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Vestergaard CL, Blainey PC, Flyvbjerg H. Single-particle trajectories reveal two-state diffusion-kinetics of hOGG1 proteins on DNA. Nucleic Acids Res 2019; 46:2446-2458. [PMID: 29361033 PMCID: PMC5861423 DOI: 10.1093/nar/gky004] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 01/05/2018] [Indexed: 12/28/2022] Open
Abstract
We reanalyze trajectories of hOGG1 repair proteins diffusing on DNA. A previous analysis of these trajectories with the popular mean-squared-displacement approach revealed only simple diffusion. Here, a new optimal estimator of diffusion coefficients reveals two-state kinetics of the protein. A simple, solvable model, in which the protein randomly switches between a loosely bound, highly mobile state and a tightly bound, less mobile state is the simplest possible dynamic model consistent with the data. It yields accurate estimates of hOGG1’s (i) diffusivity in each state, uncorrupted by experimental errors arising from shot noise, motion blur and thermal fluctuations of the DNA; (ii) rates of switching between states and (iii) rate of detachment from the DNA. The protein spends roughly equal time in each state. It detaches only from the loosely bound state, with a rate that depends on pH and the salt concentration in solution, while its rates for switching between states are insensitive to both. The diffusivity in the loosely bound state depends primarily on pH and is three to ten times higher than in the tightly bound state. We propose and discuss some new experiments that take full advantage of the new tools of analysis presented here.
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Affiliation(s)
- Christian L Vestergaard
- Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark.,Decision and Bayesian Computation, Pasteur Institute, CNRS UMR 3571, 25-28 rue du Dr Roux, 75015 Paris, France.,Bioinformatics and Biostatistics Hub, C3BI, Pasteur Institute, CNRS USR 3756, 25-28 rue du Dr Roux, 75015 Paris, France
| | - Paul C Blainey
- MIT Department of Biological Engineering and Broad Institute of Harvard and MIT, 415 Main Street, Cambridge, MA 02142, USA
| | - Henrik Flyvbjerg
- Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark
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2
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Charytoniuk T, Harasim-Symbor E, Polak A, Drygalski K, Berk K, Chabowski A, Konstantynowicz-Nowicka K. Influence of Resveratrol on Sphingolipid Metabolism in Hepatocellular Carcinoma Cells in Lipid Overload State. Anticancer Agents Med Chem 2019; 19:121-129. [DOI: 10.2174/1871520619666181224161255] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/30/2018] [Accepted: 12/10/2018] [Indexed: 12/12/2022]
Abstract
Background:
Obesity is characterized by increased long chain fatty acids (LCFA) uptake and impaired
lipid metabolism in hepatocytes. Consequently, an enhanced intracellular lipid content, including sphingolipids,
may lead to lipotoxicity. It is believed that resveratrol (RSV), one of the most extensively studied
plant-derived polyphenols, and its interaction with sphingolipid metabolism may constitute one of the major
therapeutic targets for cancer and metabolic diseases treatment.
Objective:
The aim of this study was to ascertain, whether resveratrol may affect sphingolipid metabolic pathways,
enzymes and transporters in a lipid overload state.
Methods:
The experiments were conducted on hepatocellular carcinoma cells (HepG2) incubated with RSV
and/or Palmitic Acid (PA) at the concentration of 0.5 mM and 50 µM, respectively for 16h. Intra- and extracellular
sphingolipid concentrations were assessed by high-performance liquid chromatography and gas liquid
chromatography. Moreover, the expression of caspase 3, selected fatty acid transporters and sphingolipid
metabolism pathway proteins were estimated by Western Blot.
Results:
RSV alone and together with PA significantly increased the intracellular concentration of ceramide,
sphinganine and sphingosine as well as the expression of enzymes related to de novo ceramide synthesis pathway.
Moreover, in our study, we observed augmented ceramide and sphingomyelin efflux into the incubation
media in these groups. In addition, RSV substantially reduced intracellular triacylglycerols accumulation in lipid
overload conditions.
