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Krok E, Franquelim HG, Chattopadhyay M, Orlikowska-Rzeznik H, Schwille P, Piatkowski L. Nanoscale structural response of biomimetic cell membranes to controlled dehydration. NANOSCALE 2023; 16:72-84. [PMID: 38062887 DOI: 10.1039/d3nr03078d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Although cell membranes exist in excess of water under physiological conditions, there are a number of biochemical processes, such as adsorption of biomacromolecules or membrane fusion events, that require partial or even complete transient dehydration of lipid membranes. Even though the dehydration process is crucial for understanding all fusion events, still little is known about the structural adaptation of lipid membranes when their interfacial hydration layer is perturbed. Here, we present the study of the nanoscale structural reorganization of phase-separated, supported lipid bilayers (SLBs) under a wide range of hydration conditions. Model lipid membranes were characterised using a combination of fluorescence microscopy and atomic force microscopy and, crucially, without applying any chemical or physical modifications that have previously been considered essential for maintaining the membrane integrity upon dehydration. We revealed that decreasing the hydration state of the membrane leads to an enhanced mixing of lipids characteristic of the liquid-disordered (Ld) phase with those forming the liquid-ordered (Lo) phase. This is associated with a 2-fold decrease in the hydrophobic mismatch between the Ld and Lo lipid phases and a 3-fold decrease in the line tension for the fully desiccated membrane. Importantly, the observed changes in the hydrophobic mismatch, line tension, and lipid miscibility are fully reversible upon subsequent rehydration of the membrane. These findings provide a deeper insight into the fundamental processes, such as cell-cell fusion, that require partial dehydration at the interface of two membranes.
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Affiliation(s)
- Emilia Krok
- Poznan University of Technology, Faculty of Materials Engineering and Technical Physics, Institute of Physics, Piotrowo 3, 60-965 Poznan, Poland.
| | - Henri G Franquelim
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
- Leipzig University, Research and Transfer Center for Bioactive Matter, Deutscher Platz 5, 04103 Leipzig, Germany
| | - Madhurima Chattopadhyay
- Poznan University of Technology, Faculty of Materials Engineering and Technical Physics, Institute of Physics, Piotrowo 3, 60-965 Poznan, Poland.
| | - Hanna Orlikowska-Rzeznik
- Poznan University of Technology, Faculty of Materials Engineering and Technical Physics, Institute of Physics, Piotrowo 3, 60-965 Poznan, Poland.
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Lukasz Piatkowski
- Poznan University of Technology, Faculty of Materials Engineering and Technical Physics, Institute of Physics, Piotrowo 3, 60-965 Poznan, Poland.
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2
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Porras-Gómez M, Kim H, Dronadula MT, Kambar N, Metellus CJB, Aluru NR, van der Zande A, Leal C. Multiscale compression-induced restructuring of stacked lipid bilayers: From buckling delamination to molecular packing. PLoS One 2022; 17:e0275079. [PMID: 36490254 PMCID: PMC9733850 DOI: 10.1371/journal.pone.0275079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 11/23/2022] [Indexed: 12/13/2022] Open
Abstract
Lipid membranes in nature adapt and reconfigure to changes in composition, temperature, humidity, and mechanics. For instance, the oscillating mechanical forces on lung cells and alveoli influence membrane synthesis and structure during breathing. However, despite advances in the understanding of lipid membrane phase behavior and mechanics of tissue, there is a critical knowledge gap regarding the response of lipid membranes to micromechanical forces. Most studies of lipid membrane mechanics use supported lipid bilayer systems missing the structural complexity of pulmonary lipids in alveolar membranes comprising multi-bilayer interconnected stacks. Here, we elucidate the collective response of the major component of pulmonary lipids to strain in the form of multi-bilayer stacks supported on flexible elastomer substrates. We utilize X-ray diffraction, scanning probe microscopy, confocal microscopy, and molecular dynamics simulation to show that lipid multilayered films both in gel and fluid states evolve structurally and mechanically in response to compression at multiple length scales. Specifically, compression leads to increased disorder of lipid alkyl chains comparable to the effect of cholesterol on gel phases as a direct result of the formation of nanoscale undulations in the lipid multilayers, also inducing buckling delamination and enhancing multi-bilayer alignment. We propose this cooperative short- and long-range reconfiguration of lipid multilayered films under compression constitutes a mechanism to accommodate stress and substrate topography. Our work raises fundamental insights regarding the adaptability of complex lipid membranes to mechanical stimuli. This is critical to several technologies requiring mechanically reconfigurable surfaces such as the development of electronic devices interfacing biological materials.
