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Loginov SV, Fermie J, Fokkema J, Agronskaia AV, De Heus C, Blab GA, Klumperman J, Gerritsen HC, Liv N. Correlative Organelle Microscopy: Fluorescence Guided Volume Electron Microscopy of Intracellular Processes. Front Cell Dev Biol 2022; 10:829545. [PMID: 35478966 PMCID: PMC9035751 DOI: 10.3389/fcell.2022.829545] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 03/04/2022] [Indexed: 01/19/2023] Open
Abstract
Intracellular processes depend on a strict spatial and temporal organization of proteins and organelles. Therefore, directly linking molecular to nanoscale ultrastructural information is crucial in understanding cellular physiology. Volume or three-dimensional (3D) correlative light and electron microscopy (volume-CLEM) holds unique potential to explore cellular physiology at high-resolution ultrastructural detail across cell volumes. However, the application of volume-CLEM is hampered by limitations in throughput and 3D correlation efficiency. In order to address these limitations, we describe a novel pipeline for volume-CLEM that provides high-precision (<100 nm) registration between 3D fluorescence microscopy (FM) and 3D electron microscopy (EM) datasets with significantly increased throughput. Using multi-modal fiducial nanoparticles that remain fluorescent in epoxy resins and a 3D confocal fluorescence microscope integrated into a Focused Ion Beam Scanning Electron Microscope (FIB.SEM), our approach uses FM to target extremely small volumes of even single organelles for imaging in volume EM and obviates the need for post-correlation of big 3D datasets. We extend our targeted volume-CLEM approach to include live-cell imaging, adding information on the motility of intracellular membranes selected for volume-CLEM. We demonstrate the power of our approach by targeted imaging of rare and transient contact sites between the endoplasmic reticulum (ER) and lysosomes within hours rather than days. Our data suggest that extensive ER-lysosome and mitochondria-lysosome interactions restrict lysosome motility, highlighting the unique capabilities of our integrated CLEM pipeline for linking molecular dynamic data to high-resolution ultrastructural detail in 3D.
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Affiliation(s)
- Sergey V. Loginov
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands
| | - Job Fermie
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands
- Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Jantina Fokkema
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands
| | - Alexandra V. Agronskaia
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands
| | - Cilia De Heus
- Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Gerhard A. Blab
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands
| | - Judith Klumperman
- Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Hans C. Gerritsen
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands
| | - Nalan Liv
- Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
- *Correspondence: Nalan Liv,
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Lehmann K, Shayegan M, Blab GA, Forde NR. Optical Tweezers Approaches for Probing Multiscale Protein Mechanics and Assembly. Front Mol Biosci 2020; 7:577314. [PMID: 33134316 PMCID: PMC7573139 DOI: 10.3389/fmolb.2020.577314] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 08/27/2020] [Indexed: 01/09/2023] Open
Abstract
Multi-step assembly of individual protein building blocks is key to the formation of essential higher-order structures inside and outside of cells. Optical tweezers is a technique well suited to investigate the mechanics and dynamics of these structures at a variety of size scales. In this mini-review, we highlight experiments that have used optical tweezers to investigate protein assembly and mechanics, with a focus on the extracellular matrix protein collagen. These examples demonstrate how optical tweezers can be used to study mechanics across length scales, ranging from the single-molecule level to fibrils to protein networks. We discuss challenges in experimental design and interpretation, opportunities for integration with other experimental modalities, and applications of optical tweezers to current questions in protein mechanics and assembly.
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Affiliation(s)
- Kathrin Lehmann
- Department of Physics, Simon Fraser University, Burnaby, BC, Canada.,Soft Condensed Matter and Biophysics, Utrecht University, Utrecht, Netherlands
| | - Marjan Shayegan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, United States
| | - Gerhard A Blab
- Soft Condensed Matter and Biophysics, Utrecht University, Utrecht, Netherlands
| | - Nancy R Forde
- Department of Physics, Simon Fraser University, Burnaby, BC, Canada.,Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada.,Centre for Cell Biology, Development and Disease (C2D2), Simon Fraser University, Burnaby, BC, Canada
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3
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Mohammadian S, Agronskaia AV, Blab GA, van Donselaar EG, de Heus C, Liv N, Klumperman J, Gerritsen HC. Integrated super resolution fluorescence microscopy and transmission electron microscopy. Ultramicroscopy 2020; 215:113007. [PMID: 32470633 DOI: 10.1016/j.ultramic.2020.113007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 04/14/2020] [Accepted: 04/19/2020] [Indexed: 10/24/2022]
Abstract
In correlative light and electron microscopy (CLEM), the capabilities of fluorescence microscopy (FM) and electron microscopy (EM) are united. FM combines a large field of view with high sensitivity for detecting fluorescence, which makes it an excellent tool for identifying regions of interest. EM has a much smaller field of view but offers superb resolution that allows studying cellular ultrastructure. In CLEM, the potentials of both techniques are combined but a limiting factor is the large difference in resolution between the two imaging modalities. Adding super resolution FM to CLEM reduces the resolution gap between FM and EM; it offers the possibility of identifying multiple targets within the diffraction limit and can increase correlation accuracy. CLEM is usually carried out in two separate setups, which requires transfer of the sample. This may result in distortion and damage of the specimen, which can complicate finding back regions of interest. By integrating the two imaging modalities, such problems can be avoided. Here, an integrated super resolution correlative microscopy approach is presented based on a wide-field super resolution FM integrated in a Transmission Electron Microscope (TEM). Switching imaging modalities is accomplished by rotation of the TEM sample holder. First imaging experiments are presented on sections of Lowicryl embedded Human Umbilical Vein Endothelial Cells labeled for Caveolin both with Protein A-Gold, and Alexa Fluor®647. TEM and FM images were overlaid using fiducial markers visible in both imaging modalities with an overlay accuracy of 28 ± 11 nm. This is close to the optical resolution of ~50 nm.
