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Gunther G, Malacrida L, Jameson DM, Gratton E, Sánchez SA. LAURDAN since Weber: The Quest for Visualizing Membrane Heterogeneity. Acc Chem Res 2021; 54:976-987. [PMID: 33513300 PMCID: PMC8552415 DOI: 10.1021/acs.accounts.0c00687] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Any chemist studying the interaction of molecules with lipid assemblies will eventually be confronted by the topic of membrane bilayer heterogeneity and may ultimately encounter the heterogeneity of natural membranes. In artificial bilayers, heterogeneity is defined by phase segregation that can be in the nano- and micrometer range. In biological bilayers, heterogeneity is considered in the context of small (10-200 nm) sterol and sphingolipid-enriched heterogeneous and highly dynamic domains. Several techniques can be used to assess membrane heterogeneity in living systems. Our approach is to use a fluorescent reporter molecule immersed in the bilayer, which, by changes in its spectroscopic properties, senses physical-chemistry aspects of the membrane. This dye in combination with microscopy and fluctuation techniques can give information about membrane heterogeneity at different temporal and spatial levels: going from average fluidity to number and diffusion coefficient of nanodomains. LAURDAN (6-dodecanoyl-2-(dimethylamino) naphthalene), is a fluorescent probe designed and synthesized in 1979 by Gregorio Weber with the purpose to study the phenomenon of dipolar relaxation. The spectral displacement observed when LAURDAN is either in fluid or gel phase permitted the use of the technique in the field of membrane dynamics. The quantitation of the spectral displacement was first addressed by the generalized polarization (GP) function in the cuvette, a ratio of the difference in intensity at two wavelengths divided by their sum. In 1997, GP measurements were done for the first time in the microscope, adding to the technique the spatial resolution and allowing the visualization of lipid segregation both in liposomes and cells. A new prospective to the membrane heterogeneity was obtained when LAURDAN fluorescent lifetime measurements were done in the microscope. Two channel lifetime imaging provides information on membrane polarity and dipole relaxation (the two parameters responsible for the spectral shift of LAURDAN), and the application of phasor analysis allows pixel by pixel understanding of these two parameters in the membrane. To increase temporal resolution, LAURDAN GP was combined with fluctuation correlation spectroscopy (FCS) and the motility of nanometric highly packed structures in biological membranes was registered. Lately the application of phasor analysis to spectral images from membranes labeled with LAURDAN allows us to study the full spectra pixel by pixel in an image. All these methodologies, using LAURDAN, offer the possibility to address different properties of membranes depending on the question being asked. In this Account, we will focus on the principles, advantages, and limitations of different approaches to orient the reader to select the most appropriate technique for their research.
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Affiliation(s)
- German Gunther
- Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone P. 1007, Santiago 8380492, Chile
| | - Leonel Malacrida
- Advanced Microscopy and Biophotonics Unit, Hospital de Clínicas, Universidad de la República, Montevideo-Uruguay. Advanced Bioimaging Unit, Institut Pasteur Montevideo, Av. Italia s/n, 90600 Montevideo, Uruguay
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Biosciences 222, Honolulu, Hawaii 96813, United States
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, 3210 Natural Sciences II, University of California, Irvine, Irvine, California 92697-2725, United States
| | - Susana A Sánchez
- Departamento de Polímeros, Facultad de Ciencias Químicas, Universidad de Concepción, Edmundo Larenas 129, Concepción 4070371, Chile
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Watanabe N, Suga K, Slotte JP, Nyholm TKM, Umakoshi H. Lipid-Surrounding Water Molecules Probed by Time-Resolved Emission Spectra of Laurdan. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:6762-6770. [PMID: 31021095 DOI: 10.1021/acs.langmuir.9b00303] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The hydration states of the interfacial region of lipid bilayers were investigated on the basis of the time-resolved emission spectra (TRES) analysis of 6-lauroyl-2-dimethylamino naphthalene (Laurdan), a common fluorescence probe used to analyze membrane hydration. TRES derived from long and short lifetime components were extracted from samples of different lipid species: 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl- sn-glycero-3-phosphocholine (DOPC), d- erythro- N-palmitoyl-sphingosylphosphorylcholine (PSM), and a DOPC/PSM binary bilayer system. Neither lifetime component (short or long) corresponded with the hydration properties; the short lifetime component of DOPC (1.97 ns) exhibited a peak at 440 nm, and the long lifetime components of DPPC and PSM (7.76 and 7.77 ns, respectively) exhibited peaks at the same wavelength. This similarity arose from the competition between the collisional quenching and the hydration effects of water molecules. Herein, this phenomenon was investigated using a plot of the lifetime τ and the peak position λ (τ vs λ plot), simultaneously visualizing both effects by deconvoluting the TRES. On the basis of collisional quenching theory, the distribution of the water population per lipid (water map) was generated. According to this theory, the τ vs λ plot was applied to the water map and the calculation of the number of water molecules per lipid, which is consistent with previous reports. This approach provides novel insights for the analysis of molecular hydration states using the fluorescence of Laurdan.
