151
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Andrecka J, Ortega Arroyo J, Takagi Y, de Wit G, Fineberg A, MacKinnon L, Young G, Sellers JR, Kukura P. Structural dynamics of myosin 5 during processive motion revealed by interferometric scattering microscopy. eLife 2015. [PMID: 25748137 DOI: 10.7554/elife.05413.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Myosin 5a is a dual-headed molecular motor that transports cargo along actin filaments. By following the motion of individual heads with interferometric scattering microscopy at nm spatial and ms temporal precision we found that the detached head occupies a loosely fixed position to one side of actin from which it rebinds in a controlled manner while executing a step. Improving the spatial precision to the sub-nm regime provided evidence for an ångstrom-level structural transition in the motor domain associated with the power stroke. Simultaneous tracking of both heads revealed that consecutive steps follow identical paths to the same side of actin in a compass-like spinning motion demonstrating a symmetrical walking pattern. These results visualize many of the critical unknown aspects of the stepping mechanism of myosin 5 including head-head coordination, the origin of lever-arm motion and the spatiotemporal dynamics of the translocating head during individual steps.
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Affiliation(s)
- Joanna Andrecka
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Jaime Ortega Arroyo
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Gabrielle de Wit
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Adam Fineberg
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Lachlan MacKinnon
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
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152
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Andrecka J, Ortega Arroyo J, Takagi Y, de Wit G, Fineberg A, MacKinnon L, Young G, Sellers JR, Kukura P. Structural dynamics of myosin 5 during processive motion revealed by interferometric scattering microscopy. eLife 2015; 4. [PMID: 25748137 PMCID: PMC4391024 DOI: 10.7554/elife.05413] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 03/05/2015] [Indexed: 01/21/2023] Open
Abstract
Myosin 5a is a dual-headed molecular motor that transports cargo along actin filaments. By following the motion of individual heads with interferometric scattering microscopy at nm spatial and ms temporal precision we found that the detached head occupies a loosely fixed position to one side of actin from which it rebinds in a controlled manner while executing a step. Improving the spatial precision to the sub-nm regime provided evidence for an ångstrom-level structural transition in the motor domain associated with the power stroke. Simultaneous tracking of both heads revealed that consecutive steps follow identical paths to the same side of actin in a compass-like spinning motion demonstrating a symmetrical walking pattern. These results visualize many of the critical unknown aspects of the stepping mechanism of myosin 5 including head-head coordination, the origin of lever-arm motion and the spatiotemporal dynamics of the translocating head during individual steps.
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Affiliation(s)
- Joanna Andrecka
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Jaime Ortega Arroyo
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Gabrielle de Wit
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Adam Fineberg
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Lachlan MacKinnon
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
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153
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Hosseinidoust Z, Olsson AL, Tufenkji N. Going viral: Designing bioactive surfaces with bacteriophage. Colloids Surf B Biointerfaces 2014; 124:2-16. [DOI: 10.1016/j.colsurfb.2014.05.036] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 05/25/2014] [Accepted: 05/26/2014] [Indexed: 12/22/2022]
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154
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Saxton MJ. Wanted: scalable tracers for diffusion measurements. J Phys Chem B 2014; 118:12805-17. [PMID: 25319586 PMCID: PMC4234437 DOI: 10.1021/jp5059885] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/03/2014] [Indexed: 12/02/2022]
Abstract
Scalable tracers are potentially a useful tool to examine diffusion mechanisms and to predict diffusion coefficients, particularly for hindered diffusion in complex, heterogeneous, or crowded systems. Scalable tracers are defined as a series of tracers varying in size but with the same shape, structure, surface chemistry, deformability, and diffusion mechanism. Both chemical homology and constant dynamics are required. In particular, branching must not vary with size, and there must be no transition between ordinary diffusion and reptation. Measurements using scalable tracers yield the mean diffusion coefficient as a function of size alone; measurements using nonscalable tracers yield the variation due to differences in the other properties. Candidate scalable tracers are discussed for two-dimensional (2D) diffusion in membranes and three-dimensional diffusion in aqueous solutions. Correlations to predict the mean diffusion coefficient of globular biomolecules from molecular mass are reviewed briefly. Specific suggestions for the 3D case include the use of synthetic dendrimers or random hyperbranched polymers instead of dextran and the use of core-shell quantum dots. Another useful tool would be a series of scalable tracers varying in deformability alone, prepared by varying the density of crosslinking in a polymer to make say "reinforced Ficoll" or "reinforced hyperbranched polyglycerol."