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Affiliation(s)
- Sajjad Mohammadian
- Molecular Biophysics, Department of Physics, Faculty of Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, Netherlands
| | - Alexandra V Agronskaia
- Molecular Biophysics, Department of Physics, Faculty of Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, Netherlands
| | - Gerhard A Blab
- Molecular Biophysics, Department of Physics, Faculty of Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, Netherlands
| | - Elly G van Donselaar
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Cecilia de Heus
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Nalan Liv
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Judith Klumperman
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Hans C Gerritsen
- Molecular Biophysics, Department of Physics, Faculty of Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, Netherlands.
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Mohammadian S, Fokkema J, Agronskaia AV, Liv N, de Heus C, van Donselaar E, Blab GA, Klumperman J, Gerritsen HC. High accuracy, fiducial marker-based image registration of correlative microscopy images. Sci Rep 2019; 9:3211. [PMID: 30824844 PMCID: PMC6397213 DOI: 10.1038/s41598-019-40098-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 01/28/2019] [Indexed: 12/03/2022] Open
Abstract
Fluorescence microscopy (FM) and electron microscopy (EM) are complementary techniques. FM affords examination of large fields of view and identifying regions of interest but has a low resolution. EM exhibits excellent resolution over a limited field of view. The combination of these two techniques, correlative microscopy, received considerable interest in the past years and has proven its potential in biology and material science. Accurate correlation of FM and EM images is, however, challenging due to the differences in contrast mechanism, size of field of view and resolution. We report an accurate, fast and robust method to correlate FM and EM images using low densities of fiducial markers. Here, 120 nm diameter fiducial markers consisting of fluorescently labelled silica coated gold nanoparticles are used. The method relies on recording FM, low magnification EM and high magnification EM images. Two linear transformation matrices are constructed, FM to low magnification EM and low magnification EM to high magnification EM. Combination of these matrices results in a high accuracy transformation of FM to high magnification EM coordinates. The method was tested using two different transmission electron microscopes and different Tokuyasu and Lowicryl sections. The overall accuracy of the correlation method is high, 5-30 nm.
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Affiliation(s)
- Sajjad Mohammadian
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Jantina Fokkema
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Alexandra V Agronskaia
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cecilia de Heus
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Elly van Donselaar
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Gerhard A Blab
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Hans C Gerritsen
- Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands.
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Fokkema J, Fermie J, Liv N, van den Heuvel DJ, Konings TOM, Blab GA, Meijerink A, Klumperman J, Gerritsen HC. Fluorescently Labelled Silica Coated Gold Nanoparticles as Fiducial Markers for Correlative Light and Electron Microscopy. Sci Rep 2018; 8:13625. [PMID: 30206379 PMCID: PMC6133918 DOI: 10.1038/s41598-018-31836-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/22/2018] [Indexed: 11/09/2022] Open
Abstract
In this work, gold nanoparticles coated with a fluorescently labelled (rhodamine B) silica shell are presented as fiducial markers for correlative light and electron microscopy (CLEM). The synthesis of the particles is optimized to obtain homogeneous, spherical core-shell particles of arbitrary size. Next, particles labelled with different fluorophore densities are characterized to determine under which conditions bright and (photo)stable particles can be obtained. 2 and 3D CLEM examples are presented where optimized particles are used for correlation. In the 2D example, fiducials are added to a cryosection of cells whereas in the 3D example cells are imaged after endocytosis of the fiducials. Both examples demonstrate that the particles are clearly visible in both modalities and can be used for correlation. Additionally, the recognizable core-shell structure of the fiducials proves to be very powerful in electron microscopy: it makes it possible to irrefutably identify the particles and makes it easy to accurately determine the center of the fiducials.
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Affiliation(s)
- Jantina Fokkema
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Job Fermie
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Dave J van den Heuvel
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Tom O M Konings
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Gerhard A Blab
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Andries Meijerink
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Hans C Gerritsen
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands.