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Affiliation(s)
- Marilyn Porras-Gómez
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States of America
| | - Hyunchul Kim
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States of America
| | - Mohan Teja Dronadula
- Walker Department of Mechanical Engineering, Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Nurila Kambar
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States of America
| | - Christopher J. B. Metellus
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States of America
| | - Narayana R. Aluru
- Walker Department of Mechanical Engineering, Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Arend van der Zande
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States of America,* E-mail: (AZ); (CL)
| | - Cecília Leal
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States of America,* E-mail: (AZ); (CL)
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3
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Paez-Perez M, Russell IA, Cicuta P, Di Michele L. Modulating membrane fusion through the design of fusogenic DNA circuits and bilayer composition. SOFT MATTER 2022; 18:7035-7044. [PMID: 36000473 PMCID: PMC9516350 DOI: 10.1039/d2sm00863g] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
Membrane fusion is a ubiquitous phenomenon linked to many biological processes, and represents a crucial step in liposome-based drug delivery strategies. The ability to control, ever more precisely, membrane fusion pathways would thus be highly valuable for next generation nano-medical solutions and, more generally, the design of advanced biomimetic systems such as synthetic cells. In this article, we present fusogenic nanostructures constructed from synthetic DNA which, different from previous solutions, unlock routes for modulating the rate of fusion and making it conditional to the presence of soluble DNA molecules, thus demonstrating how membrane fusion can be controlled through simple DNA-based molecular circuits. We then systematically explore the relationship between lipid-membrane composition, its biophysical properties, and measured fusion efficiency, linking our observations to the stability of transition states in the fusion pathway. Finally, we observe that specific lipid compositions lead to the emergence of complex bilayer architectures in the fusion products, such as nested morphologies, which are accompanied by alterations in biophysical behaviour. Our findings provide multiple, orthogonal strategies to program lipid-membrane fusion, which leverage the design of either the fusogenic DNA constructs or the physico/chemical properties of the membranes, and could thus be valuable in applications where some design parameters are constrained by other factors such as material cost and biocompatibility, as it is often the case in biotechnological applications.
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Affiliation(s)
- Miguel Paez-Perez
- Molecular Sciences Research Hub, Department of Chemistry, Imperial College London, Wood Lane, London, W12 0BZ, UK.
- fabriCELL, Imperial College London, Wood Lane, London, W12 0BZ, UK
| | - I Alasdair Russell
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, UK
| | - Pietro Cicuta
- Biological and Soft Systems, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
| | - Lorenzo Di Michele
- Molecular Sciences Research Hub, Department of Chemistry, Imperial College London, Wood Lane, London, W12 0BZ, UK.
- fabriCELL, Imperial College London, Wood Lane, London, W12 0BZ, UK
- Biological and Soft Systems, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
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4
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Scheu M, Komorowski K, Shen C, Salditt T. A stalk fluid forming above the transition from the lamellar to the rhombohedral phase of lipid membranes. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2021; 50:265-278. [PMID: 33590276 PMCID: PMC8071804 DOI: 10.1007/s00249-020-01493-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 12/21/2020] [Accepted: 12/31/2020] [Indexed: 02/01/2023]
Abstract
In this work, we present evidence for the formation of transient stalks in aligned multilamellar stacks of lipid membranes. Just above the phase transition from the fluid ([Formula: see text]) lamellar phase to the rhombohedral phase (R), where lipid stalks crystallize on a super-lattice within the lipid bilayer stack, we observe a characteristic scattering pattern, which can be attributed to a correlated fluid of transient stalks. Excess (off-axis) diffuse scattering with a broad modulation around the position which later transforms to a sharp peak of the rhombohedral lattice, gives evidence for the stalk fluid forming as a pre-critical effect, reminiscent of critical phenomena in the vicinity of second-order phase transitions. Using high-resolution off-specular X-ray scattering and lineshape analysis we show that this pre-critical regime is accompanied by an anomalous elasticity behavior of the membrane stack, in particular an increase in inter-bilayer compressibility, i.e., a decrease in the compression modulus.
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Affiliation(s)
- Max Scheu
- Institute for X-ray Physics, Friedrich-Hund-Platz 1, 37073, Göttingen, Germany
| | - Karlo Komorowski
- Institute for X-ray Physics, Friedrich-Hund-Platz 1, 37073, Göttingen, Germany
| | - Chen Shen
- DESY Photon Science, Notkestr.85, 22607, Hamburg, Germany
| | - Tim Salditt
- Institute for X-ray Physics, Friedrich-Hund-Platz 1, 37073, Göttingen, Germany.
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5
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Self-assembly of supported lipid multi-bilayers investigated by time-resolved X-ray diffraction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183437. [PMID: 32783887 DOI: 10.1016/j.bbamem.2020.183437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 07/30/2020] [Accepted: 07/30/2020] [Indexed: 11/23/2022]
Abstract
Supported lipid multi-bilayers or bilayer stacks are an important model membrane system, particularly suitable for surface-sensitive characterization methods like X-ray and neutron diffraction. Spreading organic solution (sOS) is one of the most widely used protocols for the preparation of lipid multi-bilayers. Despite its great popularity, the self-assembly mechanism of the bilayers is not yet fully elucidated, limiting further improvements of this protocol. In order to solve this problem, we investigated the formation process of lipid bilayers in the sOS protocol, using in-situ time-resolved X-ray diffraction, complemented by X-ray reflectivity and molecular dynamics simulation. Results reveal a simultaneous self-assembly scheme for both cholesterol-free and cholesterol-containing bilayers, with one bilayer phase forming at the surface and the other forming in the solution. The solution phase gradually transforms into the surface phase, yielding clean single phase in the end.
