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Lira RB, Dillingh LS, Schuringa JJ, Yahioglu G, Suhling K, Roos WH. Fluorescence lifetime imaging microscopy of flexible and rigid dyes probes the biophysical properties of synthetic and biological membranes. Biophys J 2024; 123:1592-1609. [PMID: 38702882 PMCID: PMC11214022 DOI: 10.1016/j.bpj.2024.04.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 03/22/2024] [Accepted: 04/30/2024] [Indexed: 05/06/2024] Open
Abstract
Sensing of the biophysical properties of membranes using molecular reporters has recently regained widespread attention. This was elicited by the development of new probes of exquisite optical properties and increased performance, combined with developments in fluorescence detection. Here, we report on fluorescence lifetime imaging of various rigid and flexible fluorescent dyes to probe the biophysical properties of synthetic and biological membranes at steady state as well as upon the action of external membrane-modifying agents. We tested the solvatochromic dyes Nile red and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (ammonium salt) (NBD), the viscosity sensor Bodipy C12, the flipper dye FliptR, as well as the dyes 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO), Bodipy C16, lissamine-rhodamine, and Atto647, which are dyes with no previous reported environmental sensitivity. The performance of the fluorescent probes, many of which are commercially available, was benchmarked with well-known environmental reporters, with Nile red and Bodipy C12 being specific reporters of medium hydration and viscosity, respectively. We show that some widely used ordinary dyes with no previous report of sensing capabilities can exhibit competing performance compared to highly sensitive commercially available or custom-based solvatochromic dyes, molecular rotors, or flipper in a wide range of biophysics experiments. Compared to other methods, fluorescence lifetime imaging is a minimally invasive and nondestructive method with optical resolution. It enables biophysical mapping at steady state or assessment of the changes induced by membrane-active molecules at subcellular level in both synthetic and biological membranes when intensity measurements fail to do so. The results have important consequences for the specific choice of the sensor and take into consideration factors such as probe sensitivity, response to environmental changes, ease and speed of data analysis, and the probe's intracellular distribution, as well as potential side effects induced by labeling and imaging.
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Affiliation(s)
- Rafael B Lira
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, the Netherlands.
| | - Laura S Dillingh
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, the Netherlands; Department of Hematology, Universitair Medisch Centrum Groningen & Rijksuniversiteit Groningen, Groningen, the Netherlands
| | - Jan-Jacob Schuringa
- Department of Hematology, Universitair Medisch Centrum Groningen & Rijksuniversiteit Groningen, Groningen, the Netherlands
| | | | - Klaus Suhling
- Department of Physics, King's College London, Strand, London, UK.
| | - Wouter H Roos
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, the Netherlands
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2
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Chung PH, Tregidgo C, Suhling K. Determining a fluorophore’s transition dipole moment from fluorescence lifetime measurements in solvents of varying refractive index. Methods Appl Fluoresc 2016; 4:045001. [DOI: 10.1088/2050-6120/4/4/045001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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3
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Wüstner D, Christensen T, Solanko LM, Sage D. Photobleaching kinetics and time-integrated emission of fluorescent probes in cellular membranes. Molecules 2014; 19:11096-130. [PMID: 25076144 PMCID: PMC6271172 DOI: 10.3390/molecules190811096] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 07/04/2014] [Accepted: 07/10/2014] [Indexed: 12/02/2022] Open
Abstract
Since the pioneering work of Hirschfeld, it is known that time-integrated emission (TiEm) of a fluorophore is independent of fluorescence quantum yield and illumination intensity. Practical implementation of this important result for determining exact probe distribution in living cells is often hampered by the presence of autofluorescence. Using kinetic modelling of photobleaching combined with pixel-wise bleach rate fitting of decay models with an updated plugin to the ImageJ program, it is shown that the TiEm of a fluorophore in living cells can be determined exactly from the product of bleaching amplitude and time constant. This applies to mono-exponential bleaching from the first excited singlet and/or triplet state and to multi-exponential combinations of such processes. The TiEm can be used to correct for illumination shading and background autofluorescence without the need for fluorescent test layers or separate imaging of non-stained cells. We apply the method to simulated images and to images of cells, whose membranes were labelled with fluorescent sterols and sphingolipids. Our bleaching model can be extended to include a probability density function (PDF) of intrinsic bleach rate constants with a memory kernel. This approach results in a time-dependent bleach rate coefficient and is exemplified for fluorescent sterols in restricted intracellular environments, like lipid droplets. We show that for small deviations from the classical exponential bleaching, the TiEm of decay functions with rate coefficients remains largely independent of fluorescence lifetime and illumination, and thereby represents a faithful measure of probe distribution.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Tanja Christensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Lukasz M Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Daniel Sage
- Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
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4
