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Zhou W, Wu T, Lew MD. Fundamental Limits in Measuring the Anisotropic Rotational Diffusion of Single Molecules. J Phys Chem A 2024; 128:5808-5815. [PMID: 38978460 DOI: 10.1021/acs.jpca.4c03160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Many biophysical techniques, such as single-molecule fluorescence correlation spectroscopy, Förster resonance energy transfer, and fluorescence anisotropy, measure the translation and rotation of biomolecules to quantify molecular processes at the nanoscale. These methods often simplify data analysis by assuming isotropic rotational diffusion, e.g., that molecules wobble within a circular cone. This simplification ignores the anisotropy present in many biological contexts that may cause molecules to exhibit different degrees of diffusion in different directions. Here, we loosen this assumption and establish a theoretical framework for describing and measuring anisotropic rotational diffusion using fluorescence imaging. We show that anisotropic wobble is directly quantified by the eigenvalues of a 3-by-3 positive-semidefinite Hermitian matrix M consisting of the second-order moments of a molecule's transition dipole μ. This formalism enables us to model the influence of unavoidable shot noise using a Hermitian perturbation matrix E; the eigenvalues of E directly bound errors in measurements of wobble via Weyl's inequality. Quantifying various perturbations E reveals that anisotropic wobble measurements are generally more sensitive to errors compared to quantifying isotropic wobble. Moreover, severe shot noise can induce negative eigenvalues in estimates of M, thereby causing the anisotropic wobble measurement to fail. Our analysis, using Fisher information, shows that techniques with worse orientation measurement sensitivity experience stronger perturbations E and require larger signal to background ratios to measure anisotropic rotational diffusion accurately. Our work provides deep insights for improving the state of the art in imaging the orientations and anisotropic rotational diffusion of single molecules.
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Affiliation(s)
- Weiyan Zhou
- Preston M. Green Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Tingting Wu
- Preston M. Green Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Matthew D Lew
- Preston M. Green Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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2
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Fernando SI, Martineau JT, Hobson RJ, Vu TN, Baker B, Mueller BD, Menon R, Jorgensen EM, Gerton JM. Simultaneous spectral differentiation of multiple fluorophores in super-resolution imaging using a glass phase plate. OPTICS EXPRESS 2023; 31:33565-33581. [PMID: 37859135 PMCID: PMC10544955 DOI: 10.1364/oe.499929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/05/2023] [Accepted: 09/10/2023] [Indexed: 10/21/2023]
Abstract
By engineering the point-spread function (PSF) of single molecules, different fluorophore species can be imaged simultaneously and distinguished by their unique PSF patterns. Here, we insert a silicon-dioxide phase plate at the Fourier plane of the detection path of a wide-field fluorescence microscope to produce distinguishable PSFs (X-PSFs) at different wavelengths. We demonstrate that the resulting PSFs can be localized spatially and spectrally using a maximum-likelihood estimation algorithm and can be utilized for hyper-spectral super-resolution microscopy of biological samples. We produced superresolution images of fixed U2OS cells using X-PSFs for dSTORM imaging with simultaneous illumination of up to three fluorophore species. The species were distinguished only by the PSF pattern. We achieved ∼21-nm lateral localization precision (FWHM) and ∼17-nm axial precision (FWHM) with an average of 1,800 - 3,500 photons per PSF and a background as high as 130 - 400 photons per pixel. The modified PSF distinguished fluorescent probes with ∼80 nm separation between spectral peaks.