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6
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Arima-Osonoi H, Miyata N, Yoshida T, Kasai S, Ohuchi K, Zhang S, Miyazaki T, Aoki H. Gas-flow humidity control system for neutron reflectivity measurements. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:104103. [PMID: 33138580 DOI: 10.1063/5.0021128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
We developed a novel humidity control system for neutron reflectivity measurements based on the two-way gas-flow method that can generate up to 85% relative humidity (RH) within a temperature range of 5 °C-85 °C. The system consists of a gas-flow-type humidity generator and a thermostatic sample chamber, each of which can independently control the temperature. The key features include rapid humidity response and long stable operation time. The humidity reaches equilibrium within 2 to 5 min during the humidity change, and the system exhibited acceptable stability over a three-day, nonstop experimental measurement duration, with a precision of ±1% RH at 85 °C and 85% RH. The sample chamber is capable of measuring substrate samples with dimensions of up to 2-in. in diameter and 5-mm in thickness. We demonstrate the reflectivity data measured at a pulsed neutron facility, MLF BL17, in the Japan Proton Accelerator Research Complex. The combined use of this system with neutrons permits in situ, time-resolved studies of the swelling process of polyvinyl alcohol and adhesive materials.
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Affiliation(s)
- Hiroshi Arima-Osonoi
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Noboru Miyata
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Tessei Yoshida
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Satoshi Kasai
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Keiichi Ohuchi
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Shuoyuan Zhang
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Tsukasa Miyazaki
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Hiroyuki Aoki
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Ibaraki 319-1195, Japan
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7
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Bader K, Müller C, Molard Y, Baro A, Ehni P, Knelles J, Laschat S. Fluorenone imidazolium salts as novel de Vries materials. RSC Adv 2020; 10:23999-24016. [PMID: 35517358 PMCID: PMC9055108 DOI: 10.1039/d0ra04650g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 06/15/2020] [Indexed: 01/09/2023] Open
Abstract
In ionic liquid crystals (ILCs) tilted mesophases such as SmC required for electro-optic devices are quite rare. We report a design concept that induced the SmC phase and enabled de Vries-like behaviour in ILCs. For this purpose, we synthesized and characterized a library of ILC derivatives ImR(On,Ym)X which consist of a rigid central fluorenone core containing an alkoxy or thioether side chain and connected via a flexible spacer to an imidazolium head group. The mesomorphic properties were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD). Temperature-dependent measurements of smectic layer spacing d by small-angle X-ray scattering (SAXS) and of optical tilt angles by POM demonstrate that ILCs ImR(On,Ym)X undergo SmA–SmC phase transitions with maximum layer contraction values between 0.4% and 2.1%. The lowest reduction factor R of 0.2 at the reduced temperature T − TAC = −10 K was calculated for Im(O12,S14)Br. Electron density calculations indicated a bilayer structure. Furthermore, temperature dependent emission studies show that self-assembling has a strong influence on the emission intensity of these ILCs. ILCs consisting of cationic head group–spacer–fluorenone central core–side chain show de Vries-like behaviour.![]()
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Affiliation(s)
- Korinna Bader
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Carsten Müller
- Institut für Physikalische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Yann Molard
- CNRS, ISCR-UMR 6226, ScanMAT-UMS 2001, University Rennes 35000 Rennes France
| | - Angelika Baro
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Philipp Ehni
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Jakob Knelles
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Sabine Laschat
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
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8
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Haenle JC, Stöckl Y, Forschner R, Haenle E, Laschat S. Fluorophobic Effect Promoting Lamellar Self-Assembly of Donor Acceptor Dyes. Chemphyschem 2018; 19:2758-2767. [PMID: 29999251 DOI: 10.1002/cphc.201800449] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Indexed: 11/07/2022]
Abstract
To combine liquid crystalline and linear optical properties in the same molecule, the fluorophobic effect was probed for the first time in donor acceptor dyes. Thus, a series of mono-, bi-, and tricyclic donor acceptor dyes with 1H,1H-perfluorinated alkyl chains of different lengths as donor units and nitrile, malononitrile or barbiturate as acceptor units was synthesized in 5 steps and 1.4-6.6 % overall yield. UV/Vis and fluorescence spectroscopy, cyclic voltammetry and DFT calculations revealed that absorption and emission maxima, Stokes shifts and LUMO energies were mainly governed by the chromophore size and acceptor strengths. The perfluorinated chain was electronically almost decoupled from the remaining chromophore and induced only slight changes of the absorption maxima as compared to the alkyl substituted counterparts. However, in contrast to the non-mesomorphic alkyl donor-substituted derivatives, the perfluorinated donors resulted in self-assembly into partially interdigitated SmA bilayers according to differential scanning calorimetry (DSC), polarizing optical microscopy (POM), X-ray diffraction (WAXS, SAXS) studies and electron density profile calculations.
