151
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Dörfler T, Eilert T, Röcker C, Nagy J, Michaelis J. Structural Information from Single-molecule FRET Experiments Using the Fast Nano-positioning System. J Vis Exp 2017:54782. [PMID: 28287526 PMCID: PMC5407667 DOI: 10.3791/54782] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Single-molecule Förster Resonance Energy Transfer (smFRET) can be used to obtain structural information on biomolecular complexes in real-time. Thereby, multiple smFRET measurements are used to localize an unknown dye position inside a protein complex by means of trilateration. In order to obtain quantitative information, the Nano-Positioning System (NPS) uses probabilistic data analysis to combine structural information from X-ray crystallography with single-molecule fluorescence data to calculate not only the most probable position but the complete three-dimensional probability distribution, termed posterior, which indicates the experimental uncertainty. The concept was generalized for the analysis of smFRET networks containing numerous dye molecules. The latest version of NPS, Fast-NPS, features a new algorithm using Bayesian parameter estimation based on Markov Chain Monte Carlo sampling and parallel tempering that allows for the analysis of large smFRET networks in a comparably short time. Moreover, Fast-NPS allows the calculation of the posterior by choosing one of five different models for each dye, that account for the different spatial and orientational behavior exhibited by the dye molecules due to their local environment. Here we present a detailed protocol for obtaining smFRET data and applying the Fast-NPS. We provide detailed instructions for the acquisition of the three input parameters of Fast-NPS: the smFRET values, as well as the quantum yield and anisotropy of the dye molecules. Recently, the NPS has been used to elucidate the architecture of an archaeal open promotor complex. This data is used to demonstrate the influence of the five different dye models on the posterior distribution.
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152
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Ryu JK, Jahn R, Yoon TY. Review: Progresses in understanding N-ethylmaleimide sensitive factor (NSF) mediated disassembly of SNARE complexes. Biopolymers 2017; 105:518-31. [PMID: 27062050 DOI: 10.1002/bip.22854] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/19/2016] [Accepted: 04/06/2016] [Indexed: 11/09/2022]
Abstract
N-ethylmaleimide sensitive factor (NSF) is a key protein of intracellular membrane traffic. NSF is a highly conserved protein belonging to the ATPases associated with other activities (AAA+ proteins). AAA+ share common domains and all transduce ATP hydrolysis into major conformational movements that are used to carry out conformational work on client proteins. Together with its cofactor SNAP, NSF is specialized on disassembling highly stable SNARE complexes that form after each membrane fusion event. Although essential for all eukaryotic cells, however, the details of this reaction have long been enigmatic. Recently, major progress has been made in both elucidating the structure of NSF/SNARE complexes and in understanding the reaction mechanism. Advances in both cryo EM and single molecule measurements suggest that NSF, together with its cofactor SNAP, imposes a tight grip on the SNARE complex. After ATP hydrolysis and phosphate release, it then builds up mechanical tension that is ultimately used to rip apart the SNAREs in a single burst. Because the AAA domains are extremely well-conserved, the molecular mechanism elucidated for NSF is presumably shared by many other AAA+ ATPases. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 518-531, 2016.
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Affiliation(s)
- Je-Kyung Ryu
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, CJ, 2628, the Netherlands
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, 37077, Germany
| | - Tae-Young Yoon
- Center for Nanomedicine, Institute for Basic Science (IBS) and Y-IBS Institute, Yonsei University, Seoul, 03722, South Korea
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153
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Whitley K, Comstock M, Chemla Y. High-Resolution Optical Tweezers Combined With Single-Molecule Confocal Microscopy. Methods Enzymol 2017; 582:137-169. [PMID: 28062033 PMCID: PMC5540136 DOI: 10.1016/bs.mie.2016.10.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We describe the design, construction, and application of an instrument combining dual-trap, high-resolution optical tweezers and a confocal microscope. This hybrid instrument allows nanomechanical manipulation and measurement simultaneously with single-molecule fluorescence detection. We present the general design principles that overcome the challenges of maximizing optical trap resolution while maintaining single-molecule fluorescence sensitivity, and provide details on the construction and alignment of the instrument. This powerful new tool is just beginning to be applied to biological problems. We present step-by-step instructions on an application of this technique that highlights the instrument's capabilities, detecting conformational dynamics in a nucleic acid-processing enzyme.
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Affiliation(s)
- K.D. Whitley
- University of Illinois at Urbana–Champaign, Urbana, IL, United States
| | - M.J. Comstock
- Michigan State University, East Lansing, MI, United States
| | - Y.R. Chemla
- University of Illinois at Urbana–Champaign, Urbana, IL, United States,Center for the Physics of Living Cells, University of Illinois at Urbana–Champaign, Urbana, IL, United States,Corresponding author:
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154
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Deng Y, Asbury CL. Simultaneous Manipulation and Super-Resolution Fluorescence Imaging of Individual Kinetochores Coupled to Microtubule Tips. Methods Mol Biol 2017; 1486:437-467. [PMID: 27844439 PMCID: PMC5376289 DOI: 10.1007/978-1-4939-6421-5_17] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
Abstract
Kinetochores are large multiprotein complexes that drive mitotic chromosome movements by mechanically coupling them to the growing and shortening tips of spindle microtubules. Kinetochores are also regulatory hubs, somehow sensing when they are erroneously attached and, in response, releasing their incorrect attachments and generating diffusible wait signals to delay anaphase until proper attachments can form. The remarkable ability of a kinetochore to sense and respond to its attachment status might stem from attachment- or tension-dependent changes in the structural arrangement of its core subcomplexes. However, direct tests of the relationship between attachment, tension, and core kinetochore structure have not previously been possible because of the difficulties of applying well-controlled forces and determining unambiguously the attachment status of individual kinetochores in vivo. The recent purification of native yeast kinetochores has enabled in vitro optical trapping-based assays of kinetochore tip-coupling and, in separate experiments, fluorescence imaging of single kinetochore particles. Here we introduce a dual instrument, combining optical trapping with multicolor total internal reflection fluorescence (TIRF) imaging, to allow kinetochore structure to be monitored directly with nanometer precision while mechanical tension is simultaneously applied. Our instrument incorporates differential interference contrast (DIC) imaging as well, to minimize the photo-bleaching of fluorescent tags during preparative bead and microtubule manipulations. A simple modification also allows the trapping laser to be easily converted into a real-time focus detection and correction system. Using this combined instrument, the distance between specific subcomplexes within a single kinetochore particle can be measured with 2-nm precision after 50 s observation time, or with 11-nm precision at 1 s temporal resolution. While our instrument was constructed specifically for studying kinetochores, it should also be useful for studying other filament-binding protein complexes, such as spindle poles, cortical microtubule attachments, focal adhesions, or other motor-cytoskeletal junctions.
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Affiliation(s)
- Yi Deng
- Department of Physiology & Biophysics, University of Washington, 1959 NE Pacific Street, Box 357290, Seattle, WA, 98195, USA
| | - Charles L Asbury
- Department of Physiology & Biophysics, University of Washington, 1959 NE Pacific Street, Box 357290, Seattle, WA, 98195, USA.
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155
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Song S, Chang J, Ma C, Tan YW. Single-Molecule Fluorescence Methods to Study Plant Hormone Signal Transduction Pathways. FRONTIERS IN PLANT SCIENCE 2017; 8:1888. [PMID: 29163610 PMCID: PMC5673658 DOI: 10.3389/fpls.2017.01888] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/18/2017] [Indexed: 05/15/2023]
Abstract
Plant-hormone-initiated signaling pathways are extremely vital for plant growth, differentiation, development, and adaptation to environmental stresses. Hormonal perception by receptors induces downstream signal transduction mechanisms that lead to plant responses. However, conventional techniques-such as genetics, biochemistry, and physiology methods-that are applied to elucidate these signaling pathways can only provide qualitative or ensemble-averaged quantitative results, and the intrinsic molecular mechanisms remain unclear. The present study developed novel methodologies based on in vitro single-molecule fluorescence assays to elucidate the complete and detailed mechanisms of plant hormone signal transduction pathways. The proposed methods are based on multicolor total internal reflection fluorescence microscopy and a flow cell model for gas environment control. The methods validate the effectiveness of single-molecule approaches for the extraction of abundant information, including oligomerization, specific gas dependence, and the interaction kinetics of different components.