Conclusion:
The above-mentioned findings suggest that RSV, at least partially, demonstrates a potential protective
effect on HepG2 cells in a lipid overload state.
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Affiliation(s)
- Tomasz Charytoniuk
- Department of Physiology, Medical University of Bialystok, Mickiewicza St 2C, 15-222 Bialystok, Poland
| | - Ewa Harasim-Symbor
- Department of Physiology, Medical University of Bialystok, Mickiewicza St 2C, 15-222 Bialystok, Poland
| | - Agnieszka Polak
- Department of Physiology, Medical University of Bialystok, Mickiewicza St 2C, 15-222 Bialystok, Poland
| | - Krzysztof Drygalski
- Department of Physiology, Medical University of Bialystok, Mickiewicza St 2C, 15-222 Bialystok, Poland
| | - Klaudia Berk
- Department of Physiology, Medical University of Bialystok, Mickiewicza St 2C, 15-222 Bialystok, Poland
| | - Adrian Chabowski
- Department of Physiology, Medical University of Bialystok, Mickiewicza St 2C, 15-222 Bialystok, Poland
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3
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Schoch RL, Barel I, Brown FLH, Haran G. Lipid diffusion in the distal and proximal leaflets of supported lipid bilayer membranes studied by single particle tracking. J Chem Phys 2018; 148:123333. [DOI: 10.1063/1.5010341] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Rafael L. Schoch
- Department of Chemical and Biological Physics, Weizmann Institute of Science, P.O. Box 26, Rehovot 7610001, Israel
| | - Itay Barel
- Department of Chemistry and Biochemistry and Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - Frank L. H. Brown
- Department of Chemistry and Biochemistry and Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - Gilad Haran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, P.O. Box 26, Rehovot 7610001, Israel
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4
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Kühler P, Weber M, Lohmüller T. Plasmonic nanoantenna arrays for surface-enhanced Raman spectroscopy of lipid molecules embedded in a bilayer membrane. ACS APPLIED MATERIALS & INTERFACES 2014; 6:8947-8952. [PMID: 24896979 DOI: 10.1021/am5023418] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate a strategy for surface-enhanced Raman spectroscopy (SERS) of supported lipid membranes with arrays of plasmonic nanoantennas. Colloidal lithography refined with plasma etching is used to synthesize arrays of triangular shaped gold nanoparticles. Reducing the separation distance between the triangle tips leads to plasmonic coupling and to a strong enhancement of the electromagnetic field in the nanotriangle gap. As a result, the Raman scattering intensity of molecules that are located at this plasmonic "hot-spot" can be increased by several orders of magnitude. The nanoantenna array is then embedded with a supported phospholipid membrane which is fluid at room temperature and spans the antenna gap. This configuration offers the advantage that molecules that are mobile within the bilayer membrane can enter the "hot-spot" region via diffusion and can therefore be measured by SERS without static entrapment or adsorption of the molecules to the antenna itself.
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Affiliation(s)
- Paul Kühler
- Photonics and Optoelectronics Group, Department of Physics and Center for NanoScience (CeNS), Ludwig Maximilian University München , Amalienstrasse 54, Munich 80799, Germany
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5
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Martos A, Petrasek Z, Schwille P. Propagation of MinCDE waves on free-standing membranes. Environ Microbiol 2013; 15:3319-26. [PMID: 24118679 DOI: 10.1111/1462-2920.12295] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 09/24/2013] [Indexed: 11/30/2022]
Abstract
As a spatial modulator of cytokinesis in Escherichia coli, the Min system cooperates with the nucleoid occlusion mechanism to target the divisome assembly towards mid-cell. Based on a reaction-diffusion mechanism powered by ATP (adenosine triphosphate) hydrolysis, the Min proteins propagate in waves on the cell membrane, resulting in oscillations between the cell poles, thus preventing the formation of the division ring everywhere but in the cell centre. The dynamic behaviour of Min proteins has been successfully reconstructed in vitro on supported lipid bilayers (SLBs), reproducing many of the features observed in the cell. However, there has been a marked discrepancy between the speed of propagation of Min protein waves in vitro, compared with the cellular system. A very plausible explanation is the different mobility of proteins on model membranes, compared with the inner membrane of bacteria. To quantitatively demonstrate how membrane diffusion influences Min wave propagation, we compared Min waves on SLBs with free-standing giant unilamellar vesicles (GUV) membranes which display higher fluidity. Intriguingly, the propagation velocity and wavelength on GUVs are three times higher than those reported on supported bilayers, but the wave period is conserved. This suggests that the shorter spatial period of the patterns in vivo might indeed be primarily explained by lower diffusion coefficients of proteins on the bacterial inner membrane.