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Affiliation(s)
| | - Yannick Stöckl
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwalding 55, 70569, Stuttgart, Germany
| | - Robert Forschner
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwalding 55, 70569, Stuttgart, Germany
| | - Elena Haenle
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwalding 55, 70569, Stuttgart, Germany
| | - Sabine Laschat
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwalding 55, 70569, Stuttgart, Germany
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9
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Xu Y, Kuhlmann J, Brennich M, Komorowski K, Jahn R, Steinem C, Salditt T. Reconstitution of SNARE proteins into solid-supported lipid bilayer stacks and X-ray structure analysis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:566-578. [PMID: 29106973 DOI: 10.1016/j.bbamem.2017.10.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/01/2017] [Accepted: 10/24/2017] [Indexed: 11/26/2022]
Abstract
SNAREs are known as an important family of proteins mediating vesicle fusion. For various biophysical studies, they have been reconstituted into supported single bilayers via proteoliposome adsorption and rupture. In this study we extended this method to the reconstitution of SNAREs into supported multilamellar lipid membranes, i.e. oriented multibilayer stacks, as an ideal model system for X-ray structure analysis (X-ray reflectivity and diffraction). The reconstitution was implemented through a pathway of proteomicelle, proteoliposome and multibilayer. To monitor the structural evolution in each step, we used small-angle X-ray scattering for the proteomicelles and proteoliposomes, followed by X-ray reflectivity and grazing-incidence small-angle scattering for the multibilayers. Results show that SNAREs can be successfully reconstituted into supported multibilayers, with high enough orientational alignment for the application of surface sensitive X-ray characterizations. Based on this protocol, we then investigated the effect of SNAREs on the structure and phase diagram of the lipid membranes. Beyond this application, this reconstitution protocol could also be useful for X-ray analysis of many further membrane proteins.
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Affiliation(s)
- Yihui Xu
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Jan Kuhlmann
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, Göttingen 37077, Germany
| | - Martha Brennich
- Structural Biology Group, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS 90181, Grenoble 38042, France
| | - Karlo Komorowski
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck Institute for Biophysical Chemistry, Am Faßberg 11, Göttingen 37077, Germany
| | - Claudia Steinem
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, Göttingen 37077, Germany
| | - Tim Salditt
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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10
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Bhattacharya G, Giri RP, Saxena H, Agrawal VV, Gupta A, Mukhopadhyay MK, Ghosh SK. X-ray Reflectivity Study of the Interaction of an Imidazolium-Based Ionic Liquid with a Soft Supported Lipid Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:1295-1304. [PMID: 28092704 DOI: 10.1021/acs.langmuir.6b03192] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Ionic liquids (ILs) are important for their antimicrobial activity and are found to be toxic to some microorganisms. To shed light on the mechanism of their activities, the interaction of an imidazolium-based IL 1-butyl-3-methylimidazolium tetrfluoroborate ([BMIM][BF4]) with E. coli bacteria and cell-membrane-mimicking lipid mono- and bilayers has been studied. The survival of the bacteria and corresponding growth inhibition are observed to be functions of the concentration of the IL. The IL alters the pressure-area isotherm of the monolayer formed at an air-water interface by the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid. The in-plane elasticity of the lipid layer is reduced as a consequence of the insertion of this IL. The X-ray reflectivity study from a polymer-supported lipid bilayer shows strong perturbation in the self-assembled structure of the bilayer due to the interaction. As a consequence, there is a considerable decrease in bilayer thickness and a corresponding increase in electron density. These results, however, depend on the chain configurations of the lipid molecules.
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Affiliation(s)
| | - R P Giri
- Saha Institute of Nuclear Physics, Bidhannagar, Kolkata 700064, India
| | | | - V V Agrawal
- National Physical Laboratory, Dr. K S Krishnan Marg, New Delhi 110012, India
| | | | - M K Mukhopadhyay
- Saha Institute of Nuclear Physics, Bidhannagar, Kolkata 700064, India
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11
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X-ray structural investigations of fusion intermediates: Lipid model systems and beyond. Semin Cell Dev Biol 2016; 60:65-77. [DOI: 10.1016/j.semcdb.2016.06.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 11/20/2022]
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12
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Rost U, Xu Y, Salditt T, Diederichsen U. Heavy-Atom Labeled Transmembrane β-Peptides: Synthesis, CD-Spectroscopy, and X-ray Diffraction Studies in Model Lipid Multilayer. Chemphyschem 2016; 17:2525-34. [DOI: 10.1002/cphc.201600289] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Ulrike Rost
- Institute for Organic and Biomolecular Chemistry; Georg-August-University Göttingen; Tammannstr. 2 37077 Göttingen Germany
| | - Yihui Xu
- Institute for X-ray Physics; Georg-August-University Göttingen; Friedrich-Hund-Platz 1 37077 Göttingen Germany
| | - Tim Salditt
- Institute for X-ray Physics; Georg-August-University Göttingen; Friedrich-Hund-Platz 1 37077 Göttingen Germany
| | - Ulf Diederichsen
- Institute for Organic and Biomolecular Chemistry; Georg-August-University Göttingen; Tammannstr. 2 37077 Göttingen Germany
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13
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Bulpett JM, Snow T, Quignon B, Beddoes CM, Tang TYD, Mann S, Shebanova O, Pizzey CL, Terrill NJ, Davis SA, Briscoe WH. Hydrophobic nanoparticles promote lamellar to inverted hexagonal transition in phospholipid mesophases. SOFT MATTER 2015; 11:8789-8800. [PMID: 26391613 DOI: 10.1039/c5sm01705j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This study focuses on how the mesophase transition behaviour of the phospholipid dioleoyl phosphatidylethanolamine (DOPE) is altered by the presence of 10 nm hydrophobic and 14 nm hydrophilic silica nanoparticles (NPs) at different concentrations. The lamellar to inverted hexagonal phase transition (Lα-HII) of phospholipids is energetically analogous to the membrane fusion process, therefore understanding the Lα-HII transition with nanoparticulate additives is relevant to how membrane fusion may be affected by these additives, in this case the silica NPs. The overriding observation is that the HII/Lα boundaries in the DOPE p-T phase diagram were shifted by the presence of NPs: the hydrophobic NPs enlarged the HII phase region and thus encouraged the inverted hexagonal (HII) phase to occur at lower temperatures, whilst hydrophilic NPs appeared to stabilise the Lα phase region. This effect was also NP-concentration dependent, with a more pronounced effect for higher concentration of the hydrophobic NPs, but the trend was less clear cut for the hydrophilic NPs. There was no evidence that the NPs were intercalated into the mesophases, and as such it was likely that they might have undergone microphase separation and resided at the mesophase domain boundaries. Whilst the loci and exact roles of the NPs invite further investigation, we tentatively discuss these results in terms of both the surface chemistry of the NPs and the effect of their curvature on the elastic bending energy considerations during the mesophase transition.
