51
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Sharma VK, Mukhopadhyay R. Deciphering interactions of ionic liquids with biomembrane. Biophys Rev 2018; 10:721-734. [PMID: 29549587 DOI: 10.1007/s12551-018-0410-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 02/27/2018] [Indexed: 12/24/2022] Open
Abstract
Ionic liquids (ILs) are a special class of low-temperature (typically < 100 °C) molten salts, which have huge upsurge interest in the field of chemical synthesis, catalysis, electrochemistry, pharmacology, and biotechnology, mainly due to their highly tunable nature and exceptional properties. However, practical uses of ILs are restricted mainly due to their adverse actions on organisms. Understanding interactions of ILs with biomembrane is prerequisite to assimilate the actions of these ionic compounds on the organism. Here, we review different biophysical methods to characterize interactions between ILs and phospholipid membrane, a model biomembrane. All these studies indicate that ILs interact profoundly with the lipid bilayer and modulate the structure, microscopic dynamics, and phase behavior of the membrane, which could be the fundamental cause of the observed toxicity of ILs. Effects of ILs on the membrane are found to be strongly dependent on the lipophilicity of the IL and are found to increase with the alkyl chain length of IL. This can be correlated with the observed higher toxicity of IL with the longer alkyl chain length. These informations would be useful to tune the toxicity of IL which is required in designing environment-friendly nontoxic solvents of the so-called green chemistry for various practical applications.
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Affiliation(s)
- V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
| | - R Mukhopadhyay
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085, India
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52
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Ib-AMP4 insertion causes surface rearrangement in the phospholipid bilayer of biomembranes: Implications from quartz-crystal microbalance with dissipation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:617-623. [DOI: 10.1016/j.bbamem.2017.10.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 10/24/2017] [Accepted: 10/25/2017] [Indexed: 11/16/2022]
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53
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Sreij R, Dargel C, Geisler P, Hertle Y, Radulescu A, Pasini S, Perez J, Moleiro LH, Hellweg T. DMPC vesicle structure and dynamics in the presence of low amounts of the saponin aescin. Phys Chem Chem Phys 2018; 20:9070-9083. [DOI: 10.1039/c7cp08027a] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Vesicle shape and bilayer parameters are studied by small-angle X-ray (SAXS) and small-angle neutron (SANS) scattering in the presence of the saponin aescin. Bilayer dynamics is studied by neutron spin-echo (NSE) spectroscopy.
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Affiliation(s)
- Ramsia Sreij
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Carina Dargel
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Philippe Geisler
- Cognitronics and Sensor Systems
- CITEC
- Bielefeld University
- Bielefeld
- Germany
| | - Yvonne Hertle
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Aurel Radulescu
- Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum (MLZ)
- Forschungszentrum Jülich GmbH
- Garching
- Germany
| | - Stefano Pasini
- Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum (MLZ)
- Forschungszentrum Jülich GmbH
- Garching
- Germany
| | | | - Lara H. Moleiro
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Thomas Hellweg
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
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54
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Nagao M, Kelley EG, Ashkar R, Bradbury R, Butler PD. Probing Elastic and Viscous Properties of Phospholipid Bilayers Using Neutron Spin Echo Spectroscopy. J Phys Chem Lett 2017; 8:4679-4684. [PMID: 28892394 DOI: 10.1021/acs.jpclett.7b01830] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The elastic and viscous properties of self-assembled amphiphilic membranes dictate the intricate hierarchy of their structure and dynamics ranging from the diffusion of individual molecules to the large-scale deformation of the membrane. We previously demonstrated that neutron spin echo spectroscopy measurements of model amphiphilic membranes can access the naturally occurring submicrosecond membrane motions, such as bending and thickness fluctuations. Here we show how the experimentally measured fluctuation parameters can be used to determine the inherent membrane properties and demonstrate how membrane viscosity and compressibility modulus are influenced by lipid composition in a series of simple phosphatidylcholine bilayers with different tail lengths as a function of temperature. This approach highlights the interdependence of the bilayer elastic and viscous properties and the collective membrane dynamics and opens new avenues to investigating the mechanical properties of more complex and biologically inspired systems.
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Affiliation(s)
- Michihiro Nagao
- NIST Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
- Center for Exploration of Energy and Matter, Department of Physics, Indiana University , Bloomington, Indiana 47408, United States
| | - Elizabeth G Kelley
- NIST Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Rana Ashkar
- Biology and Soft Matter Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Robert Bradbury
- NIST Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
- Center for Exploration of Energy and Matter, Department of Physics, Indiana University , Bloomington, Indiana 47408, United States
| | - Paul D Butler
- NIST Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
- Department of Chemical & Biomolecular Engineering, University of Delaware , Newark, Delaware 19716, United States
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55
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Time-resolved measurements of an ion channel conformational change driven by a membrane phase transition. Proc Natl Acad Sci U S A 2017; 114:10840-10845. [PMID: 28973859 DOI: 10.1073/pnas.1708070114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Using temperature-jump infrared spectroscopy, we are able to trigger a gel-to-fluid phase transition in lipid vesicles and monitor in real time how a membrane protein responds to structural changes in the membrane. The melting of lipid domains in 1,2-dimyristoyl-sn-glycero-3-phosphocholine vesicles is observed to occur in as fast as 50 ns, with a temperature dependence characteristic of critical slowing. Gramicidin D (gD) added to the membrane responds primarily to the change in thickness of the membrane on a timescale coincident with the membrane melting. Using structure-based spectral modeling, we assign the conformational changes to compression and rotation of a partially dissociated gD dimer. Free energy calculations indicate that the high rate is a result of near-barrierless diffusion on a protein energy landscape that is radically reshaped by membrane thinning. The structural changes associated with the phase transition are similar to the fluctuation modes of fluid phase membranes, highlighting the importance of understanding the dynamic nature of the membrane environment around proteins.
