during embryonic development and play an important role during cancer metastasis and tissue regeneration. In addition, it was found that MET is also relevant for infectious diseases and is the target of different bacteria, amongst them Listeria monocytogenes that induces bacterial uptake through the surface protein internalin B. Binding of ligand to the MET receptor is proposed to lead to receptor dimerization. However, it is also discussed whether preformed MET dimers exist on the cell membrane. Results To address these issues we used single-molecule fluorescence microscopy techniques. Our photobleaching experiments show that MET exists in dimers on the membrane of cells in the absence of ligand and that the proportion of MET dimers increases significantly upon ligand binding. Conclusions Our results indicate that partially preformed MET dimers may play a role in ligand binding or MET signaling. The addition of the bacterial ligand internalin B leads to an increase of MET dimers which is in agreement with the model of ligand-induced dimerization of receptor tyrosine kinases.
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Affiliation(s)
- Marina S Dietz
- Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe-University, Max-von-Laue-Str, 7, 60438 Frankfurt, Germany.
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43
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Hwang W, Bae S, Hohng S. Autofocusing system based on optical astigmatism analysis of single-molecule images. OPTICS EXPRESS 2012; 20:29353-29360. [PMID: 23388762 DOI: 10.1364/oe.20.029353] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Single-molecule fluorescence imaging has greatly contributed to our understanding of many bio-molecular systems. While reactions occurring in the range of several minutes can be readily studied using conventional single-molecule fluorescence microscopes, data acquisition for longer time scales is hindered by the focal drift of high numerical aperture objectives, which should be corrected in real time. Here, we developed a robust autofocusing system based on optical astigmatism analysis of single-molecule images. Compared to the previously developed methods, our approach has a merit of simplicity in that neither fiducial makers nor an additional laser-detector system is required. As a demonstration, we observed B-Z transition dynamics occurring for several hours.
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Affiliation(s)
- Wonseok Hwang
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, South Korea
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44
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Abstract
The deposition of peptides and proteins as amyloid fibrils is a common feature of nearly 50 medical -disorders affecting the brain or a variety of other organs and tissues. These disorders, which include Alzheimer's disease, Parkinson's disease, the prion diseases, and type II diabetes, have an enormous impact on the public health and economy of the modern world. Extensive research is therefore taking place to determine the underlying molecular mechanisms and determinants of the pathological conversion of amyloidogenic proteins from their soluble forms into fibrillar structures. The use of molecular probes and biophysical techniques, such as X-ray crystallography and particularly NMR spectroscopy, are allowing detailed analysis of the mechanism of fibril formation and of the underlying structural and chemical features of the associated pathogenicity. Nanobodies, the antigen-binding domains derived from camelid heavy-chain antibodies, are excellent tools to probe protein aggregation as a result of their exquisite specificity and high affinity and stability, along with their ease of expression and small size; the latter in particular allows them to be used very efficiently in combination with NMR spectroscopy and X-ray crystallography. In this chapter we present an overview of how nanobodies are being used to obtain detailed information on the mechanisms of amyloid formation and on the nature and origin of their links with human diseases.
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Affiliation(s)
- Erwin De Genst
- Department of Chemistry, University of Cambridge, Cambridge, UK.
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45
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Preus S, Wilhelmsson LM. Advances in quantitative FRET-based methods for studying nucleic acids. Chembiochem 2012; 13:1990-2001. [PMID: 22936620 DOI: 10.1002/cbic.201200400] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Indexed: 01/02/2023]
Abstract
Förster resonance energy transfer (FRET) is a powerful tool for monitoring molecular distances and interactions at the nanoscale level. The strong dependence of transfer efficiency on probe separation makes FRET perfectly suited for "on/off" experiments. To use FRET to obtain quantitative distances and three-dimensional structures, however, is more challenging. This review summarises recent studies and technological advances that have improved FRET as a quantitative molecular ruler in nucleic acid systems, both at the ensemble and at the single-molecule levels.
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Affiliation(s)
- Søren Preus
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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46
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Le Reste L, Hohlbein J, Gryte K, Kapanidis AN. Characterization of dark quencher chromophores as nonfluorescent acceptors for single-molecule FRET. Biophys J 2012; 102:2658-68. [PMID: 22713582 DOI: 10.1016/j.bpj.2012.04.028] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/03/2012] [Accepted: 04/06/2012] [Indexed: 11/16/2022] Open
Abstract
Dark quenchers are chromophores that primarily relax from the excited state to the ground state nonradiatively (i.e., are dark). As a result, they can serve as acceptors for Förster resonance energy transfer experiments without contributing significantly to background in the donor-emission channel, even at high concentrations. Although the advantages of dark quenchers have been exploited for ensemble bioassays, no systematic single-molecule study of dark quenchers has been performed, and little is known about their photophysical properties. Here, we present the first systematic single-molecule study of dark quenchers in conjunction with fluorophores and demonstrate the use of dark quenchers for monitoring multiple interactions and distances in multichromophore systems. Specifically, using double-stranded DNA standards labeled with two fluorophores and a dark quencher (either QSY7 or QSY21), we show that the proximity of a fluorophore and dark quencher can be monitored using the stoichiometry ratio available from alternating laser excitation spectroscopy experiments, either for single molecules diffusing in solution (using a confocal fluorescence) or immobilized on surfaces (using total-internal-reflection fluorescence). The latter experiments allowed characterization of the dark-quencher photophysical properties at the single-molecule level. We also use dark-quenchers to study the affinity and kinetics of binding of DNA Polymerase I (Klenow fragment) to DNA. The measured properties are in excellent agreement with the results of ensemble assays, validating the use of dark quenchers. Because dark-quencher-labeled biomolecules can be used in total-internal-reflection fluorescence experiments at concentrations of 1 μM or more without introducing a significant background, the use of dark quenchers should permit single-molecule Förster resonance energy transfer measurements for the large number of biomolecules that participate in interactions of moderate-to-low affinity.
