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Manko H, Burton MG, Mély Y, Godet J. Spectral Phasor Applied to Spectrally-Resolved Single Molecule Localization Microscopy. Chemphyschem 2024; 25:e202400101. [PMID: 38563617 DOI: 10.1002/cphc.202400101] [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: 01/31/2024] [Revised: 03/12/2024] [Accepted: 03/27/2024] [Indexed: 04/04/2024]
Abstract
Spectrally-resolved single-molecule localization microscopy (srSMLM) has emerged as a powerful tool for exploring the spectral properties of single emitters in localization microscopy. By simultaneously capturing the spatial positions and spectroscopic signatures of individual fluorescent molecules, srSMLM opens up the possibility of investigating an additional dimension in super-resolution imaging. However, appropriate and dedicated tools are required to fully capitalize on the spectral dimension. Here, we propose the application of the spectral phasor analysis as an effective method for summarizing and analyzing the spectral information obtained from srSMLM experiments. The spectral phasor condenses the complete spectrum of a single emitter into a two-dimensional space, preserving key spectral characteristics for single-molecule spectral exploration. We demonstrate the effectiveness of spectral phasor in efficiently classifying single Nile Red fluorescence emissions from largely overlapping cyanine fluorescence signals in dual-color PAINT experiments. Additionally, we employed spectral phasor with srSMLM to reveal subtle alterations occurring in the membrane of Gram-positive Enterococcus hirae in response to gramicidin exposure, a membrane-perturbing antibiotic treatment. Spectral phasor provides a robust, model-free analytic tool for the detailed analysis of the spectral component of srSMLM, enhancing the capabilities of multi-color spectrally-resolved single-molecule imaging.
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Affiliation(s)
- Hanna Manko
- Laboratoire de BioImagerie et Pathologies, UMR CNRS 7021, ITI InnoVec, Université de Strasbourg, Illkirch, France
| | - Matthew G Burton
- Laboratoire de BioImagerie et Pathologies, UMR CNRS 7021, ITI InnoVec, Université de Strasbourg, Illkirch, France
- Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Yves Mély
- Laboratoire de BioImagerie et Pathologies, UMR CNRS 7021, ITI InnoVec, Université de Strasbourg, Illkirch, France
| | - Julien Godet
- Laboratoire iCube, UMR CNRS 7357, Equipe IMAGeS, Université de Strasbourg, Strasbourg, France
- Groupe Méthodes Recherche Clinique, Hôpitaux Universitaires de trasbourg, France
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Gupta A, Kallianpur M, Roy DS, Engberg O, Chakrabarty H, Huster D, Maiti S. Different membrane order measurement techniques are not mutually consistent. Biophys J 2023; 122:964-972. [PMID: 36004780 PMCID: PMC10111216 DOI: 10.1016/j.bpj.2022.08.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/10/2022] [Accepted: 08/19/2022] [Indexed: 11/25/2022] Open
Abstract
"Membrane order" is a term commonly used to describe the elastic and mechanical properties of the lipid bilayer, though its exact meaning is somewhat context- and method dependent. These mechanical properties of the membrane control many cellular functions and are measured using various biophysical techniques. Here, we ask if the results obtained from various techniques are mutually consistent. Such consistency cannot be assumed a priori because these techniques probe different spatial locations and different spatial and temporal scales. We evaluate the change of membrane order induced by serotonin using nine different techniques in lipid bilayers of three different compositions. Serotonin is an important neurotransmitter present at 100s of mM concentrations in neurotransmitter vesicles, and therefore its interaction with the lipid bilayer is biologically relevant. Our measurement tools include fluorescence of lipophilic dyes (Nile Red, Laurdan, TMA-DPH, DPH), whose properties are a function of membrane order; atomic force spectroscopy, which provides a measure of the force required to indent the lipid bilayer; 2H solid-state NMR spectroscopy, which measures the molecular order of the lipid acyl chain segments; fluorescence correlation spectroscopy, which provides a measure of the diffusivity of the probe in the membrane; and Raman spectroscopy, where spectral intensity ratios are affected by acyl chain order. We find that different measures often do not correlate with each other and sometimes even yield conflicting results. We conclude that no probe provides a general measure of membrane order and that any inference based on the change of membrane order measured by a particular probe may be unreliable.
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Affiliation(s)
- Ankur Gupta
- Tata Institute of Fundamental Research, Colaba, Mumbai, India
| | | | | | - Oskar Engberg
- Institute of Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
| | | | - Daniel Huster
- Tata Institute of Fundamental Research, Colaba, Mumbai, India; Institute of Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany.
| | - Sudipta Maiti
- Tata Institute of Fundamental Research, Colaba, Mumbai, India.
