1
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Bagheri N, Chen H, Rabasovic M, Widengren J. Non-fluorescent transient states of tyrosine as a basis for label-free protein conformation and interaction studies. Sci Rep 2024; 14:6464. [PMID: 38499633 PMCID: PMC10948778 DOI: 10.1038/s41598-024-57054-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 03/13/2024] [Indexed: 03/20/2024] Open
Abstract
The amino acids tryptophan, tyrosine, and phenylalanine have been extensively used for different label-free protein studies, based on the intensity, lifetime, wavelength and/or polarization of their emitted fluorescence. Similar to most fluorescent organic molecules, these amino acids can undergo transitions into dark meta-stable states, such as triplet and photo-radical states. On the one hand, these transitions limit the fluorescence signal, but they are also highly environment-sensitive and can offer an additional set of parameters, reflecting interactions, folding states, and immediate environments around the proteins. In this work, by analyzing the average intensity of tyrosine emission under different excitation modulations with the transient state monitoring (TRAST) technique, we explored the photo physics of tyrosine as a basis for such environment-sensitive readouts. From how the dark state transitions of tyrosine varied with excitation intensity and solvent conditions we first established a photophysical model for tyrosine. Next, we studied Calmodulin (containing two tyrosines), and how its conformation is changed upon calcium binding. From these TRAST experiments, performed with 280 nm time-modulated excitation, we show that tyrosine dark state transitions clearly change with the calmodulin conformation, and may thus represent a useful source of information for (label-free) analyses of protein conformations and interactions.
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Affiliation(s)
- Niusha Bagheri
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), Albanova University Center, 106 91, Stockholm, Sweden
| | - Hongjian Chen
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), Albanova University Center, 106 91, Stockholm, Sweden
| | - Mihailo Rabasovic
- Laboratory for Biophysics, Institute of Physics Belgrade, Pregrevica 118, 11080, Zemun-Belgrade, Serbia
| | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), Albanova University Center, 106 91, Stockholm, Sweden.
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2
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Demirbay B, Baryshnikov G, Haraldsson M, Piguet J, Ågren H, Widengren J. Photo-physical characterization of high triplet yield brominated fluoresceins by transient state (TRAST) spectroscopy. Methods Appl Fluoresc 2023; 11:045011. [PMID: 37726005 DOI: 10.1088/2050-6120/acfb59] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 09/19/2023] [Indexed: 09/21/2023]
Abstract
Photo-induced dark transient states of fluorophores can pose a problem in fluorescence spectroscopy. However, their typically long lifetimes also make them highly environment sensitive, suggesting fluorophores with prominent dark-state formation yields to be used as microenvironmental sensors in bio-molecular spectroscopy and imaging. In this work, we analyzed the singlet-triplet transitions of fluorescein and three synthesized carboxy-fluorescein derivatives, with one, two or four bromines linked to the anthracence backbone. Using transient state (TRAST) spectroscopy, we found a prominent internal heavy atom (IHA) enhancement of the intersystem crossing (ISC) rates upon bromination, inferred by density functional theory calculations to take place via a higher triplet state, followed by relaxation to the lowest triplet state. A corresponding external heavy atom (EHA) enhancement was found upon adding potassium iodide (KI). Notably, increased KI concentrations still resulted in lowered triplet state buildup in the brominated fluorophores, due to relatively lower enhancements in ISC, than in the triplet decay. Together with an antioxidative effect on the fluorophores, adding KI thus generated a fluorescence enhancement of the brominated fluorophores. By TRAST measurements, analyzing the average fluorescence intensity of fluorescent molecules subject to a systematically varied excitation modulation, dark state transitions within very high triplet yield (>90%) fluorophores can be directly analyzed under biologically relevant conditions. These measurements, not possible by other techniques such as fluorescence correlation spectroscopy, opens for bio-sensing applications based on high triplet yield fluorophores, and for characterization of high triplet yield photodynamic therapy agents, and how they are influenced by IHA and EHA effects.