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56
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Nagle JF. X-ray scattering reveals molecular tilt is an order parameter for the main phase transition in a model biomembrane. Phys Rev E 2017; 96:030401. [PMID: 29346876 DOI: 10.1103/physreve.96.030401] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Indexed: 11/07/2022]
Abstract
Synchrotron diffuse x-ray scattering data reveal a dramatic softening of the molecular tilt modulus K_{θ} of the model biomembrane composed of DMPC lipids as the temperature is lowered towards the main phase transition temperature at T_{M}=24^{∘}C. Spontaneous tilt occurs below T_{M}, suggesting that tilt is a symmetry breaking order parameter. Consistent with this hypothesis, it is also found that a different lipid POPS has no spontaneous tilt below its T_{M} at 14^{∘}C and correspondingly its tilt modulus did not soften as T_{M} was approached from above. As previously known, the bending modulus K_{C} of DMPC also softens close to T_{M}, but unlike the tilt modulus, K_{C} has a maximum 3^{∘} above T_{M}, which also marks the limit of the well-known anomalous swelling regime. Tilt adds a different perspective to our previous understanding of the main phase transition in lipid bilayers.
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Affiliation(s)
- John F Nagle
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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57
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Nickels JD, Chatterjee S, Mostofian B, Stanley CB, Ohl M, Zolnierczuk P, Schulz R, Myles DAA, Standaert RF, Elkins JG, Cheng X, Katsaras J. Bacillus subtilis Lipid Extract, A Branched-Chain Fatty Acid Model Membrane. J Phys Chem Lett 2017; 8:4214-4217. [PMID: 28825491 DOI: 10.1021/acs.jpclett.7b01877] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Lipid extracts are an excellent choice of model biomembrane; however at present, there are no commercially available lipid extracts or computational models that mimic microbial membranes containing the branched-chain fatty acids found in many pathogenic and industrially relevant bacteria. We advance the extract of Bacillus subtilis as a standard model for these diverse systems, providing a detailed experimental description and equilibrated atomistic bilayer model included as Supporting Information to this Letter and at ( http://cmb.ornl.gov/members/cheng ). The development and validation of this model represents an advance that enables more realistic simulations and experiments on bacterial membranes and reconstituted bacterial membrane proteins.
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Affiliation(s)
| | | | | | | | - Michael Ohl
- Jülich Center for Neutron Science, Forschungszentrum Juelich GmbH , Outstation at SNS, Oak Ridge, Tennessee 37831, United States
| | - Piotr Zolnierczuk
- Jülich Center for Neutron Science, Forschungszentrum Juelich GmbH , Outstation at SNS, Oak Ridge, Tennessee 37831, United States
| | - Roland Schulz
- Intel Corporation , Hillsboro, Oregon 97124, United States of America
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58
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Thermal Response Analysis of Phospholipid Bilayers Using Ellipsometric Techniques. BIOSENSORS-BASEL 2017; 7:bios7030034. [PMID: 28820461 PMCID: PMC5618040 DOI: 10.3390/bios7030034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 08/15/2017] [Accepted: 08/16/2017] [Indexed: 12/29/2022]
Abstract
Biomimetic planar artificial membranes have been widely studied due to their multiple applications in several research fields. Their humectation and thermal response are crucial for reaching stability; these characteristics are related to the molecular organization inside the bilayer, which is affected by the aliphatic chain length, saturations, and molecule polarity, among others. Bilayer stability becomes a fundamental factor when technological devices are developed—like biosensors—based on those systems. Thermal studies were performed for different types of phosphatidylcholine (PC) molecules: two pure PC bilayers and four binary PC mixtures. These analyses were carried out through the detection of slight changes in their optical and structural parameters via Ellipsometry and Surface Plasmon Resonance (SPR) techniques. Phospholipid bilayers were prepared by Langmuir-Blodgett technique and deposited over a hydrophilic silicon wafer. Their molecular inclination degree, mobility, and stability of the different phases were detected and analyzed through bilayer thickness changes and their optical phase-amplitude response. Results show that certain binary lipid mixtures—with differences in its aliphatic chain length—present a co-existence of two thermal responses due to non-ideal mixing.
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59
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Mineart KP, Kelley EG, Nagao M, Prabhu VM. Processing-structure relationships of poly(ethylene glycol)-modified liposomes. SOFT MATTER 2017; 13:5228-5232. [PMID: 28730191 PMCID: PMC11112619 DOI: 10.1039/c7sm00960g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Liposomes with PEG-modified surfaces are amenable to nanocarrier applications and can be prepared via two PEGylated lipid incorporation routes: before and after extrusion (i.e., co-extrusion and post-insertion, respectively). The current study quantifies the processing influence on PEG chain partitioning between the interior and exterior liposome surfaces for the first time using small angle neutron scattering.
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Affiliation(s)
- Kenneth P Mineart
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
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60
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Room-temperature ionic liquids meet bio-membranes: the state-of-the-art. Biophys Rev 2017; 9:309-320. [PMID: 28779453 DOI: 10.1007/s12551-017-0279-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 07/12/2017] [Indexed: 10/19/2022] Open
Abstract
Room-temperature ionic liquids (RTIL) are a new class of organic salts whose melting temperature falls below the conventional limit of 100 °C. Their low vapor pressure, moreover, has made these ionic compounds the solvents of choice of the so-called green chemistry. For these and other peculiar characteristics, they are increasingly used in industrial applications. However, studies of their interaction with living organisms have highlighted mild to severe health hazards. Since their cytotoxicity shows a positive correlation with their lipophilicity, several chemical-physical studies of their interactions with biomembranes have been carried out in the last few years, aiming to identify the molecular mechanisms behind their toxicity. Cation chain length and anion nature of RTILs have seemed to affect lipophilicity and, in turn, their toxicity. However, the emerging picture raises new questions, points to the need to assess toxicity on a case-by-case basis, but also suggests a potential positive role of RTILs in pharmacology, bio-medicine and bio-nanotechnology. Here, we review this new subject of research, and comment on the future and the potential importance of this emerging field of study.