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Affiliation(s)
- Ariadna Martos
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152, Martinsried, Germany
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6
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Ott M, Shai Y, Haran G. Single-particle tracking reveals switching of the HIV fusion peptide between two diffusive modes in membranes. J Phys Chem B 2013; 117:13308-21. [PMID: 23915358 DOI: 10.1021/jp4039418] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Fusion of the HIV membrane with that of a target T cell is an essential first step in the viral infection process. Here we describe single-particle tracking (SPT) studies of a 16-amino-acid peptide derived from the HIV fusion protein (FP16), as it interacts with a supported lipid bilayer. FP16 was found to spontaneously insert into and move within the bilayer with two different modes of diffusion, a fast mode with a diffusion coefficient typical of protein motion in membranes and a much slower one. We observed transitions between the two modes: slow peptides were found to speed up, and fast peptides could slow down. Hidden Markov model analysis was employed as a method for the identification of the two modes in single-molecule trajectories and analysis of their interconversion rates. Surprisingly, the diffusion coefficients of the two modes were found to depend differently on solution viscosity. Thus, whereas the fast diffusive mode behaved as predicted by the Saffman-Delbrück theory, the slow mode behaved according to the Stokes-Einstein relation. To further characterize the two diffusive modes, FP16 molecules were studied in bilayers cooled through their liquid crystalline-to-gel phase transition. Our analysis suggested that the slow diffusive mode might originate from the formation of large objects, such as lipid domains or local protrusions, which are induced by the peptides and move together with them.
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Affiliation(s)
- Maria Ott
- Departments of Chemical Physics and ‡Biological Chemistry, Weizmann Institute of Science , Rehovot 76100, Israel
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7
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Hamm P, Zewail AH, Fleming GR. A tribute to Robin Hochstrasser. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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8
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Waichman S, Roder F, Richter CP, Birkholz O, Piehler J. Diffusion and interaction dynamics of individual membrane protein complexes confined in micropatterned polymer-supported membranes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:570-577. [PMID: 23109503 DOI: 10.1002/smll.201201530] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 09/12/2012] [Indexed: 06/01/2023]
Abstract
Micropatterned polymer-supported membranes (PSM) are established as a tool for confining the diffusion of transmembrane proteins for single molecule studies. To this end, a photochemical surface modification with hydrophobic tethers on a PEG polymer brush is implemented for capturing of lipid vesicles and subsequent fusion. Formation of contiguous membranes within micropatterns is confirmed by scanning force microscopy, fluorescence recovery after photobleaching (FRAP), and super-resolved single-molecule tracking and localization microscopy. Free diffusion of transmembrane proteins reconstituted into micropatterned PSM is demonstrated by FRAP and by single-molecule tracking. By exploiting the confinement of diffusion within micropatterned PSM, the diffusion and interaction dynamics of individual transmembrane receptors are quantitatively resolved.