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Affiliation(s)
- Baris Demirbay
- Royal Institute of Technology (KTH), Experimental Biomolecular Physics, Department of Applied Physics, Albanova University Center, SE-106 91, Stockholm, Sweden
| | - Glib Baryshnikov
- Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-60174, Norrköping, Sweden
| | - Martin Haraldsson
- Chemical Biology Consortium Sweden, Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Joachim Piguet
- Royal Institute of Technology (KTH), Experimental Biomolecular Physics, Department of Applied Physics, Albanova University Center, SE-106 91, Stockholm, Sweden
| | - Hans Ågren
- Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden
| | - Jerker Widengren
- Royal Institute of Technology (KTH), Experimental Biomolecular Physics, Department of Applied Physics, Albanova University Center, SE-106 91, Stockholm, Sweden
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3
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Petty JT, Carnahan S, Kim D, Lewis D. Long-lived Ag 10 6+ luminescence and a split DNA scaffold. J Chem Phys 2021; 154:244302. [PMID: 34241360 DOI: 10.1063/5.0056214] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular silver clusters emit across the visible to near-infrared, and specific chromophores can be formed using DNA strands. We study C4AC4TC3G that selectively coordinates and encapsulates Ag10 6+, and this chromophore has two distinct electronic transitions. The green emission is strong and prompt with ϕ = 18% and τ = 1.25 ns, and the near-infrared luminescence is weaker, slower with τ = 50 µs, and is partly quenched by oxygen, suggesting phosphorescence. This lifetime can be modulated by the DNA host, and we consider two derivatives of C4AC4TC3G with similar sequences but distinct structures. In one variant, thymine was excised to create an abasic gap in an otherwise intact strand. In the other, the covalent phosphate linkage was removed to split the DNA scaffold into two fragments. In relation to the contiguous strands, the broken template speeds the luminescence decay by twofold, and this difference may be due to greater DNA flexibility. These modifications suggest that a DNA can be structurally tuned to modulate metastable electronic states in its silver cluster adducts.
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Affiliation(s)
- Jeffrey T Petty
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA
| | - Savannah Carnahan
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA
| | - Dahye Kim
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA
| | - David Lewis
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA
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4
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Tornmalm J, Piguet J, Chmyrov V, Widengren J. Imaging of intermittent lipid-receptor interactions reflects changes in live cell membranes upon agonist-receptor binding. Sci Rep 2019; 9:18133. [PMID: 31792325 PMCID: PMC6889430 DOI: 10.1038/s41598-019-54625-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 11/11/2019] [Indexed: 12/26/2022] Open
Abstract
Protein-lipid interactions in cellular membranes modulate central cellular functions, are often transient in character, but occur too intermittently to be readily observable. We introduce transient state imaging (TRAST), combining sensitive fluorescence detection of fluorophore markers with monitoring of their dark triplet state transitions, allowing imaging of such protein-lipid interactions. We first determined the dark state kinetics of the biomembrane fluorophore 7-nitrobenz-2-oxa-1,3-diazole-4-yl (NBD) in lipid vesicles, and how its triplet state is quenched by spin-labels in the same membranes. We then monitored collisional quenching of NBD-lipid derivatives by spin-labelled stearic acids in live cell plasma membranes, and of NBD-lipid derivatives by spin-labelled G-Protein Coupled Receptors (GPCRs). We could then resolve transient interactions between the GPCRs and different lipids, how these interactions changed upon GPCR activation, thereby demonstrating a widely applicable means to image and characterize transient molecular interactions in live cell membranes in general, not within reach via traditional fluorescence readouts.
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Affiliation(s)
- Johan Tornmalm
- Experimental Biomolecular Physics, KTH, 10691, Stockholm, Sweden
| | - Joachim Piguet
- Experimental Biomolecular Physics, KTH, 10691, Stockholm, Sweden.
| | | | - Jerker Widengren
- Experimental Biomolecular Physics, KTH, 10691, Stockholm, Sweden.