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61
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Zakhvataev VE. Localized density pulses in lipid membranes on the piсosecond time scale. Biophysics (Nagoya-shi) 2017. [DOI: 10.1134/s0006350917030253] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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62
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Dolatmoradi A, Mirtaheri E, El-Zahab B. Thermo-acoustofluidic separation of vesicles based on cholesterol content. LAB ON A CHIP 2017; 17:1332-1339. [PMID: 28272605 DOI: 10.1039/c7lc00161d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Biomechanical properties of cells such as cellular stiffness have been increasingly considered as biomarkers for diseases. For instance, stiffness of cancer cells has been correlated to the malignant potential in certain cell lines. In cells, the cholesterol content plays a crucial role in determining stiffness. Changes in the cholesterol content in cellular membranes can be an indication of pathological disorders. Acoustophoresis as a separation and diagnostic tool is well positioned to help in the separation and diagnosis of cells taking advantage of its unique separation criteria of density and compressibility. However, under the same conditions, cells and vesicles secreted by these cells often have a positive contrast factor sign and thus do not yield simple separations. Thermally-assisted acoustophoresis, also referred to as thermo-acoustophoresis, solves this problem by adding a temperature dimension to the separation. In this work, we evaluate the acoustic contrast temperature (TΦ) of vesicles at different cholesterol molar ratios (Xchol) and develop a multi-stage lab-on-a-chip method to accomplish for the first time the separation of a three-vesicle mixture. Using Xchol = 0.1, 0.2, and 0.3 vesicles, we have obtained separation efficiencies exceeding 93%. The simplicity, rapidity, and label-free nature of this approach holds promise as a diagnostic and separation tool for cells and extracellular vesicles such as exosomes and microvesicles.
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Affiliation(s)
- Ata Dolatmoradi
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA.
| | - Elnaz Mirtaheri
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA.
| | - Bilal El-Zahab
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA.
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63
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Liu Y. Intermediate scattering function for macromolecules in solutions probed by neutron spin echo. Phys Rev E 2017; 95:020501. [PMID: 28297913 DOI: 10.1103/physreve.95.020501] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Indexed: 11/07/2022]
Abstract
The neutron-spin-echo method (NSE) is a powerful technique for studying internal dynamics of macromolecules in solutions because it can simultaneously probe length and time scales comparable to intramolecular density fluctuations of macromolecules. Recently, there has been increased, strong interest in studying protein internal motions using NSE. The coherent intermediate scattering function (ISF) measured by NSE depends on internal, rotational, and translational motions of macromolecules in solutions. It is thus critical, but highly nontrivial, to separate the internal motion from other motions in order to properly understand protein internal dynamics. Even though many experiments are performed at relatively high concentrations, current theories of calculating the ISF of concentrated protein solutions are either inaccurate or flawed by incorrect assumptions for realistic protein systems with anisotropic shapes. Here, a theoretical framework is developed to establish the quantitative relationship of different motions included in the ISF. This theory based on the dynamic decoupling approximation is applicable to a wide range of protein concentrations, including dilute cases. It is also, in general, useful for studying many other types of macromolecule systems studied by NSE.
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Affiliation(s)
- Yun Liu
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, USA
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64
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Bryant SJ, Wood K, Atkin R, Warr GG. Effect of protic ionic liquid nanostructure on phospholipid vesicle formation. SOFT MATTER 2017; 13:1364-1370. [PMID: 28111683 DOI: 10.1039/c6sm02652d] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The formation of bilayer-based lyotropic liquid crystals and vesicle dispersions by phospholipids in a range of protic ionic liquids has been investigated by polarizing optical microscopy using isothermal penetration scans, differential scanning calorimetry, and small angle X-ray and neutron scattering. The stability and structure of both lamellar phases and vesicle dispersions is found to depend primarily on the underlying amphiphilic nanostructure of the ionic liquid itself. This finding has significant implications for the use of ionic liquids in soft and biological materials and for biopreservation, and demonstrates how vesicle structure and properties can be controlled through selection of cation and anion. For a given ionic liquid, systematic trends in bilayer thickness, chain-melting temperature and enthalpy increase with phospholipid acyl chain length, paralleling behaviour in aqueous systems.
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Affiliation(s)
- Saffron J Bryant
- School of Chemistry, F11, The University of Sydney, NSW 2006, Australia.
| | - Kathleen Wood
- Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC NSW 2232, Australia
| | - Rob Atkin
- Discipline of Chemistry, The University of Newcastle, Newcastle, NSW 2308, Australia
| | - Gregory G Warr
- School of Chemistry, F11, The University of Sydney, NSW 2006, Australia.
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65
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Narayanan T, Wacklin H, Konovalov O, Lund R. Recent applications of synchrotron radiation and neutrons in the study of soft matter. CRYSTALLOGR REV 2017. [DOI: 10.1080/0889311x.2016.1277212] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
| | - Hanna Wacklin
- European Spallation Source ERIC, Lund, Sweden
- Physical Chemistry, Lund University, Lund, Sweden
| | | | - Reidar Lund
- Department of Chemistry, University of Oslo, Blindern, Oslo, Norway
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66
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Carrillo JMY, Katsaras J, Sumpter BG, Ashkar R. A Computational Approach for Modeling Neutron Scattering Data from Lipid Bilayers. J Chem Theory Comput 2017; 13:916-925. [DOI: 10.1021/acs.jctc.6b00968] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
| | - John Katsaras
- Department
of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
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67
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Sharma VK, Mamontov E, Ohl M, Tyagi M. Incorporation of aspirin modulates the dynamical and phase behavior of the phospholipid membrane. Phys Chem Chem Phys 2017; 19:2514-2524. [DOI: 10.1039/c6cp06202d] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Effect of aspirin on the microscopic dynamics of a membrane has been investigated using quasielastic neutron scattering and neutron spin echo techniques.