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Affiliation(s)
- Sharon Waichman
- Department of Biology, University of Osnabrück, Osnabrück, Germany
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9
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Rozovsky S, Forstner MB, Sondermann H, Groves JT. Single molecule kinetics of ENTH binding to lipid membranes. J Phys Chem B 2012; 116:5122-31. [PMID: 22471245 DOI: 10.1021/jp210045r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Transient recruitment of proteins to membranes is a fundamental mechanism by which the cell exerts spatial and temporal control over proteins' localization and interactions. Thus, the specificity and the kinetics of peripheral proteins' membrane residence are an attribute of their function. Here, we describe the membrane interactions of the interfacial epsin N-terminal homology (ENTH) domain with its target lipid phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P(2)). The direct visualization and quantification of interactions of single ENTH molecules with supported lipid bilayers is achieved using total internal reflection fluorescence microscopy (TIRFM) with a time resolution of 13 ms. This enables the recording of the kinetic behavior of ENTH interacting with membranes with physiologically relevant concentrations of PtdIns(4,5)P(2) despite the low effective binding affinity. Subsequent single fluorophore tracking permits us to build up distributions of residence times and to measure ENTH dissociation rates as a function of membrane composition. Furthermore, due to the high time resolution, we are able to resolve details of the motion of ENTH associated with a simple, homogeneous membrane. In this case ENTH's diffusive transport appears to be the result of at least three different diffusion processes.
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Affiliation(s)
- Sharon Rozovsky
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.
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10
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Mandal AK, Das DK, Das AK, Sen Mojumdar S, Bhattacharyya K. Study of γ-Cyclodextrin Host–Guest Complex and Nanotube Aggregate by Fluorescence Correlation Spectroscopy. J Phys Chem B 2011; 115:10456-61. [DOI: 10.1021/jp2053629] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amit Kumar Mandal
- Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Dibyendu Kumar Das
- Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Atanu Kumar Das
- Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Supratik Sen Mojumdar
- Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Kankan Bhattacharyya
- Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
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11
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Das DK, Mondal T, Mandal AK, Bhattacharyya K. Binding of organic dyes with human serum albumin: a single-molecule study. Chem Asian J 2011; 6:3097-103. [PMID: 21751404 DOI: 10.1002/asia.201100272] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Indexed: 11/10/2022]
Abstract
Kinetics of binding of dyes at different sites of human serum albumin (HSA) has been studied by single-molecule spectroscopy. The protein was immobilized on a glass surface. To probe different binding sites (hydrophobic and hydrophilic) two dyes, coumarin 153 (C153, neutral) and rhodamine 6G (R6G, cationic) were chosen. For both the dyes, a major (ca. 96-98%) and minor (ca. 3%) binding site were detected. Rate constants of association and dissociation were simultaneously determined from directly measuring fluctuations in fluorescence intensity (τ(off) and τ(on)) and from this the equilibrium (binding) constants were calculated. Fluorescence lifetimes at individual sites were obtained from burst-integrated lifetime analysis. Distributions of lifetime histograms for both the probes (C153 and R6G) exhibit two maxima, which indicates the presence of two binding domains in the protein. Unfolding of the protein has been studied by adding guanidinium hydrochloride (GdnHCl) to the solution. It is observed that addition of GdnHCl affects the dissociation and association kinetics and hence, binding equilibrium of the association of C153. However, the effect of binding of R6G is not affected much. It is proposed that GdnHCl affects the hydrophobic binding sites more than the hydrophilic site.