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Cebolla VL, Mateos E, Garriga R, Jarne C, Membrado L, Cossío FP, Gálvez EM, Matt M, Delgado-Camón A. Changes in Fluorescent Emission Due to Non-covalent Interactions as a General Detection Procedure for Thin-Layer Chromatography. Chemphyschem 2011; 13:291-9. [DOI: 10.1002/cphc.201100590] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Indexed: 11/11/2022]
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5
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Tregidgo C, Levitt JA, Suhling K. Effect of refractive index on the fluorescence lifetime of green fluorescent protein. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:031218. [PMID: 18601542 DOI: 10.1117/1.2937212] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The average fluorescence lifetime of the green fluorescent protein (GFP) in solution is a function of the refractive index of its environment. We report that this is also the case for GFP-tagged proteins in cells. Using time-correlated single-photon counting (TCSPC)-based fluorescence lifetime imaging (FLIM) with a confocal scanning microscope, images of GFP-tagged proteins in cells suspended in different refractive index media are obtained. It is found that the average fluorescence lifetime of GFP decreases on addition of glycerol or sucrose to the media in which the fixed cells are suspended. The inverse GFP lifetime is proportional to the refractive index squared. This is the case for GFP-tagged major histocompatibility complex (MHC) proteins with the GFP located inside the cytoplasm, and also for GPI-anchored GFP that is located outside the cell membrane. The implications of these findings are discussed with regard to total internal reflection fluorescence (TIRF) techniques where the change in refractive index is crucial in producing an evanescent wave to excite fluorophores near a glass interface. Our findings show that the GFP fluorescence lifetime is shortened in TIRF microscopy in comparison to confocal microscopy.
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Affiliation(s)
- Carolyn Tregidgo
- King's College London, Department of Physics, Strand, London, WC2R 2LS, United Kingdom
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6
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Nau WM, Hennig A, Koner AL. Squeezing Fluorescent Dyes into Nanoscale Containers—The Supramolecular Approach to Radiative Decay Engineering. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/4243_2007_007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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7
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Benninger RKP, Önfelt B, Neil MAA, Davis DM, French PMW. Fluorescence imaging of two-photon linear dichroism: cholesterol depletion disrupts molecular orientation in cell membranes. Biophys J 2004; 88:609-22. [PMID: 15520272 PMCID: PMC1305038 DOI: 10.1529/biophysj.104.050096] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The plasma membrane of cells is an ordered environment, giving rise to anisotropic orientation and restricted motion of molecules and proteins residing in the membrane. At the same time as being an organized matrix of defined structure, the cell membrane is heterogeneous and dynamic. Here we present a method where we use fluorescence imaging of linear dichroism to measure the orientation of molecules relative to the cell membrane. By detecting linear dichroism as well as fluorescence anisotropy, the orientation parameters are separated from dynamic properties such as rotational diffusion and homo energy transfer (energy migration). The sensitivity of the technique is enhanced by using two-photon excitation for higher photo-selection compared to single photon excitation. We show here that we can accurately image lipid organization in whole cell membranes and in delicate structures such as membrane nanotubes connecting two cells. The speed of our wide-field imaging system makes it possible to image changes in orientation and anisotropy occurring on a subsecond timescale. This is demonstrated by time-lapse studies showing that cholesterol depletion rapidly disrupts the orientation of a fluorophore located within the hydrophobic region of the cell membrane but not of a surface bound probe. This is consistent with cholesterol having an important role in stabilizing and ordering the lipid tails within the plasma membrane.
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Affiliation(s)
- Richard K. P. Benninger
- Department of Physics and Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Björn Önfelt
- Department of Physics and Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Mark A. A. Neil
- Department of Physics and Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Daniel M. Davis
- Department of Physics and Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Paul M. W. French
- Department of Physics and Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
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Suhling K, Siegel J, Phillips D, French PMW, Lévêque-Fort S, Webb SED, Davis DM. Imaging the environment of green fluorescent protein. Biophys J 2002; 83:3589-95. [PMID: 12496126 PMCID: PMC1302434 DOI: 10.1016/s0006-3495(02)75359-9] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
An emerging theme in cell biology is that cell surface receptors need to be considered as part of supramolecular complexes of proteins and lipids facilitating specific receptor conformations and distinct distributions, e.g., at the immunological synapse. Thus, a new goal is to develop bioimaging that not only locates proteins in live cells but can also probe their environment. Such a technique is demonstrated here using fluorescence lifetime imaging of green fluorescent protein (GFP). We first show, by time-correlated single-photon counting, that the fluorescence decay of GFP depends on the local refractive index. This is in agreement with the Strickler Berg formula, relating the Einstein A and B coefficients for absorption and spontaneous emission in molecules. We then quantitatively image, by wide-field time-gated fluorescence lifetime imaging, the refractive index of the environment of GFP. This novel approach paves the way for imaging the biophysical environment of specific GFP-tagged proteins in live cells.