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Canepa E, Relini A, Bochicchio D, Lavagna E, Mescola A. Amphiphilic Gold Nanoparticles: A Biomimetic Tool to Gain Mechanistic Insights into Peptide-Lipid Interactions. MEMBRANES 2022; 12:673. [PMID: 35877876 PMCID: PMC9324301 DOI: 10.3390/membranes12070673] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/20/2022] [Accepted: 06/22/2022] [Indexed: 02/04/2023]
Abstract
Functional peptides are now widely used in a myriad of biomedical and clinical contexts, from cancer therapy and tumor targeting to the treatment of bacterial and viral infections. Underlying this diverse range of applications are the non-specific interactions that can occur between peptides and cell membranes, which, in many contexts, result in spontaneous internalization of the peptide within cells by avoiding energy-driven endocytosis. For this to occur, the amphipathicity and surface structural flexibility of the peptides play a crucial role and can be regulated by the presence of specific molecular residues that give rise to precise molecular events. Nevertheless, most of the mechanistic details regulating the encounter between peptides and the membranes of bacterial or animal cells are still poorly understood, thus greatly limiting the biomimetic potential of these therapeutic molecules. In this arena, finely engineered nanomaterials-such as small amphiphilic gold nanoparticles (AuNPs) protected by a mixed thiol monolayer-can provide a powerful tool for mimicking and investigating the physicochemical processes underlying peptide-lipid interactions. Within this perspective, we present here a critical review of membrane effects induced by both amphiphilic AuNPs and well-known amphiphilic peptide families, such as cell-penetrating peptides and antimicrobial peptides. Our discussion is focused particularly on the effects provoked on widely studied model cell membranes, such as supported lipid bilayers and lipid vesicles. Remarkable similarities in the peptide or nanoparticle membrane behavior are critically analyzed. Overall, our work provides an overview of the use of amphiphilic AuNPs as a highly promising tailor-made model to decipher the molecular events behind non-specific peptide-lipid interactions and highlights the main affinities observed both theoretically and experimentally. The knowledge resulting from this biomimetic approach could pave the way for the design of synthetic peptides with tailored functionalities for next-generation biomedical applications, such as highly efficient intracellular delivery systems.
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Affiliation(s)
- Ester Canepa
- Department of Physics, University of Genoa, Via Dodecaneso 33, 16146 Genoa, Italy; (E.C.); (A.R.); (D.B.)
| | - Annalisa Relini
- Department of Physics, University of Genoa, Via Dodecaneso 33, 16146 Genoa, Italy; (E.C.); (A.R.); (D.B.)
| | - Davide Bochicchio
- Department of Physics, University of Genoa, Via Dodecaneso 33, 16146 Genoa, Italy; (E.C.); (A.R.); (D.B.)
| | - Enrico Lavagna
- Department of Physics, University of Genoa, Via Dodecaneso 33, 16146 Genoa, Italy; (E.C.); (A.R.); (D.B.)
| | - Andrea Mescola
- CNR-Nanoscience Institute-S3, Via Campi 213/A, 41125 Modena, Italy
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A Note of Caution: Gramicidin Affects Signaling Pathways Independently of Its Effects on Plasma Membrane Conductance. BIOMED RESEARCH INTERNATIONAL 2021; 2021:2641068. [PMID: 34722759 PMCID: PMC8553451 DOI: 10.1155/2021/2641068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 10/06/2021] [Accepted: 10/09/2021] [Indexed: 12/01/2022]
Abstract
Gramicidin is a thoroughly studied cation ionophore widely used to experimentally manipulate the plasma membrane potential (PMP). In addition, it has been established that the drug, due to its hydrophobic nature, is capable of affecting the organization of membrane lipids. We have previously shown that modifications in the plasma membrane potential of epithelial cells in culture determine reorganizations of the cytoskeleton. To elucidate the molecular mechanisms involved, we explored the effects of PMP depolarization on some putative signaling intermediates. In the course of these studies, we came across some results that could not be interpreted in terms of the properties of gramicidin as an ionic channel. The purpose of the present work is to communicate these results and, in general, to draw attention to the fact that gramicidin effects can be misleadingly attributed to its ionic or electrical properties. In addition, this work also contributes with some novel findings of the modifications provoked on the signaling intermediates by PMP depolarization and hyperpolarization.
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Canepa E, Salassi S, de Marco AL, Lambruschini C, Odino D, Bochicchio D, Canepa F, Canale C, Dante S, Brescia R, Stellacci F, Rossi G, Relini A. Amphiphilic gold nanoparticles perturb phase separation in multidomain lipid membranes. NANOSCALE 2020; 12:19746-19759. [PMID: 32966489 DOI: 10.1039/d0nr05366j] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Amphiphilic gold nanoparticles with diameters in the 2-4 nm range are promising as theranostic agents thanks to their spontaneous translocation through cell membranes. This study addresses the effects that these nanoparticles may have on a distinct feature of plasma membranes: lipid lateral phase separation. Atomic force microscopy, quartz crystal microbalance, and molecular dynamics are combined to study the interaction between model neuronal membranes, which spontaneously form ordered and disordered lipid domains, and amphiphilic gold nanoparticles having negatively charged surface functionalization. Nanoparticles are found to interact with the bilayer and form bilayer-embedded ordered aggregates. Nanoparticles also suppress lipid phase separation, in a concentration-dependent fashion. A general, yet simple thermodynamic model is developed to show that the change of lipid-lipid enthalpy is the dominant driving force towards the nanoparticle-induced destabilization of phase separation.