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5
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Sankaran J, Karampatzakis A, Rice SA, Wohland T. Quantitative imaging and spectroscopic technologies for microbiology. FEMS Microbiol Lett 2019; 365:4953418. [PMID: 29718275 DOI: 10.1093/femsle/fny075] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 03/23/2018] [Indexed: 12/17/2022] Open
Abstract
Light microscopy has enabled the observation of the structure and organisation of biofilms. Typically, the contrast in an image obtained from light microscopy is given by the time-averaged intensity that is effective in visualising the overall structure. Technological advancements in light microscopy have led to the creation of techniques that not only provide a static intensity image of the biofilm, but also enable one to quantify various dynamic physicochemical properties of biomolecules in microbial biofilms. Such light microscopy-based techniques can be grouped into two main classes, those that are based on luminescence and those that are based on scattering. Here, we review the fundamentals and applications of luminescence and scattering-based techniques, specifically, fluorescence lifetime imaging, Förster resonance energy transfer, fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single-particle tracking, transient state imaging, and Brillouin and Raman microscopy. These techniques provide information about the abundance, interactions and mobility of various molecules in the biofilms and also properties of the local microenvironment at optical resolution. Further, one could use any of these techniques to probe the real-time changes in these physical parameters upon the addition of external agents or at different stages during the growth of biofilms.
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Affiliation(s)
- Jagadish Sankaran
- Departments of Biological Sciences and Chemistry, National University of Singapore, Singapore 117558, Singapore.,Centre for BioImaging Sciences, National University of Singapore, Singapore 117557, Singapore
| | - Andreas Karampatzakis
- Centre for BioImaging Sciences, National University of Singapore, Singapore 117557, Singapore.,NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
| | - Scott A Rice
- Singapore Centre for Environmental Life Sciences Engineering and School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.,ithree Institute, University of Technology, Sydney 2007, Australia
| | - Thorsten Wohland
- Departments of Biological Sciences and Chemistry, National University of Singapore, Singapore 117558, Singapore.,Centre for BioImaging Sciences, National University of Singapore, Singapore 117557, Singapore.,NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
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6
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Liang L, Jin YX, Zhu XQ, Zhou FL, Yang Y. Real-time detection and monitoring of the drug resistance of single myeloid leukemia cells by diffused total internal reflection. LAB ON A CHIP 2018; 18:1422-1429. [PMID: 29713720 DOI: 10.1039/c8lc00088c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Real-time detection and monitoring of the drug resistance of single cells have important significance in clinical diagnosis and therapy. Traditional methods operate a number of times for each individual concentration, and innovation is required for the design of more simple and efficient manipulation platforms with necessary higher sensitivity. Here, we have developed a novel diffused total internal reflection (TIR) method to perform drug metabolism and cytotoxicity analysis of trapped myeloid leukemia cells. Molm-13 cells, a type of acute myeloid leukemia cell, were chosen and injected into the device and fittingly captured by cell traps. Differing from previous studies, a series of different concentrations of azelaic acid (AZA) drug could be used from 0 mM to 50 mM through convection and diffusion processes in a single chip, with each concentration region featuring 50 cells, with a total of 549 cell trapping units. Thanks to the high sensitivity of the TIR method, only cells with the same drug concentration could be illuminated in the detection process. By adjusting the incident angle, we could exactly detect and monitor the drug resistance of the cells using different drug concentrations and the experimental resolution of the drug concentration was as small as 5 mM. Images of the membrane integrity and morphology of the cells in the bright field were measured and we also monitored the cell viabilities in the dark field over 2 hours. The effects of AZA on the Molm-13 cells were explored in different concentrations at the single cell level. Compared with the results of the traditional MTT assay method, the experimental results are more simple and accurate. A cell death of 5% at an AZA concentration of 5 mM was observed after 30 minutes, while a concentration of 40 mM corresponded to a 98% cell death. The designed method in this study provides a novel toolkit to control and monitor drug resistance at the single cell level more easily with higher sensitivity and we believe it has significant potential application in single cell quality assessment and medicine analysis in clinical practice.
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Affiliation(s)
- L Liang
- School of Physics & technology, Key Laboratory of Artificial Micro/Nano Structure of Ministry of Education, Wuhan University, Wuhan 430072, China.