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Affiliation(s)
- Klaus Suhling
- Department of Biological Sciences, Sir Alexander Fleming Building, Imperial College of Science, Technology and Medicine, London SW7 1AZ, United Kingdom
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9
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Toptygin D, Savtchenko RS, Meadow ND, Roseman S, Brand L. Effect of the Solvent Refractive Index on the Excited-State Lifetime of a Single Tryptophan Residue in a Protein. J Phys Chem B 2002. [DOI: 10.1021/jp0133889] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dmitri Toptygin
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Regina S. Savtchenko
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Norman D. Meadow
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Saul Roseman
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Ludwig Brand
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
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10
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Davenport L, Shen B, Joseph TW, Straher MP. A novel fluorescent coronenyl-phospholipid analogue for investigations of submicrosecond lipid fluctuations. Chem Phys Lipids 2001; 109:145-56. [PMID: 11269934 DOI: 10.1016/s0009-3084(00)00214-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A fluorescent phospholipid derivative, the 2'-(4-coronenylbutyric) ester of lyso-egg phosphatidylcholine, has been synthesized for use in studies of submicrosecond lipid dynamics. Synthesis of the phospholipid derivative involves Friedel-Crafts acylation of free coronene, followed by a Huang-Minlon reduction to yield the fatty-acyl derivative, 4-coronenylbutyric acid. Esterification of the carboxylic acid with lyso-phosphatidylcholine is achieved through a mixed anhydride intermediate. The resultant coronenyl-phospholipid adduct (Cor-PC) has been incorporated into sonicated unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) for dynamic lipid studies. Fluorescence quenching studies using potassium iodide, together with steady-state emission anisotropy (EA) measurements, confirm that the coronene moiety of the phospholipid adduct resides towards the head group interfacial region of the lipid bilayer. Unique properties of this new fluorescent phospholipid adduct are its long mean fluorescence lifetime (tau av approximately 112 ns at 14 degrees C), the planar symmetry of the fluorophore and its defined bilayer location. As a consequence, depolarizing motions of the coronene moiety target submicrosecond 'gel-fluid' lipid dynamics arising from a relatively narrow bilayer distribution. Our data suggest that the sensitivity of this new long-lived fluorescent phospholipid analogue to localized transverse submicrosecond lipid dynamics can provide important biological insights into varied processes including lipid-peptide interactions, bilayer fluidity gradients and passive ion transport.
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Affiliation(s)
- L Davenport
- Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn, 2900 Bedford Avenue, New York, NY 11210, USA.
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11
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Krishna MM, Periasamy N. Location and orientation of DODCI in lipid bilayer membranes: effects of lipid chain length and unsaturation. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1461:58-68. [PMID: 10556488 DOI: 10.1016/s0005-2736(99)00149-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The location and orientation of a linear dye molecule, DODCI, in lipid bilayer membrane were determined by the effect of viscosity and refractive index of the aqueous medium on the fluorescence properties of the dye bound to the membrane. The membrane-bound dye is solubilized in two sites, one near the surface (short fluorescence lifetime) and another in the interior of the membrane (long lifetime). The ratio of the dye in the two locations and the orientation of the dye (parallel or perpendicular to the membrane) are sensitive to the lipid chain length and unsaturation in the alkyl chain. The fraction of the dye in the interior region is higher for short alkyl chains (C12>C14>C16>>C18C20) and in unsaturated lipids (C14:1>C14:0, C16:1>C16:0). These experimental results are consistent with the general principle that the penetration of an amphiphilic organic molecule in the interior region of the membrane is more when the structure of th bilayer is more fluid-like.