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van Hest JHA, Blab GA, Gerritsen HC, de Mello Donega C, Meijerink A. The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF 4 Nanocrystals. J Phys Chem C Nanomater Interfaces 2018; 122:3985-3993. [PMID: 29910843 PMCID: PMC5997401 DOI: 10.1021/acs.jpcc.7b11171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Revised: 01/25/2018] [Indexed: 06/08/2023]
Abstract
The localized inner 4f shell transitions of lanthanide ions are largely independent of the local surroundings. The luminescence properties of Ln3+ ions doped into nanocrystals (NCs) are therefore similar to those in bulk crystals. Quantum size effects, responsible for the unique size-dependent luminescence of semiconductor NCs, are generally assumed not to influence the optical properties of Ln3+-doped insulator NCs. However, phonon confinement effects have been reported to hamper relaxation between closely spaced Stark levels in Ln3+-doped NCs. At cryogenic temperatures emission and excitation from higher Stark levels was observed for Ln3+ ions in NCs only and were explained by a cutoff in the acoustic phonon spectrum. Relaxation would be inhibited as no resonant low energy (long wavelength) acoustic phonon modes can exist in nanometer sized crystals, and this prevents relaxation by direct phonon emission between closely spaced Stark levels. This phenomenon is known as a phonon bottleneck. Here, we investigate the role of phonon confinement in Ln-doped NCs. High resolution emission spectra at temperatures down to 2.2 K are reported for various Ln3+ ions (Er3+, Yb3+, Eu3+) doped into monodisperse 10 nm NaYF4 NCs and compared with spectra for bulk (microcrystalline) material. Contrary to previous reports, we find no evidence for phonon bottleneck effects in the emission spectra. Emission from closely spaced higher Stark levels is observed only at high excitation powers and is explained by laser heating. The present results indicate that previously reported effects in NCs may not be caused by phonon confinement.
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Affiliation(s)
- Jacobine
J. H. A. van Hest
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials
Science, and Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Gerhard A. Blab
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials
Science, and Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Hans C. Gerritsen
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials
Science, and Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Celso de Mello Donega
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials
Science, and Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Andries Meijerink
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials
Science, and Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
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7
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van Hest JHA, Blab GA, Gerritsen HC, de Mello Donega C, Meijerink A. Probing the Influence of Disorder on Lanthanide Luminescence Using Eu-Doped LaPO 4 Nanoparticles. J Phys Chem C Nanomater Interfaces 2017; 121:19373-19382. [PMID: 28919934 PMCID: PMC5592647 DOI: 10.1021/acs.jpcc.7b06549] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 08/11/2017] [Indexed: 05/13/2023]
Abstract
Lanthanide-doped nanocrystals (NCs) differ from their bulk counterparts due to their large surface to volume ratio. It is generally assumed that the optical properties are not affected by size effects as electronic transitions occur within the well-shielded 4f shell of the lanthanide dopant ions. However, defects and disorder in the surface layer can affect the luminescence properties. Trivalent europium is a suitable ion to investigate the subtle influence of the surface, because of its characteristic luminescence and high sensitivity to the local environment. Here, we investigate the influence of disorder in NCs on the optical properties of lanthanide dopants by studying the inhomogeneous linewidth, emission intensity ratios, and luminescence decay curves for LaPO4:Eu3+ samples of different sizes (4 nm to bulk) and core-shell configurations (core, core-isocrystalline shell, and core-silica shell). We show that the emission linewidths increase strongly for NCs. The ratio of the intensities of the forced electric dipole (ED) and magnetic dipole (MD) transitions, a measure for the local symmetry distortion around Eu3+ ions, is higher for samples with a large fraction of Eu3+ ions close to the surface. Finally, we present luminescence decay curves revealing an increased nonradiative decay rate for Eu3+ in NCs. The effects are strongest in core and core-silica shell NCs and can be reduced by growth of an isocrystalline LaPO4 shell. The present systematic study provides quantitative insight into the role of surface disorder on the optical properties of lanthanide-doped NCs. These insights are important in emerging applications of lanthanide-doped nanocrystals.
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Affiliation(s)
- Jacobine
J. H. A. van Hest
- Condensed Matter
and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
- Molecular
Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Gerhard A. Blab
- Molecular
Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Hans C. Gerritsen
- Molecular
Biophysics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Celso de Mello Donega
- Condensed Matter
and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Andries Meijerink
- Condensed Matter
and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
- E-mail: . Phone: +31 30 253 2202
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8
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van Hest JJHA, Blab GA, Gerritsen HC, Donega CDM, Meijerink A. Incorporation of Ln-Doped LaPO4 Nanocrystals as Luminescent Markers in Silica Nanoparticles. Nanoscale Res Lett 2016; 11:261. [PMID: 27209405 PMCID: PMC4875915 DOI: 10.1186/s11671-016-1465-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 05/04/2016] [Indexed: 05/15/2023]
Abstract
Lanthanide ions are promising for the labeling of silica nanoparticles with a specific luminescent fingerprint due to their sharp line emission at characteristic wavelengths. With the increasing use of silica nanoparticles in consumer products, it is important to label silica nanoparticles in order to trace the biodistribution, both in the environment and living organisms.In this work, we synthesized LaPO4 nanocrystals (NCs) with sizes ranging from 4 to 8 nm doped with europium or cerium and terbium. After silica growth using an inverse micelle method, monodisperse silica spheres were obtained with a single LaPO4 NC in the center. We demonstrate that the size of the silica spheres can be tuned in the 25-55 nm range by addition of small volumes of methanol during the silica growth reaction. Both the LaPO4 core and silica nanocrystal showed sharp line emission characteristic for europium and terbium providing unique optical labels in silica nanoparticles of variable sizes.
