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Dobrynina EA, Zykova VA, Surovtsev NV. In-plane and out-of-plane gigahertz sound velocities of saturated and unsaturated phospholipid bilayers from cryogenic to room temperatures. Chem Phys Lipids 2023; 256:105335. [PMID: 37579988 DOI: 10.1016/j.chemphyslip.2023.105335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/23/2023] [Accepted: 08/11/2023] [Indexed: 08/16/2023]
Abstract
Here, we examined the gigahertz sound velocities of hydrated multibilayers of saturated (1,2-dimyristoyl-sn-glycero-3-phosphocholine, DMPC) and unsaturated (1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC) phospholipids by Brillouin spectroscopy. Out-of-plane and in-plane (lateral) phonons were studied independently of each other. Similar strong temperature dependences of the sound velocities were found for phonons of both types. The sound velocities in the low-temperature limit were two-fold higher than that at physiological temperatures; a significant part of the changes in sound velocity occurs in the solid-like gel phase. The factors that may be involved in the peculiar behavior of sound velocity include changes in the chain conformational state, relaxation susceptibility, changes in the elastic modulus at infinite frequencies, and lateral packing of molecules.
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Affiliation(s)
- E A Dobrynina
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - V A Zykova
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - N V Surovtsev
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia.
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2
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Bolmatov D, Kinnun JJ, Katsaras J, Lavrentovich MO. Phonon-mediated lipid raft formation in biological membranes. Chem Phys Lipids 2020; 232:104979. [PMID: 32980352 DOI: 10.1016/j.chemphyslip.2020.104979] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/21/2020] [Accepted: 09/21/2020] [Indexed: 10/23/2022]
Abstract
Short-wavelength collective molecular motions, also known as phonons, have recently attracted much interest in revealing dynamic properties of biological membranes through the use of neutron and X-ray scattering, infrared and Raman spectroscopies, and molecular dynamics simulations. Experimentally detecting unique vibrational patterns such as, shear phonon excitations, viscoelastic crossovers, transverse acoustic phonon gaps, and continuous and truncated optical phonon modes in cellular membranes, to name a few, has proven non-trivial. Here, we review recent advances in liquid thermodynamics that have resulted in the development of the phonon theory of liquids. The theory has important predictions regarding the shear vibrational spectra of fluids, namely the emergence of viscoelastic crossovers and transverse acoustic phonon gaps. Furthermore, we show that these vibrational patterns are common in soft (non-crystalline) materials, including, but not limited to liquids, colloids, liquid crystals (mesogens), block copolymers, and biological membranes. The existence of viscoelastic crossovers and acoustic phonon gaps define the self-diffusion properties of cellular membranes and provide a molecular picture of the transient nature of lipid rafts (Bolmatov et al., 2020). Importantly, the timescales (picoseconds) for the formation and dissolution of transient lipid rafts match the lifetime of the formation and breakdown of interfacial water hydrogen bonds. Apart from acoustic propagating phonon modes, biological membranes can also support more energetic non-propagating optical phonon excitations, also known as standing waves or breathing modes. Importantly, optical phonons can be truncated due to the existence of finite size nanodomains made up of strongly correlated lipid-cholesterol molecular pairs. These strongly coupled molecular pairs can serve as nucleation centers for the formation of stable rafts at larger length scales, due to correlations of spontaneous fluctuations (Onsager's regression hypothesis). Finally and importantly, molecular level viscoelastic crossovers, acoustic phonon gaps, and continuous and truncated optical phonon modes may offer insights as to how lipid-lipid and lipid-protein interactions enable biological function.
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Affiliation(s)
- Dima Bolmatov
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States.
| | - Jacob J Kinnun
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
| | - John Katsaras
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States; Sample Environment Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
| | - Maxim O Lavrentovich
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States.