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Affiliation(s)
- Jennifer M Bulpett
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - Tim Snow
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - Benoit Quignon
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - Charlotte M Beddoes
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - T-Y D Tang
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - Stephen Mann
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - Olga Shebanova
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Claire L Pizzey
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Nicholas J Terrill
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Sean A Davis
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
| | - Wuge H Briscoe
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
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14
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Ibarguren M, Bomans PHH, Ruiz-Mirazo K, Frederik PM, Alonso A, Goñi FM. Thermally-induced aggregation and fusion of protein-free lipid vesicles. Colloids Surf B Biointerfaces 2015; 136:545-52. [PMID: 26454544 DOI: 10.1016/j.colsurfb.2015.09.047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 08/21/2015] [Accepted: 09/24/2015] [Indexed: 12/11/2022]
Abstract
Membrane fusion is an important phenomenon in cell biology and pathology. This phenomenon can be modeled using vesicles of defined size and lipid composition. Up to now fusion models typically required the use of chemical (polyethyleneglycol, cations) or enzymatic catalysts (phospholipases). We present here a model of lipid vesicle fusion induced by heat. Large unilamellar vesicles consisting of a phospholipid (dioleoylphosphatidylcholine), cholesterol and diacylglycerol in a 43:57:3 mol ratio were employed. In this simple system, fusion was the result of thermal fluctuations, above 60 °C. A similar system containing phospholipid and cholesterol but no diacylglycerol was observed to aggregate at and above 60 °C, in the absence of fusion. Vesicle fusion occurred under our experimental conditions only when (31)P NMR and cryo-transmission electron microscopy of the lipid mixtures used in vesicle preparation showed non-lamellar lipid phase formation (hexagonal and cubic). Non-lamellar structures are probably the result of lipid reassembly of the products of individual fusion events, or of fusion intermediates. A temperature-triggered mechanism of lipid reassembly might have occurred at various stages of protocellular evolution.
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Affiliation(s)
- Maitane Ibarguren
- Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain.
| | - Paul H H Bomans
- Soft Matter CryoTEM Research Unit, Laboratory for Materials and Interface Chemistry, P.O. Box 513, 5600MB Eindhoven, The Netherlands.
| | - Kepa Ruiz-Mirazo
- Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain; Logic and Philosophy of Science Department, University of the Basque Country, Spain.
| | - Peter M Frederik
- Soft Matter CryoTEM Research Unit, Laboratory for Materials and Interface Chemistry, P.O. Box 513, 5600MB Eindhoven, The Netherlands.
| | - Alicia Alonso
- Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain.
| | - Félix M Goñi
- Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain.
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15
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Jaksch S, Lipfert F, Koutsioubas A, Mattauch S, Holderer O, Ivanova O, Frielinghaus H, Hertrich S, Fischer SF, Nickel B. Influence of ibuprofen on phospholipid membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:022716. [PMID: 25768540 DOI: 10.1103/physreve.91.022716] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Indexed: 06/04/2023]
Abstract
A basic understanding of biological membranes is of paramount importance as these membranes comprise the very building blocks of life itself. Cells depend in their function on a range of properties of the membrane, which are important for the stability and function of the cell, information and nutrient transport, waste disposal, and finally the admission of drugs into the cell and also the deflection of bacteria and viruses. We have investigated the influence of ibuprofen on the structure and dynamics of L-α-phosphatidylcholine (SoyPC) membranes by means of grazing incidence small-angle neutron scattering, neutron reflectometry, and grazing incidence neutron spin echo spectroscopy. From the results of these experiments, we were able to determine that ibuprofen induces a two-step structuring behavior in the SoyPC films, where the structure evolves from the purely lamellar phase for pure SoyPC over a superposition of two hexagonal phases to a purely hexagonal phase at high concentrations. A relaxation, which is visible when no ibuprofen is present in the membrane, vanishes upon addition of ibuprofen. This we attribute to a stiffening of the membrane. This behavior may be instrumental in explaining the toxic behavior of ibuprofen in long-term application.