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Affiliation(s)
- Jacobine J H A van Hest
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
- Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
| | - Gerhard A Blab
- Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
| | - Hans C Gerritsen
- Molecular Biophysics, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
| | - Celso de Mello Donega
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
| | - Andries Meijerink
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands.
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van Dijk L, Paetzold UW, Blab GA, Schropp REI, di Vece M. 3D-printed external light trap for solar cells. Prog Photovolt 2016; 24:623-633. [PMID: 27667911 PMCID: PMC5020602 DOI: 10.1002/pip.2702] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 07/29/2015] [Accepted: 09/15/2015] [Indexed: 05/29/2023]
Abstract
We present a universally applicable 3D-printed external light trap for enhanced absorption in solar cells. The macroscopic external light trap is placed at the sun-facing surface of the solar cell and retro-reflects the light that would otherwise escape. The light trap consists of a reflective parabolic concentrator placed on top of a reflective cage. Upon placement of the light trap, an improvement of 15% of both the photocurrent and the power conversion efficiency in a thin-film nanocrystalline silicon (nc-Si:H) solar cell is measured. The trapped light traverses the solar cell several times within the reflective cage thereby increasing the total absorption in the cell. Consequently, the trap reduces optical losses and enhances the absorption over the entire spectrum. The components of the light trap are 3D printed and made of smoothened, silver-coated thermoplastic. In contrast to conventional light trapping methods, external light trapping leaves the material quality and the electrical properties of the solar cell unaffected. To explain the theoretical operation of the external light trap, we introduce a model that predicts the absorption enhancement in the solar cell by the external light trap. The corresponding calculated path length enhancement shows good agreement with the empirically derived value from the opto-electrical data of the solar cell. Moreover, we analyze the influence of the angle of incidence on the parasitic absorptance to obtain full understanding of the trap performance. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Lourens van Dijk
- Nanophotonics ‐ Physics of Devices, Debye Institute for Nanomaterials ScienceUtrecht University, High Tech Campus, Building 21AE Eindhoven5656The Netherlands
| | - Ulrich W. Paetzold
- Institut für Energie‐ und Klimaforschung 5 PhotovoltaikForschungszentrum Jülich GmbHJülich52425Germany
| | - Gerhard A. Blab
- Molecular Biophysics, Debye Institute for Nanomaterials ScienceUtrecht UniversityPrincetonplein 1CC Utrecht3584The Netherlands
| | - Ruud E. I. Schropp
- Department of Applied Physics, Plasma and Materials ProcessingEindhoven University of Technology (TU/e)MB Eindhoven5600The Netherlands
| | - Marcel di Vece
- Nanophotonics ‐ Physics of Devices, Debye Institute for Nanomaterials ScienceUtrecht University, High Tech Campus, Building 21AE Eindhoven5656The Netherlands
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Jose J, Blab GA, van Blaaderen A, Imhof A. Jammed elastic shells - a 3D experimental soft frictionless granular system. Soft Matter 2015; 11:1800-1813. [PMID: 25608643 DOI: 10.1039/c4sm02098g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a new experimental system of monodisperse, soft, frictionless, fluorescent labeled elastic shells for the characterization of structure, universal scaling laws and force networks in 3D jammed matter. The elastic shells in a jammed packing are deformed in such a way that at each contact one of the shells buckles with a dimple and the other remain spherical, closely resembling overlapping spheres. Using confocal microscopy, we obtained 3D stacks of images of shells at different volume fractions which were subsequently processed in ImageJ software to find their coordinates. The determination of 3D coordinates involved three steps: locating the edges of shells in all 2D slices, analyzing their shape and subsequently finding their 2D coordinates, and finally determining their 3D centers by grouping the corresponding 2D coordinates. From this analysis routine we obtained particle coordinates with sub-pixel accuracy. In a contact pair we also identified the shell that underwent buckling forming a dimple by analyzing the intensity profile of a line that connects the centers of particle pairs. The amorphous structure of the packing was analyzed as a function of distance to the jamming threshold by investigating the radial distribution function, bond order parameters, contact numbers and the number of dimples per particle (buckling number), which is a unique property of this system. We find that the power law scaling of the contact number with excess volume fraction deviated from theoretical and computer simulation predictions. In addition, the buckling number also showed a similar scaling as that of the contact number with distance to the jamming transition.
