1
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Foote A, Ishii K, Cullinane B, Tahara T, Goldsmith RH. Quantifying Microsecond Solution-Phase Conformational Dynamics of a DNA Hairpin at the Single-Molecule Level. ACS PHYSICAL CHEMISTRY AU 2024; 4:408-419. [PMID: 39069982 PMCID: PMC11274281 DOI: 10.1021/acsphyschemau.3c00066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 05/03/2024] [Accepted: 05/06/2024] [Indexed: 07/30/2024]
Abstract
Quantifying the rapid conformational dynamics of biological systems is fundamental to understanding the mechanism. However, biomolecules are complex, often containing static and dynamic heterogeneity, thus motivating the use of single-molecule methods, particularly those that can operate in solution. In this study, we measure microsecond conformational dynamics of solution-phase DNA hairpins at the single-molecule level using an anti-Brownian electrokinetic (ABEL) trap. Different conformational states were distinguished by their fluorescence lifetimes, and kinetic parameters describing transitions between these states were determined using two-dimensional fluorescence lifetime correlation (2DFLCS) analysis. Rather than combining fluorescence signals from the entire data set ensemble, long observation times of individual molecules allowed ABEL-2DFLCS to be performed on each molecule independently, yielding the underlying distribution of the system's kinetic parameters. ABEL-2DFLCS on the DNA hairpins resolved an underlying heterogeneity of fluorescence lifetimes and provided signatures of two-state exponential dynamics with rapid (
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Affiliation(s)
- Alexander
K. Foote
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Kunihiko Ishii
- Molecular
Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Ultrafast
Spectroscopy Research Team, RIKEN Center
for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Brendan Cullinane
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Tahei Tahara
- Molecular
Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Ultrafast
Spectroscopy Research Team, RIKEN Center
for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Randall H. Goldsmith
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
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2
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Chu J, Ejaz A, Lin KM, Joseph MR, Coraor AE, Drummond DA, Squires AH. Single-molecule fluorescence multiplexing by multi-parameter spectroscopic detection of nanostructured FRET labels. NATURE NANOTECHNOLOGY 2024:10.1038/s41565-024-01672-8. [PMID: 38750166 DOI: 10.1038/s41565-024-01672-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 04/05/2024] [Indexed: 05/28/2024]
Abstract
Multiplexed, real-time fluorescence detection at the single-molecule level can reveal the stoichiometry, dynamics and interactions of multiple molecular species in mixtures and other complex samples. However, fluorescence-based sensing is typically limited to the detection of just 3-4 colours at a time due to low signal-to-noise ratio, high spectral overlap and the need to maintain the chemical compatibility of dyes. Here we engineered a palette of several dozen composite fluorescent labels, called FRETfluors, for multiplexed spectroscopic measurements at the single-molecule level. FRETfluors are compact nanostructures constructed from three chemical components (DNA, Cy3 and Cy5) with tunable spectroscopic properties due to variations in geometry, fluorophore attachment chemistry and DNA sequence. We demonstrate FRETfluor labelling and detection for low-concentration (<100 fM) mixtures of mRNA, dsDNA and proteins using an anti-Brownian electrokinetic trap. In addition to identifying the unique spectroscopic signature of each FRETfluor, this trap differentiates FRETfluors attached to a target from unbound FRETfluors, enabling wash-free sensing. Although usually considered an undesirable complication of fluorescence, here the inherent sensitivity of fluorophores to the local physicochemical environment provides a new design axis complementary to changing the FRET efficiency. As a result, the number of distinguishable FRETfluor labels can be combinatorically increased while chemical compatibility is maintained, expanding prospects for spectroscopic multiplexing at the single-molecule level using a minimal set of chemical building blocks.
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Affiliation(s)
- Jiachong Chu
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Ayesha Ejaz
- Department of Chemistry, University of Chicago, Chicago, IL, USA
| | - Kyle M Lin
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL, USA
- Interdisicplinary Scientist Training Program, Pritzker School of Medicine, University of Chicago, Chicago, IL, USA
| | - Madeline R Joseph
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Aria E Coraor
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - D Allan Drummond
- Department of Biochemistry and Molecular Biophysics, University of Chicago, Chicago, IL, USA
- Department of Medicine, Section of Genetic Medicine, University of Chicago, Chicago, IL, USA
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, USA
| | - Allison H Squires
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, USA.
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3
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Zuo C, Wen Y, Chen D, Ouyang J, Li P, Dong T. Dynamic Monitoring of Biomolecular Hydrodynamic Dimensions by Magnetization Motion on Quartz Crystal Microbalance. Anal Chem 2024; 96:7421-7428. [PMID: 38691506 DOI: 10.1021/acs.analchem.3c05079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2024]
Abstract
Hydrodynamic dimension (HD) is the primary indicator of the size of bioconjugated particles and biomolecules. It is an important parameter in the study of solid-liquid two-phase dynamics. HD dynamic monitoring is crucial for precise and customized medical research as it enables the investigation of the continuous changes in the physicochemical characteristics of biomolecules in response to external stimuli. However, current HD measurements based on Brownian motion, such as dynamic light scattering (DLS), are inadequate for meeting the polydisperse sample demands of dynamic monitoring. In this paper, we propose MMQCM method samples of various types and HD dynamic monitoring. An alternating magnetic field of frequency ωm excites biomolecule-magnetic bead particles (bioMBs) to generate magnetization motion, and the quartz crystal microbalance (QCM) senses this motion to provide HD dynamic monitoring. Specifically, the magnetization motion is modulated onto the thickness-shear oscillation of the QCM at the frequency ωq. By analysis of the frequency spectrum of the QCM output signal, the ratio of the magnitudes of the real and imaginary parts of the components at frequency ωq ± 2ωm is extracted to characterize the particle size. Using the MMQCM approach, we successfully evaluated the size of bioMBs with different biomolecule concentrations. The 30 min HD dynamic monitoring was implemented. An increase of ∼10 nm in size was observed upon biomolecular structural stretching. Subsequently, the size of bioMBs gradually reduced due to the continuous dissociation of biomolecules, with a total reduction of 20∼40 nm. This HD dynamic monitoring demonstrates that the release of biomolecules can be regulated by controlling the duration of magnetic stimulation, providing valuable insights and guidance for controlled drug release in personalized precision medicine.
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Affiliation(s)
- Can Zuo
- School of Electronic, Information and Electrical Eng., Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China
| | - Yumei Wen
- School of Electronic, Information and Electrical Eng., Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China
| | - Dongyu Chen
- School of Electronic, Information and Electrical Eng., Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China
| | - Jihai Ouyang
- School of Electronic, Information and Electrical Eng., Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China
| | - Ping Li
- School of Electronic, Information and Electrical Eng., Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China
| | - Tao Dong
- Multidisciplinary Research Institute, School of Instrument Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China
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4
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Needham LM, Saavedra C, Rasch JK, Sole-Barber D, Schweitzer BS, Fairhall AJ, Vollbrecht CH, Wan S, Podorova Y, Bergsten AJ, Mehlenbacher B, Zhang Z, Tenbrake L, Saimi J, Kneely LC, Kirkwood JS, Pfeifer H, Chapman ER, Goldsmith RH. Label-free detection and profiling of individual solution-phase molecules. Nature 2024; 629:1062-1068. [PMID: 38720082 DOI: 10.1038/s41586-024-07370-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 04/02/2024] [Indexed: 05/21/2024]
Abstract
Most chemistry and biology occurs in solution, in which conformational dynamics and complexation underlie behaviour and function. Single-molecule techniques1 are uniquely suited to resolving molecular diversity and new label-free approaches are reshaping the power of single-molecule measurements. A label-free single-molecule method2-16 capable of revealing details of molecular conformation in solution17,18 would allow a new microscopic perspective of unprecedented detail. Here we use the enhanced light-molecule interactions in high-finesse fibre-based Fabry-Pérot microcavities19-21 to detect individual biomolecules as small as 1.2 kDa, a ten-amino-acid peptide, with signal-to-noise ratios (SNRs) >100, even as the molecules are unlabelled and freely diffusing in solution. Our method delivers 2D intensity and temporal profiles, enabling the distinction of subpopulations in mixed samples. Notably, we observe a linear relationship between passage time and molecular radius, unlocking the potential to gather crucial information about diffusion and solution-phase conformation. Furthermore, mixtures of biomolecule isomers of the same molecular weight and composition but different conformation can also be resolved. Detection is based on the creation of a new molecular velocity filter window and a dynamic thermal priming mechanism that make use of the interplay between optical and thermal dynamics22,23 and Pound-Drever-Hall (PDH) cavity locking24 to reveal molecular motion even while suppressing environmental noise. New in vitro ways of revealing molecular conformation, diversity and dynamics can find broad potential for applications in the life and chemical sciences.