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156
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Lin CT, Ha T. Probing Single Helicase Dynamics on Long Nucleic Acids Through Fluorescence-Force Measurement. Methods Mol Biol 2017; 1486:295-316. [PMID: 27844433 DOI: 10.1007/978-1-4939-6421-5_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Helicases are nucleic acid-dependent ATPases which can bind and remodel nucleic acids, protein-nucleic acid complexes, or both. They are involved in almost every step in cells related to nucleic acid metabolisms, including DNA replication and repair, transcription, RNA maturation and splicing, and nuclear export processes. Using single-molecule fluorescence-force spectroscopy, we have previously directly observed helicase translocation on long single-stranded DNA and revealed that two monomers of UvrD helicase are required for the initiation of unwinding function. Here, we present the details of fluorescence-force spectroscopy instrumentation, calibration, and activity assays in detail for observing the biochemical activities of helicases in real time and revealing how mechanical forces are involved in protein-nucleic acid interaction. These single-molecule approaches are generally applicable to many other protein-nucleic acid systems.
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Affiliation(s)
- Chang-Ting Lin
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, USA
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Thomas C. Jenkins Department of Biophysics and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
- Howard Hughes Medical Institute, Baltimore, MD, USA.
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157
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Kempe D, Cerminara M, Poblete S, Schöne A, Gabba M, Fitter J. Single-Molecule FRET Measurements in Additive-Enriched Aqueous Solutions. Anal Chem 2016; 89:694-702. [PMID: 27966879 DOI: 10.1021/acs.analchem.6b03147] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The addition of high amounts of chemical denaturants, salts, viscosity enhancers or macro-molecular crowding agents has an impact on the physical properties of buffer solutions. Among others, the (microscopic) viscosity, the refractive index, the dielectric constant, and the ionic strength can be affected. Here, we systematically evaluate the importance of solvent characteristics with respect to single-molecule FRET (smFRET) data. First, we present a confocal based method for the determination of fluorescence quantum yields to facilitate a fast characterization of smFRET-samples at sub-nM-concentrations. As a case study, we analyze smFRET data of structurally rigid, double-stranded DNA-oligonucleotides in aqueous buffer and in buffers with specific amounts of glycerol, guanidine hydrochloride (GdnHCl), and sodium chloride (NaCl) added. We show that the calculation of interdye distances, without taking into account solvent-induced spectral and photophysical changes of the labels, leads to deviations of up to 4 Å from the real interdye distances. Additionally, we demonstrate that electrostatic dye-dye repulsions are negligible for the interdye distance regime considered here (>50 Å). Finally, we use our approach to validate the further compaction of the already unfolded state of phosphoglycerate kinase (PGK) with decreasing denaturant concentrations, a mechanism known as coil-globule transition.
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Affiliation(s)
- Daryan Kempe
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University , 52056 Aachen, Germany
| | | | | | | | | | - Jörg Fitter
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University , 52056 Aachen, Germany
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158
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Single-Molecule Fluorescence Energy Transfer Assays for the Characterization of Reaction Pathways of miRNA-Argonaute Complex. Methods Mol Biol 2016. [PMID: 27924491 DOI: 10.1007/978-1-4939-6563-2_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Argonaute proteins are key components of the microRNA-induced silencing complexes (miRISCs) that mediate the posttranscriptional gene silencing of microRNAs and small interfering RNA (siRNAs). The complex reaction mechanism of miRISC is expected to be characterized by tracing the reaction pathways of miRISC at the single-molecule level in real time. In this chapter, we describe single-molecule fluorescence resonance energy transfer (FRET) assays to observe the target binding and reaction pathways of miRISC composed of a recombinant Argonaute and a small RNA.
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159
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Arrabito G, Cavaleri F, Montalbano V, Vetri V, Leone M, Pignataro B. Monitoring few molecular binding events in scalable confined aqueous compartments by raster image correlation spectroscopy (CADRICS). LAB ON A CHIP 2016; 16:4666-4676. [PMID: 27812580 DOI: 10.1039/c6lc01072e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The assembly of scalable liquid compartments for binding assays in array formats constitutes a topic of fundamental importance in life sciences. This challenge can be addressed by mimicking the structure of cellular compartments with biological native conditions. Here, inkjet printing is employed to develop up to hundreds of picoliter aqueous droplet arrays stabilized by oil-confinement with mild surfactants (Tween-20). The aqueous environments constitute specialized compartments in which biomolecules may exploit their function and a wide range of molecular interactions can be quantitatively investigated. Raster Image Correlation Spectroscopy (RICS) is employed to monitor in each compartment a restricted range of dynamic intermolecular events demonstrated through protein-binding assays involving the biotin/streptavidin model system.
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Affiliation(s)
- G Arrabito
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Ed. 17, V.le delle Scienze, 90128 Palermo, Italy.
| | - F Cavaleri
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Ed. 17, V.le delle Scienze, 90128 Palermo, Italy.
| | - V Montalbano
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Ed. 17, V.le delle Scienze, 90128 Palermo, Italy.
| | - V Vetri
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Ed. 17, V.le delle Scienze, 90128 Palermo, Italy. and Aten Center, Università degli Studi di Palermo, Ed. 18, V.le delle Scienze, 90128 Palermo, Italy
| | - M Leone
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Ed. 17, V.le delle Scienze, 90128 Palermo, Italy. and Aten Center, Università degli Studi di Palermo, Ed. 18, V.le delle Scienze, 90128 Palermo, Italy
| | - B Pignataro
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Ed. 17, V.le delle Scienze, 90128 Palermo, Italy. and Aten Center, Università degli Studi di Palermo, Ed. 18, V.le delle Scienze, 90128 Palermo, Italy
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160
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Glembockyte V, Lin J, Cosa G. Improving the Photostability of Red- and Green-Emissive Single-Molecule Fluorophores via Ni2+ Mediated Excited Triplet-State Quenching. J Phys Chem B 2016; 120:11923-11929. [DOI: 10.1021/acs.jpcb.6b10725] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Viktorija Glembockyte
- Department of Chemistry and
Center for Self-Assembled Chemical Structures (CSACS/CRMAA), McGill University, 801 Sherbrooke Street West, Montreal, QC, H3A 0B8, Canada
| | - Junan Lin
- Department of Chemistry and
Center for Self-Assembled Chemical Structures (CSACS/CRMAA), McGill University, 801 Sherbrooke Street West, Montreal, QC, H3A 0B8, Canada
| | - Gonzalo Cosa
- Department of Chemistry and
Center for Self-Assembled Chemical Structures (CSACS/CRMAA), McGill University, 801 Sherbrooke Street West, Montreal, QC, H3A 0B8, Canada
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161
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Henkin G, Berard D, Stabile F, Shayegan M, Leith JS, Leslie SR. Manipulating and Visualizing Molecular Interactions in Customized Nanoscale Spaces. Anal Chem 2016; 88:11100-11107. [DOI: 10.1021/acs.analchem.6b03149] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Gil Henkin
- Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
| | - Daniel Berard
- Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
| | - Francis Stabile
- Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
| | - Marjan Shayegan
- Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
| | - Jason S. Leith
- Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
| | - Sabrina R. Leslie
- Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
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162
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Lin CT, Ha T. Direct Visualization of Helicase Dynamics Using Fluorescence Localization and Optical Trapping. Methods Enzymol 2016; 582:121-136. [PMID: 28062032 DOI: 10.1016/bs.mie.2016.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Helicases control the accessibility of single-stranded (ss) nucleic acid (NA) generated as a transient intermediate during almost every step in cells related to nucleic acid metabolisms. For subsequent processing, however, helicases need to adjust the pace of unwinding adequately to avoid ssNA exposure to nucleases. Therefore, understanding how the unwinding process of helicases is regulated is crucial to address genome integrity and repair mechanisms. Using single-molecule fluorescence-force spectroscopy with fluorescence localization, we recently observed the stoichiometry of UvrD helicase, which determines the functions of UvrD: translocation and unwinding. For the first time, we provide direct evidence that a UvrD dimer is required to initiate the unwinding pathway. Moreover, with subpixel precision of fluorescence localization, the dynamic parameters of helicases can be obtained directly. Here, we present detailed single-molecule assays for observing the biochemical activities of helicases in real time and revealing how mechanical forces are involved in protein-nucleic acid interactions. These single-molecule approaches are generally applicable to many other protein-nucleic acid systems.