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Affiliation(s)
- Sanduni I. Fernando
- University of Utah Department of Physics and Astronomy, 201 James Fletcher Bldg. 115 S. 1400 E Salt Lake City, UT 84112-0830, USA
| | - Jason T. Martineau
- University of Utah Department of Physics and Astronomy, 201 James Fletcher Bldg. 115 S. 1400 E Salt Lake City, UT 84112-0830, USA
| | - Robert J. Hobson
- University of Utah School of Biological Sciences, 257 South 1400 East Salt Lake City, Utah 84112, USA
| | - Thien N. Vu
- University of Utah School of Biological Sciences, 257 South 1400 East Salt Lake City, Utah 84112, USA
| | - Brian Baker
- University of Utah Nanofab 36 S. Wasatch Drive, SMBB Room 2500 Salt Lake City, UT 84112, USA
| | - Brian D. Mueller
- University of Utah School of Biological Sciences, 257 South 1400 East Salt Lake City, Utah 84112, USA
| | - Rajesh Menon
- University of Utah Department of Electrical and Computer Engineering 50 S. Central Campus Drive, MEB Room 2110 Salt Lake City, UT 84112, USA
| | - Erik M. Jorgensen
- University of Utah School of Biological Sciences, 257 South 1400 East Salt Lake City, Utah 84112, USA
| | - Jordan M. Gerton
- University of Utah Department of Physics and Astronomy, 201 James Fletcher Bldg. 115 S. 1400 E Salt Lake City, UT 84112-0830, USA
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3
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Weiss LE, Love JF, Yoon J, Comerci CJ, Milenkovic L, Kanie T, Jackson PK, Stearns T, Gustavsson AK. Single-molecule imaging in the primary cilium. Methods Cell Biol 2023; 176:59-83. [PMID: 37164543 PMCID: PMC10509820 DOI: 10.1016/bs.mcb.2023.01.003] [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: 02/26/2023]
Abstract
The primary cilium is an important signaling organelle critical for normal development and tissue homeostasis. Its small dimensions and complexity necessitate advanced imaging approaches to uncover the molecular mechanisms behind its function. Here, we outline how single-molecule fluorescence microscopy can be used for tracking molecular dynamics and interactions and for super-resolution imaging of nanoscale structures in the primary cilium. Specifically, we describe in detail how to capture and quantify the 2D dynamics of individual transmembrane proteins PTCH1 and SMO and how to map the 3D nanoscale distributions of the inversin compartment proteins INVS, ANKS6, and NPHP3. This protocol can, with minor modifications, be adapted for studies of other proteins and cell lines to further elucidate the structure and function of the primary cilium at the molecular level.
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Affiliation(s)
- Lucien E Weiss
- Department of Engineering Physics, Polytechnique Montréal, Montreal, QC, Canada.
| | - Julia F Love
- Department of Chemistry, Rice University, Houston, TX, United States
| | | | - Colin J Comerci
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States
| | | | - Tomoharu Kanie
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, OK, United States
| | - Peter K Jackson
- Baxter Laboratory, Department of Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA, United States; Department of Pathology, Stanford University School of Medicine, Stanford, CA, United States
| | - Tim Stearns
- Department of Biology, Stanford University, Stanford, CA, United States; Rockefeller University, New York City, NY, United States
| | - Anna-Karin Gustavsson
- Department of Chemistry, Rice University, Houston, TX, United States; Department of BioSciences, Rice University, Houston, TX, United States; Institute of Biosciences and Bioengineering, Rice University, Houston, TX, United States; Smalley-Curl Institute, Rice University, Houston, TX, United States.
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4
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Zhang O, Guo Z, He Y, Wu T, Vahey MD, Lew MD. Six-Dimensional Single-Molecule Imaging with Isotropic Resolution using a Multi-View Reflector Microscope. NATURE PHOTONICS 2023; 17:179-186. [PMID: 36968242 PMCID: PMC10035538 DOI: 10.1038/s41566-022-01116-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 10/20/2022] [Indexed: 05/31/2023]
Abstract
Imaging both the positions and orientations of single fluorophores, termed single-molecule orientation-localisation microscopy, is a powerful tool to study biochemical processes. However, the limited photon budget associated with single-molecule fluorescence makes high-dimensional imaging with isotropic, nanoscale spatial resolution a formidable challenge. Here, we realise a radially and azimuthally polarized multi-view reflector (raMVR) microscope for the imaging of the 3D positions and 3D orientations of single molecules, with precision of 10.9 nm and 2.0° over a 1.5 μm depth range. The raMVR microscope achieves 6D super-resolution imaging of Nile red (NR) molecules transiently bound to lipid-coated spheres, accurately resolving their spherical morphology despite refractive-index mismatch. By observing the rotational dynamics of NR, raMVR images also resolve the infiltration of lipid membranes by amyloid-beta oligomers without covalent labelling. Finally, we demonstrate 6D imaging of cell membranes, where the orientations of specific fluorophores reveal heterogeneity in membrane fluidity. With its nearly isotropic 3D spatial resolution and orientation measurement precision, we expect the raMVR microscope to enable 6D imaging of molecular dynamics within biological and chemical systems with exceptional detail.