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Affiliation(s)
- Nozomi Watanabe
- Division of Chemical Engineering, Graduate School of Engineering Science , Osaka University , 1-3 Machikaneyama-cho , Toyonaka , Osaka 560-8531 , Japan
| | - Keishi Suga
- Division of Chemical Engineering, Graduate School of Engineering Science , Osaka University , 1-3 Machikaneyama-cho , Toyonaka , Osaka 560-8531 , Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Tykistökatu 6A , Turku FI-20520 , Finland
| | - Thomas K M Nyholm
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Tykistökatu 6A , Turku FI-20520 , Finland
| | - Hiroshi Umakoshi
- Division of Chemical Engineering, Graduate School of Engineering Science , Osaka University , 1-3 Machikaneyama-cho , Toyonaka , Osaka 560-8531 , Japan
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Begarani F, D'Autilia F, Signore G, Del Grosso A, Cecchini M, Gratton E, Beltram F, Cardarelli F. Capturing Metabolism-Dependent Solvent Dynamics in the Lumen of a Trafficking Lysosome. ACS NANO 2019; 13:1670-1682. [PMID: 30649861 DOI: 10.1021/acsnano.8b07682] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The eukaryotic cell compartmentalizes into spatially confined, membrane-enclosed, intracellular structures ( e. g., organelles, endosomes, and vesicles). Here, peculiar physicochemical properties of the local environment occur and participate in the regulation of ongoing molecular processes. In spite of the huge amount of available environmental probes, experiments on subcellular structures are severely challenged by their three-dimensional (3D) movement. This bottleneck is tackled here by focusing an excitation light beam in a periodic orbit around the structure of interest. The recorded signal is used as feedback to localize the structure position at high temporal resolution: microseconds along the orbit, milliseconds between orbits. The lysosome is selected as the intracellular target, together with 6-acetyl-2-dimethylaminonaphthalene (ACDAN) as probe of the physicochemical properties of the intralysosomal environment. Generalized polarization (GP) analysis of ACDAN emission is used to get a quantitative view on intralysosomal solvent dipolar relaxation. Thus, raster image correlation spectroscopy (RICS) analysis reveals that the ACDAN GP signal is fluctuating in the micro-to-millisecond time range during natural organelle 3D trafficking. We show that ACDAN GP fluctuations are characteristic of lysosomes in living cells, are selectively abolished by lysosomal basification, and depend on metabolic energy in the form of ATP. We argue that intralysosomal ACDAN GP fluctuates according to the ongoing organelle metabolism. Indeed, we report alterations in amplitude and timing of GP fluctuations in a cellular model of lysosomal storage disorder (LSD). The strategy proposed provides insight into the elusive local environment of a trafficking lysosome and supports similar molecular investigations at the subcellular level.