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Affiliation(s)
- C-T Lin
- Johns Hopkins University, Baltimore, MD, United States
| | - T Ha
- Johns Hopkins University, Baltimore, MD, United States; Howard Hughes Medical Institute, Baltimore, MD, United States.
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163
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Ordu O, Lusser A, Dekker NH. Recent insights from in vitro single-molecule studies into nucleosome structure and dynamics. Biophys Rev 2016; 8:33-49. [PMID: 28058066 PMCID: PMC5167136 DOI: 10.1007/s12551-016-0212-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 06/17/2016] [Indexed: 01/04/2023] Open
Abstract
Eukaryotic DNA is tightly packed into a hierarchically ordered structure called chromatin in order to fit into the micron-scaled nucleus. The basic unit of chromatin is the nucleosome, which consists of a short piece of DNA wrapped around a core of eight histone proteins. In addition to their role in packaging DNA, nucleosomes impact the regulation of essential nuclear processes such as replication, transcription, and repair by controlling the accessibility of DNA. Thus, knowledge of this fundamental DNA-protein complex is crucial for understanding the mechanisms of gene control. While structural and biochemical studies over the past few decades have provided key insights into both the molecular composition and functional aspects of nucleosomes, these approaches necessarily average over large populations and times. In contrast, single-molecule methods are capable of revealing features of subpopulations and dynamic changes in the structure or function of biomolecules, rendering them a powerful complementary tool for probing mechanistic aspects of DNA-protein interactions. In this review, we highlight how these single-molecule approaches have recently yielded new insights into nucleosomal and subnucleosomal structures and dynamics.
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Affiliation(s)
- Orkide Ordu
- Bionanoscience Department, Kavli Institute of Nanoscience,, Delft University of Technology, Van der Maasweg 9,, 2629 HZ Delft, The Netherlands
| | - Alexandra Lusser
- Division of Molecular Biology, Biocenter, Medical University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Nynke H. Dekker
- Bionanoscience Department, Kavli Institute of Nanoscience,, Delft University of Technology, Van der Maasweg 9,, 2629 HZ Delft, The Netherlands
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164
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Single-molecule fluorescence microscopy of native macromolecular complexes. Curr Opin Struct Biol 2016; 41:225-232. [PMID: 27662375 DOI: 10.1016/j.sbi.2016.09.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 09/06/2016] [Accepted: 09/07/2016] [Indexed: 12/11/2022]
Abstract
Macromolecular complexes consisting of proteins, lipids, and/or nucleic acids are ubiquitous in biological processes. Their composition, stoichiometry, order of assembly, and conformations can be heterogeneous or can change dynamically, making single-molecule studies best suited to measure these properties accurately. Recent single-molecule pull-down and other related approaches have combined the principles of conventional co-immunoprecipitation assay with single-molecule fluorescence microscopy to probe native macromolecular complexes. In this review, we present the advances in single-molecule pull-down methods and biological systems that have been investigated in such semi vivo manner.
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165
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Singh D, Sternberg SH, Fei J, Doudna JA, Ha T. Real-time observation of DNA recognition and rejection by the RNA-guided endonuclease Cas9. Nat Commun 2016; 7:12778. [PMID: 27624851 PMCID: PMC5027287 DOI: 10.1038/ncomms12778] [Citation(s) in RCA: 176] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 08/01/2016] [Indexed: 12/16/2022] Open
Abstract
Binding specificity of Cas9-guide RNA complexes to DNA is important for genome-engineering applications; however, how mismatches influence target recognition/rejection kinetics is not well understood. Here we used single-molecule FRET to probe real-time interactions between Cas9-RNA and DNA targets. The bimolecular association rate is only weakly dependent on sequence; however, the dissociation rate greatly increases from <0.006 s(-1) to >2 s(-1) upon introduction of mismatches proximal to protospacer-adjacent motif (PAM), demonstrating that mismatches encountered early during heteroduplex formation induce rapid rejection of off-target DNA. In contrast, PAM-distal mismatches up to 11 base pairs in length, which prevent DNA cleavage, still allow formation of a stable complex (dissociation rate <0.006 s(-1)), suggesting that extremely slow rejection could sequester Cas9-RNA, increasing the Cas9 expression level necessary for genome-editing, thereby aggravating off-target effects. We also observed at least two different bound FRET states that may represent distinct steps in target search and proofreading.
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Affiliation(s)
- Digvijay Singh
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Samuel H. Sternberg
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Jingyi Fei
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, USA
| | - Jennifer A. Doudna
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
- Howard Hughes Medical Institute, Berkeley, California 94720, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Innovative Genomics Initiative, University of California, Berkeley, California 94720, USA
| | - Taekjip Ha
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, USA
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166
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Dulin D, Cui TJ, Cnossen J, Docter MW, Lipfert J, Dekker NH. High Spatiotemporal-Resolution Magnetic Tweezers: Calibration and Applications for DNA Dynamics. Biophys J 2016; 109:2113-25. [PMID: 26588570 DOI: 10.1016/j.bpj.2015.10.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 10/05/2015] [Accepted: 10/13/2015] [Indexed: 11/16/2022] Open
Abstract
The observation of biological processes at the molecular scale in real time requires high spatial and temporal resolution. Magnetic tweezers are straightforward to implement, free of radiation or photodamage, and provide ample multiplexing capability, but their spatiotemporal resolution has lagged behind that of other single-molecule manipulation techniques, notably optical tweezers and AFM. Here, we present, to our knowledge, a new high-resolution magnetic tweezers apparatus. We systematically characterize the achievable spatiotemporal resolution for both incoherent and coherent light sources, different types and sizes of beads, and different types and lengths of tethered molecules. Using a bright coherent laser source for illumination and tracking at 6 kHz, we resolve 3 Å steps with a 1 s period for surface-melted beads and 5 Å steps with a 0.5 s period for double-stranded-dsDNA-tethered beads, in good agreement with a model of stochastic bead motion in the magnetic tweezers. We demonstrate how this instrument can be used to monitor the opening and closing of a DNA hairpin on millisecond timescales in real time, together with attendant changes in the hairpin dynamics upon the addition of deoxythymidine triphosphate. Our approach opens up the possibility of observing biological events at submillisecond timescales with subnanometer resolution using camera-based detection.
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Affiliation(s)
- David Dulin
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
| | - Tao Ju Cui
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Jelmer Cnossen
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Margreet W Docter
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Jan Lipfert
- Department of Physics, Nanosystems Initiative Munich and Center for Nanoscience, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Nynke H Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
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167
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Yang ST, Lim SI, Kiessling V, Kwon I, Tamm LK. Site-specific fluorescent labeling to visualize membrane translocation of a myristoyl switch protein. Sci Rep 2016; 6:32866. [PMID: 27605302 PMCID: PMC5015116 DOI: 10.1038/srep32866] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/16/2016] [Indexed: 12/20/2022] Open
Abstract
Fluorescence approaches have been widely used for elucidating the dynamics of protein-membrane interactions in cells and model systems. However, non-specific multi-site fluorescent labeling often results in a loss of native structure and function, and single cysteine labeling is not feasible when native cysteines are required to support a protein's folding or catalytic activity. Here, we develop a method using genetic incorporation of non-natural amino acids and bio-orthogonal chemistry to site-specifically label with a single fluorescent small molecule or protein the myristoyl-switch protein recoverin, which is involved in rhodopsin-mediated signaling in mammalian visual sensory neurons. We demonstrate reversible Ca(2+)-responsive translocation of labeled recoverin to membranes and show that recoverin favors membranes with negative curvature and high lipid fluidity in complex heterogeneous membranes, which confers spatio-temporal control over down-stream signaling events. The site-specific orthogonal labeling technique is promising for structural, dynamical, and functional studies of many lipid-anchored membrane protein switches.