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Affiliation(s)
- Lisa-Maria Needham
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
- School of the Biological Sciences, University of Cambridge, Cambridge, UK
| | - Carlos Saavedra
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Julia K Rasch
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Daniel Sole-Barber
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Beau S Schweitzer
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Alex J Fairhall
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Cecilia H Vollbrecht
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
- Department of Chemistry and Biochemistry, Kalamazoo College, Kalamazoo, MI, USA
| | - Sushu Wan
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Yulia Podorova
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Anders J Bergsten
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Zhao Zhang
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI, USA
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA
| | - Lukas Tenbrake
- Institut für Angewandte Physik, Universität Bonn, Bonn, Germany
| | - Jovanna Saimi
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Lucy C Kneely
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Jackson S Kirkwood
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Hannes Pfeifer
- Institut für Angewandte Physik, Universität Bonn, Bonn, Germany
| | - Edwin R Chapman
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI, USA
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA
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5
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White D, Smith MA, Chanda B, Goldsmith RH. Strategies for Overcoming the Single-Molecule Concentration Barrier. ACS MEASUREMENT SCIENCE AU 2023; 3:239-257. [PMID: 37600457 PMCID: PMC10436376 DOI: 10.1021/acsmeasuresciau.3c00002] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 04/21/2023] [Accepted: 04/24/2023] [Indexed: 08/22/2023]
Abstract
Fluorescence-based single-molecule approaches have helped revolutionize our understanding of chemical and biological mechanisms. Unfortunately, these methods are only suitable at low concentrations of fluorescent molecules so that single fluorescent species of interest can be successfully resolved beyond background signal. The application of these techniques has therefore been limited to high-affinity interactions despite most biological and chemical processes occurring at much higher reactant concentrations. Fortunately, recent methodological advances have demonstrated that this concentration barrier can indeed be broken, with techniques reaching concentrations as high as 1 mM. The goal of this Review is to discuss the challenges in performing single-molecule fluorescence techniques at high-concentration, offer applications in both biology and chemistry, and highlight the major milestones that shatter the concentration barrier. We also hope to inspire the widespread use of these techniques so we can begin exploring the new physical phenomena lying beyond this barrier.
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Affiliation(s)
- David
S. White
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Mackinsey A. Smith
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Baron Chanda
- Center
for
Investigation of Membrane Excitability Diseases, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Randall H. Goldsmith
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
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6
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Nguyen TD, Chen YI, Chen LH, Yeh HC. Recent Advances in Single-Molecule Tracking and Imaging Techniques. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2023; 16:253-284. [PMID: 37314878 DOI: 10.1146/annurev-anchem-091922-073057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Since the early 1990s, single-molecule detection in solution at room temperature has enabled direct observation of single biomolecules at work in real time and under physiological conditions, providing insights into complex biological systems that the traditional ensemble methods cannot offer. In particular, recent advances in single-molecule tracking techniques allow researchers to follow individual biomolecules in their native environments for a timescale of seconds to minutes, revealing not only the distinct pathways these biomolecules take for downstream signaling but also their roles in supporting life. In this review, we discuss various single-molecule tracking and imaging techniques developed to date, with an emphasis on advanced three-dimensional (3D) tracking systems that not only achieve ultrahigh spatiotemporal resolution but also provide sufficient working depths suitable for tracking single molecules in 3D tissue models. We then summarize the observables that can be extracted from the trajectory data. Methods to perform single-molecule clustering analysis and future directions are also discussed.
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Affiliation(s)
- Trung Duc Nguyen
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, USA;
| | - Yuan-I Chen
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, USA;
| | - Limin H Chen
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, USA;
| | - Hsin-Chih Yeh
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, USA;
- Texas Materials Institute, University of Texas at Austin, Austin, Texas, USA
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7
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Park HH, Choi AA, Xu K. Size-Dependent Suppression of Molecular Diffusivity in Expandable Hydrogels: A Single-Molecule Study. J Phys Chem B 2023; 127:3333-3339. [PMID: 37011131 DOI: 10.1021/acs.jpcb.3c00761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
By repurposing the recently popularized expansion microscopy to control the meshwork size of hydrogels, we examine the size-dependent suppression of molecular diffusivity in the resultant tuned hydrogel nanomatrices over a wide range of polymer fractions of ∼0.14-7 wt %. With our recently developed single-molecule displacement/diffusivity mapping (SMdM) microscopy methods, we thus show that with a fixed meshwork size, larger molecules exhibit more impeded diffusion and that, for the same molecule, diffusion is progressively more suppressed as the meshwork size is reduced; this effect is more prominent for the larger molecules. Moreover, we show that the meshwork-induced obstruction of diffusion is uncoupled from the suppression of diffusion due to increased solution viscosities. Thus, the two mechanisms, respectively, being diffuser-size-dependent and independent, may separately scale down molecular diffusivity to produce the final diffusion slowdown in complex systems like the cell.
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Affiliation(s)
- Ha H Park
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Alexander A Choi
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
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8
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Needham LM, Saavedra C, Rasch JK, Sole-Barber D, Schweitzer BS, Fairhall AJ, Vollbrecht CH, Mehlenbacher B, Zhang Z, Tenbrake L, Pfeifer H, Chapman ER, Goldsmith RH. Label-free observation of individual solution phase molecules. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.24.534170. [PMID: 36993572 PMCID: PMC10055403 DOI: 10.1101/2023.03.24.534170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The vast majority of chemistry and biology occurs in solution, and new label-free analytical techniques that can help resolve solution-phase complexity at the single-molecule level can provide new microscopic perspectives of unprecedented detail. Here, we use the increased light-molecule interactions in high-finesse fiber Fabry-Pérot microcavities to detect individual biomolecules as small as 1.2 kDa with signal-to-noise ratios >100, even as the molecules are freely diffusing in solution. Our method delivers 2D intensity and temporal profiles, enabling the distinction of sub-populations in mixed samples. Strikingly, we observe a linear relationship between passage time and molecular radius, unlocking the potential to gather crucial information about diffusion and solution-phase conformation. Furthermore, mixtures of biomolecule isomers of the same molecular weight can also be resolved. Detection is based on a novel molecular velocity filtering and dynamic thermal priming mechanism leveraging both photo-thermal bistability and Pound-Drever-Hall cavity locking. This technology holds broad potential for applications in life and chemical sciences and represents a major advancement in label-free in vitro single-molecule techniques.
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Affiliation(s)
- Lisa-Maria Needham
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | - Carlos Saavedra
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
| | - Julia K. Rasch
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
| | | | | | - Alex J. Fairhall
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
| | | | | | - Zhao Zhang
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin-Madison, WI, USA
| | - Lukas Tenbrake
- Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany
| | - Hannes Pfeifer
- Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany
| | - Edwin R. Chapman
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin-Madison, WI, USA
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9
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Waheeda K, Kitchel H, Wang Q, Chiu PL. Molecular mechanism of Rubisco activase: Dynamic assembly and Rubisco remodeling. Front Mol Biosci 2023; 10:1125922. [PMID: 36845545 PMCID: PMC9951593 DOI: 10.3389/fmolb.2023.1125922] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 01/31/2023] [Indexed: 02/12/2023] Open
Abstract
Ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase (Rubisco) enzyme is the limiting step of photosynthetic carbon fixation, and its activation is regulated by its co-evolved chaperone, Rubisco activase (Rca). Rca removes the intrinsic sugar phosphate inhibitors occupying the Rubisco active site, allowing RuBP to split into two 3-phosphoglycerate (3PGA) molecules. This review summarizes the evolution, structure, and function of Rca and describes the recent findings regarding the mechanistic model of Rubisco activation by Rca. New knowledge in these areas can significantly enhance crop engineering techniques used to improve crop productivity.
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Affiliation(s)
- Kazi Waheeda
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States,Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, United States
| | - Heidi Kitchel
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States,Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, United States
| | - Quan Wang
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Po-Lin Chiu
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States,Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, United States,*Correspondence: Po-Lin Chiu,
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10
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Lavania A, Carpenter WB, Oltrogge LM, Perez D, Turnšek JB, Savage DF, Moerner WE. Exploring Masses and Internal Mass Distributions of Single Carboxysomes in Free Solution Using Fluorescence and Interferometric Scattering in an Anti-Brownian Trap. J Phys Chem B 2022; 126:8747-8759. [PMID: 36282790 PMCID: PMC9639131 DOI: 10.1021/acs.jpcb.2c05939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Carboxysomes are self-assembled bacterial microcompartments that facilitate carbon assimilation by colocalizing the enzymes of CO2 fixation within a protein shell. These microcompartments can be highly heterogeneous in their composition and filling, so measuring the mass and loading of an individual carboxysome would allow for better characterization of its assembly and function. To enable detailed and extended characterizations of single nanoparticles in solution, we recently demonstrated an improved interferometric scattering anti-Brownian electrokinetic (ISABEL) trap, which tracks the position of a single nanoparticle via its scattering of a near-infrared beam and applies feedback to counteract its Brownian motion. Importantly, the scattering signal can be related to the mass of nanoscale proteinaceous objects, whose refractive indices are well-characterized. We calibrate single-particle scattering cross-section measurements in the ISABEL trap and determine individual carboxysome masses in the 50-400 MDa range by analyzing their scattering cross sections with a core-shell model. We further investigate carboxysome loading by combining mass measurements with simultaneous fluorescence reporting from labeled internal components. This method may be extended to other biological objects, such as viruses or extracellular vesicles, and can be combined with orthogonal fluorescence reporters to achieve precise physical and chemical characterization of individual nanoscale biological objects.