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Affiliation(s)
- Ester Canepa
- Department of Chemistry and Industrial Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa, Italy.
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Efimova SS, Ostroumova OS. The Disordering Effect of Plant Metabolites on Model Lipid Membranes of Various Thickness. ACTA ACUST UNITED AC 2020. [DOI: 10.1134/s1990519x2005003x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Patel J, Chowdhury EA, Noorani B, Bickel U, Huang J. Isoflurane increases cell membrane fluidity significantly at clinical concentrations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183140. [PMID: 31790694 DOI: 10.1016/j.bbamem.2019.183140] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Revised: 11/18/2019] [Accepted: 11/27/2019] [Indexed: 01/17/2023]
Abstract
There is an on-going debate whether anesthetic drugs, such as isoflurane, can cause meaningful structural changes in cell membranes at clinical concentrations. In this study, the effects of isoflurane on lipid membrane fluidity were investigated using fluorescence anisotropy and spectroscopy. In order to get a complete picture, four very different membrane systems (erythrocyte ghosts, a 5-lipid mixture that mimics brain endothelial cell membrane, POPC/Chol, and pure DPPC) were selected for the study. In all four systems, we found that fluorescence anisotropies of DPH-PC, nile-red, and TMA-DPH decrease significantly at the isoflurane concentrations of 1 mM and 5 mM. Furthermore, the excimer/monomer (E/M) ratio of dipyrene-PC jumps immediately after the addition of isoflurane. We found that isoflurane is quite effective to loosen up highly ordered lipid domains with saturated lipids. Interestingly, 1 mM isoflurane causes a larger decrease of nile-red fluorescence anisotropy in erythrocyte ghosts than 52.2 mM of ethanol, which is three times the legal limit of blood alcohol level. Our results paint a consistent picture that isoflurane at clinical concentrations causes significant and immediate increase of membrane fluidity in a wide range of membrane systems.
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Affiliation(s)
- Jigesh Patel
- Department of Physics and Astronomy, Texas Tech University, Lubbock, TX 79409, United States of America
| | - Ekram A Chowdhury
- Department of Pharmaceutical Sciences, Texas Tech University Health Science Center, Amarillo, TX 79106, United States of America
| | - Behnam Noorani
- Department of Pharmaceutical Sciences, Texas Tech University Health Science Center, Amarillo, TX 79106, United States of America
| | - Ulrich Bickel
- Department of Pharmaceutical Sciences, Texas Tech University Health Science Center, Amarillo, TX 79106, United States of America
| | - Juyang Huang
- Department of Physics and Astronomy, Texas Tech University, Lubbock, TX 79409, United States of America.
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Schulze Greiving VC, de Boer HL, Bomer JG, van den Berg A, Le Gac S. Integrated microfluidic biosensing platform for simultaneous confocal microscopy and electrophysiological measurements on bilayer lipid membranes and ion channels. Electrophoresis 2017; 39:496-503. [PMID: 29193178 DOI: 10.1002/elps.201700346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/04/2017] [Accepted: 11/05/2017] [Indexed: 01/19/2023]
Abstract
Combining high-resolution imaging and electrophysiological recordings is key for various types of experimentation on lipid bilayers and ion channels. Here, we propose an integrated biosensing platform consisting of a microfluidic cartridge and a dedicated chip-holder to conduct such dual measurements on suspended lipid bilayers, in a user-friendly manner. To illustrate the potential of the integrated platform, we characterize lipid bilayers in terms of thickness and fluidity while simultaneously monitoring single ion channel currents. For that purpose, POPC lipid bilayers are supplemented with a fluorescently-tagged phospholipid (NBD-PE, 1% mol) for Fluorescence Recovery After Photobleaching (FRAP) measurements and a model ion channel (gramicidin, 1 nM). These combined measurements reveal that NBD-PE has no effect on the lipid bilayer thickness while gramicidin induces thinning of the membrane. Furthermore, the presence of gramicidin does not alter the lipid bilayer fluidity. Surprisingly, in lipid bilayers supplemented with both probes, a reduction in gramicidin open probability and lifetime is observed compared to lipid bilayers with gramicidin only, suggesting an influence of NBD-PE on the gramicidin ion function. Altogether, our proposed microfluidic biosensing platform in combination with the herein presented multi-parametric measurement scheme paves the way to explore the interdependent relationship between lipid bilayer properties and ion channel function.
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Affiliation(s)
- Verena C Schulze Greiving
- BIOS, Lab on a chip Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Hans L de Boer
- BIOS, Lab on a chip Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Johan G Bomer
- BIOS, Lab on a chip Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Albert van den Berg
- BIOS, Lab on a chip Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Séverine Le Gac
- BIOS, Lab on a chip Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
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