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Affiliation(s)
- Sung-Tae Yang
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Sung In Lim
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Inchan Kwon
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904, USA
- School of Materials Science and Engineering, and Department of Biomedical Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
| | - Lukas K. Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
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168
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Nakamura A, Tasaki T, Ishiwata D, Yamamoto M, Okuni Y, Visootsat A, Maximilien M, Noji H, Uchiyama T, Samejima M, Igarashi K, Iino R. Single-molecule Imaging Analysis of Binding, Processive Movement, and Dissociation of Cellobiohydrolase Trichoderma reesei Cel6A and Its Domains on Crystalline Cellulose. J Biol Chem 2016; 291:22404-22413. [PMID: 27609516 DOI: 10.1074/jbc.m116.752048] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 08/24/2016] [Indexed: 11/06/2022] Open
Abstract
Trichoderma reesei Cel6A (TrCel6A) is a cellobiohydrolase that hydrolyzes crystalline cellulose into cellobiose. Here we directly observed the reaction cycle (binding, surface movement, and dissociation) of single-molecule intact TrCel6A, isolated catalytic domain (CD), cellulose-binding module (CBM), and CBM and linker (CBM-linker) on crystalline cellulose Iα The CBM-linker showed a binding rate constant almost half that of intact TrCel6A, whereas those of the CD and CBM were only one-tenth of intact TrCel6A. These results indicate that the glycosylated linker region largely contributes to initial binding on crystalline cellulose. After binding, all samples showed slow and fast dissociations, likely caused by the two different bound states due to the heterogeneity of cellulose surface. The CBM showed much higher specificity to the high affinity site than to the low affinity site, whereas the CD did not, suggesting that the CBM leads the CD to the hydrophobic surface of crystalline cellulose. On the cellulose surface, intact molecules showed slow processive movements (8.8 ± 5.5 nm/s) and fast diffusional movements (30-40 nm/s), whereas the CBM-Linker, CD, and a catalytically inactive full-length mutant showed only fast diffusional movements. These results suggest that both direct binding and surface diffusion contribute to searching of the hydrolysable point of cellulose chains. The duration time constant for the processive movement was 7.7 s, and processivity was estimated as 68 ± 42. Our results reveal the role of each domain in the elementary steps of the reaction cycle and provide the first direct evidence of the processive movement of TrCel6A on crystalline cellulose.
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Affiliation(s)
- Akihiko Nakamura
- From the Okazaki Institute for Integrative Bioscience and.,the Department of Functional Molecular Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Kanagawa 240-0193, Japan
| | - Tomoyuki Tasaki
- the Department of Applied Chemistry, Graduate School of Engineering, University of Tokyo, Tokyo 113-8656, Japan
| | - Daiki Ishiwata
- From the Okazaki Institute for Integrative Bioscience and
| | | | - Yasuko Okuni
- From the Okazaki Institute for Integrative Bioscience and
| | - Akasit Visootsat
- the Department of Biochemistry, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
| | - Morice Maximilien
- the National Chemical Engineering Institute in Paris, Paris 75005, France
| | - Hiroyuki Noji
- the Department of Applied Chemistry, Graduate School of Engineering, University of Tokyo, Tokyo 113-8656, Japan
| | - Taku Uchiyama
- the Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan, and
| | - Masahiro Samejima
- the Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan, and
| | - Kiyohiko Igarashi
- the Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan, and.,the VTT Technical Research Centre of Finland, Espoo FI-02044 VTT, Finland
| | - Ryota Iino
- From the Okazaki Institute for Integrative Bioscience and .,the Department of Functional Molecular Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Kanagawa 240-0193, Japan.,Institute for Molecular Science, National Institutes of Natural Sciences, Aichi 444-8787, Japan
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169
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Zheng Q, Jockusch S, Zhou Z, Altman RB, Zhao H, Asher W, Holsey M, Mathiasen S, Geggier P, Javitch JA, Blanchard SC. Electronic tuning of self-healing fluorophores for live-cell and single-molecule imaging. Chem Sci 2016; 8:755-762. [PMID: 28377799 PMCID: PMC5299821 DOI: 10.1039/c6sc02976k] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Mechanistic investigation of self-healing fluorophores leads to a general approach for highly photostable fluorophores across the spectrum.
Bright, long-lasting organic fluorophores enable a broad range of imaging applications. “Self-healing” fluorophores, in which intra-molecularly linked protective agents quench photo-induced reactive species, exhibit both enhanced photostability and biological compatibility. However, the self-healing strategy has yet to achieve its predicted potential, particularly in the presence of ambient oxygen where live-cell imaging studies must often be performed. To identify key bottlenecks in this technology that can be used to guide further engineering developments, we synthesized a series of Cy5 derivatives linked to the protective agent cyclooctatetraene (COT) and examined the photophysical mechanisms curtailing their performance. The data obtained reveal that the photostability of self-healing fluorophores is limited by reactivity of the COT protective agent. The addition of electron withdrawing substituents to COT reduced its susceptibility to reactions with molecular oxygen and the fluorophore to which it is attached and increased its capacity to participate in triplet energy transfer. Exploiting these insights, we designed and synthesized a suite of modified COT-fluorophores spanning the visible spectrum that exhibited markedly increased intra-molecular photostabilization. Under ambient oxygen conditions, the photostability of Cy3 and Cy5 fluorophore derivatives increased by 3- and 9-fold in vitro and by 2- and 6-fold in living cells, respectively. We further show that this approach can improve a silicon rhodamine fluorophore. These findings offer a clear strategy for achieving the full potential of the self-healing approach and its application to the gamut of fluorophore species commonly used for biomedical imaging.
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Affiliation(s)
- Qinsi Zheng
- Tri-Institutional Training Program in Chemical Biology, Weill Cornell Medicine, New York, NY
| | | | - Zhou Zhou
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY
| | - Roger B Altman
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY
| | - Hong Zhao
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY
| | - Wesley Asher
- Departments of Psychiatry and Pharmacology, Columbia University College of Physicians & Surgeons
| | - Michael Holsey
- Departments of Psychiatry and Pharmacology, Columbia University College of Physicians & Surgeons
| | - Signe Mathiasen
- Departments of Psychiatry and Pharmacology, Columbia University College of Physicians & Surgeons
| | - Peter Geggier
- Departments of Psychiatry and Pharmacology, Columbia University College of Physicians & Surgeons
| | - Jonathan A Javitch
- Departments of Psychiatry and Pharmacology, Columbia University College of Physicians & Surgeons; Division of Molecular Therapeutics, New York State Psychiatric Institute
| | - Scott C Blanchard
- Tri-Institutional Training Program in Chemical Biology, Weill Cornell Medicine, New York, NY; Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY
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170
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Abstract
The production of a single mRNA is the result of many sequential steps, from docking of transcription factors to polymerase initiation, elongation, splicing, and, finally, termination. Much of our knowledge about the fundamentals of RNA synthesis and processing come from ensemble in vitro biochemical measurements. Single-molecule approaches are very much in this same reductionist tradition but offer exquisite sensitivity in space and time along with the ability to observe heterogeneous behavior and actually manipulate macromolecules. These techniques can also be applied in vivo, allowing one to address questions in living cells that were previously restricted to reconstituted systems. In this review, we examine the unique insights that single-molecule techniques have yielded on the mechanisms of gene expression.
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Affiliation(s)
- Huimin Chen
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Daniel R Larson
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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171
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The number of α-synuclein proteins per vesicle gives insights into its physiological function. Sci Rep 2016; 6:30658. [PMID: 27477055 PMCID: PMC4967914 DOI: 10.1038/srep30658] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/07/2016] [Indexed: 12/25/2022] Open
Abstract
Although it is well established that the protein α-synuclein (αS) plays an important role in Parkinson’s disease, its physiological function remains largely unknown. It has been reported to bind membranes and to play a role in membrane remodeling processes. The mechanism by which αS remodels membranes is still debated; it may either affect its physical properties or act as a chaperone for other membrane associated proteins. To obtain insight into the role of αS in membrane remodeling we investigated the number of αS proteins associated with single small vesicles in a neuronal cell model. Using single-molecule microscopy and photo-bleaching approaches, we most frequently found 70 αS-GFPs per vesicle. Although this number is high enough to modulate physical membrane properties, it is also strikingly similar to the number of synaptobrevins, a putative interaction partner of αS, per vesicle. We therefore hypothesize a dual, synergistic role for αS in membrane remodeling.