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Affiliation(s)
- Dibyendu Kumar Das
- Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
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12
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Knight JD, Lerner MG, Marcano-Velázquez JG, Pastor RW, Falke JJ. Single molecule diffusion of membrane-bound proteins: window into lipid contacts and bilayer dynamics. Biophys J 2011; 99:2879-87. [PMID: 21044585 DOI: 10.1016/j.bpj.2010.08.046] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 07/12/2010] [Accepted: 08/12/2010] [Indexed: 11/19/2022] Open
Abstract
Membrane targeting proteins are recruited to specific membranes during cell signaling events, including signals at the leading edge of chemotaxing cells. Recognition and binding to specific lipids play a central role in targeting reactions, but it remains difficult to analyze the molecular features of such protein-lipid interactions. We propose that the surface diffusion constant of peripheral membrane-bound proteins contains useful information about protein-lipid contacts and membrane dynamics. To test this hypothesis, we use single-molecule fluorescence microscopy to probe the effects of lipid binding stoichiometry on the diffusion constants of engineered proteins containing one to three pleckstrin homology domains coupled by flexible linkers. Within error, the lateral diffusion constants of these engineered constructs are inversely proportional to the number of tightly bound phosphatidylinositol-(3,4,5)-trisphosphate lipids. The same trend is observed in coarse-grained molecular dynamics simulations and hydrodynamic bead calculations of lipid multimers connected by model tethers. Overall, single molecule diffusion measurements are found to provide molecular information about protein-lipid interactions. Moreover, the experimental and computational results independently indicate that the frictional contributions of multiple, coupled but well-separated lipids are additive, analogous to the free-draining limit for isotropic fluids--an insight with significant implications for theoretical description of bilayer lipid dynamics.
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Affiliation(s)
- Jefferson D Knight
- Molecular Biophysics Program and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, USA
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13
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Giannone G, Hosy E, Levet F, Constals A, Schulze K, Sobolevsky AI, Rosconi MP, Gouaux E, Tampé R, Choquet D, Cognet L. Dynamic superresolution imaging of endogenous proteins on living cells at ultra-high density. Biophys J 2010; 99:1303-10. [PMID: 20713016 DOI: 10.1016/j.bpj.2010.06.005] [Citation(s) in RCA: 278] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 05/26/2010] [Accepted: 06/04/2010] [Indexed: 11/16/2022] Open
Abstract
Versatile superresolution imaging methods, able to give dynamic information of endogenous molecules at high density, are still lacking in biological science. Here, superresolved images and diffusion maps of membrane proteins are obtained on living cells. The method consists of recording thousands of single-molecule trajectories that appear sequentially on a cell surface upon continuously labeling molecules of interest. It allows studying any molecules that can be labeled with fluorescent ligands including endogenous membrane proteins on living cells. This approach, named universal PAINT (uPAINT), generalizes the previously developed point-accumulation-for-imaging-in-nanoscale-topography (PAINT) method for dynamic imaging of arbitrary membrane biomolecules. We show here that the unprecedented large statistics obtained by uPAINT on single cells reveal local diffusion properties of specific proteins, either in distinct membrane compartments of adherent cells or in neuronal synapses.
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Affiliation(s)
- Gregory Giannone
- Centre National de la Recherche Scientifique UMR 5091, Cellular Physiology of the Synapse, Bordeaux, France
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14
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Macháň R, Hof M. Lipid diffusion in planar membranes investigated by fluorescence correlation spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1377-91. [DOI: 10.1016/j.bbamem.2010.02.014] [Citation(s) in RCA: 197] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 02/10/2010] [Accepted: 02/10/2010] [Indexed: 11/25/2022]
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15
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Giocondi MC, Yamamoto D, Lesniewska E, Milhiet PE, Ando T, Le Grimellec C. Surface topography of membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:703-18. [DOI: 10.1016/j.bbamem.2009.09.015] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 09/11/2009] [Accepted: 09/20/2009] [Indexed: 12/24/2022]
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16
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Macháň R, Hof M. Recent developments in fluorescence correlation spectroscopy for diffusion measurements in planar lipid membranes. Int J Mol Sci 2010; 11:427-457. [PMID: 20386647 PMCID: PMC2852847 DOI: 10.3390/ijms11020427] [Citation(s) in RCA: 44] [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: 12/03/2009] [Revised: 01/11/2010] [Accepted: 01/15/2010] [Indexed: 12/11/2022] Open
Abstract
Fluorescence correlation spectroscopy (FCS) is a single molecule technique used mainly for determination of mobility and local concentration of molecules. This review describes the specific problems of FCS in planar systems and reviews the state of the art experimental approaches such as 2-focus, Z-scan or scanning FCS, which overcome most of the artefacts and limitations of standard FCS. We focus on diffusion measurements of lipids and proteins in planar lipid membranes and review the contributions of FCS to elucidating membrane dynamics and the factors influencing it, such as membrane composition, ionic strength, presence of membrane proteins or frictional coupling with solid support.
