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Nagao M, Seto H. Neutron scattering studies on dynamics of lipid membranes. BIOPHYSICS REVIEWS 2023; 4:021306. [PMID: 38504928 PMCID: PMC10903442 DOI: 10.1063/5.0144544] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 05/01/2023] [Indexed: 03/21/2024]
Abstract
Neutron scattering methods are powerful tools for the study of the structure and dynamics of lipid bilayers in length scales from sub Å to tens to hundreds nm and the time scales from sub ps to μs. These techniques also are nondestructive and, perhaps most importantly, require no additives to label samples. Because the neutron scattering intensities are very different for hydrogen- and deuterium-containing molecules, one can replace the hydrogen atoms in a molecule with deuterium to prepare on demand neutron scattering contrast without significantly altering the physical properties of the samples. Moreover, recent advances in neutron scattering techniques, membrane dynamics theories, analysis tools, and sample preparation technologies allow researchers to study various aspects of lipid bilayer dynamics. In this review, we focus on the dynamics of individual lipids and collective membrane dynamics as well as the dynamics of hydration water.
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Affiliation(s)
| | - Hideki Seto
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
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Gilbert J, Ermilova I, Nagao M, Swenson J, Nylander T. Effect of encapsulated protein on the dynamics of lipid sponge phase: a neutron spin echo and molecular dynamics simulation study. NANOSCALE 2022; 14:6990-7002. [PMID: 35470842 DOI: 10.1039/d2nr00882c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Lipid membranes are highly mobile systems with hierarchical, time and length scale dependent, collective motions including thickness fluctuations, undulations, and topological membrane changes, which play an important role in membrane interactions. In this work we have characterised the effect of encapsulating two industrially important enzymes, β-galactosidase and aspartic protease, in lipid sponge phase nanoparticles on the dynamics of the lipid membrane using neutron spin echo (NSE) spectroscopy and molecular dynamics (MD) simulations. From NSE, reduced membrane dynamics were observed upon enzyme encapsulation, which were dependent on the enzyme concentration and type. By fitting the intermediate scattering functions (ISFs) with a modified Zilman and Granek model including nanoparticle diffusion, an increase in membrane bending rigidity was observed, with a larger effect for β-galactosidase than aspartic protease at the same concentration. MD simulations for the system with and without aspartic protease showed that the lipids relax more slowly in the system with protein due to the replacement of the lipid carbonyl-water hydrogen bonds with lipid-protein hydrogen bonds. This indicates that the most likely cause of the increase in membrane rigidity observed in the NSE measurements was dehydration of the lipid head groups. The dynamics of the protein itself were also studied, which showed a stable secondary structure of protein over the simulation, indicating no unfolding events occurred.
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Affiliation(s)
- Jennifer Gilbert
- Division of Physical Chemistry, Department of Chemistry, Naturvetarvägen 14, Lund University, 22362 Lund, Sweden.
- NanoLund, Lund University, Professorsgatan 1, 223 63 Lund, Sweden
| | - Inna Ermilova
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Michihiro Nagao
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - Jan Swenson
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Tommy Nylander
- Division of Physical Chemistry, Department of Chemistry, Naturvetarvägen 14, Lund University, 22362 Lund, Sweden.
- NanoLund, Lund University, Professorsgatan 1, 223 63 Lund, Sweden
- Lund Institute of Advanced Neutron and X-Ray Science, Scheelevägen 19, 223 70 Lund, Sweden
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Nagao M, Bradbury R, Ansar SM, Kitchens CL. Effect of gold nanoparticle incorporation into oil-swollen surfactant lamellar membranes. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:065102. [PMID: 33344674 PMCID: PMC7744122 DOI: 10.1063/4.0000041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 11/25/2020] [Indexed: 05/08/2023]
Abstract
An oil-swollen surfactant membrane is employed to measure the effects of incorporated hydrophobically functionalized gold nanoparticles (AuNPs) on the structure and dynamics of the membranes. While maintaining an average AuNP diameter of approximately 5 nm, the membrane thickness was varied from 5 nm to 7.5 nm by changing the amount of oil in the membrane. The membranes become softer as the proportion of oil is increased, while the thickness fluctuations become slower. We attribute this to an increased fluctuation wavelength. Incorporation of AuNPs in the membrane induces membrane thinning and softening. Oil molecules surround the nanoparticles in the membrane and help their relatively homogeneous distribution. AuNPs significantly alter the membrane's structure and dynamics through thinning of the membrane, increased compressibility, and possible diffusion of AuNPs inside the membrane.