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172
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Husbands AY, Aggarwal V, Ha T, Timmermans MCP. In Planta Single-Molecule Pull-Down Reveals Tetrameric Stoichiometry of HD-ZIPIII:LITTLE ZIPPER Complexes. THE PLANT CELL 2016; 28:1783-94. [PMID: 27385814 PMCID: PMC5006705 DOI: 10.1105/tpc.16.00289] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 07/03/2016] [Indexed: 05/12/2023]
Abstract
Deciphering complex biological processes markedly benefits from approaches that directly assess the underlying biomolecular interactions. Most commonly used approaches to monitor protein-protein interactions typically provide nonquantitative readouts that lack statistical power and do not yield information on the heterogeneity or stoichiometry of protein complexes. Single-molecule pull-down (SiMPull) uses single-molecule fluorescence detection to mitigate these disadvantages and can quantitatively interrogate interactions between proteins and other compounds, such as nucleic acids, small molecule ligands, and lipids. Here, we establish SiMPull in plants using the HOMEODOMAIN LEUCINE ZIPPER III (HD-ZIPIII) and LITTLE ZIPPER (ZPR) interaction as proof-of-principle. Colocalization analysis of fluorophore-tagged HD-ZIPIII and ZPR proteins provides strong statistical evidence of complex formation. In addition, we use SiMPull to directly quantify YFP and mCherry maturation probabilities, showing these differ substantially from values obtained in mammalian systems. Leveraging these probabilities, in conjunction with fluorophore photobleaching assays on over 2000 individual complexes, we determined HD-ZIPIII:ZPR stoichiometry. Intriguingly, these complexes appear as heterotetramers, comprising two HD-ZIPIII and two ZPR molecules, rather than heterodimers as described in the current model. This surprising result raises new questions about the regulation of these key developmental factors and is illustrative of the unique contribution SiMPull is poised to make to in planta protein interaction studies.
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Affiliation(s)
- Aman Y Husbands
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724
| | - Vasudha Aggarwal
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205 Howard Hughes Medical Institute, Baltimore, Maryland 21205
| | - Marja C P Timmermans
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724 Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
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173
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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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174
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Ramesh BS, Giorgakis E, Lopez-Davila V, Dashtarzheneha AK, Loizidou M. Detection of cell surface calreticulin as a potential cancer biomarker using near-infrared emitting gold nanoclusters. NANOTECHNOLOGY 2016; 27:285101. [PMID: 27255548 DOI: 10.1088/0957-4484/27/28/285101] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Calreticulin (CRT) is a cytoplasmic calcium-binding protein. The aim of this study was to investigate CRT presence in cancer with the use of fluorescent gold nanoclusters (AuNCs) and to explore AuNC synthesis using mercaptosuccinic acid (MSA) as a coating agent. MSA-coated AuNCs conferred well-dispersed, bio-stable, water-soluble nanoparticles with bioconjugation capacity and 800-850 nm fluorescence after broad-band excitation. Cell-viability assay revealed good AuNC tolerability. A native CRT amino-terminus corresponding peptide sequence was synthesised and used to generate rabbit site-specific antibodies. Target specificity was demonstrated with antibody blocking in colorectal and breast cancer cell models; human umbilical vein endothelial cells served as controls. We demonstrated a novel route of AuNC/MSA manufacture and CRT presence on colonic and breast cancerous cell surface. AuNCs served as fluorescent bio-probes specifically recognising surface-bound CRT. These results are promising in terms of AuNC application in cancer theranostics and CRT use as surface biomarker in human cancer.
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Affiliation(s)
- Bala Subramaniyam Ramesh
- Research Department of Nanotechnology, Division of Surgery and Interventional Science, University College London, Pond Street, London NW3 2QG, UK
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175
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Peng J, Zhang Z. Unraveling low-resolution structural data of large biomolecules by constructing atomic models with experiment-targeted parallel cascade selection simulations. Sci Rep 2016; 6:29360. [PMID: 27377017 PMCID: PMC4932515 DOI: 10.1038/srep29360] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 06/17/2016] [Indexed: 11/09/2022] Open
Abstract
Various low-resolution experimental techniques have gained more and more popularity in obtaining structural information of large biomolecules. In order to interpret the low-resolution structural data properly, one may need to construct an atomic model of the biomolecule by fitting the data using computer simulations. Here we develop, to our knowledge, a new computational tool for such integrative modeling by taking the advantage of an efficient sampling technique called parallel cascade selection (PaCS) simulation. For given low-resolution structural data, this PaCS-Fit method converts it into a scoring function. After an initial simulation starting from a known structure of the biomolecule, the scoring function is used to pick conformations for next cycle of multiple independent simulations. By this iterative screening-after-sampling strategy, the biomolecule may be driven towards a conformation that fits well with the low-resolution data. Our method has been validated using three proteins with small-angle X-ray scattering data and two proteins with electron microscopy data. In all benchmark tests, high-quality atomic models, with generally 1-3 Å from the target structures, are obtained. Since our tool does not need to add any biasing potential in the simulations to deform the structure, any type of low-resolution data can be implemented conveniently.
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Affiliation(s)
- Junhui Peng
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Zhiyong Zhang
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
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176
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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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177
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Tian H, Fürstenberg A, Huber T. Labeling and Single-Molecule Methods To Monitor G Protein-Coupled Receptor Dynamics. Chem Rev 2016; 117:186-245. [DOI: 10.1021/acs.chemrev.6b00084] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- He Tian
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Alexandre Fürstenberg
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Thomas Huber
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
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178
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Luo W, Wu M, Li S, Xu Y, Ye Z, Wei L, Chen B, Xu QH, Xiao L. Nanoprecipitation of Fluorescent Conjugated Polymer onto the Surface of Plasmonic Nanoparticle for Fluorescence/Dark-Field Dual-Modality Single Particle Imaging. Anal Chem 2016; 88:6827-35. [DOI: 10.1021/acs.analchem.6b01350] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Wenjuan Luo
- College
of Chemistry, Nankai Univeristy, Tianjin, 300071, China
- Dynamic Optical Microscopic Imaging Laboratory, Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, 410082, China
| | - Ming Wu
- State
Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510641, China
| | - Shuang Li
- State
Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510641, China
- Department
of Chemistry, National University of Singapore, 117543, Singapore
| | - Yueling Xu
- College
of Chemistry, Nankai Univeristy, Tianjin, 300071, China
| | - Zhongju Ye
- Dynamic Optical Microscopic Imaging Laboratory, Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, 410082, China
| | - Lin Wei
- Dynamic Optical Microscopic Imaging Laboratory, Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, 410082, China
| | - Bo Chen
- Dynamic Optical Microscopic Imaging Laboratory, Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, 410082, China
| | - Qing-Hua Xu
- Department
of Chemistry, National University of Singapore, 117543, Singapore
| | - Lehui Xiao
- College
of Chemistry, Nankai Univeristy, Tianjin, 300071, China
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179
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Maruani A, Richards DA, Chudasama V. Dual modification of biomolecules. Org Biomol Chem 2016; 14:6165-78. [PMID: 27278999 DOI: 10.1039/c6ob01010e] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
With the advent of novel bioorthogonal reactions and "click" chemistry, an increasing number of strategies for the single labelling of proteins and oligonucleotides have emerged. Whilst several methods exist for the site-selective introduction of a single chemical moiety, site-selective and bioorthogonal dual modification of biomolecules remains a challenge. The introduction of multiple modules enables a plethora of permutations and combinations and can generate a variety of bioconjuguates with many potential applications. From de novo approaches on oligomers to the post-translational functionalisation of proteins, this review will highlight the main strategies to dually modify biomolecules.
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Affiliation(s)
- Antoine Maruani
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H OAJ, UK.
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180
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Abstract
The repair of DNA by homologous recombination is an essential, efficient, and high-fidelity process that mends DNA lesions formed during cellular metabolism; these lesions include double-stranded DNA breaks, daughter-strand gaps, and DNA cross-links. Genetic defects in the homologous recombination pathway undermine genomic integrity and cause the accumulation of gross chromosomal abnormalities-including rearrangements, deletions, and aneuploidy-that contribute to cancer formation. Recombination proceeds through the formation of joint DNA molecules-homologously paired but metastable DNA intermediates that are processed by several alternative subpathways-making recombination a versatile and robust mechanism to repair damaged chromosomes. Modern biophysical methods make it possible to visualize, probe, and manipulate the individual molecules participating in the intermediate steps of recombination, revealing new details about the mechanics of genetic recombination. We review and discuss the individual stages of homologous recombination, focusing on common pathways in bacteria, yeast, and humans, and place particular emphasis on the molecular mechanisms illuminated by single-molecule methods.