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Affiliation(s)
- Abhijit
A. Lavania
- Department
of Chemistry, Stanford University, Stanford, California94305, United States,Department
of Applied Physics, Stanford University, Stanford, California94305, United States
| | - William B. Carpenter
- Department
of Chemistry, Stanford University, Stanford, California94305, United States
| | - Luke M. Oltrogge
- Department
of Molecular and Cell Biology, University
of California Berkeley, Berkeley, California94720, United States
| | - Davis Perez
- Department
of Chemistry, Stanford University, Stanford, California94305, United States
| | - Julia B. Turnšek
- Department
of Molecular and Cell Biology, University
of California Berkeley, Berkeley, California94720, United States
| | - David F. Savage
- Department
of Molecular and Cell Biology, University
of California Berkeley, Berkeley, California94720, United States
| | - W. E. Moerner
- Department
of Chemistry, Stanford University, Stanford, California94305, United States,Department
of Applied Physics, Stanford University, Stanford, California94305, United States,
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11
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Huang Y, Darr CM, Gangopadhyay K, Gangopadhyay S, Bok S, Chakraborty S. Applications of machine learning tools for ultra-sensitive detection of lipoarabinomannan with plasmonic grating biosensors in clinical samples of tuberculosis. PLoS One 2022; 17:e0275658. [PMID: 36282804 PMCID: PMC9595565 DOI: 10.1371/journal.pone.0275658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 09/21/2022] [Indexed: 11/06/2022] Open
Abstract
Background Tuberculosis is one of the top ten causes of death globally and the leading cause of death from a single infectious agent. Eradicating the Tuberculosis epidemic by 2030 is one of the top United Nations Sustainable Development Goals. Early diagnosis is essential to achieving this goal because it improves individual prognosis and reduces transmission rates of asymptomatic infected. We aim to support this goal by developing rapid and sensitive diagnostics using machine learning algorithms to minimize the need for expert intervention. Methods and findings A single molecule fluorescence immunosorbent assay was used to detect Tuberculosis biomarker lipoarabinomannan from a set of twenty clinical patient samples and a control set of spiked human urine. Tuberculosis status was separately confirmed by GeneXpert MTB/RIF and cell culture. Two machine learning algorithms, an automatic and a semiautomatic model, were developed and trained by the calibrated lipoarabinomannan titration assay data and then tested against the ground truth patient data. The semiautomatic model differed from the automatic model by an expert review step in the former, which calibrated the lower threshold to determine single molecules from background noise. The semiautomatic model was found to provide 88.89% clinical sensitivity, while the automatic model resulted in 77.78% clinical sensitivity. Conclusions The semiautomatic model outperformed the automatic model in clinical sensitivity as a result of the expert intervention applied during calibration and both models vastly outperformed manual expert counting in terms of time-to-detection and completion of analysis. Meanwhile, the clinical sensitivity of the automatic model could be improved significantly with a larger training dataset. In short, semiautomatic, and automatic Gaussian Mixture Models have a place in supporting rapid detection of Tuberculosis in resource-limited settings without sacrificing clinical sensitivity.
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Affiliation(s)
- Yilun Huang
- Department of Statistics, University of Missouri, Columbia, Missouri, United States of America
| | - Charles M. Darr
- Department of Electrical Engineering & Computer Science, Center for Nano/Micro Systems & Nanotechnology, University of Missouri, Columbia, Missouri, United States of America
| | - Keshab Gangopadhyay
- Department of Electrical Engineering & Computer Science, Center for Nano/Micro Systems & Nanotechnology, University of Missouri, Columbia, Missouri, United States of America
| | - Shubhra Gangopadhyay
- Department of Electrical Engineering & Computer Science, Center for Nano/Micro Systems & Nanotechnology, University of Missouri, Columbia, Missouri, United States of America
- * E-mail: (SG); (SB); (SC)
| | - Sangho Bok
- Department of Electrical Engineering & Computer Science, Center for Nano/Micro Systems & Nanotechnology, University of Missouri, Columbia, Missouri, United States of America
- Department of Electrical & Computer Engineering, University of Denver, Denver, Colorado, United States of America
- * E-mail: (SG); (SB); (SC)
| | - Sounak Chakraborty
- Department of Statistics, University of Missouri, Columbia, Missouri, United States of America
- * E-mail: (SG); (SB); (SC)
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12
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Wan Z, Ma G, Zhang P, Wang S. Single-Protein Identification by Simultaneous Size and Charge Imaging Using Evanescent Scattering Microscopy. ACS Sens 2022; 7:2625-2633. [PMID: 36000947 PMCID: PMC9509435 DOI: 10.1021/acssensors.2c01008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Separation and identification of different proteins is one of the most fundamental tasks in biochemistry that is typically achieved by electrophoresis and Western blot techniques. Yet, it is challenging to perform such an analysis with a small sample size. Using a principle analogous to these conventional approaches, we present a label-free, single-molecule technique to identify different proteins based on the difference in their size, charge, and antibody binding. We tether single protein molecules to a sensor surface with a flexible polymer and drive them into oscillation by applying an alternating electric field. By tracking the nanometer-scale oscillation of each protein molecule via high-resolution scattering microscopy, the size and charge of each protein molecule can be determined simultaneously. Changes induced by varying the buffer pH and antibody binding are also investigated, which allows us to further expand the separation ability and identify two different proteins in a mixture. We anticipate our technique will contribute to single protein analysis and biosensing.
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Affiliation(s)
- Zijian Wan
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, USA
- School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, USA
| | - Guangzhong Ma
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, USA
| | - Pengfei Zhang
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, USA
| | - Shaopeng Wang
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, USA
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287, USA
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13
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Fu Y, Zhang X, Liu J, Qian G, Xu ZP, Zhang R. Fluorescence detection and imaging of intracellular sulphite using a remote light activatable photochromic nanoprobe. J Mater Chem B 2022; 10:3366-3374. [PMID: 35383812 DOI: 10.1039/d2tb00021k] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The development of a responsive fluorescent probe for the detection of a particular biomolecule in a specific site at the desired moment is important in the fields of bioanalysis and imaging, molecular biology and biomedical research. In this work, we report the development of a remote-light activatable nanoprobe for the fluorescence detection of sulphite in pure aqueous solution and its imaging applications in living cells. The nanoprobe, Poly-Cm-SP, is fabricated simply by wrapping photochromic molecules (Cm-SP) into a polymer nanoparticle. Upon alternate UV/Vis light irradiation for several seconds, the Poly-Cm-SP nanoprobe exhibits red/blue fluorescence switch due to the inactive/active FRET processes from coumarins to the SP/MR isomers of the photochromic molecule. In the presence of sulphite, the specific reaction of sulphite with the electron deficit "CC" bond of the MR isomer occurs, resulting in an inefficient FRET process and thus exhibiting a constant "ON" blue channel fluorescence signal. After UV-light irradiation, the formation of activated Poly-Cm-MRin situ thus enables the detection of sulphite through recording the ratiometric changes of fluorescence signals at both blue and red channels. The Poly-Cm-SP nanoprobe possesses excellent biocompatibility and lysosome distribution capability, allowing it to be used for photochromic imaging and sulphite detection in the lysosomes of living macrophage cells. This work thus offers a new remote-light activatable nanoprobe for the detection and imaging of sulphite in biological systems.
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Affiliation(s)
- Youxin Fu
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Xing Zhang
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD 4072, Australia. .,School of Environmental Science and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Jianping Liu
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Guangren Qian
- School of Environmental Science and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Zhi Ping Xu
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Run Zhang
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD 4072, Australia.
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14
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Sielaff H, Dienerowitz F, Dienerowitz M. Single-molecule FRET combined with electrokinetic trapping reveals real-time enzyme kinetics of individual F-ATP synthases. NANOSCALE 2022; 14:2327-2336. [PMID: 35084006 DOI: 10.1039/d1nr05754e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a key technique to observe conformational changes in molecular motors and to access the details of single-molecule static and dynamic disorder during catalytic processes. However, studying freely diffusing molecules in solution is limited to a few tens of milliseconds, while surface attachment often bears the risk to restrict their natural motion. In this paper we combine smFRET and electrokinetic trapping (ABEL trap) to non-invasively hold single FOF1-ATP synthases for up to 3 s within the detection volume, thereby extending the observation time by a factor of 10 as compared to Brownian diffusion without surface attachment. In addition, we are able to monitor complete reaction cycles and to selectively trap active molecules based on their smFRET signal, thus speeding up the data acquisition process. We demonstrate the capability of our method to study the dynamics of single molecules by recording the ATP-hydrolysis driven rotation of individual FOF1-ATP synthase molecules over numerous reaction cycles and extract their kinetic rates. We argue that our method is not limited to motor proteins. Instead, it can be applied to monitor conformational changes with millisecond time resolution for a wide range of enzymes, thereby making it a versatile tool for studying protein dynamics.
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Affiliation(s)
- Hendrik Sielaff
- Department of Chemistry, Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, 117557 Singapore, Singapore
| | - Frank Dienerowitz
- Ernst-Abbe-Hochschule Jena, University of Applied Sciences, Carl-Zeiss-Promenade 2, 07745 Jena, Germany
| | - Maria Dienerowitz
- Single-Molecule Microscopy Group, Universitätsklinikum Jena, Nonnenplan 2-4, 07743 Jena, Germany.