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7
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Tornmalm J, Widengren J. Label-free monitoring of ambient oxygenation and redox conditions using the photodynamics of flavin compounds and transient state (TRAST) spectroscopy. Methods 2017; 140-141:178-187. [PMID: 29179988 DOI: 10.1016/j.ymeth.2017.11.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 11/21/2017] [Indexed: 10/18/2022] Open
Abstract
Transient state (TRAST) monitoring can determine population dynamics of long-lived, dark transient states of fluorescent molecules, detecting only the average fluorescence intensity from a sample, when subject to different excitation pulse trains. Like Fluorescence Correlation Spectroscopy (FCS), TRAST unites the detection sensitivity of fluorescence with the environmental sensitivity of long-lived non-fluorescent states, but does not rely on detection of stochastic fluorescence fluctuations from individual molecules. Relaxed requirements on noise suppression, detection quantum yield and time-resolution of the instrument, as well as on fluorescence brightness of the molecules studied, make TRAST broadly applicable, opening also for investigations based on less bright, auto-fluorescent molecules. In this work, we applied TRAST to study the transient state population dynamics within the auto-fluorescent coenzymes flavin adenine dinucleotide (FAD) and flavin-mononucleotide (FMN). From the experimental TRAST data, we defined state models, and determined rate parameters for triplet state and redox transitions within FMN and FAD, stacking and un-stacking rates of external redox active quenching agents and by the adenine moiety of FAD itself. TRAST experiments were found to be well capable to resolve these transitions in FMN and FAD, and to track how the transitions are influenced by ambient oxygenation and redox conditions. This work demonstrates that TRAST provides a useful tool to follow local oxygenation and redox conditions via FMN and FAD fluorescence, and forms the basis for measurements on flavo-proteins and of redox and metabolic conditions in more complex environments, such as in live cells.
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Affiliation(s)
- Johan Tornmalm
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), Albanova University Center, 106 91 Stockholm, Sweden.
| | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), Albanova University Center, 106 91 Stockholm, Sweden.
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8
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Karampatzakis A, Sankaran J, Kandaswamy K, Rice SA, Cohen Y, Wohland T. Measurement of oxygen concentrations in bacterial biofilms using transient state monitoring by single plane illumination microscopy. Biomed Phys Eng Express 2017. [DOI: 10.1088/2057-1976/aa6db7] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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9
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Hevekerl H, Tornmalm J, Widengren J. Fluorescence-based characterization of non-fluorescent transient states of tryptophan - prospects for protein conformation and interaction studies. Sci Rep 2016; 6:35052. [PMID: 27748381 PMCID: PMC5066179 DOI: 10.1038/srep35052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/15/2016] [Indexed: 02/02/2023] Open
Abstract
Tryptophan fluorescence is extensively used for label-free protein characterization. Here, we show that by analyzing how the average tryptophan fluorescence intensity varies with excitation modulation, kinetics of tryptophan dark transient states can be determined in a simple, robust and reliable manner. Thereby, highly environment-, protein conformation- and interaction-sensitive information can be recorded, inaccessible via traditional protein fluorescence readouts. For verification, tryptophan transient state kinetics were determined under different environmental conditions, and compared to literature data. Conformational changes in a spider silk protein were monitored via the triplet state kinetics of its tryptophan residues, reflecting their exposure to an air-saturated aqueous solution. Moreover, tryptophan fluorescence anti-bunching was discovered, reflecting local pH and buffer conditions, previously observed only by ultrasensitive measurements in highly fluorescent photo-acids. Taken together, the presented approach, broadly applicable under biologically relevant conditions, has the potential to become a standard biophysical approach for protein conformation, interaction and microenvironment studies.