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Affiliation(s)
- Oumeng Zhang
- Department of Electrical and Systems Engineering
| | | | | | - Tingting Wu
- Department of Electrical and Systems Engineering
| | - Michael D. Vahey
- Department of Biomedical Engineering
- Center for Biomolecular Condensates
| | - Matthew D. Lew
- Department of Electrical and Systems Engineering
- Center for Biomolecular Condensates
- Institute of Materials Science and Engineering, Washington University in St. Louis, Missouri 63130, USA
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5
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Wu T, Lu P, Rahman MA, Li X, Lew MD. Deep-SMOLM: deep learning resolves the 3D orientations and 2D positions of overlapping single molecules with optimal nanoscale resolution. OPTICS EXPRESS 2022; 30:36761-36773. [PMID: 36258598 PMCID: PMC9662599 DOI: 10.1364/oe.470146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 09/08/2022] [Accepted: 09/08/2022] [Indexed: 06/01/2023]
Abstract
Dipole-spread function (DSF) engineering reshapes the images of a microscope to maximize the sensitivity of measuring the 3D orientations of dipole-like emitters. However, severe Poisson shot noise, overlapping images, and simultaneously fitting high-dimensional information-both orientation and position-greatly complicates image analysis in single-molecule orientation-localization microscopy (SMOLM). Here, we report a deep-learning based estimator, termed Deep-SMOLM, that achieves superior 3D orientation and 2D position measurement precision within 3% of the theoretical limit (3.8° orientation, 0.32 sr wobble angle, and 8.5 nm lateral position using 1000 detected photons). Deep-SMOLM also demonstrates state-of-art estimation performance on overlapping images of emitters, e.g., a 0.95 Jaccard index for emitters separated by 139 nm, corresponding to a 43% image overlap. Deep-SMOLM accurately and precisely reconstructs 5D information of both simulated biological fibers and experimental amyloid fibrils from images containing highly overlapped DSFs at a speed ~10 times faster than iterative estimators.
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Affiliation(s)
- Tingting Wu
- Department of Electrical and Systems Engineering,
Washington University in St. Louis, Missouri 63130, USA
- Center for Science and Engineering of Living Systems,
Washington University in St. Louis, Missouri 63130, USA
| | - Peng Lu
- Department of Biomedical Engineering, Washington University in St. Louis, Missouri 63130, USA
- Department of Radiology, Washington University School of Medicine, Missouri 63110, USA
- These authors contributed equally to this work
| | - Md Ashequr Rahman
- Department of Biomedical Engineering, Washington University in St. Louis, Missouri 63130, USA
- Department of Radiology, Washington University School of Medicine, Missouri 63110, USA
- These authors contributed equally to this work
| | - Xiao Li
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA
- These authors contributed equally to this work
| | - Matthew D. Lew
- Department of Electrical and Systems Engineering,
Washington University in St. Louis, Missouri 63130, USA
- Center for Science and Engineering of Living Systems,
Washington University in St. Louis, Missouri 63130, USA
- Institute of Materials Science and Engineering,
Washington University in St. Louis, Missouri 63130, USA
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6
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Wu T, Lu J, Lew MD. Dipole-spread-function engineering for simultaneously measuring the 3D orientations and 3D positions of fluorescent molecules. OPTICA 2022; 9:505-511. [PMID: 35601691 PMCID: PMC9122034 DOI: 10.1364/optica.451899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 04/03/2022] [Indexed: 06/01/2023]
Abstract
Interactions between biomolecules are characterized by both where they occur and how they are organized, e.g., the alignment of lipid molecules to form a membrane. However, spatial and angular information are mixed within the image of a fluorescent molecule-the microscope's dipole-spread function (DSF). We demonstrate the pixOL algorithm for simultaneously optimizing all pixels within a phase mask to produce an engineered Green's tensor-the dipole extension of point-spread function engineering. The pixOL DSF achieves optimal precision for measuring simultaneously the 3D orientation and 3D location of a single molecule, i.e., 4.1° orientation, 0.44 sr wobble angle, 23.2 nm lateral localization, and 19.5 nm axial localization precisions in simulations over a 700-nm depth range using 2500 detected photons. The pixOL microscope accurately and precisely resolves the 3D positions and 3D orientations of Nile red within a spherical supported lipid bilayer, resolving both membrane defects and differences in cholesterol concentration in 6 dimensions.