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15
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Squires A, Wang Q, Dahlberg P, Moerner WE. A bottom-up perspective on photodynamics and photoprotection in light-harvesting complexes using anti-Brownian trapping. J Chem Phys 2022; 156:070901. [DOI: 10.1063/5.0079042] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
| | - Quan Wang
- Genomics, Princeton University, United States of America
| | | | - W. E. Moerner
- Department of Chemistry, Stanford University, United States of America
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16
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Beckwith JS, Yang H. Sub-millisecond Translational and Orientational Dynamics of a Freely Moving Single Nanoprobe. J Phys Chem B 2021; 125:13436-13443. [PMID: 34851653 DOI: 10.1021/acs.jpcb.1c08917] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This paper presents a new experiment with which we are able to measure the 3D translational motion of a single particle at 10 μs time resolution and with ∼10 nm spatial resolution while at the same time determining the 3D orientation of the same single particle with 250 μs time resolution. These high time resolutions are ∼40 times greater than previous simultaneous measurements of 3D position and 3D orientation. Detailed numerical simulations and experiments are used to demonstrate that the technique can measure 3D orientation at the shot-noise limit. The microscope is also able to simultaneously measure the length or width (with the other assumed) of the plasmonic nanorods used here in situ and nondestructively, which should yield a greater understanding of the underlying dynamics. This technique should be applicable to a broad range of problems where environments which change in space and time may perturb physical and chemical dynamics.
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Affiliation(s)
- Joseph S Beckwith
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
| | - Haw Yang
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
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17
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Wilson H, Wang Q. Joint Detection of Change Points in Multichannel Single-Molecule Measurements. J Phys Chem B 2021; 125:13425-13435. [PMID: 34870418 DOI: 10.1021/acs.jpcb.1c08869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Recent developments in single-molecule measurement technology have expanded the capability to measure multiple parameters. These emergent modalities provide more holistic observations of complex biomolecular processes and call for new analysis methods to detect state changes in multichannel data. Here we develop an algorithm called MULLR (MUlti-channel Log-Likelihood Ratio test) to jointly identify change points in multichannel single-molecule measurements. MULLR is an extension of the popular single-channel implementation for change point detection based on a binary segmentation and log-likelihood ratio test framework. We validate the algorithm on simulated data and characterize the power of detection and false positive rate. We show that MULLR can identify change points in experimental multichannel data and naturally works with different noise statistics and time resolutions across channels. Further, we quantify the benefit of MULLR compared to single-channel analysis. We envision that the MULLR algorithm will be useful to a range of multiparameter single-molecule measurements.
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Affiliation(s)
- Hugh Wilson
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08540, United States
| | - Quan Wang
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08540, United States
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18
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Ma G, Wan Z, Yang Y, Jing W, Wang S. Three-Dimensional Tracking of Tethered Particles for Probing Nanometer-Scale Single-Molecule Dynamics Using a Plasmonic Microscope. ACS Sens 2021; 6:4234-4243. [PMID: 34786931 DOI: 10.1021/acssensors.1c01927] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Three-dimensional (3D) tracking of surface-tethered single particles reveals the dynamics of the molecular tether. However, most 3D tracking techniques lack precision, especially in the axial direction, for measuring the dynamics of biomolecules with a spatial scale of several nanometers. Here, we present a plasmonic imaging technique that can track the motion of ∼100 tethered particles in 3D simultaneously with sub-nanometer axial precision and single-digit nanometer lateral precision at millisecond time resolution. By tracking the 3D coordinates of a tethered particle with high spatial resolution, we are able to determine the dynamics of single short DNA and study its interaction with enzymes. We further show that the particle motion pattern can be used to identify specific and nonspecific interactions in immunoassays. We anticipate that our 3D tracking technique can contribute to the understanding of molecular dynamics and interactions at the single-molecule level.
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Affiliation(s)
- Guangzhong Ma
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, United States
| | - Zijian Wan
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, United States
- School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Yunze Yang
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, United States
| | - Wenwen Jing
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, United States
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Shaopeng Wang
- Biodesign Center for Biosensors and Bioelectronics, Arizona State University, Tempe, Arizona 85287, United States
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287, United States
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19
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Beckwith JS, Yang H. Information bounds in determining the 3D orientation of a single emitter or scatterer using point-detector-based division-of-amplitude polarimetry. J Chem Phys 2021; 155:144110. [PMID: 34654316 DOI: 10.1063/5.0065034] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Determining the 3D orientation of a single molecule or particle, encoded in its polar and azimuthal angles, is of interest for a variety of fields, being relevant to a range of questions in elementary chemical reactivity, biomolecular motors, and nanorheology. A popular experimental method, known as division-of-amplitude polarimetry, for determining the real-time orientation of a single particle is to split the emitted/scattered light into multiple polarizations and to measure the light intensity using point detectors at these polarizations during a time interval Δt. Here, we derive the Cramér-Rao lower bounds for this method from the perspective of information theory in the cases of utilizing a chromophore or a scattering particle as a 3D orientation probe. Such Cramér-Rao lower bounds are new for using this experimental method to measure the full 3D orientation in both the scattering case and the fluorescence case. These results show that, for a scatterer, the information content of one photon is 1.16 deg-2 in the polar and 58.71 deg-2 in the azimuthal angles, respectively. For a chromophore, the information content of one photon is 2.54 deg-2 in the polar and 80.29 deg-2 in the azimuthal angles. In addition, the Cramér-Rao lower bound scales with the square root of the total signal photons. To determine orientation to an uncertainty of one degree requires 7.40 × 104 and 2.34 × 103 photons for the polar and the azimuthal angles, respectively, for fluorescence, whereas it takes 1.62 × 105 and 3.20 × 103 photons for scattering. This work provides experimentalists new guidelines by which future experiments can be designed and interpreted.
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Affiliation(s)
- Joseph S Beckwith
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Haw Yang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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20
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Probing DNA-protein interactions using single-molecule diffusivity contrast. BIOPHYSICAL REPORTS 2021; 1:100009. [PMID: 36425309 PMCID: PMC9680706 DOI: 10.1016/j.bpr.2021.100009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 07/20/2021] [Indexed: 11/28/2022]
Abstract
Single-molecule fluorescence investigations of protein-nucleic acid interactions require robust means to identify the binding state of individual substrate molecules in real time. Here, we show that diffusivity contrast, widely used in fluorescence correlation spectroscopy at the ensemble level and in single-particle tracking on individual (but slowly diffusing) species, can be used as a general readout to determine the binding state of single DNA molecules with unlabeled proteins in solution. We first describe the technical basis of drift-free single-molecule diffusivity measurements in an anti-Brownian electrokinetic trap. We then cross-validate our method with protein-induced fluorescence enhancement, a popular technique to detect protein binding on nucleic acid substrates with single-molecule sensitivity. We extend an existing hydrodynamic modeling framework to link measured diffusivity to particular DNA-protein structures and obtain good agreement between the measured and predicted diffusivity values. Finally, we show that combining diffusivity contrast with protein-induced fluorescence enhancement allows simultaneous mapping of binding stoichiometry and location on individual DNA-protein complexes, potentially enhancing single-molecule views of relevant biophysical processes.
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21
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Wilson H, Wang Q. ABEL-FRET: tether-free single-molecule FRET with hydrodynamic profiling. Nat Methods 2021; 18:816-820. [PMID: 34127856 DOI: 10.1038/s41592-021-01173-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 05/04/2021] [Indexed: 02/03/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) has become a versatile and widespread method to probe nanoscale conformation and dynamics. However, current experimental modalities often resort to molecule immobilization for long observation times and do not always approach the resolution limit of FRET-based nanoscale metrology. Here we present ABEL-FRET, an immobilization-free platform for smFRET measurements with ultrahigh resolving power in FRET efficiency. Importantly, single-molecule diffusivity is used to provide additional size and shape information for hydrodynamic profiling of individual molecules, which, together with the concurrently measured intramolecular conformation through FRET, enables a holistic and dynamic view of biomolecules and their complexes.
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Affiliation(s)
- Hugh Wilson
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Quan Wang
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
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22
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Recent developments in the characterization of nucleic acid hybridization kinetics. CURRENT OPINION IN BIOMEDICAL ENGINEERING 2021; 19. [PMID: 34368519 DOI: 10.1016/j.cobme.2021.100305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hybridization of nucleic acids (NAs) is a fundamental molecular mechanism that drives many cellular processes and enables new biotechnologies as well as therapeutics. However, existing methods that measure hybridization kinetics of nucleic acids are either performed at the ensemble level or constrained to non-native physiological conditions. Recent advances in 3D single-molecule tracking techniques break these limitations by allowing multiple annealing and melting events to be observed on a single oligonucleotide freely diffusing inside a live mammalian cell. This review provides an overview of diverse approaches to measuring NA hybridization kinetics at the single-molecule level and in live cells, and concludes with a synopsis of unresolved challenges and opportunities in the live-cell hybridization kinetics measurements. Important discoveries made by NA kinetics measurements and biotechnologies that can be improved with a deeper understanding of hybridization kinetics are also described.