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Affiliation(s)
- Heike Hevekerl
- Royal Institute of Technology (KTH), Dept Applied Physics, Experimental Biomolecular Physics, Albanova Univ Center, 106 91 Stockholm, Sweden
| | - Johan Tornmalm
- Royal Institute of Technology (KTH), Dept Applied Physics, Experimental Biomolecular Physics, Albanova Univ Center, 106 91 Stockholm, Sweden
| | - Jerker Widengren
- Royal Institute of Technology (KTH), Dept Applied Physics, Experimental Biomolecular Physics, Albanova Univ Center, 106 91 Stockholm, Sweden
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10
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Chmyrov V, Spielmann T, Hevekerl H, Widengren J. Trans–Cis Isomerization of Lipophilic Dyes Probing Membrane Microviscosity in Biological Membranes and in Live Cells. Anal Chem 2015; 87:5690-7. [DOI: 10.1021/acs.analchem.5b00863] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Volodymyr Chmyrov
- Experimental
Biomolecular
Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm 106 91, Sweden
| | - Thiemo Spielmann
- Experimental
Biomolecular
Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm 106 91, Sweden
| | - Heike Hevekerl
- Experimental
Biomolecular
Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm 106 91, Sweden
| | - Jerker Widengren
- Experimental
Biomolecular
Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm 106 91, Sweden
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11
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Mücksch J, Spielmann T, Sisamakis E, Widengren J. Transient state imaging of live cells using single plane illumination and arbitrary duty cycle excitation pulse trains. JOURNAL OF BIOPHOTONICS 2015; 8:392-400. [PMID: 24706633 DOI: 10.1002/jbio.201400015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 03/14/2014] [Accepted: 03/19/2014] [Indexed: 06/03/2023]
Abstract
We demonstrate the applicability of Single Plane Illumination Microscopy to Transient State Imaging (TRAST), offering sensitive microenvironmental information together with optical sectioning and reduced overall excitation light exposure of the specimen. The concept is verified by showing that transition rates can be determined accurately for free dye in solution and that fluorophore transition rates can be resolved pixel-wise in live cells. Furthermore, we derive a new theoretical framework for analyzing TRAST data acquired with arbitrary duty cycle pulse trains. By this analysis it is possible to reduce the overall measurement time and thereby enhance the frame rates in TRAST imaging.
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Affiliation(s)
- Jonas Mücksch
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Albanova University Center, 106 91, Stockholm, Sweden
| | - Thiemo Spielmann
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Albanova University Center, 106 91, Stockholm, Sweden
| | - Evangelos Sisamakis
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Albanova University Center, 106 91, Stockholm, Sweden
| | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Albanova University Center, 106 91, Stockholm, Sweden.
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12
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Hevekerl H, Widengren J. Determination of molecular stoichiometry without reference samples by analyzing fluorescence blinking with and without excitation synchronization. Methods Appl Fluoresc 2015; 3:025001. [PMID: 29148486 DOI: 10.1088/2050-6120/3/2/025001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Stoichiometry of molecular complexes plays a crucial role in biology. Moreover, for quantitative fluorescence studies, it is often useful to know the number of fluorophores labeled onto the molecules studied. In this work, we propose an approach to determine the number of independent fluorescence emitters on fluorescent molecules based on fluorescence blinking caused by photo-induced triplet state formation, photo-isomerization or charge transfer. The fluorescence blinking is measured under two different excitation regimes, on the same setup, and in one and the same sample. By comparing the fluorescence fluctuations under continuous excitation using Fluorescence Correlation Spectroscopy (FCS), when all the fluorophores are blinking independently of each other, with those occurring under square-pulsed excitation using Transient State (TRAST) spectroscopy, when all fluorophores are blinking in a synchronized manner, the number of fluorophores per molecule can be determined. No calibration sample is needed and the approach is independent of experimental conditions and of the specific environment of the molecules under study.The approach was experimentally validated by labeling double stranded DNA (dsDNA) with different concentrations of the intercalating dye YOYO-1 Iodide. The sample was then measured consecutively by TRAST and FCS and the number of fluorophores per molecule was calculated. The determined numbers were found to agree well with the number of fluorophores per dsDNA, as determined from FCS measurements using additional calibration samples.
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Affiliation(s)
- Heike Hevekerl
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
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13
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Spielmann T, Xu L, Gad AKB, Johansson S, Widengren J. Transient state microscopy probes patterns of altered oxygen consumption in cancer cells. FEBS J 2014; 281:1317-1332. [PMID: 24418170 DOI: 10.1111/febs.12709] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 12/06/2013] [Accepted: 01/01/2014] [Indexed: 11/30/2022]
Abstract
Altered cellular metabolism plays an important role in many diseases, not least in many forms of cancer, where cellular metabolic pathways requiring lower oxygen consumption are often favored (the so-called Warburg effect). In this work, we have applied fluorescence-based transient state imaging and have exploited the environment sensitivity of long-lived dark states of fluorophores, in particular triplet state decay rates, to image the oxygen consumption of living cells. Our measurements can resolve differences in oxygen concentrations between different regions of individual cells, between different cell types, and also based on what metabolic pathways the cells use. In MCF-7 breast cancer cells, higher oxygen consumption can be detected when they rely on glutamine instead of glucose as their main metabolite, predominantly undergoing oxidative phosphorylation rather than glycolysis. By use of the high triplet yield dye Eosin Y the irradiance requirements during the measurements can be kept low. This reduces the instrumentation requirements, and harmful biological effects from high excitation doses can be avoided. Taken together, our imaging approach is widely applicable and capable of detecting subtle changes in oxygen consumption in live cells, stemming from the Warburg effect or reflecting other differences in the cellular metabolism. This may lead to new diagnostic means as well as advance our understanding of the interplay between cellular metabolism and major disease categories, such as cancer.