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Affiliation(s)
- Jissy Jose
- Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 1, 3584 CC, Utrecht, The Netherlands.
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Revalee JD, Blab GA, Wilson HD, Kahn JD, Meiners JC. Tethered particle motion reveals that LacI·DNA loops coexist with a competitor-resistant but apparently unlooped conformation. Biophys J 2014; 106:705-15. [PMID: 24507611 DOI: 10.1016/j.bpj.2013.12.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 11/26/2013] [Accepted: 12/12/2013] [Indexed: 10/25/2022] Open
Abstract
The lac repressor protein (LacI) efficiently represses transcription of the lac operon in Escherichia coli by binding to two distant operator sites on the bacterial DNA and causing the intervening DNA to form a loop. We employed single-molecule tethered particle motion to observe LacI-mediated loop formation and breakdown in DNA constructs that incorporate optimized operator binding sites and intrinsic curvature favorable to loop formation. Previous bulk competition assays indirectly measured the loop lifetimes in these optimized DNA constructs as being on the order of days; however, we measured these same lifetimes to be on the order of minutes for both looped and unlooped states. In a range of single-molecule DNA competition experiments, we found that the resistance of the LacI-DNA complex to competitive binding is a function of both the operator strength and the interoperator sequence. To explain these findings, we present what we believe to be a new kinetic model of loop formation and DNA competition. In this proposed new model, we hypothesize a new unlooped state in which the unbound DNA-binding domain of the LacI protein interacts nonspecifically with nonoperator DNA adjacent to the operator site at which the second LacI DNA-binding domain is bound.
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Affiliation(s)
- Joel D Revalee
- Department of Physics, University of Michigan, Ann Arbor, Michigan
| | - Gerhard A Blab
- Debye Institute, Molecular Biophysics, Utrecht University, Utrecht, The Netherlands
| | - Henry D Wilson
- LSA Biophysics, University of Michigan, Ann Arbor, Michigan
| | - Jason D Kahn
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland
| | - Jens-Christian Meiners
- Department of Physics, University of Michigan, Ann Arbor, Michigan; LSA Biophysics, University of Michigan, Ann Arbor, Michigan.
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12
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Fereidouni F, Blab GA, Gerritsen HC. Phasor based analysis of FRET images recorded using spectrally resolved lifetime imaging. Methods Appl Fluoresc 2014; 2:035001. [DOI: 10.1088/2050-6120/2/3/035001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Zuckermann MJ, Bromley EH, Angstmann CN, Blab GA, Forde NR, Linke H, Curmi PM. Introducing a Kinesin-Inspired Nanomotor Concept. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.4287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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14
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Knaus H, Blab GA, Gerritsen HC, Wösten HA. Nonlinear Spectral Imaging of Fungal Metabolism. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.1204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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15
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Abstract
A method, is presented for blind unmixing spectrally resolved fluorescence lifetime images. The method is based on the combined analysis of spectral and lifetime phasors and allows unmixing of up to three components without any prior knowledge. Fractional intensities, spectra and decay curves of the individual components can be extracted with this new technique. The reliability and sensitivity are investigated and the possibility of extending the method to unmix more components is discussed. The method is evaluated on mixtures of fluorescent dyes and labeled cells.
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Affiliation(s)
- Farzad Fereidouni
- Utrecht University, Debye Institute, Department of Molecular Biophysics, Utrecht 3584CC, The Netherlands
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16
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Balaz M, Nimen C, Graczyk M, Blab GA, Curmi PM, Davies R, Forde NR, Woolfson DN, Linke H. The Inchworm: Construction of a Biomolecular Motor with a Power Stroke. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.1126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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17
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Farré A, Shayegan M, López-Quesada C, Blab GA, Montes-Usategui M, Forde NR, Martín-Badosa E. Positional stability of holographic optical traps. Opt Express 2011; 19:21370-21384. [PMID: 22108987 DOI: 10.1364/oe.19.021370] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The potential of digital holography for complex manipulation of micron-sized particles with optical tweezers has been clearly demonstrated. By contrast, its use in quantitative experiments has been rather limited, partly due to fluctuations introduced by the spatial light modulator (SLM) that displays the kinoforms. This is an important issue when high temporal or spatial stability is a concern. We have investigated the performance of both an analog-addressed and a digitally-addressed SLM, measuring the phase fluctuations of the modulated beam and evaluating the resulting positional stability of a holographic trap. We show that, despite imparting a more unstable modulation to the wavefront, our digitally-addressed SLM generates optical traps in the sample plane stable enough for most applications. We further show that traps produced by the analog-addressed SLM exhibit a superior pointing stability, better than 1 nm, which is comparable to that of non-holographic tweezers. These results suggest a means to implement precision force measurement experiments with holographic optical tweezers (HOTs).