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Affiliation(s)
- V. K. Sharma
- Solid State Physics Division
- Bhabha Atomic Research Centre
- Mumbai 400085
- India
| | - E. Mamontov
- Chemical and Engineering Materials Division
- Neutron Sciences Directorate
- Oak Ridge National Laboratory
- Oak Ridge
- USA
| | - M. Ohl
- Jülich Center for Neutron Science
- Oak Ridge
- USA
| | - M. Tyagi
- National Institute of Standards and Technology Center for Neutron Research
- Gaithersburg
- USA
- Department of Materials Science and Engineering
- University of Maryland
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68
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Bradbury R, Nagao M. Effect of charge on the mechanical properties of surfactant bilayers. SOFT MATTER 2016; 12:9383-9390. [PMID: 27830216 DOI: 10.1039/c6sm01686c] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Charge effects on the mechanical properties of surfactant bilayers have been measured, for a system with a low ionic strength, using small-angle neutron scattering and neutron spin echo spectroscopy. We report that, not only does increasing the surface charge density lead to greater structural ordering and a stiffening of the membrane, which is consistent with classical theory of charge effects on membranes, but also that the relaxation rate of the membrane thickness fluctuations decreases without affecting the fluctuation amplitude. From the relaxation rate we demonstrate, using recent theory, that the viscosity of the surfactant membrane is increased with surface charge density, which suggests that the amount of charge controls the diffusion behavior of inclusions inside the membrane. The present results confirm that the thickness fluctuation relaxation rate and amplitude are tuned independently since the membrane viscosity is only influencing the relaxation rate. This work demonstrates that charge stabilization of lamellar bilayers is not merely affected by intermembrane interactions and structural ordering but that intramembrane dynamics also have a significant contribution.
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Affiliation(s)
- Robert Bradbury
- Center for Exploration of Energy and Matter, Department of Physics, Indiana University, Bloomington, Indiana, USA. and National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland, USA
| | - Michihiro Nagao
- Center for Exploration of Energy and Matter, Department of Physics, Indiana University, Bloomington, Indiana, USA. and National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland, USA
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69
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Helgeson ME. Colloidal behavior of nanoemulsions: Interactions, structure, and rheology. Curr Opin Colloid Interface Sci 2016. [DOI: 10.1016/j.cocis.2016.06.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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70
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Dolatmoradi A, El-Zahab B. Thermally-assisted ultrasonic separation of giant vesicles. LAB ON A CHIP 2016; 16:3449-53. [PMID: 27477522 PMCID: PMC5010174 DOI: 10.1039/c6lc00765a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report on a newly-developed membrane stiffness-based separation of vesicles using a thermally-assisted acoustophoretic approach. By tuning the temperature, we achieved the separation of vesicles of the same size, shape, and charge but with different stiffness values. It was observed that at a specific transition point, the acoustic contrast factor of vesicles changed sign from positive to negative. This change was mainly due to the change in the acoustic compressibility of the vesicles, which is inversely proportional to stiffness. The acoustic contrast temperature, corresponding to the temperature at which the acoustic contrast factor switches sign, was determined to be unique to the composition of the vesicles. This unique temperature signature allowed us to develop a separation method of vesicles with distinct membrane stiffness with target outlet purities exceeding 95%. Our studies suggest that this method may be applied for the separation of cells affected by diseases that affect the cellular stiffness.
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Affiliation(s)
- Ata Dolatmoradi
- Department of Mechanical and Materials Engineering, Florida International University, Miami 33174, FL, USA.
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71
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Bryant SJ, Atkin R, Warr GG. Spontaneous vesicle formation in a deep eutectic solvent. SOFT MATTER 2016; 12:1645-1648. [PMID: 26701210 DOI: 10.1039/c5sm02660a] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Solvent penetration experiments and small-angle X-ray scattering reveal that phospholipids dissolved in a deep eutectic solvent (DES) spontaneously self-assemble into vesicles above the lipid chain melting temperature. This means DESs are one of the few nonaqueous solvents that mediate amphiphile self-assembly, joining a select set of H-bonding molecular solvents and ionic liquids.
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Affiliation(s)
- Saffron J Bryant
- School of Chemistry, The University of Sydney, Sydney, NSW, Australia2006.
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72
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Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells. Sci Rep 2016; 6:19627. [PMID: 26790980 PMCID: PMC4726155 DOI: 10.1038/srep19627] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 12/14/2015] [Indexed: 11/08/2022] Open
Abstract
Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolution inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. Our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. These observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture.
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73
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Marquardt D, Heberle FA, Nickels JD, Pabst G, Katsaras J. On scattered waves and lipid domains: detecting membrane rafts with X-rays and neutrons. SOFT MATTER 2015; 11:9055-72. [PMID: 26428538 PMCID: PMC4719199 DOI: 10.1039/c5sm01807b] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/21/2015] [Indexed: 05/28/2023]
Abstract
In order to understand the biological role of lipids in cell membranes, it is necessary to determine the mesoscopic structure of well-defined model membrane systems. Neutron and X-ray scattering are non-invasive, probe-free techniques that have been used extensively in such systems to probe length scales ranging from angstroms to microns, and dynamics occurring over picosecond to millisecond time scales. Recent developments in the area of phase separated lipid systems mimicking membrane rafts will be presented, and the underlying concepts of the different scattering techniques used to study them will be discussed in detail.
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Affiliation(s)
- Drew Marquardt
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, Graz, Austria. and BioTechMed-Graz, Graz, Austria
| | - Frederick A Heberle
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. and Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
| | - Jonathan D Nickels
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. and Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
| | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, Graz, Austria. and BioTechMed-Graz, Graz, Austria
| | - John Katsaras
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. and Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
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74
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Boţan A, Joly L, Fillot N, Loison C. Mixed Mechanism of Lubrication by Lipid Bilayer Stacks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12197-12202. [PMID: 26381720 DOI: 10.1021/acs.langmuir.5b02786] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Although the key role of lipid bilayer stacks in biological lubrication is generally accepted, the mechanisms underlying their extreme efficiency remain elusive. In this article, we report molecular dynamics simulations of lipid bilayer stacks undergoing load and shear. When the hydration level is reduced, the velocity accommodation mechanism changes from viscous shear in hydration water to interlayer sliding in the bilayers. This enables stacks of hydrated lipid bilayers to act as efficient boundary lubricants for various hydration conditions, structures, and mechanical loads. We also propose an estimation for the friction coefficient; thanks to the strong hydration forces between lipid bilayers, the high local viscosity is not in contradiction with low friction coefficients.