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Affiliation(s)
- Jason C Bell
- Department of Microbiology and Molecular Genetics, and Department of Molecular and Cellular Biology, University of California, Davis, California 95616;
| | - Stephen C Kowalczykowski
- Department of Microbiology and Molecular Genetics, and Department of Molecular and Cellular Biology, University of California, Davis, California 95616;
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181
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Ohyanagi T, Shima T, Okada Y, Tsukasaki Y, Komatsuzaki A, Tsuboi S, Jin T. Compact and stable SNAP ligand-conjugated quantum dots as a fluorescent probe for single-molecule imaging of dynein motor protein. Chem Commun (Camb) 2016; 51:14836-9. [PMID: 26267231 DOI: 10.1039/c5cc05526a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Compact SNAP ligand-conjugated quantum dots (<10 nm) with high colloidal stability over a wide range of pH (5-9) have been synthesized as fluorescent probe for the single-molecule imaging of dynein motor protein.
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Affiliation(s)
- Tatsuya Ohyanagi
- Laboratory for Nano-Bio Probes, Quantitative Biology Center (QBiC), Riken, Furuedai 6-2-3, Suita, Osaka 565-0874, Japan.
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182
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Calderon CP. Motion blur filtering: A statistical approach for extracting confinement forces and diffusivity from a single blurred trajectory. Phys Rev E 2016; 93:053303. [PMID: 27301001 DOI: 10.1103/physreve.93.053303] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Indexed: 12/13/2022]
Abstract
Single particle tracking (SPT) can aid in understanding a variety of complex spatiotemporal processes. However, quantifying diffusivity and confinement forces from individual live cell trajectories is complicated by inter- and intratrajectory kinetic heterogeneity, thermal fluctuations, and (experimentally resolvable) statistical temporal dependence inherent to the underlying molecule's time correlated confined dynamics experienced in the cell. The problem is further complicated by experimental artifacts such as localization uncertainty and motion blur. The latter is caused by the tagged molecule emitting photons at different spatial positions during the exposure time of a single frame. The aforementioned experimental artifacts induce spurious time correlations in measured SPT time series that obscure the information of interest (e.g., confinement forces and diffusivity). We develop a maximum likelihood estimation (MLE) technique that decouples the above noise sources and systematically treats temporal correlation via time series methods. This ultimately permits a reliable algorithm for extracting diffusivity and effective forces in confined or unconfined environments. We illustrate how our approach avoids complications inherent to mean square displacement or autocorrelation techniques. Our algorithm modifies the established Kalman filter (which does not handle motion blur artifacts) to provide a likelihood based time series estimation procedure. The result extends A. J. Berglund's motion blur model [Phys. Rev. E 82, 011917 (2010)PLEEE81539-375510.1103/PhysRevE.82.011917] to handle confined dynamics. The approach can also systematically utilize (possibly time dependent) localization uncertainty estimates afforded by image analysis if available. This technique, which explicitly treats confinement and motion blur within a time domain MLE framework, uses an exact likelihood (time domain methods facilitate analyzing nonstationary signals). Our estimator is demonstrated to be consistent over a wide range of exposure times (5 to 100 ms), diffusion coefficients (1×10^{-3} to 1μm^{2}/s), and confinement widths (100 nm to 2μm). We demonstrate that neglecting motion blur or confinement can substantially bias estimation of kinetic parameters of interest to researchers. The technique also permits one to check statistical model assumptions against measured individual trajectories without "ground truth." The ability to reliably and consistently extract motion parameters in trajectories exhibiting confined and/or non-stationary dynamics, without exposure time artifacts corrupting estimates, is expected to aid in directly comparing trajectories obtained from different experiments or imaging modalities. A Python implementation is provided (open-source code will be maintained on GitHub; see also the Supplemental Material with this paper).
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183
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184
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Gyimesi M, Harami GM, Kocsis ZS, Kovács M. Recent adaptations of fluorescence techniques for the determination of mechanistic parameters of helicases and translocases. Methods 2016; 108:24-39. [PMID: 27133766 DOI: 10.1016/j.ymeth.2016.04.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/22/2016] [Accepted: 04/25/2016] [Indexed: 01/11/2023] Open
Abstract
Helicases and translocases are nucleic acid (NA)-based molecular motors that use the free energy liberated during the nucleoside triphosphate (NTP, usually ATP) hydrolysis cycle for unidirectional translocation along their NA (DNA, RNA or heteroduplex) substrates. Determination of the kinetic and thermodynamic parameters of their mechanoenzymatic cycle serves as a basis for the exploration of their physiological behavior and various cellular functions. Here we describe how recent adaptations of fluorescence-based solution kinetic methods can be used to determine practically all important mechanistic parameters of NA-based motor proteins. We outline practically useful analysis procedures for equilibrium, steady-state and transient kinetic data. This analysis can be used to quantitatively characterize the enzymatic steps of the NTP hydrolytic cycle, the binding site size, stoichiometry and energetics of protein-NA interactions, the rate and processivity of translocation along and unwinding of NA strands, and the mechanochemical coupling between these processes. The described methods yield insights into the functional role of the enzymes, and also greatly aid the design and interpretation of single-molecule experiments as well as the engineering of enzymatic properties for biotechnological applications.
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Affiliation(s)
- Máté Gyimesi
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary.
| | - Gábor M Harami
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary.
| | - Zsuzsa S Kocsis
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary.
| | - Mihály Kovács
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary.
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185
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Bernstein J, Fricks J. Analysis of single particle diffusion with transient binding using particle filtering. J Theor Biol 2016; 401:109-21. [PMID: 27107737 DOI: 10.1016/j.jtbi.2016.04.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 10/27/2015] [Accepted: 04/11/2016] [Indexed: 12/27/2022]
Abstract
Diffusion with transient binding occurs in a variety of biophysical processes, including movement of transmembrane proteins, T cell adhesion, and caging in colloidal fluids. We model diffusion with transient binding as a Brownian particle undergoing Markovian switching between free diffusion when unbound and diffusion in a quadratic potential centered around a binding site when bound. Assuming the binding site is the last position of the particle in the unbound state and Gaussian observational error obscures the true position of the particle, we use particle filtering to predict when the particle is bound and to locate the binding sites. Maximum likelihood estimators of diffusion coefficients, state transition probabilities, and the spring constant in the bound state are computed with a stochastic Expectation-Maximization (EM) algorithm.
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Affiliation(s)
- Jason Bernstein
- Department of Statistics, Pennsylvania State University, University Park, PA 16802, United States
| | - John Fricks
- Department of Statistics, Pennsylvania State University, University Park, PA 16802, United States.
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186
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Laszlo AH, Derrington IM, Gundlach JH. MspA nanopore as a single-molecule tool: From sequencing to SPRNT. Methods 2016; 105:75-89. [PMID: 27045943 PMCID: PMC4967004 DOI: 10.1016/j.ymeth.2016.03.026] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/10/2016] [Accepted: 03/29/2016] [Indexed: 11/15/2022] Open
Abstract
Single-molecule picometer resolution nanopore tweezers (SPRNT) is a new tool for analyzing the motion of nucleic acids through molecular motors. With SPRNT, individual enzymatic motions along DNA as small as 40 pm can be resolved on sub-millisecond time scales. Additionally, SPRNT reveals an enzyme’s exact location with respect to a DNA strand’s nucleotide sequence, enabling identification of sequence-specific behaviors. SPRNT is enabled by a mutant version of the biological nanopore formed by Mycobacterium smegmatis porin A (MspA). SPRNT is strongly rooted in nanopore sequencing and therefore requires a solid understanding of basic principles of nanopore sequencing. Furthermore, SPRNT shares tools developed for nanopore sequencing and extends them to analysis of single-molecule kinetics. As such, this review begins with a brief history of our work developing the nanopore MspA for nanopore sequencing. We then describe the underlying principles of SPRNT, how it works in detail, and propose some potential future uses. We close with a comparison of SPRNT to other techniques and we present the methods that will enable others to use SPRNT.
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Affiliation(s)
- Andrew H Laszlo
- University of Washington, Department of Physics, 3910 15th Ave NE, Seattle, WA 98195, USA
| | - Ian M Derrington
- University of Washington, Department of Physics, 3910 15th Ave NE, Seattle, WA 98195, USA
| | - Jens H Gundlach
- University of Washington, Department of Physics, 3910 15th Ave NE, Seattle, WA 98195, USA.