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Affiliation(s)
- Michael J. Saxton
- Department of Biochemistry
and Molecular Medicine, University of California, One Shields Ave., Davis, California 95616, United States
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155
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Dulin D, Barland S, Hachair X, Pedaci F. Efficient illumination for microsecond tracking microscopy. PLoS One 2014; 9:e107335. [PMID: 25251462 PMCID: PMC4175081 DOI: 10.1371/journal.pone.0107335] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 08/15/2014] [Indexed: 12/02/2022] Open
Abstract
The possibility to observe microsecond dynamics at the sub-micron scale, opened by recent technological advances in fast camera sensors, will affect many biophysical studies based on particle tracking in optical microscopy. A main limiting factor for further development of fast video microscopy remains the illumination of the sample, which must deliver sufficient light to the camera to allow microsecond exposure times. Here we systematically compare the main illumination systems employed in holographic tracking microscopy, and we show that a superluminescent diode and a modulated laser diode perform the best in terms of image quality and acquisition speed, respectively. In particular, we show that the simple and inexpensive laser illumination enables less than s camera exposure time at high magnification on a large field of view without coherence image artifacts, together with a good hologram quality that allows nm-tracking of microscopic beads to be performed. This comparison of sources can guide in choosing the most efficient illumination system with respect to the specific application.
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Affiliation(s)
- David Dulin
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Stephane Barland
- Université de Nice Sophia Antipolis, Institut Non-Lineaire de Nice, CNRS UMR 7335, Valbonne, France
| | | | - Francesco Pedaci
- Centre de Biochimie Structurale, CNRS UMR5048, UM1, INSERM UMR1054, Department of Single-Molecule Biophysics, Montpellier, France
- * E-mail:
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156
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Spillane K, Ortega-Arroyo J, de Wit G, Eggeling C, Ewers H, Wallace MI, Kukura P. High-speed single-particle tracking of GM1 in model membranes reveals anomalous diffusion due to interleaflet coupling and molecular pinning. NANO LETTERS 2014; 14:5390-7. [PMID: 25133992 PMCID: PMC4160260 DOI: 10.1021/nl502536u] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The biological functions of the cell membrane are influenced by the mobility of its constituents, which are thought to be strongly affected by nanoscale structure and organization. Interactions with the actin cytoskeleton have been proposed as a potential mechanism with the control of mobility imparted through transmembrane "pickets" or GPI-anchored lipid nanodomains. This hypothesis is based on observations of molecular mobility using various methods, although many of these lack the spatiotemporal resolution required to fully capture all the details of the interaction dynamics. In addition, the validity of certain experimental approaches, particularly single-particle tracking, has been questioned due to a number of potential experimental artifacts. Here, we use interferometric scattering microscopy to track molecules labeled with 20-40 nm scattering gold beads with simultaneous <2 nm spatial and 20 μs temporal precision to investigate the existence and mechanistic origin of anomalous diffusion in bilayer membranes. We use supported lipid bilayers as a model system and demonstrate that the label does not influence time-dependent diffusion in the small particle limit (≤40 nm). By tracking the motion of the ganglioside lipid GM1 bound to the cholera toxin B subunit for different substrates and lipid tail properties, we show that molecular pinning and interleaflet coupling between lipid tail domains on a nanoscopic scale suffice to induce transient immobilization and thereby anomalous subdiffusion on the millisecond time scale.
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Affiliation(s)
- Katelyn
M. Spillane
- Physical
and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Jaime Ortega-Arroyo
- Physical
and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Gabrielle de Wit
- Physical
and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Christian Eggeling
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford, Weatherall
Institute of Molecular Medicine, University
of Oxford, Oxford OX3 9DS, United Kingdom
| | - Helge Ewers
- Randall
Division of Cell and Molecular Biophysics, King’s College, London SE1 1UL, United Kingdom
| | - Mark I. Wallace
- Physical
and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Philipp Kukura
- Physical
and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
- E-mail: . Phone: +44 18652-75401
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157
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Mashaghi A, Mashaghi S, Reviakine I, Heeren RMA, Sandoghdar V, Bonn M. Label-free characterization of biomembranes: from structure to dynamics. Chem Soc Rev 2014; 43:887-900. [PMID: 24253187 DOI: 10.1039/c3cs60243e] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We review recent progress in the study of the structure and dynamics of phospholipid membranes and associated proteins, using novel label-free analytical tools. We describe these techniques and illustrate them with examples highlighting current capabilities and limitations. Recent advances in applying such techniques to biological and model membranes for biophysical studies and biosensing applications are presented, and future prospects are discussed.