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23
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DNA hybridisation kinetics using single-molecule fluorescence imaging. Essays Biochem 2021; 65:27-36. [PMID: 33491734 PMCID: PMC8056036 DOI: 10.1042/ebc20200040] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 12/17/2020] [Accepted: 12/21/2020] [Indexed: 01/05/2023]
Abstract
Deoxyribonucleic acid (DNA) hybridisation plays a key role in many biological processes and nucleic acid biotechnologies, yet surprisingly there are many aspects about the process which are still unknown. Prior to the invention of single-molecule microscopy, DNA hybridisation experiments were conducted at the ensemble level, and thus it was impossible to directly observe individual hybridisation events and understand fully the kinetics of DNA hybridisation. In this mini-review, recent single-molecule fluorescence-based studies of DNA hybridisation are discussed, particularly for short nucleic acids, to gain more insight into the kinetics of DNA hybridisation. As well as looking at single-molecule studies of intrinsic and extrinsic factors affecting DNA hybridisation kinetics, the influence of the methods used to detect hybridisation of single DNAs is considered. Understanding the kinetics of DNA hybridisation not only gives insight into an important biological process but also allows for further advancements in the growing field of nucleic acid biotechnology.
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24
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Dienerowitz M, Howard JAL, Quinn SD, Dienerowitz F, Leake MC. Single-molecule FRET dynamics of molecular motors in an ABEL trap. Methods 2021; 193:96-106. [PMID: 33571667 DOI: 10.1016/j.ymeth.2021.01.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 01/22/2021] [Accepted: 01/29/2021] [Indexed: 02/07/2023] Open
Abstract
Single-molecule Förster resonance energy transfer (smFRET) of molecular motors provides transformative insights into their dynamics and conformational changes both at high temporal and spatial resolution simultaneously. However, a key challenge of such FRET investigations is to observe a molecule in action for long enough without restricting its natural function. The Anti-Brownian ELectrokinetic Trap (ABEL trap) sets out to combine smFRET with molecular confinement to enable observation times of up to several seconds while removing any requirement of tethered surface attachment of the molecule in question. In addition, the ABEL trap's inherent ability to selectively capture FRET active molecules accelerates the data acquisition process. In this work we exemplify the capabilities of the ABEL trap in performing extended timescale smFRET measurements on the molecular motor Rep, which is crucial for removing protein blocks ahead of the advancing DNA replication machinery and for restarting stalled DNA replication. We are able to monitor single Rep molecules up to 6 seconds with sub-millisecond time resolution capturing multiple conformational switching events during the observation time. Here we provide a step-by-step guide for the rational design, construction and implementation of the ABEL trap for smFRET detection of Rep in vitro. We include details of how to model the electric potential at the trap site and use Hidden Markov analysis of the smFRET trajectories.
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Affiliation(s)
- Maria Dienerowitz
- Single-Molecule Microscopy Group, Universitätsklinikum Jena, Nonnenplan 2 - 4, 07743 Jena, Germany.
| | - Jamieson A L Howard
- Department of Physics, University of York, Heslington, York YO10 5DD, UK; Department of Biology, University of York, Heslington, York YO10 5DD, UK
| | - Steven D Quinn
- Department of Physics, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK
| | - Frank Dienerowitz
- Ernst-Abbe-Hochschule Jena, University of Applied Sciences, Carl-Zeiss-Promenade 2, 07745 Jena, Germany
| | - Mark C Leake
- Department of Physics, University of York, Heslington, York YO10 5DD, UK; Department of Biology, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK
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25
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Abstract
Optical studies of single molecules have taught us much over the past three decades, but these individual quantum-mechanical objects continue to have promise as probes of nanoscale structure and dynamics in complex systems.
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Affiliation(s)
- W E Moerner
- Departments of Chemistry and of Applied Physics (courtesy), Stanford University, Stanford, California 94305-4401, United States
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26
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Shechtman Y. Recent advances in point spread function engineering and related computational microscopy approaches: from one viewpoint. Biophys Rev 2020; 12:10.1007/s12551-020-00773-7. [PMID: 33210213 PMCID: PMC7755951 DOI: 10.1007/s12551-020-00773-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2020] [Indexed: 01/13/2023] Open
Abstract
This personal hybrid review piece, written in light of my recipience of the UIPAB 2020 young investigator award, contains a mixture of my scientific biography and work so far. This paper is not intended to be a comprehensive review, but only to highlight my contributions to computation-related aspects of super-resolution microscopy, as well as their origins and future directions.
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Affiliation(s)
- Yoav Shechtman
- Department of Biomedical Engineering and Lorry Lokey Interdisciplinary Center for Life Sciences and Engineering, Technion-Israel Institute of Technology, 3200003, Haifa, Israel.
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27
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Optical imaging of single-protein size, charge, mobility, and binding. Nat Commun 2020; 11:4768. [PMID: 32958747 PMCID: PMC7505846 DOI: 10.1038/s41467-020-18547-w] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 08/31/2020] [Indexed: 12/28/2022] Open
Abstract
Detection and identification of proteins are typically achieved by analyzing protein size, charge, mobility and binding to antibodies, which are critical for biomedical research and disease diagnosis and treatment. Despite the importance, measuring these quantities with one technology and at the single-molecule level has not been possible. Here we tether a protein to a surface with a flexible polymer, drive it into oscillation with an electric field, and image the oscillation with a near field optical imaging method, from which we determine the size, charge, and mobility of the protein. We also measure antibody binding and conformation changes in the protein. The work demonstrates a capability for comprehensive protein analysis and precision protein biomarker detection at the single molecule level. Protein identification at the single-molecule level is the ultimate goal for biological research and disease diagnosis. Here, the authors identify the size, charge, mobility, and binding of individual protein molecules by measuring the optical and electrical responses of each protein molecule tethered to a surface.
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28
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Coscia BJ, Calderon CP, Shirts MR. Statistical Inference of Transport Mechanisms and Long Time Scale Behavior from Time Series of Solute Trajectories in Nanostructured Membranes. J Phys Chem B 2020; 124:8110-8123. [PMID: 32790365 DOI: 10.1021/acs.jpcb.0c05010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Appropriate time series modeling of complex diffusion in soft matter systems on the microsecond time scale can provide a path toward inferring transport mechanisms and predicting bulk properties characteristic of much longer time scales. In this work we apply nonparametric Bayesian time series analysis, more specifically the sticky hierarchical Dirichlet process autoregressive hidden Markov model (HDP-AR-HMM) to solute center-of-mass trajectories generated from long molecular dynamics (MD) simulations in a cross-linked inverted hexagonal phase lyotropic liquid crystal (LLC) membrane in order to automatically detect a variety of solute dynamical modes. We can better understand the mechanisms controlling these dynamical modes by grouping the states identified by the HDP-AR-HMM into clusters based on multiple metrics aimed at distinguishing solute behavior based on their fluctuations, dwell times in each state, and positions within the inhomogeneous membrane structure. We analyze predominant clusters in order to relate their dynamical parameters to physical interactions between solutes and the membrane. Along with parameters of individual states, the HDP-AR-HMM simultaneously infers a transition matrix which allows us to stochastically propagate solute behavior from all of the independent trajectories onto arbitrary length time scales while still preserving the qualitative behavior characteristic of the MD trajectories. This affords a direct connection to important macroscopic observables used to characterize performance like solute flux and selectivity. This work provides a promising way to simultaneously identify transport mechanisms in nanoporous materials and project complex diffusive behavior on long time scales. Our enhanced understanding of the diverse range of solute behavior allows us to hypothesize design changes to LLC monomers aimed toward controlling the rates of solute passage, thus improving the selective performance of LLC membranes.
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Affiliation(s)
- Benjamin J Coscia
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Christopher P Calderon
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.,Ursa Analytics, Inc., Denver, Colorado 80212, United States
| | - Michael R Shirts
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
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29
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Single-molecule diffusometry reveals no catalysis-induced diffusion enhancement of alkaline phosphatase as proposed by FCS experiments. Proc Natl Acad Sci U S A 2020; 117:21328-21335. [PMID: 32817484 PMCID: PMC7474647 DOI: 10.1073/pnas.2006900117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Recent experiments have suggested that the energy released by a chemical reaction can propel its enzyme catalyst (for example, alkaline phosphatase). However, this topic remains controversial, partially due to the indirect and ensemble nature of existing measurements. Here, we used recently developed single-molecule approaches to monitor directly the motions of individual proteins in aqueous solution and find that single alkaline phosphatase enzymes do not diffuse faster under catalysis. Instead, we demonstrate that interactions between the fluorescent dye and the enzyme’s substrate can produce the signature of apparent diffusion enhancement in fluorescence correlation spectroscopy, the standard ensemble assay currently used to study enzyme diffusion and indicate that single-molecule approaches provide a more robust means to investigate diffusion at the nanoscale. Theoretical and experimental observations that catalysis enhances the diffusion of enzymes have generated exciting implications about nanoscale energy flow, molecular chemotaxis, and self-powered nanomachines. However, contradictory claims on the origin, magnitude, and consequence of this phenomenon continue to arise. To date, experimental observations of catalysis-enhanced enzyme diffusion have relied almost exclusively on fluorescence correlation spectroscopy (FCS), a technique that provides only indirect, ensemble-averaged measurements of diffusion behavior. Here, using an anti-Brownian electrokinetic (ABEL) trap and in-solution single-particle tracking, we show that catalysis does not increase the diffusion of alkaline phosphatase (ALP) at the single-molecule level, in sharp contrast to the ∼20% enhancement seen in parallel FCS experiments using p-nitrophenyl phosphate (pNPP) as substrate. Combining comprehensive FCS controls, ABEL trap, surface-based single-molecule fluorescence, and Monte Carlo simulations, we establish that pNPP-induced dye blinking at the ∼10-ms timescale is responsible for the apparent diffusion enhancement seen in FCS. Our observations urge a crucial revisit of various experimental findings and theoretical models––including those of our own––in the field, and indicate that in-solution single-particle tracking and ABEL trap are more reliable means to investigate diffusion phenomena at the nanoscale.