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Affiliation(s)
- Sebastian Jaksch
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Frederik Lipfert
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Alexandros Koutsioubas
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Stefan Mattauch
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Olaf Holderer
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Oxana Ivanova
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Henrich Frielinghaus
- Forschungszentrum Jülich GmbH, JCNS at Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - Samira Hertrich
- Ludwig-Maximilians-Universität, Department für Physik und CeNS, Geschwister-Scholl-Platz 1, D-80539 München, Germany
| | - Stefan F Fischer
- Ludwig-Maximilians-Universität, Department für Physik und CeNS, Geschwister-Scholl-Platz 1, D-80539 München, Germany
| | - Bert Nickel
- Ludwig-Maximilians-Universität, Department für Physik und CeNS, Geschwister-Scholl-Platz 1, D-80539 München, Germany
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16
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Abstract
In this chapter the use of X-ray diffraction to study the structure of lyotropic phases and lipid model membranes is described. Determination of the phase symmetry and lattice parameters from small-angle X-ray scattering (SAXS), and of the nature of the hydrocarbon chain packing from wide-angle X-ray scattering (WAXS), are discussed. Methods by which the sign of the interfacial curvature of non-lamellar phases may be determined are then presented. Finally, the calculation of electron density profiles from the intensities of the observed Bragg peaks is described, for the lamellar phase and for the inverse hexagonal phase.
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Affiliation(s)
- Arwen I I Tyler
- Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK,
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17
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Khattari Z, Köhler S, Xu Y, Aeffner S, Salditt T. Stalk formation as a function of lipid composition studied by X-ray reflectivity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:41-50. [PMID: 25261611 DOI: 10.1016/j.bbamem.2014.08.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 07/24/2014] [Accepted: 08/08/2014] [Indexed: 10/24/2022]
Abstract
We have investigated the structure and interaction of solid-supported multilamellar phospholipid bilayers in view of stalk formation as model systems for membrane fusion. The multi-component bilayers were composed of ternary and quaternary mixtures, containing phosphatidylcholines, phosphatidylethanolamines, sphingomyelin, cholesterol, diacylglycerol, and phosphatidylinositol. Analysis of the obtained electron density profiles and the pressure-distance curves reveals systematic changes in structure and hydration repulsion. The osmotic pressure needed to induce stalk formation at the transition from the fluid lamellar to the rhombohedral phase indicates how membrane fusion properties are modified by bilayer composition.
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Affiliation(s)
- Ziad Khattari
- Department of Physics, Hashemite University, 13115 Zarqa, Jordan.
| | - Sebastian Köhler
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Yihui Xu
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sebastian Aeffner
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Tim Salditt
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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18
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Ghosh SK, Salgin B, Pontoni D, Reusch T, Keil P, Vogel D, Rohwerder M, Reichert H, Salditt T. Structure and Volta potential of lipid multilayers: effect of X-ray irradiation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:815-824. [PMID: 23231362 DOI: 10.1021/la304139w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The effect of hard X-ray radiation on the structure and electrostatics of solid-supported lipid multilayer membranes is investigated using a scanning Kelvin probe (SKP) integrated with a high-energy synchrotron beamline to enable in situ measurements of the membranes' local Volta potential (V(p)) during X-ray structural characterization. The undulator radiation employed does not induce any detectable structural damage, but the V(p) of both bare and lipid-modified substrates is found to undergo strong radiation-induced shifts, almost immediately after X-ray exposure. Sample regions that are macroscopically distant (~cm) from the irradiated region experience an exponential V(p) growth with a characteristic time constant of several minutes. The V(p) variations occurring upon periodic on/off X-ray beam switching are fully or partially reversible depending on the location and time-scale of the SKP measurement. The general relevance of these findings for synchrotron-based characterization of biomolecular thin films is critically reviewed.
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Affiliation(s)
- S K Ghosh
- Institute for X-ray Physics, University of Göttingen, Göttingen, Germany.
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19
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Weinhausen B, Aeffner S, Reusch T, Salditt T. Acyl-chain correlation in membrane fusion intermediates: x-ray diffraction from the rhombohedral lipid phase. Biophys J 2012; 102:2121-9. [PMID: 22824276 DOI: 10.1016/j.bpj.2012.03.069] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 03/24/2012] [Accepted: 03/27/2012] [Indexed: 11/16/2022] Open
Abstract
We have studied the acyl-chain conformation in stalk phases of model membranes by x-ray diffraction from oriented samples. As an equilibrium lipid phase induced by dehydration, the stalk or rhombohedral phase exhibits lipidic passages (stalks) between adjacent bilayers, representing a presumed intermediate state in membrane fusion. From the detailed analysis of the acyl-chain correlation peak, we deduce the structural parameters of the acyl-chain fluid above, at, and below the transition from the lamellar to rhombohedral state, at the molecular level.