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Affiliation(s)
- Alireza Mashaghi
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
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158
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Haiden C, Wopelka T, Jech M, Keplinger F, Vellekoop MJ. Sizing of metallic nanoparticles confined to a microfluidic film applying dark-field particle tracking. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9607-9615. [PMID: 25036522 DOI: 10.1021/la5016675] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present Brownian motion-based sizing of individual submicron and nanoparticles in liquid samples. The advantage of our approach is that particles can freely diffuse in a 10 μm thin liquid film and are therefore always within the focal depth of a low numerical aperture objective. Particles are visualized with dark-field microscopy, and the resulting diffraction-limited spots are tracked over a wide field of view of several hundred micrometers. Consequently, it is ascertained that long 2D trajectories are acquired, which leads to significantly increased particle sizing precision. The hydrodynamic diameters of metal particles with nominal sizes ranging from 70 to 200 nm in aqueous solution were determined by tracking for up to 2 min, and it was investigated if the diffusion characteristics were influenced by the proximity of substrates. This was not the case, and the estimated diameters were in good agreement with the values obtained by electron microscopy, thus validating the particle sizing principle. Furthermore, we measured a sample mixture to demonstrate the distinction of close particle sizes and performed the conjugation of a model protein (BSA) on the nanoparticle surface. An average increase in the radius of 9 nm was determined, which corresponds to the size of the BSA protein.
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Affiliation(s)
- Christoph Haiden
- Institute of Sensor and Actuator Systems, Vienna University of Technology , Gusshausstrasse 27-29, A-1040 Vienna, Austria
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159
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Piliarik M, Sandoghdar V. Direct optical sensing of single unlabelled proteins and super-resolution imaging of their binding sites. Nat Commun 2014; 5:4495. [DOI: 10.1038/ncomms5495] [Citation(s) in RCA: 197] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 06/24/2014] [Indexed: 01/05/2023] Open
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160
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Lin YH, Chang WL, Hsieh CL. Shot-noise limited localization of single 20 nm gold particles with nanometer spatial precision within microseconds. OPTICS EXPRESS 2014; 22:9159-70. [PMID: 24787806 DOI: 10.1364/oe.22.009159] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Single-particle tracking (SPT) is a powerful approach to investigate dynamics without ensemble average. Continuing effort has been made to track smaller particles with better spatial precision at higher speed. In this work, we demonstrate SPT of 20 nm gold nanoparticle (GNP) with 2 nm spatial precision up to 500 kHz by using microsecond interferometric scattering (μs-iSCAT) microscopy. The linear scattering signal from single GNPs is detected by a high-speed CMOS camera via interference. Through this homodyne detection, shot-noise limited sensitivity, and therefore optimal localization precision are achieved at high speed where considerable electronic noise is present. Using μs-iSCAT microscopy, we observe anomalous diffusion of GNPs labeled to lipid molecules in a supported bilayer membrane prepared on a glass substrate. The combination of nanometer spatial precision and microsecond temporal resolution provides the opportunity to study rapid motions of nano-objects on molecular scale with unprecedented clarity.