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Affiliation(s)
- Filippo Begarani
- Laboratorio NEST, Scuola Normale Superiore , Pisa 56127 , Italy
- Center for Nanotechnology Innovation@NEST (CNI@NEST) , Pisa 56127 , Italy
| | | | | | - Ambra Del Grosso
- NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore , Pisa 56127 , Italy
| | - Marco Cecchini
- NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore , Pisa 56127 , Italy
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering , University of California , Irvine , California 92697-2715 , United States
| | - Fabio Beltram
- Laboratorio NEST, Scuola Normale Superiore , Pisa 56127 , Italy
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Gunther G, Jameson DM, Aguilar J, Sánchez SA. Scanning fluorescence correlation spectroscopy comes full circle. Methods 2018; 140-141:52-61. [DOI: 10.1016/j.ymeth.2018.01.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/23/2018] [Accepted: 01/30/2018] [Indexed: 11/26/2022] Open
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Brewer J, Thoke HS, Stock RP, Bagatolli LA. Enzymatic studies on planar supported membranes using a widefield fluorescence LAURDAN Generalized Polarization imaging approach. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:888-895. [DOI: 10.1016/j.bbamem.2017.01.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 01/15/2017] [Accepted: 01/19/2017] [Indexed: 12/01/2022]
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Bagatolli LA, Needham D. Quantitative optical microscopy and micromanipulation studies on the lipid bilayer membranes of giant unilamellar vesicles. Chem Phys Lipids 2014; 181:99-120. [PMID: 24632023 DOI: 10.1016/j.chemphyslip.2014.02.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 02/25/2014] [Accepted: 02/26/2014] [Indexed: 12/01/2022]
Abstract
This manuscript discusses basic methodological aspects of optical microscopy and micromanipulation methods to study membranes and reviews methods to generate giant unilamellar vesicles (GUVs). In particular, we focus on the use of fluorescence microscopy and micropipet manipulation techniques to study composition-structure-property materials relationships of free-standing lipid bilayer membranes. Because their size (∼5-100 μm diameter) that is well above the resolution limit of regular light microscopes, GUVs are suitable membrane models for optical microscopy and micromanipulation experimentation. For instance, using different fluorescent reporters, fluorescence microscopy allows strategies to study membrane lateral structure/dynamics at the level of single vesicles of diverse compositions. The micropipet manipulation technique on the other hand, uses Hoffman modulation contrast microscopy and allows studies on the mechanical, thermal, molecular exchange and adhesive-interactive properties of compositionally different membranes under controlled environmental conditions. The goal of this review is to (i) provide a historical perspective for both techniques; (ii) present and discuss some of their most important contributions to our understanding of lipid bilayer membranes; and (iii) outline studies that would utilize both techniques simultaneously on the same vesicle thus bringing the ability to characterize structure and strain responses together with the direct application of well-defined stresses to a single membrane or observe the effects of adhesive spreading. Knowledge gained by these studies has informed several applications of lipid membranes including their use as lung surfactants and drug delivery systems for cancer.
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Affiliation(s)
- Luis A Bagatolli
- Membrane Biophysics and Biophotonics Group/MEMPHYS - Center for Biomembrane Physics, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
| | - David Needham
- DNRF Niels Bohr Professorship, Center for Single Particle Science and Engineering, Institute for Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark; Department of Mechanical Engineering and Material Science, Duke University, Durham, NC, USA
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Laurdan generalized polarization fluctuations measures membrane packing micro-heterogeneity in vivo. Proc Natl Acad Sci U S A 2012; 109:7314-9. [PMID: 22529342 DOI: 10.1073/pnas.1118288109] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cellular membranes are heterogeneous in composition, and the prevailing theory holds that the structures responsible for this heterogeneity in vivo are small structures (10-200 nm), sterol- and sphingolipid-enriched, of different sizes, highly dynamic denominated rafts. Rafts are postulated to be platforms, which by sequestering different membrane components can compartmentalize cellular processes and regulate signaling pathways. Despite an enormous effort in this area, the existence of these domains is still under debate due to the characteristics of the structures itself: small in size and highly mobile, which from the technical point of view implies using techniques with high spatial and temporal resolution. In this report we measured rapid fluctuations of the normalized ratio of the emission intensity at two wavelengths of Laurdan, a membrane fluorescent dye sensitive to local membrane packing. We observed generalized polarization fluctuations in the plasma membrane of intact rabbit erythrocytes and Chinese hamster ovary cells that can be explained by the existence of tightly packed micro-domains moving in a more fluid background phase. These structures, which display different lipid packing, have different sizes; they are found in the same cell and in the entire cell population. The small size and characteristic high lipid packing indicate that these micro-domains have properties that have been proposed for lipid rafts.