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30
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Abstract
Anti-Brownian electrokinetic trapping is a method for trapping single particles in liquid based on particle position measurements and the application of feedback voltages. To achieve trapping in the axial direction, information on the axial particle position is required. However, existing strategies for determining the axial position that are based on measuring the size of the first diffraction ring, theory fitting, advanced optical setups or pre-determined axial image stacks are impractical for anisotropic particles. In this work, axial electrokinetic trapping of anisotropic particles is realized in devices with planar, transparent electrodes. The trapping algorithm uses Fourier-Bessel decomposition of standard microscopy images and is learning from the correlation between applied voltages and changes in the particle appearance. No previous knowledge on the particle appearance, theory fitting or advanced optical setup is required. The particle motion in the trap and the influence of screening of the electric field on this motion are analyzed. The axial trapping method opens new possibilities for measuring properties of anisotropic or isotropic particles and forces acting on such particles.
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31
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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32
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Chen YI, Chang YJ, Nguyen TD, Liu C, Phillion S, Kuo YA, Vu HT, Liu A, Liu YL, Hong S, Ren P, Yankeelov TE, Yeh HC. Measuring DNA Hybridization Kinetics in Live Cells Using a Time-Resolved 3D Single-Molecule Tracking Method. J Am Chem Soc 2019; 141:15747-15750. [PMID: 31509386 DOI: 10.1021/jacs.9b08036] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Single-molecule detection enables direct characterization of annealing/melting kinetics of nucleic acids without the need for synchronization of molecular states, but the current experiments are not carried out in a native cellular context. Here we describe an integrated 3D single-molecule tracking and lifetime measurement method that can follow individual DNA molecules diffusing inside a mammalian cell and observe multiple annealing and melting events on the same molecules. By comparing the hybridization kinetics of the same DNA strand in vitro, we found the association constants can be 13- to 163-fold higher in the molecular crowding cellular environment.
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Affiliation(s)
- Yuan-I Chen
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Yin-Jui Chang
- Department of Mechanical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Trung Duc Nguyen
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Cong Liu
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Stephanie Phillion
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Yu-An Kuo
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Huong T Vu
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Angela Liu
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Yen-Liang Liu
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Soonwoo Hong
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Pengyu Ren
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Thomas E Yankeelov
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States.,Oden Institute for Computational Engineering and Sciences, University of Texas at Austin , Austin , Texas 78712 , United States.,Department of Diagnostic Medicine , University of Texas at Austin , Austin , Texas 78712 , United States.,Department of Oncology , University of Texas at Austin , Austin , Texas 78712 , United States.,Livestrong Cancer Institutes, University of Texas at Austin , Austin , Texas 78712 , United States
| | - Hsin-Chih Yeh
- Department of Biomedical Engineering , University of Texas at Austin , Austin , Texas 78712 , United States.,Texas Materials Institute, University of Texas at Austin , Austin , Texas 78712 , United States
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33
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Bespalova MI, Mahanta S, Krishnan M. Single-molecule trapping and measurement in solution. Curr Opin Chem Biol 2019; 51:113-121. [DOI: 10.1016/j.cbpa.2019.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 05/01/2019] [Accepted: 05/13/2019] [Indexed: 01/27/2023]
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34
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High-throughput smFRET analysis of freely diffusing nucleic acid molecules and associated proteins. Methods 2019; 169:21-45. [PMID: 31356875 DOI: 10.1016/j.ymeth.2019.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 06/24/2019] [Accepted: 07/22/2019] [Indexed: 11/21/2022] Open
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a powerful technique for nanometer-scale studies of single molecules. Solution-based smFRET, in particular, can be used to study equilibrium intra- and intermolecular conformations, binding/unbinding events and conformational changes under biologically relevant conditions without ensemble averaging. However, single-spot smFRET measurements in solution are slow. Here, we detail a high-throughput smFRET approach that extends the traditional single-spot confocal geometry to a multispot one. The excitation spots are optically conjugated to two custom silicon single photon avalanche diode (SPAD) arrays. Two-color excitation is implemented using a periodic acceptor excitation (PAX), allowing distinguishing between singly- and doubly-labeled molecules. We demonstrate the ability of this setup to rapidly and accurately determine FRET efficiencies and population stoichiometries by pooling the data collected independently from the multiple spots. We also show how the high throughput of this approach can be used o increase the temporal resolution of single-molecule FRET population characterization from minutes to seconds. Combined with microfluidics, this high-throughput approach will enable simple real-time kinetic studies as well as powerful molecular screening applications.
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35
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Squires A, Lavania AA, Dahlberg PD, Moerner WE. Interferometric Scattering Enables Fluorescence-Free Electrokinetic Trapping of Single Nanoparticles in Free Solution. NANO LETTERS 2019; 19:4112-4117. [PMID: 31117762 PMCID: PMC6604838 DOI: 10.1021/acs.nanolett.9b01514] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/13/2019] [Indexed: 05/05/2023]
Abstract
Anti-Brownian traps confine single particles in free solution by closed-loop feedback forces that directly counteract Brownian motion. Extended-duration measurements on trapped objects allow detailed characterization of photophysical and transport properties as well as observation of infrequent or rare dynamics. However, this approach has been generally limited to particles that can be tracked by fluorescence emission. Here we present the Interferometric Scattering Anti-Brownian ELectrokinetic (ISABEL) trap, which uses interferometric scattering rather than fluorescence to monitor particle position. By decoupling the ability to track (and therefore trap) a particle from collection of its spectroscopic data, the ISABEL trap enables confinement and extended study of single particles that do not fluoresce, only weakly fluoresce, or exhibit intermittent fluorescence or photobleaching. This new technique significantly expands the range of nanoscale objects that may be investigated at the single-particle level in free solution.
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Affiliation(s)
- Allison
H. Squires
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Abhijit A. Lavania
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Department
of Applied Physics, Stanford University, Stanford, California 94305, United States
| | - Peter D. Dahlberg
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - W. E. Moerner
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Department
of Applied Physics, Stanford University, Stanford, California 94305, United States
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36
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Whaley-Mayda L, Penwell SB, Tokmakoff A. Fluorescence-Encoded Infrared Spectroscopy: Ultrafast Vibrational Spectroscopy on Small Ensembles of Molecules in Solution. J Phys Chem Lett 2019; 10:1967-1972. [PMID: 30942587 DOI: 10.1021/acs.jpclett.9b00748] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Fluorescence-encoded infrared (FEIR) spectroscopy is an ultrafast technique that uses a visible pulse to up-convert information about IR-driven vibrations into a fluorescent electronic population. Here we present an updated experimental approach to FEIR that achieves high sensitivity through confocal microscopy, high repetition rate excitation, and single-photon counting. We demonstrate the sensitivity of our experiment by measuring ultrafast vibrational transients and Fourier transform spectra of increasingly dilute solutions of a coumarin dye. We collect high-quality data at 40 μM (∼2 orders of magnitude below the limit for conventional IR) and make measurements down to the 10-100 nM range (∼5 orders of magnitude) before background signals become overwhelming. At 10 nM we measure the average number of molecules in the focal volume to be ∼20 using fluorescence correlation spectroscopy. This level of sensitivity opens up the possibility of performing fluctuation correlation vibrational spectroscopy or-with further improvement-single-molecule measurements.
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Affiliation(s)
- Lukas Whaley-Mayda
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Samuel B Penwell
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics , The University of Chicago , Chicago , Illinois 60637 , United States
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37
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Transition from stochastic events to deterministic ensemble average in electron transfer reactions revealed by single-molecule conductance measurement. Proc Natl Acad Sci U S A 2019; 116:3407-3412. [PMID: 30737288 DOI: 10.1073/pnas.1814825116] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Electron transfer reactions can now be followed at the single-molecule level, but the connection between the microscopic and macroscopic data remains to be understood. By monitoring the conductance of a single molecule, we show that the individual electron transfer reaction events are stochastic and manifested as large conductance fluctuations. The fluctuation probability follows first-order kinetics with potential dependent rate constants described by the Butler-Volmer relation. Ensemble averaging of many individual reaction events leads to a deterministic dependence of the conductance on the external electrochemical potential that follows the Nernst equation. This study discloses a systematic transition from stochastic kinetics of individual reaction events to deterministic thermodynamics of ensemble averages and provides insights into electron transfer processes of small systems, consisting of a single molecule or a small number of molecules.
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38
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Foote AK, Manger LH, Holden MR, Margittai M, Goldsmith RH. Time-resolved multirotational dynamics of single solution-phase tau proteins reveals details of conformational variation. Phys Chem Chem Phys 2019; 21:1863-1871. [PMID: 30632561 PMCID: PMC6449148 DOI: 10.1039/c8cp06971a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Intrinsically disordered proteins (IDPs) are crucial to many cellular processes and have been linked to neurodegenerative diseases. Single molecules of tau, an IDP associated with Alzheimer's disease, are trapped in solution using a microfluidic device, and a time-resolved fluorescence anisotropy decay is recorded for each molecule. Multiple rotational components are resolved and a novel k-means algorithm is used to sort the molecules into two families of conformations. Differences in rotational dynamics suggest a change in the rigidity and steric hindrance surrounding a sequence (306VQIVYK311) which is central to paired helical filament formation. This single-molecule approach can be applied to other IDPs to resolve heterogeneous populations and underlying differences in conformational dynamics.