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Affiliation(s)
- Tingting Wu
- Department of Electrical and Systems Engineering, Washington University in St. Louis, Missouri 63130, USA
- Center for Science and Engineering of Living Systems, Washington University in St. Louis, Missouri 63130, USA
| | - Jin Lu
- Department of Electrical and Systems Engineering, Washington University in St. Louis, Missouri 63130, USA
- Center for Science and Engineering of Living Systems, Washington University in St. Louis, Missouri 63130, USA
| | - Matthew D. Lew
- Department of Electrical and Systems Engineering, Washington University in St. Louis, Missouri 63130, USA
- Center for Science and Engineering of Living Systems, Washington University in St. Louis, Missouri 63130, USA
- Institute of Materials Science and Engineering, Washington University in St. Louis, Missouri 63130, USA
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Zhang O, Zhou W, Lu J, Wu T, Lew MD. Resolving the Three-Dimensional Rotational and Translational Dynamics of Single Molecules Using Radially and Azimuthally Polarized Fluorescence. NANO LETTERS 2022; 22:1024-1031. [PMID: 35073487 PMCID: PMC8893020 DOI: 10.1021/acs.nanolett.1c03948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We report a radially and azimuthally polarized (raPol) microscope for high detection and estimation performance in single-molecule orientation-localization microscopy (SMOLM). With 5000 photons detected from Nile red (NR) transiently bound within supported lipid bilayers (SLBs), raPol SMOLM achieves 2.9 nm localization precision, 1.5° orientation precision, and 0.17 sr precision in estimating rotational wobble. Within DPPC SLBs, SMOLM imaging reveals the existence of randomly oriented binding pockets that prevent NR from freely exploring all orientations. Treating the SLBs with cholesterol-loaded methyl-β-cyclodextrin (MβCD-chol) causes NR's orientational diffusion to be dramatically reduced, but curiously NR's median lateral displacements drastically increase from 20.8 to 75.5 nm (200 ms time lag). These jump diffusion events overwhelmingly originate from cholesterol-rich nanodomains within the SLB. These detailed measurements of single-molecule rotational and translational dynamics are made possible by raPol's high measurement precision and are not detectable in standard SMLM.
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Rimoli CV, Valades-Cruz CA, Curcio V, Mavrakis M, Brasselet S. 4polar-STORM polarized super-resolution imaging of actin filament organization in cells. Nat Commun 2022; 13:301. [PMID: 35027553 PMCID: PMC8758668 DOI: 10.1038/s41467-022-27966-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 12/20/2021] [Indexed: 11/18/2022] Open
Abstract
Single-molecule localization microscopy provides insights into the nanometer-scale spatial organization of proteins in cells, however it does not provide information on their conformation and orientation, which are key functional signatures. Detecting single molecules' orientation in addition to their localization in cells is still a challenging task, in particular in dense cell samples. Here, we present a polarization-splitting scheme which combines Stochastic Optical Reconstruction Microscopy (STORM) with single molecule 2D orientation and wobbling measurements, without requiring a strong deformation of the imaged point spread function. This method called 4polar-STORM allows, thanks to a control of its detection numerical aperture, to determine both single molecules' localization and orientation in 2D and to infer their 3D orientation. 4polar-STORM is compatible with relatively high densities of diffraction-limited spots in an image, and is thus ideally placed for the investigation of dense protein assemblies in cells. We demonstrate the potential of this method in dense actin filament organizations driving cell adhesion and motility.
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Affiliation(s)
- Caio Vaz Rimoli
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France
| | - Cesar Augusto Valades-Cruz
- Institut Curie, PSL Research University, UMR144 CNRS, Space-Time imaging of organelles and Endomembranes Dynamics Team, F-75005, Paris, France
- Inria Centre Rennes-Bretagne Atlantique, SERPICO Project Team, F-35042, Rennes, France
| | - Valentina Curcio
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France
| | - Manos Mavrakis
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France.
| | - Sophie Brasselet
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France.