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Affiliation(s)
| | | | - Siyam M. Ansar
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, USA
| | - Christopher L. Kitchens
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, USA
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Kelley EG, Butler PD, Ashkar R, Bradbury R, Nagao M. Scaling relationships for the elastic moduli and viscosity of mixed lipid membranes. Proc Natl Acad Sci U S A 2020; 117:23365-23373. [PMID: 32883879 PMCID: PMC7519290 DOI: 10.1073/pnas.2008789117] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The elastic and viscous properties of biological membranes play a vital role in controlling cell functions that require local reorganization of the membrane components as well as dramatic shape changes such as endocytosis, vesicular trafficking, and cell division. These properties are widely acknowledged to depend on the unique composition of lipids within the membrane, yet the effects of lipid mixing on the membrane biophysical properties remain poorly understood. Here, we present a comprehensive characterization of the structural, elastic, and viscous properties of fluid membranes composed of binary mixtures of lipids with different tail lengths. We show that the mixed lipid membrane properties are not simply additive quantities of the single-component analogs. Instead, the mixed membranes are more dynamic than either of their constituents, quantified as a decrease in their bending modulus, area compressibility modulus, and viscosity. While the enhanced dynamics are seemingly unexpected, we show that the measured moduli and viscosity for both the mixed and single-component bilayers all scale with the area per lipid and collapse onto respective master curves. This scaling links the increase in dynamics to mixing-induced changes in the lipid packing and membrane structure. More importantly, the results show that the membrane properties can be manipulated through lipid composition the same way bimodal blends of surfactants, liquid crystals, and polymers are used to engineer the mechanical properties of soft materials, with broad implications for understanding how lipid diversity relates to biomembrane function.
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Affiliation(s)
- Elizabeth G Kelley
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899;
| | - Paul D Butler
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716
- Department of Chemistry, The University of Tennessee, Knoxville, TN 37996
| | - Rana Ashkar
- Physics Department, Virginia Tech, Blacksburg, VA 20461
- Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA 20461
| | - Robert Bradbury
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Center for Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408
| | - Michihiro Nagao
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Center for Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19716
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Influence of Chemically Disrupted Photosynthesis on Cyanobacterial Thylakoid Dynamics in Synechocystis sp. PCC 6803. Sci Rep 2019; 9:5711. [PMID: 30952892 PMCID: PMC6450941 DOI: 10.1038/s41598-019-42024-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 03/18/2019] [Indexed: 12/22/2022] Open
Abstract
The photosynthetic machinery of the cyanobacterium Synechocystis sp. PCC 6803 resides in flattened membrane sheets called thylakoids, situated in the peripheral part of the cellular cytoplasm. Under photosynthetic conditions these thylakoid membranes undergo various dynamical processes that could be coupled to their energetic functions. Using Neutron Spin Echo Spectroscopy (NSE), we have investigated the undulation dynamics of Synechocystis sp. PCC 6803 thylakoids under normal photosynthetic conditions and under chemical treatment with DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea), an herbicide that disrupts photosynthetic electron transfer. Our measurements show that DCMU treatment has a similar effect as dark conditions, with differences in the undulation modes of the untreated cells compared to the chemically inhibited cells. We found that the disrupted membranes are 1.5-fold more rigid than the native membranes during the dark cycle, while in light they relax approximately 1.7-fold faster than native and they are 1.87-fold more flexible. The strength of the herbicide disruption effect is characterized further by the damping frequency of the relaxation mode and the decay rate of the local shape fluctuations. In the dark, local thicknesses and shape fluctuations relax twice as fast in native membranes, at 17% smaller mode amplitude, while in light the decay rate of local fluctuations is 1.2-fold faster in inhibited membranes than in native membranes, at 56% higher amplitude. The disrupted electron transfer chain and the decreased proton motive force within the lumenal space partially explain the variations observed in the mechanical properties of the Synechocystis membranes, and further support the hypothesis that the photosynthetic process is tied to thylakoid rigidity in this type of cyanobacterial cell.
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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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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: 11] [Impact Index Per Article: 1.4] [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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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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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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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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Woodka AC, Butler PD, Porcar L, Farago B, Nagao M. Lipid bilayers and membrane dynamics: insight into thickness fluctuations. PHYSICAL REVIEW LETTERS 2012; 109:058102. [PMID: 23006210 DOI: 10.1103/physrevlett.109.058102] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Indexed: 05/08/2023]
Abstract
Thickness fluctuations have long been predicted in biological membranes but never directly observed experimentally. Here, we utilize neutron spin echo spectroscopy to experimentally reveal such fluctuations in a pure, fully saturated, phosphocholine lipid bilayer system. These fluctuations appear as an excess in the dynamics of undulation fluctuations. Like the bending rigidity, the thickness fluctuations change dramatically as the lipid transition temperature is crossed, appearing to be completely suppressed below the transition. Above the transition, the relaxation rate is on the order of 100 ns and is independent of temperature. The amplitude of the thickness fluctuations is 3.7 Å ± 0.7 Å, which agrees well with theoretical calculations and molecular dynamics simulations. The dependence of the fluctuations on lipid tail lengths is also investigated and determined to be minimal in the range of 14 to 18 carbon tails.
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Affiliation(s)
- Andrea C Woodka
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
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