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Bagatolli LA. LAURDAN Fluorescence Properties in Membranes: A Journey from the Fluorometer to the Microscope. SPRINGER SERIES ON FLUORESCENCE 2012. [DOI: 10.1007/4243_2012_42] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Farkas ER, Webb WW. Precise and millidegree stable temperature control for fluorescence imaging: application to phase transitions in lipid membranes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:093704. [PMID: 20886984 PMCID: PMC2955721 DOI: 10.1063/1.3483263] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 08/05/2010] [Indexed: 05/29/2023]
Abstract
We present the design of a custom temperature-controlled chamber suitable for water or oil immersion fluorescence microscopy and its application to phase behavior in lipid bilayer vesicles. The apparatus is self-contained and portable, suitable for multiuser microscopy facilities. It offers a higher temperature resolution and stability than any comparable commercial apparatus, on the order of millidegrees. We demonstrate the utility of the system in the study of miscibility transitions in model membranes. The temperature-dependent phase behavior of model membrane systems that display liquid-ordered (L(o)) phase coexistence with the liquid-disordered (L(d)) phase is relevant to understanding the existence of heterogeneities in biological cell plasma membranes, ubiquitously termed "lipid rafts."
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Affiliation(s)
- Elaine R Farkas
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
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Sánchez SA, Tricerri MA, Ossato G, Gratton E. Lipid packing determines protein-membrane interactions: challenges for apolipoprotein A-I and high density lipoproteins. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1798:1399-408. [PMID: 20347719 PMCID: PMC2883020 DOI: 10.1016/j.bbamem.2010.03.019] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2009] [Revised: 03/18/2010] [Accepted: 03/19/2010] [Indexed: 12/16/2022]
Abstract
Protein and protein-lipid interactions, with and within specific areas in the cell membrane, are critical in order to modulate the cell signaling events required to maintain cell functions and viability. Biological bilayers are complex, dynamic platforms, and thus in vivo observations usually need to be preceded by studies on model systems that simplify and discriminate the different factors involved in lipid-protein interactions. Fluorescence microscopy studies using giant unilamellar vesicles (GUVs) as membrane model systems provide a unique methodology to quantify protein binding, interaction, and lipid solubilization in artificial bilayers. The large size of lipid domains obtainable on GUVs, together with fluorescence microscopy techniques, provides the possibility to localize and quantify molecular interactions. Fluorescence Correlation Spectroscopy (FCS) can be performed using the GUV model to extract information on mobility and concentration. Two-photon Laurdan Generalized Polarization (GP) reports on local changes in membrane water content (related to membrane fluidity) due to protein binding or lipid removal from a given lipid domain. In this review, we summarize the experimental microscopy methods used to study the interaction of human apolipoprotein A-I (apoA-I) in lipid-free and lipid-bound conformations with bilayers and natural membranes. Results described here help us to understand cholesterol homeostasis and offer a methodological design suited to different biological systems.
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Affiliation(s)
- Susana A Sánchez
- Laboratory for Fluorescence Dynamics (LFD), University of California at Irvine, Biomedical Engineering Department, Irvine, CA 92697-2715, USA.