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Affiliation(s)
- Arnau Farré
- Optical Trapping Lab – Grup de Biofotònica, Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès, 1 08028 Barcelona, Spain
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18
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Samii L, Blab GA, Bromley EHC, Linke H, Curmi PMG, Zuckermann MJ, Forde NR. Time-dependent motor properties of multipedal molecular spiders. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 84:031111. [PMID: 22060332 DOI: 10.1103/physreve.84.031111] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 06/13/2011] [Indexed: 05/31/2023]
Abstract
Molecular spiders are synthetic biomolecular walkers that use the asymmetry resulting from cleavage of their tracks to bias the direction of their stepping motion. Using Monte Carlo simulations that implement the Gillespie algorithm, we investigate the dependence of the biased motion of molecular spiders, along with binding time and processivity, on tunable experimental parameters, such as number of legs, span between the legs, and unbinding rate of a leg from a substrate site. We find that an increase in the number of legs increases the spiders' processivity and binding time but not their mean velocity. However, we can increase the mean velocity of spiders with simultaneous tuning of the span and the unbinding rate of a spider leg from a substrate site. To study the efficiency of molecular spiders, we introduce a time-dependent expression for the thermodynamic efficiency of a molecular motor, allowing us to account for the behavior of spider populations as a function of time. Based on this definition, we find that spiders exhibit transient motor function over time scales of many hours and have a maximum efficiency on the order of 1%, weak compared to other types of molecular motors.
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Affiliation(s)
- Laleh Samii
- Department of Physics, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
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19
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Farré A, van der Horst A, Blab GA, Downing BPB, Forde NR. Stretching single DNA molecules to demonstrate high-force capabilities of holographic optical tweezers. J Biophotonics 2010; 3:224-233. [PMID: 20151444 DOI: 10.1002/jbio.200900107] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The well calibrated force-extension behaviour of single double-stranded DNA molecules was used as a standard to investigate the performance of phase-only holographic optical tweezers at high forces. Specifically, the characteristic overstretch transition at 65 pN was found to appear where expected, demonstrating (1) that holographic optical trap calibration using thermal fluctuation methods is valid to high forces; (2) that the holographic optical traps are harmonic out to >250 nm of 2.1 mum particle displacement; and (3) that temporal modulations in traps induced by the spatial light modulator (SLM) do not affect the ability of optical traps to hold and steer particles against high forces. These studies demonstrate a new high-force capability for holographic optical traps achievable by SLM technologies.
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Affiliation(s)
- Arnau Farré
- Department of Physics, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada
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21
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Lopez BJ, Balaz M, Blab GA, Linke H. Parallel Single-Molecule Study of DNA Repressor Kinetics. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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22
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Samii L, Zuckermann MJ, Blab GA, Linke H, Forde NR. Biased Motion and Molecular Motor Properties of Molecular Spiders. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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23
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Chen YF, Blab GA, Meiners JC. Stretching submicron biomolecules with constant-force axial optical tweezers. Biophys J 2009; 96:4701-8. [PMID: 19486692 DOI: 10.1016/j.bpj.2009.03.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 12/04/2008] [Accepted: 03/06/2009] [Indexed: 11/27/2022] Open
Abstract
Optical tweezers have become powerful tools to manipulate biomolecular systems, but are increasingly difficult to use when the size of the molecules is <1 microm. Many important biological structures and processes, however, occur on the submicron length scale. Therefore, we developed and characterized an optical manipulation protocol that makes this length scale accessible by stretching the molecule in the axial direction of the laser beam, thus avoiding limiting artifacts from steric hindrances from the microscope coverslip and other surface effects. The molecule is held under constant mechanical tension by a combination of optical gradient forces and backscattering forces, eliminating the need for electronic feedback. We demonstrate the utility of this method through a measurement of the force-extension relationship of a 1298 bp ds-DNA molecule.
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Affiliation(s)
- Yih-Fan Chen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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24
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Bromley EHC, Kuwada NJ, Zuckermann MJ, Donadini R, Samii L, Blab GA, Gemmen GJ, Lopez BJ, Curmi PMG, Forde NR, Woolfson DN, Linke H. The Tumbleweed: towards a synthetic proteinmotor. HFSP J 2009; 3:204-12. [PMID: 19639042 DOI: 10.2976/1.3111282] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Accepted: 03/12/2009] [Indexed: 11/19/2022]
Abstract
Biomolecular motors have inspired the design and construction of artificial nanoscale motors and machines based on nucleic acids, small molecules, and inorganic nanostructures. However, the high degree of sophistication and efficiency of biomolecular motors, as well as their specific biological function, derives from the complexity afforded by protein building blocks. Here, we discuss a novel bottom-up approach to understanding biological motors by considering the construction of synthetic protein motors. Specifically, we present a design for a synthetic protein motor that moves along a linear track, dubbed the "Tumbleweed." This concept uses three discrete ligand-dependent DNA-binding domains to perform cyclically ligand-gated, rectified diffusion along a synthesized DNA molecule. Here we describe how de novo peptide design and molecular biology could be used to produce the Tumbleweed, and we explore the fundamental motor operation of such a design using numerical simulations. The construction of this and more sophisticated protein motors is an exciting challenge that is likely to enhance our understanding of the structure-function relationship in biological motors.
