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Wickersham CE, Lipman EA. Tracking DNA Synthesis with Single-Molecule Strand Displacement. J Phys Chem B 2018; 122:11546-11553. [PMID: 30284831 DOI: 10.1021/acs.jpcb.8b07440] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously shown that double-stranded DNA labeled with a periodic series of fluorescent dyes can be used to track a single helicase. Here we demonstrate how this technique can be adapted to follow processive DNA synthesis. By monitoring strand displacement, we track the motion of a single ϕ29 DNA polymerase without labeling or altering the enzyme or the template strand, and without applying any force. We observe a wide range of speeds, with the highest exceeding by several times those observed in earlier in vitro single-molecule experiments. Because this method enables repeated observations of the same polymerase traversing identical segments of DNA, it should prove useful for determining the effects of sequence on DNA replication and transcription. In addition, future measurements of this type may allow us to examine in detail the interactions of individual DNA polymerases with other components of the replisome.
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Wallace B, Atzberger PJ. Förster resonance energy transfer: Role of diffusion of fluorophore orientation and separation in observed shifts of FRET efficiency. PLoS One 2017; 12:e0177122. [PMID: 28542211 PMCID: PMC5438121 DOI: 10.1371/journal.pone.0177122] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 04/21/2017] [Indexed: 12/14/2022] Open
Abstract
Förster resonance energy transfer (FRET) is a widely used single-molecule technique for measuring nanoscale distances from changes in the non-radiative transfer of energy between donor and acceptor fluorophores. For macromolecules and complexes this observed transfer efficiency is used to infer changes in molecular conformation under differing experimental conditions. However, sometimes shifts are observed in the FRET efficiency even when there is strong experimental evidence that the molecular conformational state is unchanged. We investigate ways in which such discrepancies can arise from kinetic effects. We show that significant shifts can arise from the interplay between excitation kinetics, orientation diffusion of fluorophores, separation diffusion of fluorophores, and non-emitting quenching.
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Affiliation(s)
- Bram Wallace
- Department of Mathematics, University of California Santa Barbara, Santa Barbara, CA, 93106, United States of America
| | - Paul J. Atzberger
- Department of Mathematics, University of California Santa Barbara, Santa Barbara, CA, 93106, United States of America
- Department of Mechanical Engineering, University of California Santa Barbara, Santa Barbara, CA, 93106, United States of America
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Sun B, Wang MD. Single-molecule perspectives on helicase mechanisms and functions. Crit Rev Biochem Mol Biol 2015; 51:15-25. [DOI: 10.3109/10409238.2015.1102195] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Random coil negative control reproduces the discrepancy between scattering and FRET measurements of denatured protein dimensions. Proc Natl Acad Sci U S A 2015; 112:6631-6. [PMID: 25964362 DOI: 10.1073/pnas.1418673112] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Small-angle scattering studies generally indicate that the dimensions of unfolded single-domain proteins are independent (to within experimental uncertainty of a few percent) of denaturant concentration. In contrast, single-molecule FRET (smFRET) studies invariably suggest that protein unfolded states contract significantly as the denaturant concentration falls from high (∼6 M) to low (∼1 M). Here, we explore this discrepancy by using PEG to perform a hitherto absent negative control. This uncharged, highly hydrophilic polymer has been shown by multiple independent techniques to behave as a random coil in water, suggesting that it is unlikely to expand further on the addition of denaturant. Consistent with this observation, small-angle neutron scattering indicates that the dimensions of PEG are not significantly altered by the presence of either guanidine hydrochloride or urea. smFRET measurements on a PEG construct modified with the most commonly used FRET dye pair, however, produce denaturant-dependent changes in transfer efficiency similar to those seen for a number of unfolded proteins. Given the vastly different chemistries of PEG and unfolded proteins and the significant evidence that dye-free PEG is well-described as a denaturant-independent random coil, this similarity raises questions regarding the interpretation of smFRET data in terms of the hydrogen bond- or hydrophobically driven contraction of the unfolded state at low denaturant.
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Cordova JC, Das DK, Manning HW, Lang MJ. Combining single-molecule manipulation and single-molecule detection. Curr Opin Struct Biol 2014; 28:142-8. [DOI: 10.1016/j.sbi.2014.08.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 07/24/2014] [Accepted: 08/12/2014] [Indexed: 11/24/2022]
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RUEDAS-RAMA MJ, ALVAREZ-PEZ JM, ORTE A. SOLVING SINGLE BIOMOLECULES BY ADVANCED FRET-BASED SINGLE-MOLECULE FLUORESCENCE TECHNIQUES. ACTA ACUST UNITED AC 2014. [DOI: 10.1142/s1793048013300041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The use of Förster resonance energy transfer (FRET) has undergone a renaissance in the last two decades, especially in the study of structure of biomolecules, biomolecular interactions, and dynamics. Thanks to powerful advances in single-molecule fluorescence (SMF) techniques, seeing molecules at work is a reality, which has helped to build up the mindset of molecular machines. In the last few years, many technical developments have broadened the applications of SMF-FRET, expanding the amount of information that can be recovered from individual molecules. Here, we focus on the non-standard SMF-FRET techniques, such as two-color coincidence detection (TCCD), alternating laser excitation (ALEX), multiparameter fluorescence detection (MFD); the addition of fluorescence lifetime as an orthogonal dimension in single-molecule experiments; or the development of novel and improved methods of analysis constituting to a set of advanced methodologies that may become routine tools in a close future. [Formula: see text]Special Issue Comment: This review about advanced single-molecule FRET techniques is specially related to the review by Jørgensen and Hatzakis,6 who detail experimetal strategies to solve the activity of single enzymes. The advanced techniques described in our paper may serve as interesting alternatives when applied to enzyme studies. Our manuscript is also related to the reviews in this Special Issue that deal with model solving.22,130