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Affiliation(s)
- Thiemo Spielmann
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
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14
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Functional Imaging of Cerebral Oxygenation with Intrinsic Optical Contrast and Phosphorescent Probes. NEUROMETHODS 2014. [DOI: 10.1007/978-1-62703-785-3_14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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15
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Bag N, Wohland T. Imaging fluorescence fluctuation spectroscopy: new tools for quantitative bioimaging. Annu Rev Phys Chem 2013; 65:225-48. [PMID: 24328446 DOI: 10.1146/annurev-physchem-040513-103641] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fluorescence fluctuation spectroscopy (FFS) techniques provide information at the single-molecule level with excellent time resolution. Usually applied at a single spot in a sample, they have been recently extended into imaging formats, referred to as imaging FFS. They provide spatial information at the optical diffraction limit and temporal information in the microsecond to millisecond range. This review provides an overview of the different modalities in which imaging FFS techniques have been implemented and discusses present imaging FFS capabilities and limitations. A combination of imaging FFS and nanoscopy would allow one to record information with the detailed spatial information of nanoscopy, which is ∼20 nm and limited only by fluorophore size and labeling density, and the time resolution of imaging FFS, limited by the fluorescence lifetime. This combination would provide new insights into biological events by providing spatiotemporal resolution at unprecedented levels.
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Affiliation(s)
- Nirmalya Bag
- Departments of Biological Sciences and Chemistry, and NUS Center for Bio-Imaging Sciences (CBIS), National University of Singapore, 117557 Singapore; ,
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16
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Hevekerl H, Spielmann T, Chmyrov A, Widengren J. Förster Resonance Energy Transfer beyond 10 nm: Exploiting the Triplet State Kinetics of Organic Fluorophores. J Phys Chem B 2011; 115:13360-70. [DOI: 10.1021/jp206770s] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Heike Hevekerl
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Thiemo Spielmann
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Andriy Chmyrov
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
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17
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Chmyrov A, Sandén T, Widengren J. Recovery of Photoinduced Reversible Dark States Utilized for Molecular Diffusion Measurements. Anal Chem 2010; 82:9998-10005. [DOI: 10.1021/ac1014047] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andriy Chmyrov
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Tor Sandén
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, SE-10691 Stockholm, Sweden
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18
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Widengren J. Fluorescence-based transient state monitoring for biomolecular spectroscopy and imaging. J R Soc Interface 2010; 7:1135-44. [PMID: 20375039 PMCID: PMC2894879 DOI: 10.1098/rsif.2010.0146] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 03/15/2010] [Indexed: 11/12/2022] Open
Abstract
To increase read-out speed, sensitivity or specificity, an often applied strategy in fluorescence-based biomolecular spectroscopy and imaging is to simultaneously record two or more of the fluorescence parameters: intensity, lifetime, polarization or wavelength. This review highlights how additional, to-date largely unexploited, information can be extracted by monitoring long-lived, photo-induced transient states of organic dyes and their dynamics. Two major approaches are presented, where the transient state information is obtained either from fluorescence fluctuation analysis or by recording the time-averaged fluorescence response to a time-modulated excitation. The two approaches combine the detection sensitivity of the fluorescence signal with the environmental sensitivity of the long-lived transient states. For both techniques, proof-of-principle experiments are reviewed, and advantages, limitations and possible applications for biomolecular cellular biology studies are discussed.
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Affiliation(s)
- Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), Albanova University Center, Stockholm 106 91, Sweden.
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