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25
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Lasne D, Blab GA, De Giorgi F, Ichas F, Lounis B, Cognet L. Label-free optical imaging of mitochondria in live cells. Opt Express 2007; 15:14184-93. [PMID: 19550692 DOI: 10.1364/oe.15.014184] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The far-field optical imaging of mitochondria of live cells without the use of any label is demonstrated. It uses a highly sensitive photothermal method and has a resolution comparable to confocal fluorescence setups. The morphological states of mitochondria were followed under different physiological treatments, and the role of cytochrome c was ruled out as the main origin of the photothermal signals. This label free optical method provides a high contrast imaging of live mitochondria and should find many applications in biosciences.
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26
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Lasne D, Blab GA, Berciaud S, Heine M, Groc L, Choquet D, Cognet L, Lounis B. Single nanoparticle photothermal tracking (SNaPT) of 5-nm gold beads in live cells. Biophys J 2006; 91:4598-604. [PMID: 16997874 PMCID: PMC1779909 DOI: 10.1529/biophysj.106.089771] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tracking individual nano-objects in live cells during arbitrary long times is a ubiquitous need in modern biology. We present here a method for tracking individual 5-nm gold nanoparticles on live cells. It relies on the photothermal effect and the detection of the Laser Induced Scattering around a NanoAbsorber (LISNA). The key point for recording trajectories at video rate is the use of a triangulation procedure. The effectiveness of the method is tested against single fluorescent molecule tracking in live COS7 cells on subsecond timescales. We further demonstrate recordings for several minutes of AMPA receptors trajectories on the plasma membrane of live neurons. Single Nanoparticle Photothermal Tracking has the unique potential to record arbitrary long trajectory of membrane proteins using nonfluorescent nanometer-sized labels.
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Affiliation(s)
- David Lasne
- Centre de Physique Moléculaire Optique et Hertzienne, CNRS (UMR 5798) and Université Bordeaux 1, Talence Cedex, France
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27
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Blab GA, Cognet L, Berciaud S, Alexandre I, Husar D, Remacle J, Lounis B. Optical readout of gold nanoparticle-based DNA microarrays without silver enhancement. Biophys J 2005; 90:L13-5. [PMID: 16284272 PMCID: PMC1367045 DOI: 10.1529/biophysj.105.076182] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present a novel readout scheme for gold nanoparticle-based DNA microarrays relying on "Laser-Induced Scattering around a NanoAbsorber". It provides direct counting of individual nanoparticles present on each array spot and stable signals, without any silver enhancement. Given the detection of nanometer-sized particles, which minimize the steric hindrance, the linear dynamic range of the method is particularly large and well suited for microarray detection.
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28
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Berciaud S, Cognet L, Blab GA, Lounis B. Photothermal heterodyne imaging of individual nonfluorescent nanoclusters and nanocrystals. Phys Rev Lett 2004; 93:257402. [PMID: 15697940 DOI: 10.1103/physrevlett.93.257402] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Indexed: 05/22/2023]
Abstract
We introduce a new, highly sensitive, and simple heterodyne optical method for imaging individual nonfluorescent nanoclusters and nanocrystals. A 2 order of magnitude improvement of the signal is achieved compared to previous methods. This allows for the unprecedented detection of individual small absorptive objects such as metallic clusters (of 67 atoms) or nonluminescent semiconductor nanocrystals. The measured signals are in agreement with a calculation based on the scattering field theory from a photothermal-induced modulated index of refraction profile around the nanoparticle.
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Affiliation(s)
- Stéphane Berciaud
- Centre de Physique Moléculaire Optique et Hertzienne, CNRS (UMR 5798) et Université Bordeaux I, 351, cours de la Libération, 33405 Talence Cedex, France
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29
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Lommerse PHM, Blab GA, Cognet L, Harms GS, Snaar-Jagalska BE, Spaink HP, Schmidt T. Single-molecule imaging of the H-ras membrane-anchor reveals domains in the cytoplasmic leaflet of the cell membrane. Biophys J 2004; 86:609-16. [PMID: 14695305 PMCID: PMC1303830 DOI: 10.1016/s0006-3495(04)74139-9] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In the last decade evidence has accumulated that small domains of 50-700 nm in diameter are located in the exoplasmic leaflet of the plasma membrane. Most of these domains supposedly consist of specific sets of lipids and proteins, and are believed to coordinate signal transduction cascades. Whether similar domains are also present in the cytoplasmic leaflet of the plasma membrane is unclear so far. To investigate the presence of cytoplasmic leaflet domains, the H-Ras membrane-targeting sequence was fused to the C-terminus of the enhanced yellow fluorescent protein. Using single-molecule fluorescence microscopy, trajectories of individual molecules diffusing in the cytoplasmic leaflet of the plasma membrane were recorded. From these trajectories, the diffusion of individual membrane-anchored enhanced yellow fluorescent protein molecules was studied in live cells on timescales from 5 to 200 ms. The results show that the diffusion of 30-40% of the molecules is constrained in domains with a typical size of 200 nm. Neither breakdown of actin nor cholesterol extraction changed the domain characteristics significantly, indicating that the observed domains may not be related to the membrane domains identified so far.