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Affiliation(s)
- Alexander K Foote
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, WI 53706, USA.
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39
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Zhang H, Zheng X, Kwok RTK, Wang J, Leung NLC, Shi L, Sun JZ, Tang Z, Lam JWY, Qin A, Tang BZ. In situ monitoring of molecular aggregation using circular dichroism. Nat Commun 2018; 9:4961. [PMID: 30470749 PMCID: PMC6251920 DOI: 10.1038/s41467-018-07299-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 10/15/2018] [Indexed: 11/17/2022] Open
Abstract
The aggregation of molecules plays an important role in determining their function. Electron microscopy and other methods can only characterize the variation of microstructure, but are not capable of monitoring conformational changes. These techniques are also complicated, expensive and time-consuming. Here, we demonstrate a simple method to monitor in-situ and in real-time the conformational change of (R)-1,1'-binaphthyl-based polymers during the aggregation process using circular dichroism. Based on results from molecular dynamics simulations and experimental circular dichroism measurements, polymers with "open" binaphthyl rings are found to show stronger aggregation-annihilated circular dichroism effects, with more negative torsion angles between the two naphthalene rings. In contrast, the polymers with "locked" rings show a more restrained aggregation-annihilated circular dichroism effect, with only a slight change of torsion angle. This work provides an approach to monitor molecular aggregation in a simple, accurate, and efficient way.
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Affiliation(s)
- Haoke Zhang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 310027, Hangzhou, China
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xiaoyan Zheng
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, 100081, Beijing, China
| | - Ryan T K Kwok
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Jia Wang
- Center for Aggregation-Induced Emission, SCUT-HKUST Joint Research Institute, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, 510640, Guangzhou, China
| | - Nelson L C Leung
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Lin Shi
- Laboratory for Nanosystem and Hierarchy Fabrication, National Center for Nanoscience and Technology, 100190, Beijing, China
| | - Jing Zhi Sun
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 310027, Hangzhou, China
| | - Zhiyong Tang
- Laboratory for Nanosystem and Hierarchy Fabrication, National Center for Nanoscience and Technology, 100190, Beijing, China
| | - Jacky W Y Lam
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Anjun Qin
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 310027, Hangzhou, China.
- Center for Aggregation-Induced Emission, SCUT-HKUST Joint Research Institute, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, 510640, Guangzhou, China.
| | - Ben Zhong Tang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 310027, Hangzhou, China.
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
- Center for Aggregation-Induced Emission, SCUT-HKUST Joint Research Institute, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, 510640, Guangzhou, China.
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40
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Yang HY, Moerner WE. Resolving Mixtures in Solution by Single-Molecule Rotational Diffusivity. NANO LETTERS 2018; 18:5279-5287. [PMID: 30001492 DOI: 10.1021/acs.nanolett.8b02280] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Sensing the size of individual molecules in an ensemble has proven to be a powerful tool to investigate biomolecular interactions and association-dissociation processes. In biologically relevant solution environments, molecular size is often sensed by translational or rotational diffusivity. The rotational diffusivity is more sensitive to the size and conformation of the molecules as it is inversely proportional to the cube of the hydrodynamic radius, as opposed to the inverse linear dependence of the translational diffusion coefficient. Single-molecule rotational diffusivity has been measured with time-resolved fluorescence anisotropy decay, but the ability to sense different sizes has been restricted by the limited number of photons available or has required surface attachment to observe each molecule longer, and the attachment may be perturbative. To address these limitations, we show how to measure and monitor single-molecule rotational diffusivity by combining the solution-phase Anti-Brownian ELectrokinetic (ABEL) trap and maximum likelihood analysis of time-resolved fluorescence anisotropy based on the information inherent in each detected photon. We demonstrate this approach by resolving a mixture of single- and double-stranded fluorescently labeled DNA molecules at equilibrium, freely rotating in a native solution environment. The rotational diffusivity, fluorescence brightness and lifetime, and initial and steady-state anisotropy are simultaneously determined for each trapped single DNA molecule. The time resolution and precision of this method are analyzed using statistical signal analysis and simulations. We present key parameters that define the usefulness of a particular fluorescent label for extracting molecular size information from single-molecule rotational diffusivity measurements.
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Affiliation(s)
- Hsiang-Yu Yang
- Department of Chemistry , Stanford University , Stanford , California 94305-4401 , United States
| | - W E Moerner
- Department of Chemistry , Stanford University , Stanford , California 94305-4401 , United States
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41
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Sielaff H, Duncan TM, Börsch M. The regulatory subunit ε in Escherichia coli F OF 1-ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:775-788. [PMID: 29932911 DOI: 10.1016/j.bbabio.2018.06.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 06/13/2018] [Accepted: 06/14/2018] [Indexed: 11/16/2022]
Abstract
F-type ATP synthases are extraordinary multisubunit proteins that operate as nanomotors. The Escherichia coli (E. coli) enzyme uses the proton motive force (pmf) across the bacterial plasma membrane to drive rotation of the central rotor subunits within a stator subunit complex. Through this mechanical rotation, the rotor coordinates three nucleotide binding sites that sequentially catalyze the synthesis of ATP. Moreover, the enzyme can hydrolyze ATP to turn the rotor in the opposite direction and generate pmf. The direction of net catalysis, i.e. synthesis or hydrolysis of ATP, depends on the cell's bioenergetic conditions. Different control mechanisms have been found for ATP synthases in mitochondria, chloroplasts and bacteria. This review discusses the auto-inhibitory behavior of subunit ε found in FOF1-ATP synthases of many bacteria. We focus on E. coli FOF1-ATP synthase, with insights into the regulatory mechanism of subunit ε arising from structural and biochemical studies complemented by single-molecule microscopy experiments.
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Affiliation(s)
- Hendrik Sielaff
- Single-Molecule Microscopy Group, Jena University Hospital, Friedrich Schiller University, Jena, Germany
| | - Thomas M Duncan
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Michael Börsch
- Single-Molecule Microscopy Group, Jena University Hospital, Friedrich Schiller University, Jena, Germany.
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42
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Wang Q, Serban AJ, Wachter RM, Moerner WE. Single-molecule diffusometry reveals the nucleotide-dependent oligomerization pathways of Nicotiana tabacum Rubisco activase. J Chem Phys 2018. [PMID: 29604852 DOI: 10.1101/191742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023] Open
Abstract
Oligomerization plays an important role in the function of many proteins, but a quantitative picture of the oligomer distribution has been difficult to obtain using existing techniques. Here we describe a method that combines sub-stoichiometric labeling and recently developed single-molecule diffusometry to measure the size distribution of oligomers under equilibrium conditions in solution, one molecule at a time. We use this technique to characterize the oligomerization behavior of Nicotiana tabacum (Nt) Rubisco activase (Nt-Rca), a chaperone-like AAA-plus ATPase essential in regulating carbon fixation during photosynthesis. We directly observed monomers, dimers, and a tetramer/hexamer mixture and extracted their fractional abundance as a function of protein concentration. We show that the oligomerization pathway of Nt-Rca is nucleotide dependent: ATPγS binding strongly promotes tetramer/hexamer formation from dimers and results in a preferred tetramer/hexamer population for concentrations in the 1-10 μM range. Furthermore, we directly observed dynamic assembly and disassembly processes of single complexes in real time and from there estimated the rate of subunit exchange to be ∼0.1 s-1 with ATPγS. On the other hand, ADP binding destabilizes Rca complexes by enhancing the rate of subunit exchange by >2 fold. These observations provide a quantitative starting point to elucidate the structure-function relations of Nt-Rca complexes. We envision the method to fill a critical gap in defining and quantifying protein assembly pathways in the small-oligomer regime.
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Affiliation(s)
- Quan Wang
- Department of Chemistry, Stanford University, Stanford, California 94035, USA
| | - Andrew J Serban
- School of Molecular Sciences and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85281, USA
| | - Rebekka M Wachter
- School of Molecular Sciences and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85281, USA
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, California 94035, USA
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43
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Wang Q, Serban AJ, Wachter RM, Moerner WE. Single-molecule diffusometry reveals the nucleotide-dependent oligomerization pathways of Nicotiana tabacum Rubisco activase. J Chem Phys 2018; 148:123319. [PMID: 29604852 DOI: 10.1063/1.5005930] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oligomerization plays an important role in the function of many proteins, but a quantitative picture of the oligomer distribution has been difficult to obtain using existing techniques. Here we describe a method that combines sub-stoichiometric labeling and recently developed single-molecule diffusometry to measure the size distribution of oligomers under equilibrium conditions in solution, one molecule at a time. We use this technique to characterize the oligomerization behavior of Nicotiana tabacum (Nt) Rubisco activase (Nt-Rca), a chaperone-like AAA-plus ATPase essential in regulating carbon fixation during photosynthesis. We directly observed monomers, dimers, and a tetramer/hexamer mixture and extracted their fractional abundance as a function of protein concentration. We show that the oligomerization pathway of Nt-Rca is nucleotide dependent: ATPγS binding strongly promotes tetramer/hexamer formation from dimers and results in a preferred tetramer/hexamer population for concentrations in the 1-10 μM range. Furthermore, we directly observed dynamic assembly and disassembly processes of single complexes in real time and from there estimated the rate of subunit exchange to be ∼0.1 s-1 with ATPγS. On the other hand, ADP binding destabilizes Rca complexes by enhancing the rate of subunit exchange by >2 fold. These observations provide a quantitative starting point to elucidate the structure-function relations of Nt-Rca complexes. We envision the method to fill a critical gap in defining and quantifying protein assembly pathways in the small-oligomer regime.