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D'Angelo G, Nibali VC, Wanderlingh U, Branca C, De Francesco A, Sacchetti F, Petrillo C, Paciaroni A. Multiple Interacting Collective Modes and Phonon Gap in Phospholipid Membranes. J Phys Chem Lett 2018; 9:4367-4372. [PMID: 30024172 DOI: 10.1021/acs.jpclett.8b01658] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We combine Brillouin neutron scattering measurements with recent inelastic X-ray scattering [ Zhernenkov et al. Nat. Commun. 2016 , 7 , 11575 ] to propose a model for the collective dynamics of phospholipid bilayers. Neutron and X-ray spectra were fitted by the model response function associated with the Hamiltonian of an interacting-phonon system. This approach allows for a comprehensive and unprecedented picture of the vibrational collective features of phospholipids. At low wavevectors Q, the dispersion relations can be interpreted in terms of two acoustic-like modes, one longitudinal and one transverse, plus a dispersionless optic-like mode. The transverse mode of the liquid phase shows a phonon gap that can be linked to a passive transport mechanism through membranes, an interpretation that was proposed in Zhernenkov et al. At higher Q values, the interaction of the longitudinal acoustic excitation with the dispersionless mode gives rise to a pattern that is consistent with avoided-crossing behavior. Evidence is found for a slow- to fast-sound transition, similar to bulk water and other biomolecules.
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Affiliation(s)
- Giovanna D'Angelo
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra , Universitá degli Studi di Messina , Viale F. Stagno d'Alcontres 31 , 98166 Messina , Italy
| | - Valeria Conti Nibali
- Lehrstuhl fur Physikalische Chemie II , Ruhr Universitat , 44801 Bochum , Germany
| | - Ulderico Wanderlingh
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra , Universitá degli Studi di Messina , Viale F. Stagno d'Alcontres 31 , 98166 Messina , Italy
| | - Caterina Branca
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra , Universitá degli Studi di Messina , Viale F. Stagno d'Alcontres 31 , 98166 Messina , Italy
| | - Alessio De Francesco
- Consiglio Nazionale delle Ricerche , Istituto Officina dei Materiali OGG, c/o Institut Laue Langevin , 71 Ave. des Martyrs , BP 156 F-38042 Grenoble Cedex , France
| | - Francesco Sacchetti
- Dipartimento di Fisica e Geologia , Universitá degli Studi di Perugia , Via Pascoli , 06123 Perugia , Italy
| | - Caterina Petrillo
- Dipartimento di Fisica e Geologia , Universitá degli Studi di Perugia , Via Pascoli , 06123 Perugia , Italy
| | - Alessandro Paciaroni
- Dipartimento di Fisica e Geologia , Universitá degli Studi di Perugia , Via Pascoli , 06123 Perugia , Italy
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Alsop RJ, Himbert S, Dhaliwal A, Schmalzl K, Rheinstädter MC. Aspirin locally disrupts the liquid-ordered phase. ROYAL SOCIETY OPEN SCIENCE 2018; 5:171710. [PMID: 29515878 PMCID: PMC5830767 DOI: 10.1098/rsos.171710] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 01/23/2018] [Indexed: 06/12/2023]
Abstract
Local structure and dynamics of lipid membranes play an important role in membrane function. The diffusion of small molecules, the curvature of lipids around a protein and the existence of cholesterol-rich lipid domains (rafts) are examples for the membrane to serve as a functional interface. The collective fluctuations of lipid tails, in particular, are relevant for diffusion of membrane constituents and small molecules in and across membranes, and for structure and formation of membrane domains. We studied the effect of aspirin (acetylsalicylic acid, ASA) on local structure and dynamics of membranes composed of dimyristoylphosphocholine (DMPC) and cholesterol. Aspirin is a common analgesic, but is also used in the treatment of cholesterol. Using coherent inelastic neutron scattering experiments and molecular dynamics (MD) simulations, we present evidence that ASA binds to liquid-ordered, raft-like domains and disturbs domain organization and dampens collective fluctuations. By hydrogen-bonding to lipid molecules, ASA forms 'superfluid' complexes with lipid molecules that can organize laterally in superlattices and suppress cholesterol's ordering effect.