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Affiliation(s)
- M M Krishna
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India
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12
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13
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Fluorescence of organic dyes in lipid membranes: Site of solubilization and effects of viscosity and refractive index on lifetimes. J Fluoresc 1998. [DOI: 10.1007/bf02758241] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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14
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Mitchell DC, Litman BJ. Molecular order and dynamics in bilayers consisting of highly polyunsaturated phospholipids. Biophys J 1998; 74:879-91. [PMID: 9533699 PMCID: PMC1302567 DOI: 10.1016/s0006-3495(98)74011-1] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The time-resolved fluorescence emission and decay of fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to characterize equilibrium and dynamic bilayer structural properties of symmetrically substituted phosphatidylcholines (PCs) with acyl chains containing no, one, four, or six double bonds and mixed-chain phosphatidylcholines with a saturated sn-1 chain and one, four, or six double bonds in the sn-2 chain. Both the Brownian rotational diffusion (BRD) model and the wobble-in-cone model were fit to all differential polarization data, and the descriptions of the data provided by the BRD model were found to be statistically superior. Global analysis of differential polarization data revealed two statistically equivalent solutions. The solution corresponding to a bimodal orientational distribution function, f(theta), was selected based on the effects of temperature on f(theta) and previous measurements on fixed, oriented bilayers. The overall equilibrium acyl chain order in these bilayers was analyzed by comparing the orientational probability distribution for DPH, f(theta) sin theta, with a random orientational distribution. Orientational order decreased and probe dynamics increased in mixed-chain species as the unsaturation of the sn-2 chain was increased. The degree of orientational order dropped dramatically in the dipolyunsaturated species compared with the mixed-chain phosphatidylcholines, which contained a polyunsaturated sn-2 chain. In terms of both orientational order and probe dynamics, the differences between the highly polyunsaturated species and the monounsaturated species were much greater than the differences between the monounsaturated species and a disaturated PC.
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Affiliation(s)
- D C Mitchell
- Section of Fluorescence Studies, Laboratory of Membrane Biophysics and Biochemistry, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA.
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15
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Krishna MM, Periasamy N. Spectrally constrained global analysis of fluorescence decays in biomembrane systems. Anal Biochem 1997; 253:1-7. [PMID: 9356133 DOI: 10.1006/abio.1997.2339] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Dynamic and steady-state fluorescence spectroscopic properties of a dye probe measured in a multicomponent biological system are often required to be separated into the spectra and lifetimes of individual spectroscopically distinct species. The conventional method of obtaining decay-associated spectra fails when the lifetimes of the fluorophore in the membrane phase and in the aqueous phase are very close to each other. This paper describes a global analysis method which takes advantage of the known spectrum and lifetime of the dye in the aqueous phase. This method is used to identify the spectra for two fluorescent species (lifetimes, 0.84 and 1.97 ns) of the dye DODCI in EggPC vesicle membranes by keeping the spectrum and lifetime (0.68 ns) of the dye in the aqueous phase as fixed parameters. The structural identity of the two membrane-bound dye species was established by the effect of refractive index and/or viscosity of the aqueous medium on the lifetimes.
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Affiliation(s)
- M M Krishna
- Chemical Physics Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai, Colaba, 400 005, India
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16
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Affiliation(s)
- L Davenport
- Department of Chemistry, Brooklyn College, City University of New York 11210, USA
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17
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Ladokhin AS, Holloway PW. Fluorescence of membrane-bound tryptophan octyl ester: a model for studying intrinsic fluorescence of protein-membrane interactions. Biophys J 1995; 69:506-17. [PMID: 8527665 PMCID: PMC1236276 DOI: 10.1016/s0006-3495(95)79924-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The fluorescence of a membrane-bound tryptophan derivative (tryptophan octyl ester, TOE) has been examined as a model for tryptophan fluorescence from proteins in membrane environments. The depth-dependent fluorescence quenching of TOE by brominated lipids was found to proceed via a dynamic mechanism with vertical fluctuations playing a central role in the process. The activation energy for the quenching was estimated to be 1.3 kcal/mole. The data were analyzed using the distribution analysis (DA) method, which extends the conventional parallax method to account more realistically for the transbilayer distributions of both probe and quencher and for possible variations in the probe's accessibility. DA provides a better fit than the parallax method to data collected with TOE in membranes formed of lipids brominated at either the 4,5, the 6,7, the 9,10, or the 11,12 positions of the sn-2 acyl chain. DA yields information on the fluorophore's most probable depth in the membrane, its conformational heterogeneity, and its accessibility to the lipid phase. Previously reported data on cytochrome b5 and melittin were reanalyzed together with data obtained with TOE. This new analysis demonstrates conformational heterogeneity in melittin and provides estimates of the freedom of motion and exposure to the lipid phase of membrane-embedded tryptophans of cytochrome b5.
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Affiliation(s)
- A S Ladokhin
- Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kiev
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18
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Toptygin D, Brand L. Determination of DPH order parameters in unoriented vesicles. J Fluoresc 1995; 5:39-50. [DOI: 10.1007/bf00718781] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/1994] [Accepted: 09/27/1994] [Indexed: 10/26/2022]
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Temperature effects on the solubilization behavior of some 3H-indoles in water and microheterogeneous media. J Photochem Photobiol A Chem 1995. [DOI: 10.1016/1010-6030(94)03939-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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