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Affiliation(s)
- Alexandru Boţan
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon , 69622 Villeurbanne, France
| | - Laurent Joly
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon , 69622 Villeurbanne, France
| | - Nicolas Fillot
- LaMCoS, UMR5259 INSA-Lyon-CNRS, Université de Lyon , 69622 Villeurbanne, France
| | - Claire Loison
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon , 69622 Villeurbanne, France
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75
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Wolfe AJ, Mohammad MM, Thakur AK, Movileanu L. Global redesign of a native β-barrel scaffold. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:19-29. [PMID: 26456555 DOI: 10.1016/j.bbamem.2015.10.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Revised: 10/03/2015] [Accepted: 10/07/2015] [Indexed: 11/30/2022]
Abstract
One persistent challenge in membrane protein design is accomplishing extensive modifications of proteins without impairing their functionality. A truncation derivative of the ferric hydroxamate uptake component A (FhuA), which featured the deletion of the 160-residue cork domain and five large extracellular loops, produced the conversion of a non-conductive, monomeric, 22-stranded β-barrel protein into a large-conductance protein pore. Here, we show that this redesigned β-barrel protein tolerates an extensive alteration in the internal surface charge, encompassing 25 negative charge neutralizations. By using single-molecule electrophysiology, we noted that a commonality of various truncation FhuA protein pores was the occurrence of 33% blockades of the unitary current at very high transmembrane potentials. We determined that these current transitions were stimulated by their interaction with an external cationic polypeptide, which occurred in a fashion dependent on the surface charge of the pore interior as well as the polypeptide characteristics. This study shows promise for extensive engineering of a large monomeric β-barrel protein pore in molecular biomedical diagnosis, therapeutics, and biosensor technology.
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Affiliation(s)
- Aaron J Wolfe
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA; Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA
| | - Mohammad M Mohammad
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA
| | - Avinash K Thakur
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA; Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA; Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA; The Syracuse Biomaterials Institute, Syracuse University, 121 Link Hall, Syracuse, NY 13244, USA.
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76
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Nickels JD, Cheng X, Mostofian B, Stanley C, Lindner B, Heberle FA, Perticaroli S, Feygenson M, Egami T, Standaert RF, Smith JC, Myles DAA, Ohl M, Katsaras J. Mechanical Properties of Nanoscopic Lipid Domains. J Am Chem Soc 2015; 137:15772-80. [DOI: 10.1021/jacs.5b08894] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jonathan D. Nickels
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
- Department
of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
- Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, United States
| | - Xiaolin Cheng
- Center
for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department
of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Barmak Mostofian
- Center
for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | | | - Benjamin Lindner
- Center
for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Frederick A. Heberle
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
- Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, United States
| | - Stefania Perticaroli
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
- Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, United States
| | - Mikhail Feygenson
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
| | - Takeshi Egami
- Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, United States
| | - Robert F. Standaert
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
- Department
of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jeremy C. Smith
- Center
for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department
of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Dean A. A. Myles
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
| | - Michael Ohl
- Jülich Center for Neutron Science, Oak
Ridge, Tennessee 37831, United States
| | - John Katsaras
- Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States
- Department
of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
- Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, United States
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77
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Mukherjee D, Porter A, Ryan M, Schwander S, Chung KF, Tetley T, Zhang J, Georgopoulos P. Modeling In Vivo Interactions of Engineered Nanoparticles in the Pulmonary Alveolar Lining Fluid. NANOMATERIALS 2015; 5:1223-1249. [PMID: 26240755 PMCID: PMC4521411 DOI: 10.3390/nano5031223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Increasing use of engineered nanomaterials (ENMs) in consumer products may result in widespread human inhalation exposures. Due to their high surface area per unit mass, inhaled ENMs interact with multiple components of the pulmonary system, and these interactions affect their ultimate fate in the body. Modeling of ENM transport and clearance in vivo has traditionally treated tissues as well-mixed compartments, without consideration of nanoscale interaction and transformation mechanisms. ENM agglomeration, dissolution and transport, along with adsorption of biomolecules, such as surfactant lipids and proteins, cause irreversible changes to ENM morphology and surface properties. The model presented in this article quantifies ENM transformation and transport in the alveolar air to liquid interface and estimates eventual alveolar cell dosimetry. This formulation brings together established concepts from colloidal and surface science, physics, and biochemistry to provide a stochastic framework capable of capturing essential in vivo processes in the pulmonary alveolar lining layer. The model has been implemented for in vitro solutions with parameters estimated from relevant published in vitro measurements and has been extended here to in vivo systems simulating human inhalation exposures. Applications are presented for four different ENMs, and relevant kinetic rates are estimated, demonstrating an approach for improving human in vivo pulmonary dosimetry.
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Affiliation(s)
- Dwaipayan Mukherjee
- Environmental and Occupational Health Sciences Institute (EOHSI), Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA; E-Mail:
- Department of Environmental and Occupational Medicine, Robert Wood Johnson Medical School, Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA
- Department of Chemical and Biochemical Engineering, Rutgers University, 98 Brett Road, Piscataway, NJ 08854, USA
| | - Alexandra Porter
- Department of Materials and London Centre of Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK; E-Mails: (A.P.); (M.R.)
| | - Mary Ryan
- Department of Materials and London Centre of Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK; E-Mails: (A.P.); (M.R.)
| | - Stephan Schwander
- Department of Environmental and Occupational Health, School of Public Health, Rutgers University, 683 Hoes Lane West, Piscataway, NJ 08854, USA; E-Mail:
| | - Kian Fan Chung
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK; E-Mails: (K.F.C.); (T.T.)
| | - Teresa Tetley
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK; E-Mails: (K.F.C.); (T.T.)