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161
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Hsieh CL, Spindler S, Ehrig J, Sandoghdar V. Tracking Single Particles on Supported Lipid Membranes: Multimobility Diffusion and Nanoscopic Confinement. J Phys Chem B 2014; 118:1545-54. [DOI: 10.1021/jp412203t] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Chia-Lung Hsieh
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
| | - Susann Spindler
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
| | - Jens Ehrig
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
| | - Vahid Sandoghdar
- Max Planck Institute
for the Science of Light and Friedrich Alexander University, 91058 Erlangen, Germany
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162
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Affiliation(s)
- Wei Wang
- Center for Bioelectronics and Biosensors, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
| | - Nongjian Tao
- Center for Bioelectronics and Biosensors, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
- Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287, USA
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163
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Ortega Arroyo J, Andrecka J, Spillane KM, Billington N, Takagi Y, Sellers JR, Kukura P. Label-free, all-optical detection, imaging, and tracking of a single protein. NANO LETTERS 2014; 14:2065-70. [PMID: 24597479 PMCID: PMC4186656 DOI: 10.1021/nl500234t] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/28/2014] [Indexed: 05/21/2023]
Abstract
Optical detection of individual proteins requires fluorescent labeling. Cavity and plasmonic methodologies enhance single molecule signatures in the absence of any labels but have struggled to demonstrate routine and quantitative single protein detection. Here, we used interferometric scattering microscopy not only to detect but also to image and nanometrically track the motion of single myosin 5a heavy meromyosin molecules without the use of labels or any nanoscopic amplification. Together with the simple experimental arrangement, an intrinsic independence from strong electronic transition dipoles and a detection limit of <60 kDa, our approach paves the way toward nonresonant, label-free sensing and imaging of nanoscopic objects down to the single protein level.
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Affiliation(s)
- J. Ortega Arroyo
- Physical
and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - J. Andrecka
- Physical
and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - K. M. Spillane
- Physical
and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - N. Billington
- Laboratory
of Molecular Physiology, National Heart,
Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Y. Takagi
- Laboratory
of Molecular Physiology, National Heart,
Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - J. R. Sellers
- Laboratory
of Molecular Physiology, National Heart,
Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - P. Kukura
- Physical
and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
- E-mail:
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164
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Andrecka J, Spillane KM, Ortega-Arroyo J, Kukura P. Direct observation and control of supported lipid bilayer formation with interferometric scattering microscopy. ACS NANO 2013; 7:10662-70. [PMID: 24251388 DOI: 10.1021/nn403367c] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Supported lipid bilayers (SLB) are frequently used to study processes associated with or mediated by lipid membranes. The mechanism by which SLBs form is a matter of debate, largely due to the experimental difficulty associated with observing the adsorption and rupture of individual vesicles. Here, we used interferometric scattering microscopy (iSCAT) to directly visualize membrane formation from nanoscopic vesicles in real time. We observed a number of previously proposed phenomena such as vesicle adsorption, rupture, movement, and a wave-like bilayer spreading. By varying the vesicle size and the lipid-surface interaction strength, we rationalized and tuned the relative contributions of these phenomena to bilayer formation. Our results support a model where the interplay between bilayer edge tension and the overall interaction energy with the surface determine the mechanism of SLB formation. The unique combination of sensitivity, speed, and label-free imaging capability of iSCAT provides exciting prospects not only for investigations of SLB formation, but also for studies of assembly and disassembly processes on the nanoscale with previously unattainable accuracy and sensitivity.
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Affiliation(s)
- Joanna Andrecka
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom
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165
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Herrmann LO, Baumberg JJ. Watching single nanoparticles grow in real time through supercontinuum spectroscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:3743-3747. [PMID: 23650155 DOI: 10.1002/smll.201300958] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Indexed: 06/02/2023]
Abstract
A fast dark-field scattering technique capturing full broadband spectra with millisecond time-resolution enables us to monitor the growth or assembly of single nano-objects in situ and in real time. Applying this technique to study the growth of single gold nanorods, together with scanning electron microscopy and finite-difference time-domain simulations, reveals precise quantitative information about gold nanorod growth kinetics.
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Affiliation(s)
- Lars O Herrmann
- NanoPhotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
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166
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Mojarad N, Sandoghdar V, Krishnan M. Measuring three-dimensional interaction potentials using optical interference. OPTICS EXPRESS 2013; 21:9377-9389. [PMID: 23609648 DOI: 10.1364/oe.21.009377] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We describe the application of three-dimensional (3D) scattering interferometric (iSCAT) imaging to the measurement of spatial interaction potentials for nano-objects in solution. We study electrostatically trapped gold particles in a nanofluidic device and present details on axial particle localization in the presence of a strongly reflecting interface. Our results demonstrate high-speed (~kHz) particle tracking with subnanometer localization precision in the axial and average 2.5 nm in the lateral dimension. A comparison of the measured levitation heights of trapped particles with the calculated values for traps of various geometries reveals good agreement. Our work demonstrates that iSCAT imaging delivers label-free, high-speed and accurate 3D tracking of nano-objects conducive to probing weak and long-range interaction potentials in solution.
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Affiliation(s)
- Nassir Mojarad
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen, Switzerland
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