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187
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Abstract
The CRISPR-Cas system has emerged as a fascinating and important genome editing tool. It is now widely used in biology, biotechnology, and biomedical research in both academic and industrial settings. To improve the specificity and efficiency of Cas nucleases and to extend the applications of these systems for other areas of research, an understanding of their precise working mechanisms is crucial. In this review, we summarize current studies on the molecular structures and dynamic functions of type I and type II Cas nucleases, with a focus on target DNA searching and cleavage processes as revealed by single-molecule observations. [BMB Reports 2016; 49(4): 201-207].
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Affiliation(s)
- Seung Hwan Lee
- Center for Genome Engineering, Institute for Basic Science, Seoul 08826
| | - Sangsu Bae
- Department of Chemistry
- Institute for Materials Design, Hanyang University, Seoul 04763, Korea
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188
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Ng JD, Upadhyay SP, Marquard AN, Lupo KM, Hinton DA, Padilla NA, Bates DM, Goldsmith RH. Single-Molecule Investigation of Initiation Dynamics of an Organometallic Catalyst. J Am Chem Soc 2016; 138:3876-83. [PMID: 26944030 DOI: 10.1021/jacs.6b00357] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The action of molecular catalysts comprises multiple microscopic kinetic steps whose nature is of central importance in determining catalyst activity and selectivity. Single-molecule microscopy enables the direct examination of these steps, including elucidation of molecule-to-molecule variability. Such molecular diversity is particularly important for the behavior of molecular catalysts supported at surfaces. We present the first combined investigation of the initiation dynamics of an operational palladium cross-coupling catalyst at the bulk and single-molecule levels, including under turnover conditions. Base-initiated kinetics reveal highly heterogeneous behavior indicative of diverse catalyst population. Unexpectedly, this distribution becomes more heterogeneous at increasing base concentration. We model this behavior with a two-step saturation mechanism and identify specific microscopic steps where chemical variability must exist in order to yield observed behavior. Critically, we reveal how structural diversity at a surface translates into heterogeneity in catalyst behavior, while demonstrating how single-molecule experiments can contribute to understanding of molecular catalysts.
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Affiliation(s)
- James D Ng
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Sunil P Upadhyay
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Angela N Marquard
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Katherine M Lupo
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Daniel A Hinton
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Nicolas A Padilla
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Desiree M Bates
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Randall H Goldsmith
- Department of Chemistry, The University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
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189
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Best RB, Hofmann H, Nettels D, Schuler B. Quantitative interpretation of FRET experiments via molecular simulation: force field and validation. Biophys J 2016; 108:2721-31. [PMID: 26039173 DOI: 10.1016/j.bpj.2015.04.038] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 04/23/2015] [Accepted: 04/27/2015] [Indexed: 12/14/2022] Open
Abstract
Molecular simulation is a valuable and complementary tool that may assist with the interpretation of single-molecule Förster resonance energy transfer (FRET) experiments, if the energy function is of sufficiently high quality. Here we present force-field parameters for one of the most common pairs of chromophores used in experiments, AlexaFluor 488 and 594. From microsecond molecular-dynamics simulations, we are able to recover both experimentally determined equilibrium constants and association/dissociation rates of the chromophores with free tryptophan, as well as the decay of fluorescence anisotropy of a labeled protein. We find that it is particularly important to obtain a correct balance of solute-water interactions in the simulations in order to faithfully capture the experimental anisotropy decays, which provide a sensitive benchmark for fluorophore mobility. Lastly, by a combination of experiment and simulation, we address a potential complication in the interpretation of experiments on polyproline, used as a molecular ruler for FRET experiments, namely the potential association of one of the chromophores with the polyproline helix. Under conditions where simulations accurately capture the fluorescence anisotropy decay, we find at most a modest, transient population of conformations in which the chromophores associate with the polyproline. Explicit calculation of FRET transfer efficiencies for short polyprolines yields results in good agreement with experiment. These results illustrate the potential power of a combination of molecular simulation and experiment in quantifying biomolecular dynamics.
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Affiliation(s)
- Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
| | - Hagen Hofmann
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Zurich, Switzerland.
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190
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Quérard J, Le Saux T, Gautier A, Alcor D, Croquette V, Lemarchand A, Gosse C, Jullien L. Kinetics of Reactive Modules Adds Discriminative Dimensions for Selective Cell Imaging. Chemphyschem 2016; 17:1396-413. [PMID: 26833808 DOI: 10.1002/cphc.201500987] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Indexed: 11/07/2022]
Abstract
Living cells are chemical mixtures of exceptional interest and significance, whose investigation requires the development of powerful analytical tools fulfilling the demanding constraints resulting from their singular features. In particular, multiplexed observation of a large number of molecular targets with high spatiotemporal resolution appears highly desirable. One attractive road to address this analytical challenge relies on engaging the targets in reactions and exploiting the rich kinetic signature of the resulting reactive module, which originates from its topology and its rate constants. This review explores the various facets of this promising strategy. We first emphasize the singularity of the content of a living cell as a chemical mixture and suggest that its multiplexed observation is significant and timely. Then, we show that exploiting the kinetics of analytical processes is relevant to selectively detect a given analyte: upon perturbing the system, the kinetic window associated to response read-out has to be matched with that of the targeted reactive module. Eventually, we introduce the state-of-the-art of cell imaging exploiting protocols based on reaction kinetics and draw some promising perspectives.
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Affiliation(s)
- Jérôme Quérard
- Ecole Normale Supérieure-PSL Research University; Département de Chimie; 24, rue Lhomond F-75005 Paris France
- Sorbonne Universités; UPMC Univ Paris 06, PASTEUR; F-75005 Paris France
- CNRS, UMR 8640 PASTEUR; F-75005 Paris France
| | - Thomas Le Saux
- Ecole Normale Supérieure-PSL Research University; Département de Chimie; 24, rue Lhomond F-75005 Paris France
- Sorbonne Universités; UPMC Univ Paris 06, PASTEUR; F-75005 Paris France
- CNRS, UMR 8640 PASTEUR; F-75005 Paris France
| | - Arnaud Gautier
- Ecole Normale Supérieure-PSL Research University; Département de Chimie; 24, rue Lhomond F-75005 Paris France
- Sorbonne Universités; UPMC Univ Paris 06, PASTEUR; F-75005 Paris France
- CNRS, UMR 8640 PASTEUR; F-75005 Paris France
| | - Damien Alcor
- INSERM U1065, C3M; 151 route Saint Antoine de Ginestière, BP 2 3194 F-06204 Nice Cedex 3 France
| | - Vincent Croquette
- Ecole Normale Supérieure; Département de Physique and Département de Biologie, Laboratoire de Physique Statistique UMR CNRS-ENS 8550; 24 rue Lhomond F-75005 Paris France
| | - Annie Lemarchand
- Sorbonne Universités; UPMC Univ Paris 06, Laboratoire de Physique Théorique de la Matière Condensée; 4 place Jussieu, case courrier 121 75252 Paris cedex 05 France
- CNRS, UMR 7600 LPTMC; 75005 Paris France
| | - Charlie Gosse
- Laboratoire de Photonique et de Nanostructures, LPN-CNRS; route de Nozay 91460 Marcoussis France
| | - Ludovic Jullien
- Ecole Normale Supérieure-PSL Research University; Département de Chimie; 24, rue Lhomond F-75005 Paris France
- Sorbonne Universités; UPMC Univ Paris 06, PASTEUR; F-75005 Paris France
- CNRS, UMR 8640 PASTEUR; F-75005 Paris France
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191
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Chung HS, Louis JM, Gopich IV. Analysis of Fluorescence Lifetime and Energy Transfer Efficiency in Single-Molecule Photon Trajectories of Fast-Folding Proteins. J Phys Chem B 2016; 120:680-99. [PMID: 26812046 DOI: 10.1021/acs.jpcb.5b11351] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In single-molecule Förster resonance energy transfer (FRET) spectroscopy, the dynamics of molecular processes are usually determined by analyzing the fluorescence intensity of donor and acceptor dyes. Since FRET efficiency is related to fluorescence lifetimes, additional information can be extracted by analyzing fluorescence intensity and lifetime together. For fast processes where individual states are not well separated in a trajectory, it is not easy to obtain the lifetime information. Here, we present analysis methods to utilize fluorescence lifetime information from single-molecule FRET experiments, and apply these methods to three fast-folding, two-state proteins. By constructing 2D FRET efficiency-lifetime histograms, the correlation can be visualized between the FRET efficiency and fluorescence lifetimes in the presence of the submicrosecond to millisecond dynamics. We extend the previously developed method for analyzing delay times of donor photons to include acceptor delay times. To determine the kinetics and lifetime parameters accurately, we used a maximum likelihood method. We found that acceptor blinking can lead to inaccurate parameters in the donor delay time analysis. This problem can be solved by incorporating acceptor blinking into a model. While the analysis of acceptor delay times is not affected by acceptor blinking, it is more sensitive to the shape of the delay time distribution resulting from a broad conformational distribution in the unfolded state.