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Affiliation(s)
- M. J. RUEDAS-RAMA
- Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Cartuja Campus, Granada, 18071, Spain
| | - J. M. ALVAREZ-PEZ
- Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Cartuja Campus, Granada, 18071, Spain
| | - A. ORTE
- Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Cartuja Campus, Granada, 18071, Spain
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Zhou R, Kunzelmann S, Webb MR, Ha T. Detecting intramolecular conformational dynamics of single molecules in short distance range with subnanometer sensitivity. NANO LETTERS 2011; 11:5482-8. [PMID: 22023515 PMCID: PMC3237907 DOI: 10.1021/nl2032876] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Single molecule detection is useful for characterizing nanoscale objects such as biological macromolecules, nanoparticles and nanodevices with nanometer spatial resolution. Fluorescence resonance energy transfer (FRET) is widely used as a single-molecule assay to monitor intramolecular dynamics in the distance range of 3-8 nm. Here we demonstrate that self-quenching of two rhodamine derivatives can be used to detect small conformational dynamics corresponding to subnanometer distance changes in a FRET-insensitive short-range at the single molecule level. A ParM protein mutant labeled with two rhodamines works as a single molecule adenosine 5'-diphosphate (ADP) sensor that has 20 times brighter fluorescence signal in the ADP bound state than the unbound state. Single molecule time trajectories show discrete transitions between fluorescence on and off states that can be directly ascribed to ADP binding and dissociation events. The conformational changes observed with 20:1 contrast are only 0.5 nm in magnitude and are between crystallographic distances of 1.6 and 2.1 nm, demonstrating exquisite sensitivity to short distance scale changes. The systems also allowed us to gain information on the photophysics of self-quenching induced by rhodamine stacking: (1) photobleaching of either of the two rhodamines eliminates quenching of the other rhodamine fluorophore and (2) photobleaching from the highly quenched, stacked state is only 2-fold slower than from the unstacked state.
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Affiliation(s)
- Ruobo Zhou
- Department of Physics and Center for the Physics of Living Cells, University of Illinois, Urbana-Champaign, Illinois 61801, United States
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Wickersham CE, Kerr DHS, Lipman EA. Synthesis of extended nanoscale optical encoders. Bioconjug Chem 2010; 21:2234-8. [PMID: 21069998 DOI: 10.1021/bc100215j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
An optical encoder is a device that uses an interrupted light source-sensor pair to map linear or rotational motion onto a periodic signal. Simple, inexpensive optical encoders are used for precise positioning in machines such as desktop printers, disk drives, and astronomical telescopes. A strand of DNA labeled with a series of Förster resonance energy transfer acceptor dyes can perform the same function at the nanometer scale, producing a periodic fluorescence signal that encodes the movement of a single donor-labeled molecular motor with high spatial and temporal resolution. Previous measurements of this type have employed encoders limited to five acceptor dyes, and hence five signal periods, restricting the range of motion that could be followed. Here we describe two methods for synthesizing double-stranded DNA containing several to hundreds of regularly spaced dyes on one strand. Distinct functional groups incorporated at the encoder ends enable tethering for single-molecule measurements.
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Affiliation(s)
- Charles E Wickersham
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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Luzzietti N, Brutzer H, Klaue D, Schwarz FW, Staroske W, Clausing S, Seidel R. Efficient preparation of internally modified single-molecule constructs using nicking enzymes. Nucleic Acids Res 2010; 39:e15. [PMID: 21071409 PMCID: PMC3035433 DOI: 10.1093/nar/gkq1004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Investigations of enzymes involved in DNA metabolism have strongly benefited from the establishment of single molecule techniques. These experiments frequently require elaborate DNA substrates, which carry chemical labels or nucleic acid tertiary structures. Preparing such constructs often represents a technical challenge: long modified DNA molecules are usually produced via multi-step processes, involving low efficiency intermolecular ligations of several fragments. Here, we show how long stretches of DNA (>50 bp) can be modified using nicking enzymes to produce complex DNA constructs. Multiple different chemical and structural modifications can be placed internally along DNA, in a specific and precise manner. Furthermore, the nicks created can be resealed efficiently yielding intact molecules, whose mechanical properties are preserved. Additionally, the same strategy is applied to obtain long single-strand overhangs subsequently used for efficient ligation of ss- to dsDNA molecules. This technique offers promise for a wide range of applications, in particular single-molecule experiments, where frequently multiple internal DNA modifications are required.
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Affiliation(s)
- Nicholas Luzzietti
- Biotechnology Center, Technische Universität Dresden, D-01062 Dresden, Germany
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Insight into helicase mechanism and function revealed through single-molecule approaches. Q Rev Biophys 2010; 43:185-217. [PMID: 20682090 DOI: 10.1017/s0033583510000107] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Helicases are a class of nucleic acid (NA) motors that catalyze NTP-dependent unwinding of NA duplexes into single strands, a reaction essential to all areas of NA metabolism. In the last decade, single-molecule (sm) technology has proven to be highly useful in revealing mechanistic insight into helicase activity that is not always detectable via ensemble assays. A combination of methods based on fluorescence, optical and magnetic tweezers, and flow-induced DNA stretching has enabled the study of helicase conformational dynamics, force generation, step size, pausing, reversal and repetitive behaviors during translocation and unwinding by helicases working alone and as part of multiprotein complexes. The contributions of these sm investigations to our understanding of helicase mechanism and function will be discussed.
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Hohlbein J, Gryte K, Heilemann M, Kapanidis AN. Surfing on a new wave of single-molecule fluorescence methods. Phys Biol 2010; 7:031001. [DOI: 10.1088/1478-3975/7/3/031001] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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