| | - Junfeng Zhang
- Nicholas School of the Environment and Duke Global Health Institute, Duke University, 9 Circuit Drive, Durham, NC 27708, USA; E-Mail:
| | - Panos Georgopoulos
- Environmental and Occupational Health Sciences Institute (EOHSI), Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA; E-Mail:
- Department of Environmental and Occupational Medicine, Robert Wood Johnson Medical School, Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA
- Department of Chemical and Biochemical Engineering, Rutgers University, 98 Brett Road, Piscataway, NJ 08854, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-848-445-0159
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78
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Ashkar R, Nagao M, Butler PD, Woodka AC, Sen MK, Koga T. Tuning membrane thickness fluctuations in model lipid bilayers. Biophys J 2015; 109:106-12. [PMID: 26153707 PMCID: PMC4571027 DOI: 10.1016/j.bpj.2015.05.033] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 05/22/2015] [Accepted: 05/28/2015] [Indexed: 11/21/2022] Open
Abstract
Membrane thickness fluctuations have been associated with a variety of critical membrane phenomena, such as cellular exchange, pore formation, and protein binding, which are intimately related to cell functionality and effective pharmaceuticals. Therefore, understanding how these fluctuations are controlled can remarkably impact medical applications involving selective macromolecule binding and efficient cellular drug intake. Interestingly, previous reports on single-component bilayers show almost identical thickness fluctuation patterns for all investigated lipid tail-lengths, with similar temperature-independent membrane thickness fluctuation amplitude in the fluid phase and a rapid suppression of fluctuations upon transition to the gel phase. Presumably, in vivo functions require a tunability of these parameters, suggesting that more complex model systems are necessary. In this study, we explore lipid tail-length mismatch as a regulator for membrane fluctuations. Unilamellar vesicles of an equimolar mixture of dimyristoylphosphatidylcholine and distearoylphosphatidylcholine molecules, with different tail-lengths and melting transition temperatures, are used as a model system for this next level of complexity. Indeed, this binary system exhibits a significant response of membrane dynamics to thermal variations. The system also suggests a decoupling of the amplitude and the relaxation time of the membrane thickness fluctuations, implying a potential for independent control of these two key parameters.
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Affiliation(s)
- Rana Ashkar
- National Institute of Standards and Technology (NIST) Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland; Department of Material Science and Engineering, University of Maryland, College Park, Maryland
| | - Michihiro Nagao
- National Institute of Standards and Technology (NIST) Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland; Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana.
| | - Paul D Butler
- National Institute of Standards and Technology (NIST) Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland; Department of Chemical & Biomolecular Engineering, University of Delaware, Newark, Delaware
| | - Andrea C Woodka
- Department of Chemistry & Life Science, United States Military Academy, West Point, New York
| | - Mani K Sen
- Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York
| | - Tadanori Koga
- Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York; Chemical and Molecular Engineering Program, Stony Brook University, Stony Brook, New York
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79
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Abstract
Water is crucial to the structure and function of biological membranes. In fact, the membrane's basic structural unit, i.e. the lipid bilayer, is self-assembled and stabilized by the so-called hydrophobic effect, whereby lipid molecules unable to hydrogen bond with water aggregate in order to prevent their hydrophobic portions from being exposed to water. However, this is just the beginning of the lipid-bilayer-water relationship. This mutual interaction defines vesicle stability in solution, controls small molecule permeation, and defines the spacing between lamella in multi-lamellar systems, to name a few examples. This chapter will describe the structural and dynamical properties central to these, and other water- lipid bilayer interactions.
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Affiliation(s)
- Jonathan D Nickels
- Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
| | - John Katsaras
- Biology & Soft Matter and Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
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80
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Biehl R, Richter D. Slow internal protein dynamics in solution. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:503103. [PMID: 25419898 DOI: 10.1088/0953-8984/26/50/503103] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Large-scale domain dynamics in proteins are found when flexible linkers or hinges connect domains. The related conformational changes are often related to the function of the protein,for example by arranging the active center after substrate binding or allowing transport and release of products. The adaptation of a specific active structure is referred to as ‘induced fit’ and is challenged by models such as ‘conformational sampling’. Newer models about protein unction include some flexibility within the protein structure or even internal dynamics of the protein. As larger domains contribute to the configurational changes, the timescale of the involved motions is slowed down. The role of slow domain dynamics is being increasingly recognized as essential to understanding the function of proteins. Neutron spin echospectroscopy (NSE) is a technique that is able to access the related timescales from 0.1 up to several hundred nanoseconds and simultaneously covers the length scale relevant for protein domain movements of several nanometers distance between domains. Here we focus on these large-scale domain fluctuations and show how the structure and dynamics of proteins can be assessed by small-angle neutron scattering and NSE.
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81
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Jablin MS, Akabori K, Nagle JF. Experimental support for tilt-dependent theory of biomembrane mechanics. PHYSICAL REVIEW LETTERS 2014; 113:248102. [PMID: 25541806 DOI: 10.1103/physrevlett.113.248102] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Indexed: 06/04/2023]
Abstract
Recent simulations have indicated that the traditional model for topographical fluctuations in biomembranes should be enriched to include molecular tilt. Here we report the first experimental data supporting this enrichment. Utilizing a previously posited tilt-dependent model, a height-height correlation function was derived. The x-ray scattering from a liquid crystalline stack of oriented fluid phase lipid bilayers was calculated and compared with experiment. By fitting the measured scattering intensity, both the bending modulus K(c)=8.3±0.6×10⁻²⁰ J and the tilt modulus K(θ)=95±7 mN/m were determined for DOPC lipid bilayers at 30 °C.
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Affiliation(s)
- M S Jablin
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - K Akabori
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - J F Nagle
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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82
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Mell M, Moleiro LH, Hertle Y, López-Montero I, Cao FJ, Fouquet P, Hellweg T, Monroy F. Fluctuation dynamics of bilayer vesicles with intermonolayer sliding: experiment and theory. Chem Phys Lipids 2014; 185:61-77. [PMID: 25455136 DOI: 10.1016/j.chemphyslip.2014.11.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 11/24/2014] [Accepted: 11/27/2014] [Indexed: 10/24/2022]
Abstract
The presence of coupled modes of membrane motion in closed shells is extensively predicted by theory. The bilayer structure inherent to lipid vesicles is suitable to support hybrid modes of curvature motion coupling membrane bending with the local reorganization of the bilayer material through relaxation of the dilatational stresses. Previous experiments evidenced the existence of such hybrid modes facilitating membrane bending at high curvatures in lipid vesicles [Rodríguez-García, R., Arriaga, L.R., Mell, M., Moleiro, L.H., López-Montero, I., Monroy, F., 2009. Phys. Rev. Lett. 102, 128201.]. For lipid bilayers that are able to undergo intermonolayer sliding, the experimental fluctuation spectra are found compatible with a bimodal schema. The usual tension/bending fluctuations couple with the hybrid modes in a mechanical interplay, which becomes progressively efficient with increasing vesicle radius, to saturate at infinity radius into the behavior expected for a flat membrane. Grounded on the theory of closed shells, we propose an approximated expression of the bimodal spectrum, which predicts the observed dependencies on the vesicle radius. The dynamical features obtained from the autocorrelation functions of the vesicle fluctuations are found in quantitative agreement with the proposed theory.