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Affiliation(s)
- Hoi Sung Chung
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
| | - John M Louis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
| | - Irina V Gopich
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
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192
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193
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Goldschen-Ohm MP, Klenchin VA, White DS, Cowgill JB, Cui Q, Goldsmith RH, Chanda B. Structure and dynamics underlying elementary ligand binding events in human pacemaking channels. eLife 2016; 5:e20797. [PMID: 27858593 PMCID: PMC5115869 DOI: 10.7554/elife.20797] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/01/2016] [Indexed: 01/07/2023] Open
Abstract
Although molecular recognition is crucial for cellular signaling, mechanistic studies have relied primarily on ensemble measures that average over and thereby obscure underlying steps. Single-molecule observations that resolve these steps are lacking due to diffraction-limited resolution of single fluorophores at relevant concentrations. Here, we combined zero-mode waveguides with fluorescence resonance energy transfer (FRET) to directly observe binding at individual cyclic nucleotide-binding domains (CNBDs) from human pacemaker ion channels critical for heart and brain function. Our observations resolve the dynamics of multiple distinct steps underlying cyclic nucleotide regulation: a slow initial binding step that must select a 'receptive' conformation followed by a ligand-induced isomerization of the CNBD. X-ray structure of the apo CNBD and atomistic simulations reveal that the isomerization involves both local and global transitions. Our approach reveals fundamental mechanisms underpinning ligand regulation of pacemaker channels, and is generally applicable to weak-binding interactions governing a broad spectrum of signaling processes.
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Affiliation(s)
| | - Vadim A Klenchin
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States
| | - David S White
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States,Department of Chemistry, University of Wisconsin-Madison, Madison, United States
| | - John B Cowgill
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States
| | - Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, United States
| | - Randall H Goldsmith
- Department of Chemistry, University of Wisconsin-Madison, Madison, United States
| | - Baron Chanda
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States,Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, United States,
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194
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Moses M, Hedegård P, Hatzakis N. Quantification of Functional Dynamics of Membrane Proteins Reconstituted in Nanodiscs Membranes by Single Turnover Functional Readout. Methods Enzymol 2016; 581:227-256. [DOI: 10.1016/bs.mie.2016.08.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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195
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Probing the kinetic and thermodynamic consequences of the tetraloop/tetraloop receptor monovalent ion-binding site in P4-P6 RNA by smFRET. Biochem Soc Trans 2016; 43:172-8. [PMID: 25849913 DOI: 10.1042/bst20140268] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Structured RNA molecules play roles in central biological processes and understanding the basic forces and features that govern RNA folding kinetics and thermodynamics can help elucidate principles that underlie biological function. Here we investigate one such feature, the specific interaction of monovalent cations with a structured RNA, the P4-P6 domain of the Tetrahymena ribozyme. We employ single molecule FRET (smFRET) approaches as these allow determination of folding equilibrium and rate constants over a wide range of stabilities and thus allow direct comparisons without the need for extrapolation. These experiments provide additional evidence for specific binding of monovalent cations, Na+ and K+, to the RNA tetraloop-tetraloop receptor (TL-TLR) tertiary motif. These ions facilitate both folding and unfolding, consistent with an ability to help order the TLR for binding and further stabilize the tertiary contact subsequent to attainment of the folding transition state.
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196
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Saad ST, Metherell AJ, Baggaley E, Ward MD. Synthesis and photophysical properties of Ir(iii)/Re(i) dyads: control of Ir→Re photoinduced energy transfer. Dalton Trans 2016; 45:11568-79. [DOI: 10.1039/c6dt01614f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The extent of Ir→Re photoinduced energy transfer in Ir(iii)/Re(i) dyads can be controlled using a solvent-sensitive conformationally flexible bridging ligand.
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Affiliation(s)
- Suad T. Saad
- Department of Chemistry
- University of Sheffield
- Sheffield S3 7HF
- UK
- College of Sciences WSCI
| | | | | | - Michael D. Ward
- Department of Chemistry
- University of Sheffield
- Sheffield S3 7HF
- UK
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197
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Uchihashi T, Watanabe H, Fukuda S, Shibata M, Ando T. Functional extension of high-speed AFM for wider biological applications. Ultramicroscopy 2016; 160:182-196. [DOI: 10.1016/j.ultramic.2015.10.017] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 09/25/2015] [Accepted: 10/12/2015] [Indexed: 11/24/2022]
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198
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Light-Enhanced Fluorescence of Multi-Level Cavitands Possessing Pyridazine Upper rim. J Fluoresc 2015; 26:679-88. [PMID: 26715516 DOI: 10.1007/s10895-015-1754-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 12/14/2015] [Indexed: 10/22/2022]
Abstract
Completely different fluorescence behaviour of cavitands based on a same calix[4]resorcinarene compound was observed. While the fluorescence intensity of the parent compound, tetramethyl-cavitand (1) slowly faded as a result of UV-light exposure, the emission of the three-level cavitand with pyridazine moieties at the upper rim (5a) was enhanced by the excitation in the UV-region. The structure of fluorescence emission (characterized by excitation-emission matrices) and the absorption of 5a remained unaltered. The analysis of fluorescence decay curves reveals the presence of two separated components assigned to two individual emitting species. The measured significant increase of the average lifetime and quantum yield is the consequence of the UV-light induced transition between the different states of 5a. These observations can be explained by the structural difference between 5a and 1. As a counterpart of the naked cavitand (1) with methyl substituents at the upper rim only, 5a has three additional moieties benzene, triazole and pyridazine levels. Computational studies proved the existence of two conformational isomers of 5a. Upon ultraviolet light excitation a "dark" to "light" conformational transition occurs between the two isomers. This hypothesis was confirmed by anisotropy decay measurements.
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199
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Zheng Q, Jockusch S, Rodríguez-Calero GG, Zhou Z, Zhao H, Altman RB, Abruña HD, Blanchard SC. Intra-molecular triplet energy transfer is a general approach to improve organic fluorophore photostability. Photochem Photobiol Sci 2015; 15:196-203. [PMID: 26700693 DOI: 10.1039/c5pp00400d] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Bright, long-lasting and non-phototoxic organic fluorophores are essential to the continued advancement of biological imaging. Traditional approaches towards achieving photostability, such as the removal of molecular oxygen and the use of small-molecule additives in solution, suffer from potentially toxic side effects, particularly in the context of living cells. The direct conjugation of small-molecule triplet state quenchers, such as cyclooctatetraene (COT), to organic fluorophores has the potential to bypass these issues by restoring reactive fluorophore triplet states to the ground state through intra-molecular triplet energy transfer. Such methods have enabled marked improvement in cyanine fluorophore photostability spanning the visible spectrum. However, the generality of this strategy to chemically and structurally diverse fluorophore species has yet to be examined. Here, we show that the proximal linkage of COT increases the photon yield of a diverse range of organic fluorophores widely used in biological imaging applications, demonstrating that the intra-molecular triplet energy transfer mechanism is a potentially general approach for improving organic fluorophore performance and photostability.
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Affiliation(s)
- Qinsi Zheng
- Tri-Institutional Training Program in Chemical Biology, Weill Medical College of Cornell University, New York, NY, USA
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200
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Larda ST, Pichugin D, Prosser RS. Site-Specific Labeling of Protein Lysine Residues and N-Terminal Amino Groups with Indoles and Indole-Derivatives. Bioconjug Chem 2015; 26:2376-83. [DOI: 10.1021/acs.bioconjchem.5b00457] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sacha Thierry Larda
- Department
of Chemistry, University of Toronto, UTM, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada
| | - Dmitry Pichugin
- Department
of Chemistry, University of Toronto, UTM, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada
| | - Robert Scott Prosser
- Department
of Chemistry, University of Toronto, UTM, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada
- Department
of Biochemistry, University of Toronto, 1 King’s College Circle, Toronto, Ontario M5S 1A8, Canada
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