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Impact of membrane-anchored fluorescent probes on the mechanical properties of lipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1333-7. [DOI: 10.1016/j.bbamem.2010.03.026] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 03/30/2010] [Accepted: 03/31/2010] [Indexed: 12/19/2022]
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Celli A, Gratton E. Dynamics of lipid domain formation: fluctuation analysis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:1368-76. [PMID: 20025848 DOI: 10.1016/j.bbamem.2009.12.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 11/14/2009] [Accepted: 12/02/2009] [Indexed: 01/02/2023]
Abstract
Scanning-fluctuation correlation spectroscopy was used to detect subresolution organizational fluctuations in the lipid liquid-crystalline phase for single lipid model systems. We used the fluorescent probe Laurdan which is sensitive to the amount of water in the membrane to show that there is a spatial heterogeneity on the scale of few pixels (the size of the pixel is 50 nm). We calculated the pixel variance of the GP function and we found that the variance has a peak at the phase transition for 3 different samples made of pure lipids. The pixel variance has an abrupt change at the phase transition of the membrane and then it slowly decreases at higher temperature. The relatively large variance of the GP indicates that the liquid phase of the membrane is quite heterogeneous even several degrees higher than the phase transition temperature. We interpreted this result as evidence of an underlying microscale structure of the membrane in which water is not uniformly distributed at the micron scale. Imaging of these microstructures shows that the pixels with different GP tend to concentrate in specific domains in the membrane. In the case of single lipid membrane, the statistical and fluctuation analysis of the GP data shows that even such simple lipid systems are capable of generating and maintaining stable structural and organizational heterogeneities.
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Affiliation(s)
- Anna Celli
- Dermatology Department, University of California San Francisco, San Francisco, CA 94121, USA
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Fidorra M, Garcia A, Ipsen J, Härtel S, Bagatolli L. Lipid domains in giant unilamellar vesicles and their correspondence with equilibrium thermodynamic phases: A quantitative fluorescence microscopy imaging approach. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2142-9. [DOI: 10.1016/j.bbamem.2009.08.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/27/2009] [Accepted: 08/07/2009] [Indexed: 01/21/2023]
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Phase diagrams of lipid mixtures relevant to the study of membrane rafts. Biochim Biophys Acta Mol Cell Biol Lipids 2008; 1781:665-84. [PMID: 18952002 DOI: 10.1016/j.bbalip.2008.09.002] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 08/10/2008] [Accepted: 09/09/2008] [Indexed: 12/15/2022]
Abstract
The present paper reviews the phase properties of phosphatidylcholine-sphingomyelin-cholesterol mixtures, that are often used as models for membrane "raft" microdomains. The available data based on X-ray, microscopic and spectroscopic observations, surface pressure and calorimetric measurements, and detergent solubilization assays, are critically evaluated and rationalized in terms of triangular phase diagrams. The remaining uncertainties are discussed specifically and separately from the data on which a consensus appears to exist.
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Site-directed fluorescence labeling of a membrane protein with BADAN: probing protein topology and local environment. Biophys J 2008; 94:3945-55. [PMID: 18234831 DOI: 10.1529/biophysj.107.125807] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The work presented here describes a new and simple method based on site-directed fluorescence labeling using the BADAN label that permits the examination of protein-lipid interactions in great detail. We applied this technique to a membrane-embedded, mainly alpha-helical reference protein, the M13 major coat protein. Using a high-throughput approach, 40 site-specific cysteine mutants were prepared of the 50-residues long protein. The steady-state fluorescence spectra were analyzed using a three-component spectral model that enabled the separation of Stokes shift contributions from water and internal label dynamics, and protein topology. We found that most of the fluorescence originated from BADAN labels that were hydrogen-bonded to water molecules even within the hydrophobic core of the membrane. Our spectral decomposition method revealed the embedment and topology of the labeled protein in the membrane bilayer under various conditions of headgroup charge and lipid chain length, as well as key characteristics of the membrane such as hydration level and local polarity, provided by the local dielectric constant.
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