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Hummert J, Tashev SA, Herten DP. An update on molecular counting in fluorescence microscopy. Int J Biochem Cell Biol 2021; 135:105978. [PMID: 33865985 DOI: 10.1016/j.biocel.2021.105978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/14/2021] [Accepted: 04/08/2021] [Indexed: 01/18/2023]
Abstract
Quantitative assessment of protein complexes, such as receptor clusters in the context of cellular signalling, has become a pressing objective in cell biology. The advancements in the field of single molecule fluorescence microscopy have led to different approaches for counting protein copy numbers in various cellular structures. This has resulted in an increasing interest in robust calibration protocols addressing photophysical properties of fluorescent labels and the effect of labelling efficiencies. Here, we want to give an update on recent methods for protein counting with a focus on novel calibration protocols. In this context, we discuss different types of calibration samples and identify some of the challenges arising in molecular counting experiments. Some recently published applications offer potential approaches to tackle these challenges.
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Affiliation(s)
- Johan Hummert
- College of Medical and Dental Sciences & School of Chemistry, University of Birmingham, Birmingham, UK; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, UK
| | - Stanimir Asenov Tashev
- College of Medical and Dental Sciences & School of Chemistry, University of Birmingham, Birmingham, UK; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, UK
| | - Dirk-Peter Herten
- College of Medical and Dental Sciences & School of Chemistry, University of Birmingham, Birmingham, UK; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, UK.
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Tenopala-Carmona F, Fronk S, Bazan GC, Samuel IDW, Penedo JC. Real-time observation of conformational switching in single conjugated polymer chains. SCIENCE ADVANCES 2018; 4:eaao5786. [PMID: 29487904 PMCID: PMC5817931 DOI: 10.1126/sciadv.aao5786] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 01/22/2018] [Indexed: 05/30/2023]
Abstract
Conjugated polymers (CPs) are an important class of organic semiconductors that combine novel optoelectronic properties with simple processing from organic solvents. It is important to study CP conformation in solution to understand the physics of these materials and because it affects the properties of solution-processed films. Single-molecule techniques are unique in their ability to extract information on a chain-to-chain basis; however, in the context of CPs, technical challenges have limited their general application to host matrices or semiliquid environments that constrain the conformational dynamics of the polymer. We introduce a conceptually different methodology that enables measurements in organic solvents using the single-end anchoring of polymer chains to avoid diffusion while preserving polymer flexibility. We explore the effect of organic solvents and show that, in addition to chain-to-chain conformational heterogeneity, collapsed and extended polymer segments can coexist within the same chain. The technique enables real-time solvent-exchange measurements, which show that anchored CP chains respond to sudden changes in solvent conditions on a subsecond time scale. Our results give an unprecedented glimpse into the mechanism of solvent-induced reorganization of CPs and can be expected to lead to a new range of techniques to investigate and conformationally manipulate CPs.
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Affiliation(s)
- Francisco Tenopala-Carmona
- Organic Semiconductor Centre, Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
| | - Stephanie Fronk
- Department of Materials and Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Guillermo C. Bazan
- Department of Materials and Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ifor D. W. Samuel
- Organic Semiconductor Centre, Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
| | - J. Carlos Penedo
- Organic Semiconductor Centre, Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
- Biomedical Sciences Research Complex, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
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Grußmayer KS, Herten DP. Time-resolved molecule counting by photon statistics across the visible spectrum. Phys Chem Chem Phys 2018; 19:8962-8969. [PMID: 28300271 DOI: 10.1039/c7cp00363c] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In the past few years quantification of fluorescently labeled (bio-) molecules has become of increasing importance and several approaches have been developed to address this task. Counting by photon statistics measures the distribution of multiple photon detection events that carry information about the number and brightness of independently emitting fluorophores. The method enables absolute and non-destructive quantification, with the quality of estimates critically depending on the ability to accurately measure said photon statistics. Here, we present a combination of simulations and experiments that relate fundamental properties of fluorophores, i.e. their molecular brightness and photostability, to important experimental conditions, i.e. excitation power and acquisition time. Thereby, experimental settings and analysis parameters can be quantitatively evaluated, making counting by photon statistics a robust method for absolute counting of the number of emitters in a diffraction limited observation volume. We show that the time-resolution of counting varies with the fluorophore brightness and can be as fast as 10-100 ms. At the same time, the range of suitable fluorophores can be easily assessed. We evaluated the brightness and photostability of 16 organic dyes across the visible spectrum, providing information crucial for a range of single-molecule spectroscopy applications. This opens up exciting possibilities to analyze absolute stoichiometries in dynamic multi-component complexes.
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Affiliation(s)
- K S Grußmayer
- Physikalisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.
| | - D-P Herten
- Physikalisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.
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Eder T, Stangl T, Gmelch M, Remmerssen K, Laux D, Höger S, Lupton JM, Vogelsang J. Switching between H- and J-type electronic coupling in single conjugated polymer aggregates. Nat Commun 2017; 8:1641. [PMID: 29158508 PMCID: PMC5696370 DOI: 10.1038/s41467-017-01773-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 10/13/2017] [Indexed: 11/21/2022] Open
Abstract
The aggregation of conjugated polymers and electronic coupling of chromophores play a central role in the fundamental understanding of light and charge generation processes. Here we report that the predominant coupling in isolated aggregates of conjugated polymers can be switched reversibly between H-type and J-type coupling by partially swelling and drying the aggregates. Aggregation is identified by shifts in photoluminescence energy, changes in vibronic peak ratio, and photoluminescence lifetime. This experiment unravels the internal electronic structure of the aggregate and highlights the importance of the drying process in the final spectroscopic properties. The electronic coupling after drying is tuned between H-type and J-type by changing the side chains of the conjugated polymer, but can also be entirely suppressed. The types of electronic coupling correlate with chain morphology, which is quantified by excitation polarization spectroscopy and the efficiency of interchromophoric energy transfer that is revealed by the degree of single-photon emission.
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Affiliation(s)
- Theresa Eder
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Thomas Stangl
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Max Gmelch
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Klaas Remmerssen
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Dirk Laux
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Sigurd Höger
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - John M Lupton
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Jan Vogelsang
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
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