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Affiliation(s)
- Michael Mell
- Departamento de Química Física I, Universidad Complutense de Madrid, E-28040 Madrid, Spain
| | - Lara H Moleiro
- Departamento de Química Física I, Universidad Complutense de Madrid, E-28040 Madrid, Spain; Physikalische Chemie I, Univeristät Bayreuth, Universitätsstraße 30, D-95447 Bayreuth, Germany
| | - Yvonne Hertle
- Physikalische und Biophysikalische Chemie I, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Iván López-Montero
- Departamento de Química Física I, Universidad Complutense de Madrid, E-28040 Madrid, Spain
| | - Francisco J Cao
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, E-28040 Madrid, Spain
| | - Peter Fouquet
- TOF/HR Group, Institut Laue Langevin, 6 Rue Jules Horowitz, BP156, F-38042 Grenoble Cedex 9, France
| | - Thomas Hellweg
- Physikalische und Biophysikalische Chemie I, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Francisco Monroy
- Departamento de Química Física I, Universidad Complutense de Madrid, E-28040 Madrid, Spain.
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83
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Ramakrishnan N, Sunil Kumar PB, Radhakrishnan R. Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins. PHYSICS REPORTS 2014; 543:1-60. [PMID: 25484487 PMCID: PMC4251917 DOI: 10.1016/j.physrep.2014.05.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein-lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across the various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham - Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this description, the protein is expressed in the form of a spontaneous curvature field. The approaches include field theoretical methods limited to the small deformation regime, triangulated surfaces and particle-based computational models to investigate the large-deformation regimes observed in the natural state of many biological membranes. Applications of these methods to understand the properties of biological membranes in homogeneous and inhomogeneous environments of proteins, whose underlying curvature fields are either isotropic or anisotropic, are discussed. The diversity in the curvature fields elicits a rich variety of morphological states, including tubes, discs, branched tubes, and caveola. Mapping the thermodynamic stability of these states as a function of tuning parameters such as concentration and strength of curvature induction of the proteins is discussed. The relative stabilities of these self-organized shapes are examined through free-energy calculations. The suite of methods discussed here can be tailored to applications in specific cellular settings such as endocytosis during cargo trafficking and tubulation of filopodial structures in migrating cells, which makes these methods a powerful complement to experimental studies.
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Affiliation(s)
- N. Ramakrishnan
- Department of Chemical and Biomolecular Engineering, Department of Bioengineering, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104
| | - P. B. Sunil Kumar
- Department of Physics, Indian Institute of Technology Madras, Chennai, India - 600036
| | - Ravi Radhakrishnan
- Department of Chemical and Biomolecular Engineering, Department of Bioengineering, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104
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84
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Reusch T, Schülein FJR, Nicolas JD, Osterhoff M, Beerlink A, Krenner HJ, Müller M, Wixforth A, Salditt T. Collective lipid bilayer dynamics excited by surface acoustic waves. PHYSICAL REVIEW LETTERS 2014; 113:118102. [PMID: 25260008 DOI: 10.1103/physrevlett.113.118102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Indexed: 06/03/2023]
Abstract
We use standing surface acoustic waves to induce coherent phonons in model lipid multilayers deposited on a piezoelectric surface. Probing the structure by phase-controlled stroboscopic x-ray pulses we find that the internal lipid bilayer electron density profile oscillates in response to the externally driven motion of the lipid film. The structural response to the well-controlled motion is a strong indication that bilayer structure and membrane fluctuations are intrinsically coupled, even though these structural changes are averaged out in equilibrium and time integrating measurements. Here the effects are revealed by a timing scheme with temporal resolution on the picosecond scale in combination with the sub-nm spatial resolution, enabled by high brilliance synchrotron x-ray reflectivity.
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Affiliation(s)
- T Reusch
- Institut für Röntgenphysik, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - F J R Schülein
- Lehrstuhl für Experimentalphysik I, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany and Nanosystems Initiative Munich, Schellingstrasse 4, 80799 Munich, Germany
| | - J D Nicolas
- Institut für Röntgenphysik, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - M Osterhoff
- Institut für Röntgenphysik, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - A Beerlink
- Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22605 Hamburg, Germany
| | - H J Krenner
- Lehrstuhl für Experimentalphysik I, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany and Nanosystems Initiative Munich, Schellingstrasse 4, 80799 Munich, Germany
| | - M Müller
- Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - A Wixforth
- Lehrstuhl für Experimentalphysik I, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany and Nanosystems Initiative Munich, Schellingstrasse 4, 80799 Munich, Germany
| | - T Salditt
- Institut für Röntgenphysik, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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85
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86
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Hoffmann I, Michel R, Sharp M, Holderer O, Appavou MS, Polzer F, Farago B, Gradzielski M. Softening of phospholipid membranes by the adhesion of silica nanoparticles--as seen by neutron spin-echo (NSE). NANOSCALE 2014; 6:6945-52. [PMID: 24838980 DOI: 10.1039/c4nr00774c] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The interactions between nanoparticles and vesicles are of significant interest both from a fundamental as well as from a practical point of view, as vesicles can serve as a model system for cell membranes. Accordingly the effect of nanoparticles that bind to the vesicle bilayer is very important with respect to understanding their biological impact and also may shed some light on the mechanisms behind the effect of nanotoxicity. In this study we have investigated the influence of small adsorbed silica nanoparticles (SiNPs) on the structure of zwitterionic DOPC vesicles. By a combination of SANS, cryo-TEM, and DLS, we observed that the SiNPs are bound to the outer vesicle surface without significantly affecting the vesicle structure. Most interestingly, by means of neutron spin-echo (NSE) local bilayer fluctuations were studied and one finds a small but marked decrease of the membrane rigidity upon binding of the nanoparticles. This surprising finding may be a relevant aspect for the further understanding of the effects that nanoparticles have on phospholipid bilayers.
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Affiliation(s)
- Ingo Hoffmann
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin, Germany.