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Affiliation(s)
- Quan Wang
- Department of Chemistry, Stanford University, Stanford, California 94035, USA
| | - Andrew J Serban
- School of Molecular Sciences and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85281, USA
| | - Rebekka M Wachter
- School of Molecular Sciences and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85281, USA
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, California 94035, USA
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44
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Heitkamp T, Grisshammer R, Börsch M. Towards monitoring conformational changes of the GPCR neurotensin receptor 1 by single-molecule FRET. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2018; 10498. [PMID: 30013286 DOI: 10.1117/12.2286787] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neurotensin receptor 1 (NTSR1) is a G protein-coupled receptor that is important for signaling in the brain and the gut. Its agonist ligand neurotensin (NTS), a 13-amino-acid peptide, binds with nanomolar affinity from the extracellular side to NTSR1 and induces conformational changes that trigger intracellular signaling processes. Our goal is to monitor the conformational dynamics of single fluorescently labeled NTSR1. For this, we fused the fluorescent protein mNeonGreen to the C terminus of NTSR1, purified the receptor fusion protein from E. coli membranes, and reconstituted NTSR1 into liposomes with E. coli polar lipids. Using single-molecule anisotropy measurements, NTSR1 was found to be monomeric in liposomes, with a small fraction being dimeric and oligomeric, showing homoFRET. Similar results were obtained for NTSR1 in detergent solution. Furthermore, we demonstrated agonist binding to NTSR1 by time-resolved single-molecule Förster resonance energy transfer (smFRET), using neurotensin labeled with the fluorophore ATTO594.
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Affiliation(s)
- Thomas Heitkamp
- Single-Molecule Microscopy Group, Jena University Hospital, Friedrich Schiller University Jena, Nonnenplan 2 - 4, 07743 Jena, Germany
| | - Reinhard Grisshammer
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, 50 South Drive, Bethesda, MD 20814, USA
| | - Michael Börsch
- Single-Molecule Microscopy Group, Jena University Hospital, Friedrich Schiller University Jena, Nonnenplan 2 - 4, 07743 Jena, Germany
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45
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Manger LH, Foote AK, Wood SL, Holden MR, Heylman KD, Margittai M, Goldsmith RH. Revealing Conformational Variants of Solution-Phase Intrinsically Disordered Tau Protein at the Single-Molecule Level. Angew Chem Int Ed Engl 2017; 56:15584-15588. [PMID: 29063723 PMCID: PMC5831721 DOI: 10.1002/anie.201708242] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/05/2017] [Indexed: 11/09/2022]
Abstract
Intrinsically disordered proteins, such as tau protein, adopt a variety of conformations in solution, complicating solution-phase structural studies. We employed an anti-Brownian electrokinetic (ABEL) trap to prolong measurements of single tau proteins in solution. Once trapped, we recorded the fluorescence anisotropy to investigate the diversity of conformations sampled by the single molecules. A distribution of anisotropy values obtained from trapped tau protein is conspicuously bimodal while those obtained by trapping a globular protein or individual fluorophores are not. Time-resolved fluorescence anisotropy measurements were used to provide an explanation of the bimodal distribution as originating from a shift in the compaction of the two different families of conformations.
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Affiliation(s)
- Lydia H Manger
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Alexander K Foote
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Sharla L Wood
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Michael R Holden
- Department of Chemistry & Biochemistry, University of Denver, 2190 East Iliff Ave., Denver, CO, 80208, USA
| | - Kevin D Heylman
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Martin Margittai
- Department of Chemistry & Biochemistry, University of Denver, 2190 East Iliff Ave., Denver, CO, 80208, USA
| | - Randall H Goldsmith
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
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46
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Revealing Conformational Variants of Solution-Phase Intrinsically Disordered Tau Protein at the Single-Molecule Level. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201708242] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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47
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Tang J, Sun Y, Pang S, Han KY. Spatially encoded fast single-molecule fluorescence spectroscopy with full field-of-view. Sci Rep 2017; 7:10945. [PMID: 28887471 PMCID: PMC5591195 DOI: 10.1038/s41598-017-10837-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 08/15/2017] [Indexed: 11/09/2022] Open
Abstract
We report a simple single-molecule fluorescence imaging method that increases the temporal resolution of any type of array detector by >5-fold with full field-of-view. We spread single-molecule spots to adjacent pixels by rotating a mirror in the detection path during the exposure time of a single frame, which encodes temporal information into the spatial domain. Our approach allowed us to monitor fast blinking of an organic dye, the dissociation kinetics of very short DNA and conformational changes of biomolecules with much improved temporal resolution than the conventional method. Our technique is useful when a large field-of-view is required, for example, in the case of weakly interacting biomolecules or cellular imaging.
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Affiliation(s)
- Jialei Tang
- CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida, USA
| | - Yangyang Sun
- CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida, USA
| | - Shuo Pang
- CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida, USA
| | - Kyu Young Han
- CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida, USA.
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48
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Li N, Zhao R, Sun Y, Ye Z, He K, Fang X. Single-molecule imaging and tracking of molecular dynamics in living cells. Natl Sci Rev 2017. [DOI: 10.1093/nsr/nww055] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Abstract
Unlike the ensemble-averaging measurements, the single-molecule imaging and tracking (SMIT) in living cells provides the real-time quantitative information about the locations, kinetics, dynamics and interactions of individual molecules in their native environments with high spatiotemporal resolution and minimal perturbation. The past decade has witnessed a transforming development in the methods of SMIT with living cells, including fluorescent probes, labeling strategies, fluorescence microscopy, and detection and tracking algorithms. In this review, we will discuss these aspects with a particular focus on their recent advancements. We will then describe representative single-molecule studies to illustrate how the single-molecule approaches can be applied to monitor biomolecular interaction/reaction dynamics, and extract the molecular mechanistic information for different cellular systems.
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Affiliation(s)
- Nan Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rong Zhao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yahong Sun
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zi Ye
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kangmin He
- Department of Cell Biology, Harvard Medical School, and Cellular and Molecular Medicine Program, Boston Children's Hospital, Boston, MA 02115, USA
| | - Xiaohong Fang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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49
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Lee A, Tsekouras K, Calderon C, Bustamante C, Pressé S. Unraveling the Thousand Word Picture: An Introduction to Super-Resolution Data Analysis. Chem Rev 2017; 117:7276-7330. [PMID: 28414216 PMCID: PMC5487374 DOI: 10.1021/acs.chemrev.6b00729] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Super-resolution microscopy provides direct insight into fundamental biological processes occurring at length scales smaller than light's diffraction limit. The analysis of data at such scales has brought statistical and machine learning methods into the mainstream. Here we provide a survey of data analysis methods starting from an overview of basic statistical techniques underlying the analysis of super-resolution and, more broadly, imaging data. We subsequently break down the analysis of super-resolution data into four problems: the localization problem, the counting problem, the linking problem, and what we've termed the interpretation problem.
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Affiliation(s)
- Antony Lee
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Konstantinos Tsekouras
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | | | - Carlos Bustamante
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California at Berkeley, Berkeley, California 94720, United States
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California 94720, United States
- Institute for Quantitative Biosciences-QB3, University of California at Berkeley, Berkeley, California 94720, United States
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, United States
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, United States
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, California 94720, United States
- Kavli Energy Nanosciences Institute, University of California at Berkeley, Berkeley, California 94720, United States
| | - Steve Pressé
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Department of Chemistry and Chemical Biology, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
- Department of Cell and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
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50
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Serag MF, Habuchi S. Conserved linear dynamics of single-molecule Brownian motion. Nat Commun 2017; 8:15675. [PMID: 28585925 PMCID: PMC5467176 DOI: 10.1038/ncomms15675] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 04/19/2017] [Indexed: 12/31/2022] Open
Abstract
Macromolecular diffusion in homogeneous fluid at length scales greater than the size of the molecule is regarded as a random process. The mean-squared displacement (MSD) of molecules in this regime increases linearly with time. Here we show that non-random motion of DNA molecules in this regime that is undetectable by the MSD analysis can be quantified by characterizing the molecular motion relative to a latticed frame of reference. Our lattice occupancy analysis reveals unexpected sub-modes of motion of DNA that deviate from expected random motion in the linear, diffusive regime. We demonstrate that a subtle interplay between these sub-modes causes the overall diffusive motion of DNA to appear to conform to the linear regime. Our results show that apparently random motion of macromolecules could be governed by non-random dynamics that are detectable only by their relative motion. Our analytical approach should advance broad understanding of diffusion processes of fundamental relevance.
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Affiliation(s)
- Maged F. Serag
- Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Satoshi Habuchi
- Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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