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Affiliation(s)
- Britta Weinhausen
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Göttingen, Germany
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20
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Pozzi D, Marchini C, Cardarelli F, Amenitsch H, Garulli C, Bifone A, Caracciolo G. Transfection efficiency boost of cholesterol-containing lipoplexes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2335-43. [DOI: 10.1016/j.bbamem.2012.05.017] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 05/08/2012] [Accepted: 05/14/2012] [Indexed: 10/28/2022]
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21
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Risselada HJ, Marelli G, Fuhrmans M, Smirnova YG, Grubmüller H, Marrink SJ, Müller M. Line-tension controlled mechanism for influenza fusion. PLoS One 2012; 7:e38302. [PMID: 22761674 PMCID: PMC3386277 DOI: 10.1371/journal.pone.0038302] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 05/03/2012] [Indexed: 11/19/2022] Open
Abstract
Our molecular simulations reveal that wild-type influenza fusion peptides are able to stabilize a highly fusogenic pre-fusion structure, i.e. a peptide bundle formed by four or more trans-membrane arranged fusion peptides. We rationalize that the lipid rim around such bundle has a non-vanishing rim energy (line-tension), which is essential to (i) stabilize the initial contact point between the fusing bilayers, i.e. the stalk, and (ii) drive its subsequent evolution. Such line-tension controlled fusion event does not proceed along the hypothesized standard stalk-hemifusion pathway. In modeled influenza fusion, single point mutations in the influenza fusion peptide either completely inhibit fusion (mutants G1V and W14A) or, intriguingly, specifically arrest fusion at a hemifusion state (mutant G1S). Our simulations demonstrate that, within a line-tension controlled fusion mechanism, these known point mutations either completely inhibit fusion by impairing the peptide's ability to stabilize the required peptide bundle (G1V and W14A) or stabilize a persistent bundle that leads to a kinetically trapped hemifusion state (G1S). In addition, our results further suggest that the recently discovered leaky fusion mutant G13A, which is known to facilitate a pronounced leakage of the target membrane prior to lipid mixing, reduces the membrane integrity by forming a 'super' bundle. Our simulations offer a new interpretation for a number of experimentally observed features of the fusion reaction mediated by the prototypical fusion protein, influenza hemagglutinin, and might bring new insights into mechanisms of other viral fusion reactions.
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Affiliation(s)
- Herre Jelger Risselada
- Theoretical Molecular Biophysics Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
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22
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Energetics of stalk intermediates in membrane fusion are controlled by lipid composition. Proc Natl Acad Sci U S A 2012; 109:E1609-18. [PMID: 22589300 DOI: 10.1073/pnas.1119442109] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have used X-ray diffraction on the rhombohedral phospholipid phase to reconstruct stalk structures in different pure lipids and lipid mixtures with unprecedented resolution, enabling a quantitative analysis of geometry, as well as curvature and hydration energies. Electron density isosurfaces are used to study shape and curvature properties of the bent lipid monolayers. We observe that the stalk structure is highly universal in different lipid systems. The associated curvatures change in a subtle, but systematic fashion upon changes in lipid composition. In addition, we have studied the hydration interaction prior to the transition from the lamellar to the stalk phase. The results indicate that facilitating dehydration is the key to promote stalk formation, which becomes favorable at an approximately constant interbilayer separation of 9.0 ± 0.5 Å for the investigated lipid compositions.
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23
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Risselada HJ, Grubmüller H. How SNARE molecules mediate membrane fusion: recent insights from molecular simulations. Curr Opin Struct Biol 2012; 22:187-96. [PMID: 22365575 DOI: 10.1016/j.sbi.2012.01.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 01/11/2012] [Accepted: 01/13/2012] [Indexed: 10/28/2022]
Abstract
SNARE molecules are the core constituents of the protein machinery that facilitate fusion of synaptic vesicles with the presynaptic plasma membrane, resulting in the release of neurotransmitter. On a molecular level, SNARE complexes seem to play a quite versatile and involved role during all stages of fusion. In addition to merely triggering fusion by forcing the opposing membranes into close proximity, SNARE complexes are now seen to also overcome subsequent fusion barriers and to actively guide the fusion reaction up to the expansion of the fusion pore. Here, we review recent advances in the understanding of SNARE-mediated membrane fusion by molecular simulations.
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Affiliation(s)
- Herre Jelger Risselada
- Theoretical Molecular Biophysics Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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24
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Qian S, Huang HW. A novel phase of compressed bilayers that models the prestalk transition state of membrane fusion. Biophys J 2012; 102:48-55. [PMID: 22225797 DOI: 10.1016/j.bpj.2011.11.4009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 11/16/2011] [Accepted: 11/17/2011] [Indexed: 01/02/2023] Open
Abstract
The force model of protein-mediated membrane fusion hypothesizes that fusion is driven by mechanical forces exerted on the membranes, but many details are unknown. Here, we investigated by x-ray diffraction the consequence of applying compressive force on a stack of membranes against the hydration barrier. We found that as the osmotic pressure increased, the lamellar phase transformed first to a new phase of tetragonal lattice (T-phase) over a narrow range of relative humidity, and then to a phase of rhombohedral lattice. The unit cell structure changed from parallel bilayers to a bent configuration with a point contact between adjacent bilayers and then to the stalk hemifusion configuration. The T-phase is discussed as a possible transition state in the membrane merging pathway of fusion. We estimate the work required to form the T-phase and the subsequent hemifusion-stalk-resembling R-phase. The work for the formation of a stalk is compatible with the energy estimated to be released by several SNARE complexes.