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87
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Characterization of the water defect at the HIV-1 gp41 membrane spanning domain in bilayers with and without cholesterol using molecular simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1396-405. [PMID: 24440660 DOI: 10.1016/j.bbamem.2014.01.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 12/24/2013] [Accepted: 01/08/2014] [Indexed: 12/23/2022]
Abstract
The membrane spanning domain (MSD) of human immunodeficiency virus 1 (HIV-1) envelope glycoprotein gp41 is important for fusion and infection. We used molecular dynamics (MD) simulations (3.4 μs total) to relate membrane and peptide properties that lead to water solvation of the α-helical gp41 MSD's midspan arginine in pure dipalmitoylphosphatidylcholine (DPPC) and in 50/50 DPPC/cholesterol membranes. We find that the midspan arginine is solvated by water that penetrates the inner leaflet, leading to a so-called water defect. The water defect is surprisingly robust across initial conditions and membrane compositions, but the presence of cholesterol modulates its behavior in several key ways. In the cholesterol-containing membranes, fluctuations in membrane thickness and water penetration depth are localized near the midspan arginine, and the MSD helices display a tightly regulated tilt angle. In the cholesterol-free membranes, thickness fluctuations are not as strongly correlated to the peptide position and tilt angles vary significantly depending on protein position relative to boundaries between domains of differing thickness. Cholesterol in an HIV-1 viral membrane is required for infection. Therefore, this work suggests that the colocalized water defect and membrane thickness fluctuations in cholesterol-containing viral membranes play an important role in fusion by bringing the membrane closer to a stability limit that must be crossed for fusion to occur.
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88
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Lee V, Hawa T. Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength. J Chem Phys 2013; 139:124905. [DOI: 10.1063/1.4821816] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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89
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Brüning B, Stehle R, Falus P, Farago B. Influence of charge density on bilayer bending rigidity in lipid vesicles: a combined dynamic light scattering and neutron spin-echo study. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:77. [PMID: 23884623 DOI: 10.1140/epje/i2013-13077-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 12/18/2012] [Accepted: 12/20/2012] [Indexed: 05/21/2023]
Abstract
We report a combined dynamic light scattering and neutron spin-echo study on vesicles composed of the uncharged stabilizing lipid 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). Mechanical properties of a model membrane and thus the corresponding bilayer undulation dynamics can be specifically tuned by changing its composition through lipid headgroup or acyl chain properties. We compare the undulation dynamics in lipid vesicles composed of DMPC/DOTAP to vesicles composed of a mixture of the uncharged helper lipid DMPC with the also uncharged reference lipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We have performed dynamic light scattering on the lipid mixtures to investigate changes in lipid vesicle size and the corresponding center-of-mass diffusion. We study lipid translational diffusion in the membrane plane and local bilayer undulations using neutron spin-echo spectroscopy, on two distinct time scales, namely around 25 ns and around 150 ns. Finally, we calculate the respective bilayer bending rigidities κ for both types of lipid vesicles. We find that on the local length scale inserting lipid headgroup charge into the membrane influences the bilayer undulation dynamics and bilayer bending rigidity κ less than inserting lipid acyl chain unsaturation: We observe a bilayer softening with increasing inhomogenity of the lipid mixture, which could be caused by a hydrophobic mismatch between the acyl chains of the respective lipid components, causing a lateral phase segregation (domain formation) in the membrane plane.
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Affiliation(s)
- B Brüning
- Helmholtz Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany.
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90
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Mell M, Moleiro LH, Hertle Y, Fouquet P, Schweins R, López-Montero I, Hellweg T, Monroy F. Bending stiffness of biological membranes: what can be measured by neutron spin echo? THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:75. [PMID: 23852577 DOI: 10.1140/epje/i2013-13075-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 04/10/2013] [Accepted: 05/21/2013] [Indexed: 06/02/2023]
Abstract
Large vesicles obtained by the extrusion method represent adequate membrane models to probe membrane dynamics with neutron radiation. Particularly, the shape fluctuations around the spherical average topology can be recorded by neutron spin echo (NSE). In this paper we report on the applicable theories describing the scattering contributions from bending-dominated shape fluctuations in diluted vesicle dispersions, with a focus on the relative relevance of the master translational mode with respect to the internal fluctuations. Different vesicle systems, including bilayer and non-bilayer membranes, have been scrutinized. We describe the practical ranges where the exact theory of bending fluctuations is applicable to obtain the values of the bending modulus from experiments, and we discuss about the possible internal modes that could be alternatively contributing to shape fluctuations.
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Affiliation(s)
- Michael Mell
- Departamento de Química Física I, Universidad Complutense de Madrid, E-28040 Madrid, Spain
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91
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Heymann JB, Winkler DC, Yim YI, Eisenberg E, Greene LE, Steven AC. Clathrin-coated vesicles from brain have small payloads: a cryo-electron tomographic study. J Struct Biol 2013; 184:43-51. [PMID: 23688956 DOI: 10.1016/j.jsb.2013.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 04/25/2013] [Accepted: 05/09/2013] [Indexed: 02/02/2023]
Abstract
Clathrin coats, which stabilize membrane curvature during endocytosis and vesicular trafficking, form highly polymorphic fullerene lattices. We used cryo-electron tomography to visualize coated particles in isolates from bovine brain. The particles range from ∼66 to ∼134nm in diameter, and only 20% of them (all ⩾80nm) contain vesicles. The remaining 80% are clathrin "baskets", presumably artifactual assembly products. Polyhedral models were built for 54 distinct coat geometries. In true coated vesicles (CVs), most vesicles are offset to one side, leaving a crescent of interstitial space between the coat and the membrane for adaptor proteins and other components. The latter densities are fewer on the membrane-proximal side, which may represent the last part of the vesicle to bud off. A small number of densities - presumably cargo proteins - are associated with the interior surface of the vesicles. The clathrin coat, adaptor proteins, and vesicle membrane contribute almost all of the mass of a CV, with most cargoes accounting for only a few percent. The assembly of a CV therefore represents a massive biosynthetic effort to internalize a relatively diminutive payload. Such a high investment may be needed to overcome the resistance of membranes to high curvature.
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Affiliation(s)
- J Bernard Heymann
- Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, MD 20892, United States.
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