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Affiliation(s)
- Radek Macháň
- J. Heyrovský Institute of Physical Chemistry of ASCR, v.v.i., Dolejškova 2155/3, 182 23 Prague, Czech Republic; E-Mail:
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of ASCR, v.v.i., Dolejškova 2155/3, 182 23 Prague, Czech Republic; E-Mail:
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17
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Pieczonka NPW, Moula G, Aroca RF. SERRS for single-molecule detection of dye-labeled phospholipids in Langmuir-Blodgett monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:11261-11264. [PMID: 19715331 DOI: 10.1021/la902486w] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The coupling of molecular excitations to localized surface plasmon resonances (LSPR) in silver or gold nanostructures is at the center of single-molecule detection (SMD) using surface-enhanced Raman scattering (SERS). The effect is attributed to the enhanced scattering power caused by coupling with the surface plasmons of the metal. The most efficient coupling is attained when the excitation is in resonance with the molecule and the nanostructure, the case of surface-enhanced resonance Raman scattering (SERRS). This incredible effect has the potential to be a powerful optical tool when used in conjunction with vibrationally differentiable chromophores. Here we present a unique study where the targeted system is a phospholipid that is tagged with a xanthene dye (the SERRS probe), a chromophore that dominates the Raman signal when the laser is in resonance with its absorption. The labeled phospholipid was incorporated into a single fatty acid Langmuir monolayer at varying concentrations and transferred onto a silver nanoparticle film to form Langmuir-Blodgett (LB) monolayers. Because the xanthene dye is tagged to a much larger molecule, the chances of dye aggregation (formation of dimers or higher aggregates) is negligible. Single-molecule detection of the dye tag (SERRS probe monomer) is readily achieved and demonstrated through the use of doped LB monolayers, Raman microscopy, spectral mapping, and efficient coupling of the laser line into the dye absorption band and plasmon resonances.
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Affiliation(s)
- N P W Pieczonka
- Materials and Surface Science Group, Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4
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19
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Knight JD, Falke JJ. Single-molecule fluorescence studies of a PH domain: new insights into the membrane docking reaction. Biophys J 2009; 96:566-82. [PMID: 19167305 DOI: 10.1016/j.bpj.2008.10.020] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Accepted: 10/23/2008] [Indexed: 01/15/2023] Open
Abstract
Proteins containing membrane targeting domains play essential roles in many cellular signaling pathways. However, important features of the membrane-bound state are invisible to bulk methods, thereby hindering mechanistic analysis of membrane targeting reactions. Here we use total internal reflection fluorescence microscopy (TIRFM), combined with single particle tracking, to probe the membrane docking mechanism of a representative pleckstrin homology (PH) domain isolated from the general receptor for phosphoinositides, isoform 1 (GRP1). The findings show three previously undescribed features of GRP1 PH domain docking to membranes containing its rare target lipid, phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P(3)]. First, analysis of surface diffusion kinetics on supported lipid bilayers shows that in the absence of other anionic lipids, the PI(3,4,5)P(3)-bound protein exhibits the same diffusion constant as a single lipid molecule. Second, the binding of the anionic lipid phosphatidylserine to a previously unidentified secondary binding site slows both diffusion and dissociation kinetics. Third, TIRFM enables direct observation of rare events in which dissociation from the membrane surface is followed by transient diffusion through solution and rapid rebinding to a nearby, membrane-associated target lipid. Overall, this study shows that in vitro single-molecule TIRFM provides a new window into the molecular mechanisms of membrane docking reactions.
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Affiliation(s)
- Jefferson D Knight
- Molecular Biophysics Program, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, USA
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