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Affiliation(s)
- Piet H M Lommerse
- Department of Biophysics, Leiden University, Leiden, The Netherlands
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30
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Abstract
A method that combines fluorescence imaging and spectroscopy of single molecules at room temperature is presented. This approach allows us to identify a number of imaged molecules unequivocally by simultaneously recording their fluorescence emission spectra. Furthermore, their spectral characteristics not only allow us to separate different fluorescent labels quantitatively and qualitatively but also provide information on the microenvironment of the molecules. This new method was successfully tested on a system of yellow-green and red fluorescent 20-nm latex beads, and its usefulness in studies of biological systems was illustrated for a preparation of combined binary ratio labeling-fluorescence in situ hybridization-stained mouse chromosomes.
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Affiliation(s)
- Gerhard A Blab
- Department of Biophysics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
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31
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Abstract
We describe a simple and straightforward approach for homogeneous and isothermal detection of individual rolling circle replication (RCR) products, which represent individual padlock probe circularization events. The RCR products constitute tens of kilobases long single-stranded tandem repeated copies of the probe sequence, and in solution, they fold into micrometer-sized random coils. The method is based on the local enrichment of fluorescence-labeled probes that hybridize to the coiled RCR products compared to the concentration of free probes in solution. We present a detailed characterization of the fluorescence-labeled products using a highly sensitive and fast microscopy setup. At a 10(4)-fold excess of free label, we were able to detect and follow individual RCR products at a signal-to-background noise ratio of 27. This high signal-to-background noise ratio leaves room for analysis in a simple detection device at higher speeds or at lower labeling ratios.
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Affiliation(s)
- Gerhard A Blab
- Department of Biophysics, Huygens Laboratory, Leiden University, Leiden, The Netherlands
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33
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Harms GS, Cognet L, Lommerse PH, Blab GA, Kahr H, Gamsjäger R, Spaink HP, Soldatov NM, Romanin C, Schmidt T. Single-molecule imaging of l-type Ca(2+) channels in live cells. Biophys J 2001; 81:2639-46. [PMID: 11606277 PMCID: PMC1301731 DOI: 10.1016/s0006-3495(01)75907-3] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
L-type Ca(2+) channels are an important means by which a cell regulates the Ca(2+) influx into the cytosol on electrical stimulation. Their structure and dynamics in the plasma membrane, including their molecular mobility and aggregation, is of key interest for the in-depth understanding of their function. Construction of a fluorescent variant by fusion of the yellow-fluorescent protein to the ion channel and expression in a human cell line allowed us to address its dynamic embedding in the membrane at the level of individual channels in vivo. We report on the observation of individual fluorescence-labeled human cardiac L-type Ca(2+) channels using wide-field fluorescence microscopy in living cells. Our fluorescence and electrophysiological data indicate that L-type Ca(2+) channels tend to form larger aggregates which are mobile in the plasma membrane.
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Affiliation(s)
- G S Harms
- Department of Biophysics, Leiden University, 2333 CA Leiden, The Netherlands
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34
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Harms GS, Cognet L, Lommerse PH, Blab GA, Schmidt T. Autofluorescent proteins in single-molecule research: applications to live cell imaging microscopy. Biophys J 2001; 80:2396-408. [PMID: 11325739 PMCID: PMC1301428 DOI: 10.1016/s0006-3495(01)76209-1] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The spectral and photophysical characteristics of the autofluorescent proteins were analyzed and compared to flavinoids to test their applicability for single-molecule microscopy in live cells. We compare 1) the number of photons emitted by individual autofluorescent proteins in artificial and in vivo situations, 2) the saturation intensities of the various autofluorescent proteins, and 3) the maximal emitted photons from individual fluorophores in order to specify their use for repetitive imaging and dynamical analysis. It is found that under relevant conditions and for millisecond integration periods, the autofluorescent proteins have photon emission rates of approximately 3000 photons/ms (with the exception of DsRed), saturation intensities from 6 to 50 kW/cm2, and photobleaching yields from 10(-4) to 10(-5). Definition of a detection ratio led to the conclusion that the yellow-fluorescent protein mutant eYFP is superior compared to all the fluorescent proteins for single-molecule studies in vivo. This finding was subsequently used for demonstration of the applicability of eYFP in biophysical research. From tracking the lateral and rotational diffusion of eYFP in artificial material, and when bound to membranes of live cells, eYFP is found to dynamically track the entity to which it is anchored.
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Affiliation(s)
- G S Harms
- Department of Biophysics, Leiden University, Leiden, The Netherlands
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