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Affiliation(s)
- Ludovic Le Reste
- Biological Physics Research Group, Department of Physics, University of Oxford, Oxford, United Kingdom.
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47
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Microfluidic strategies applied to biomarker discovery and validation for multivariate diagnostics. Bioanalysis 2012; 3:2233-51. [PMID: 21985417 DOI: 10.4155/bio.11.224] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Complex diseases are caused by combinatorial genetic, environmental and lifestyle factors. The emergence of multibiomarker tests to define these diseases and to identify the early, presymptomatic stages offers several advantages to the conventional use of single marker tests. The development of multibiomarker protein-based tests remains constrained by technological and operational limitations in assaying hundreds to thousands of proteins in thousands of samples. In order to develop a multibiomarker test that stratifies risk for Type 2 diabetes, we took a candidate-driven immunoassay approach utilizing a microfluidics platform to analyze 89 candidate proteins in thousands of samples, which allowed us to move from discovery to a commercial test in 2 years. Future multibiomarker test development will be enhanced by advancements in the number of proteins that can be analyzed, analytical sensitivity and throughput, and sample volume requirements, all of which depend on the further advancement of microfluidics, detection technologies and affinity-based reagents.
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48
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Ishikawa-Ankerhold HC, Ankerhold R, Drummen GPC. Advanced fluorescence microscopy techniques--FRAP, FLIP, FLAP, FRET and FLIM. Molecules 2012; 17:4047-132. [PMID: 22469598 PMCID: PMC6268795 DOI: 10.3390/molecules17044047] [Citation(s) in RCA: 284] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 03/21/2012] [Accepted: 03/21/2012] [Indexed: 12/19/2022] Open
Abstract
Fluorescence microscopy provides an efficient and unique approach to study fixed and living cells because of its versatility, specificity, and high sensitivity. Fluorescence microscopes can both detect the fluorescence emitted from labeled molecules in biological samples as images or photometric data from which intensities and emission spectra can be deduced. By exploiting the characteristics of fluorescence, various techniques have been developed that enable the visualization and analysis of complex dynamic events in cells, organelles, and sub-organelle components within the biological specimen. The techniques described here are fluorescence recovery after photobleaching (FRAP), the related fluorescence loss in photobleaching (FLIP), fluorescence localization after photobleaching (FLAP), Förster or fluorescence resonance energy transfer (FRET) and the different ways how to measure FRET, such as acceptor bleaching, sensitized emission, polarization anisotropy, and fluorescence lifetime imaging microscopy (FLIM). First, a brief introduction into the mechanisms underlying fluorescence as a physical phenomenon and fluorescence, confocal, and multiphoton microscopy is given. Subsequently, these advanced microscopy techniques are introduced in more detail, with a description of how these techniques are performed, what needs to be considered, and what practical advantages they can bring to cell biological research.
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Affiliation(s)
- Hellen C. Ishikawa-Ankerhold
- Ludwig Maximilian University of Munich, Institute of Anatomy and Cell Biology, Schillerstr. 42, 80336 München, Germany
| | - Richard Ankerhold
- Carl Zeiss Microimaging GmbH, Kistlerhofstr. 75, 81379 München, Germany
| | - Gregor P. C. Drummen
- Bionanoscience and Bio-Imaging Program, Cellular Stress and Ageing Program, Bio&Nano-Solutions, Helmutstr. 3A, 40472 Düsseldorf, Germany
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49
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Kapanidis AN, Crawford R. Colorful Molecular Diagnostics. Clin Chem 2012; 58:659-60. [DOI: 10.1373/clinchem.2011.180802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Achillefs N Kapanidis
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Robert Crawford
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Oxford, UK
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50
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Wang L, Wang Y, Ragauskas AJ. Determination of cellulase colocalization on cellulose fiber with quantitative FRET measured by acceptor photobleaching and spectrally unmixing fluorescence microscopy. Analyst 2012; 137:1319-24. [PMID: 22311108 DOI: 10.1039/c2an15938d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The determination of cellulase distribution on the surface of cellulose fiber is an important parameter to understand when determining the interaction between cellulase and cellulose and/or the cooperation of different types of cellulases during the enzymatic hydrolysis of cellulose. In this communication, a strategy is presented to quantitatively determine the cellulase colocalization using the fluorescence resonance energy transfer (FRET) methodology, which is based on acceptor photobleaching and spectrally unmixing fluorescence microscopy. FRET monitoring of cellulase colocalization was achieved by labeling cellulases with an appropriate pair of FRET dyes and by adopting an appropriate FRET model. We describe here that the adapted acceptor photobleaching FRET method can be successfully used to quantify cellulase colocalization regarding their binding to a cellulose fiber at a resolution <10 nm. This developed quantitative FRET method is promising for further studying the interactions between cellulase and cellulose and between different types of cellulases.
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Affiliation(s)
- Liqun Wang
- BioEnergy Science Center, Institute of Paper Science and Technology, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA
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