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Affiliation(s)
- Shuo Qian
- Department of Physics and Astronomy, Rice University, Houston, Texas, USA
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25
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Ghosh SK, Aeffner S, Salditt T. Effect of PIP2 on Bilayer Structure and Phase Behavior of DOPC: An X-ray Scattering Study. Chemphyschem 2011; 12:2633-40. [DOI: 10.1002/cphc.201100154] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 06/16/2011] [Indexed: 01/16/2023]
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26
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Schneggenburger PE, Beerlink A, Weinhausen B, Salditt T, Diederichsen U. Peptide model helices in lipid membranes: insertion, positioning, and lipid response on aggregation studied by X-ray scattering. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2011; 40:417-36. [PMID: 21181143 PMCID: PMC3070074 DOI: 10.1007/s00249-010-0645-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 11/08/2010] [Accepted: 11/12/2010] [Indexed: 11/18/2022]
Abstract
Studying membrane active peptides or protein fragments within the lipid bilayer environment is particularly challenging in the case of synthetically modified, labeled, artificial, or recently discovered native structures. For such samples the localization and orientation of the molecular species or probe within the lipid bilayer environment is the focus of research prior to an evaluation of their dynamic or mechanistic behavior. X-ray scattering is a powerful method to study peptide/lipid interactions in the fluid, fully hydrated state of a lipid bilayer. For one, the lipid response can be revealed by observing membrane thickening and thinning as well as packing in the membrane plane; at the same time, the distinct positions of peptide moieties within lipid membranes can be elucidated at resolutions of up to several angstroms by applying heavy-atom labeling techniques. In this study, we describe a generally applicable X-ray scattering approach that provides robust and quantitative information about peptide insertion and localization as well as peptide/lipid interaction within highly oriented, hydrated multilamellar membrane stacks. To this end, we have studied an artificial, designed β-helical peptide motif in its homodimeric and hairpin variants adopting different states of oligomerization. These peptide lipid complexes were analyzed by grazing incidence diffraction (GID) to monitor changes in the lateral lipid packing and ordering. In addition, we have applied anomalous reflectivity using synchrotron radiation as well as in-house X-ray reflectivity in combination with iodine-labeling in order to determine the electron density distribution ρ(z) along the membrane normal (z axis), and thereby reveal the hydrophobic mismatch situation as well as the position of certain amino acid side chains within the lipid bilayer. In the case of multiple labeling, the latter technique is not only applicable to demonstrate the peptide's reconstitution but also to generate evidence about the relative peptide orientation with respect to the lipid bilayer.
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Affiliation(s)
- Philipp E. Schneggenburger
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
| | - André Beerlink
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Britta Weinhausen
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Tim Salditt
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Ulf Diederichsen
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
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27
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Risselada HJ, Kutzner C, Grubmüller H. Caught in the Act: Visualization of SNARE-Mediated Fusion Events in Molecular Detail. Chembiochem 2011; 12:1049-55. [DOI: 10.1002/cbic.201100020] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Indexed: 11/10/2022]
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28
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Post-prandial rise of microvesicles in peripheral blood of healthy human donors. Lipids Health Dis 2011; 10:47. [PMID: 21418650 PMCID: PMC3071324 DOI: 10.1186/1476-511x-10-47] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Accepted: 03/21/2011] [Indexed: 01/09/2023] Open
Abstract
Background Microvesicles isolated from body fluids are membrane - enclosed fragments of cell interior which carry information on the status of the organism. It is yet unclear how metabolism affects the number and composition of microvesicles in isolates from the peripheral blood. Aim To study the post - prandial effect on microvesicles in isolates from the peripheral blood of 21 healthy donors, in relation to blood cholesterol and blood glucose concentrations. Results The average number of microvesicles in the isolates increased 5 hours post - prandially by 52%; the increase was statistically significant (p = 0.01) with the power P = 0.68, while the average total blood cholesterol concentration, average low density lipoprotein cholesterol concentration (LDL-C) and average high density lipoprotein cholesterol concentration (HDL-C) all remained within 2% of their fasting values. We found an 11% increase in triglycerides (p = 0.12) and a 6% decrease in blood glucose (p < 0.01, P = 0.74). The post - prandial number of microvesicles negatively correlated with the post - fasting total cholesterol concentration (r = - 0.46, p = 0.035) while the difference in the number of microvesicles in the isolates between post - prandial and post - fasting states negatively correlated with the respective difference in blood glucose concentration (r = - 0.39, p = 0.05). Conclusions In a population of healthy human subjects the number of microvesicles in isolates from peripheral blood increased in the post - prandial state. The increase in the number of microvesicles was affected by the fasting concentration of cholesterol and correlated with the decrease in blood glucose.
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29
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Müller M, Schick M. An Alternate Path for Fusion and its Exploration by Field-Theoretic Means. CURRENT TOPICS IN MEMBRANES 2011; 68:295-323. [DOI: 10.1016/b978-0-12-385891-7.00012-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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30
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Brüning B, Rheinstädter MC, Hiess A, Weinhausen B, Reusch T, Aeffner S, Salditt T. Influence of cholesterol on the collective dynamics of the phospholipid acyl chains in model membranes. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 31:419-428. [PMID: 20405158 DOI: 10.1140/epje/i2010-10574-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 02/18/2010] [Accepted: 03/12/2010] [Indexed: 05/29/2023]
Abstract
We have studied the packing and collective dynamics of the phospholipid acyl chains in a model membrane composed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and cholesterol in varied phase state. After a structural characterization of this two-component model bilayer using X-ray reflectivity, we have carried out coherent inelastic neutron scattering to investigate the chain dynamics. Both DMPC/cholesterol membranes exhibited much sharper and more pronounced low-energy inelastic excitations than a pure DMPC membrane. In the high-energy regime above 10 meV, the insertion of cholesterol into the membrane was found to shift the position of the inelastic excitation towards values otherwise found in the pure lipids gel phase. Thus, the dissipative collective short-range dynamics of the acyl chains is strongly influenced by the presence of cholesterol.
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Affiliation(s)
- B Brüning
- Institut Laue-Langevin, B.P. 156, 38042, Grenoble, France.
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