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Ding T, Lew MD. Single-Molecule Localization Microscopy of 3D Orientation and Anisotropic Wobble Using a Polarized Vortex Point Spread Function. J Phys Chem B 2021; 125:12718-12729. [PMID: 34766758 PMCID: PMC8662813 DOI: 10.1021/acs.jpcb.1c08073] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Within condensed matter, single fluorophores are sensitive probes of their chemical environments, but it is difficult to use their limited photon budget to image precisely their positions, 3D orientations, and rotational diffusion simultaneously. We demonstrate the polarized vortex point spread function (PSF) for measuring these parameters, including characterizing the anisotropy of a molecule's wobble, simultaneously from a single image. Even when imaging dim emitters (∼500 photons detected), the polarized vortex PSF can obtain 12 nm localization precision, 4°-8° orientation precision, and 26° wobble precision. We use the vortex PSF to measure the emission anisotropy of fluorescent beads, the wobble dynamics of Nile red (NR) within supported lipid bilayers, and the distinct orientation signatures of NR in contact with amyloid-beta fibrils, oligomers, and tangles. The unparalleled sensitivity of the vortex PSF transforms single-molecule microscopes into nanoscale orientation imaging spectrometers, where the orientations and wobbles of individual probes reveal structures and organization of soft matter that are nearly impossible to perceive by using molecular positions alone.
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Affiliation(s)
- Tianben Ding
- Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Center for Science and Engineering of Living Systems, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Matthew D Lew
- Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Center for Science and Engineering of Living Systems, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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10
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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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Shepherd JW, Payne-Dwyer AL, Lee JE, Syeda A, Leake MC. Combining single-molecule super-resolved localization microscopy with fluorescence polarization imaging to study cellular processes. JPHYS PHOTONICS 2021. [DOI: 10.1088/2515-7647/ac015d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Super-resolution microscopy has catalyzed valuable insights into the sub-cellular, mechanistic details of many different biological processes across a wide range of cell types. Fluorescence polarization spectroscopy tools have also enabled important insights into cellular processes through identifying orientational changes of biological molecules typically at an ensemble level. Here, we combine these two biophysical methodologies in a single home-made instrument to enable the simultaneous detection of orthogonal fluorescence polarization signals from single fluorescent protein molecules used as common reporters on the localization of proteins in cellular processes. These enable measurement of spatial location to a super-resolved precision better than the diffraction-limited optical resolution, as well as estimation of molecular stoichiometry based on the brightness of individual fluorophores. In this innovation we have adapted a millisecond timescale microscope used for single-molecule detection to enable splitting of fluorescence polarization emissions into two separate imaging channels for s- and p-polarization signals, which are imaged onto separate halves of the same high sensitivity back-illuminated CMOS camera detector. We applied this fluorescence polarization super-resolved imaging modality to a range of test fluorescent samples relevant to the study of biological processes, including purified monomeric green fluorescent protein, single combed DNA molecules, and protein assemblies and complexes from live Escherichia coli and Saccharomyces cerevisiae cells. Our findings are qualitative but demonstrate promise in showing how fluorescence polarization and super-resolved localization microscopy can be combined on the same sample to enable simultaneous measurements of polarization and stoichiometry of tracked molecular complexes, as well as the translational diffusion coefficient.
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12
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Zhang O, Lew MD. Single-molecule orientation localization microscopy I: fundamental limits. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2021; 38:277-287. [PMID: 33690541 DOI: 10.1364/josaa.411981] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 01/05/2021] [Indexed: 06/12/2023]
Abstract
Precisely measuring the three-dimensional position and orientation of individual fluorophores is challenging due to the substantial photon shot noise in single-molecule experiments. Facing this limited photon budget, numerous techniques have been developed to encode 2D and 3D position and 2D and 3D orientation information into fluorescence images. In this work, we adapt classical and quantum estimation theory and propose a mathematical framework to derive the best possible precision for measuring the position and orientation of dipole-like emitters for any fixed imaging system. We find that it is impossible to design an instrument that achieves the maximum sensitivity limit for measuring all possible rotational motions. Further, our vectorial dipole imaging model shows that the best quantum-limited localization precision is 4%-8% worse than that suggested by a scalar monopole model. Overall, we conclude that no single instrument can be optimized for maximum precision across all possible 2D and 3D localization and orientation measurement tasks.
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