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Affiliation(s)
- Richard J. Alsop
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Sebastian Himbert
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Alexander Dhaliwal
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Karin Schmalzl
- JCNS, Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at ILL, Grenoble, France
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5
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Bolmatov D, Zhernenkov M, Sharpnack L, Agra-Kooijman DM, Kumar S, Suvorov A, Pindak R, Cai YQ, Cunsolo A. Emergent Optical Phononic Modes upon Nanoscale Mesogenic Phase Transitions. NANO LETTERS 2017; 17:3870-3876. [PMID: 28548861 DOI: 10.1021/acs.nanolett.7b01324] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The investigation of phononic collective excitations in soft matter systems at the molecular scale has always been challenging due to limitations of experimental techniques in resolving low-energy modes. Recent advances in inelastic X-ray scattering (IXS) enabled the study of such systems with unprecedented spectral contrast at meV excitation energies. In particular, it has become possible to shed light on the low-energy collective motions in materials whose morphology and phase behavior can easily be manipulated, such as mesogenic systems. The understanding of collective mode behavior with a Q-dependence is the key to implement heat management based on the control of a sample structure. The latter has great potential for a large number of energy-inspired innovations. As a first step toward this goal, we carried out high contrast IXS measurements on a liquid crystal sample, D7AOB, which exhibits solid-like dynamic features, such as the coexistence of longitudinal and transverse phononic modes. For the first time, we found that these terahertz phononic excitations persist in the crystal, smectic A, and isotropic phases. Furthermore, the intermediate smectic A phase is shown to support a van der Waals-mediated nonhydrodynamic mode with an optical-like phononic behavior. The tunability of the collective excitations at nanometer-terahertz scales via selection of the sample mesogenic phase represents a new opportunity to manipulate optomechanical properties of soft metamaterials.
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Affiliation(s)
- Dima Bolmatov
- National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Mikhail Zhernenkov
- National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Lewis Sharpnack
- Department of Physics, Kent State University , Kent, Ohio 44242, United States
| | | | - Satyendra Kumar
- Department of Physics, Kent State University , Kent, Ohio 44242, United States
- Division of Research and Department of Physics, University at Albany , Albany, New York 12222, United States
| | - Alexey Suvorov
- National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Ronald Pindak
- National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Yong Q Cai
- National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Alessandro Cunsolo
- National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
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6
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Wang Z, Chiang WS, Le P, Fratini E, Li M, Alatas A, Baglioni P, Chen SH. One role of hydration water in proteins: key to the "softening" of short time intraprotein collective vibrations of a specific length scale. SOFT MATTER 2014; 10:4298-4303. [PMID: 24789017 DOI: 10.1039/c4sm00257a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
High resolution inelastic X-ray scattering (IXS) experiments show that the "phonon energy softening" and "phonon population enhancement" observed in a hydrated native protein when increasing the temperature from 200 K to physiological temperature are not directly related to the protein structure. Such phenomena were also observed in a denatured sample without a defined tertiary structure and with a limited residual secondary structure. However, in a dry sample, such "softening" is strongly suppressed. These facts suggest that the above-mentioned protein "softening" phenomenon is water-induced. In addition, increasing the hydration level can also induce "phonon energy softening" at room temperature, but not at 200 K. This change may be due to a qualitative difference in the dynamics of hydration water at 200 K and at room temperature.
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Affiliation(s)
- Zhe Wang
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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7
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Brüning BA, Prévost S, Stehle R, Steitz R, Falus P, Farago B, Hellweg T. Bilayer undulation dynamics in unilamellar phospholipid vesicles: effect of temperature, cholesterol and trehalose. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2412-9. [PMID: 24950248 DOI: 10.1016/j.bbamem.2014.06.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/02/2014] [Accepted: 06/09/2014] [Indexed: 10/25/2022]
Abstract
We report a combined dynamic light scattering (DLS) and neutron spin-echo (NSE) study on the local bilayer undulation dynamics of phospholipid vesicles composed of 1,2-dimyristoyl-glycero-3-phosphatidylcholine (DMPC) under the influence of temperature and the additives cholesterol and trehalose. The additives affect vesicle size and self-diffusion. Mechanical properties of the membrane and corresponding bilayer undulations are tuned by changing lipid headgroup or acyl chain properties through temperature or composition. On the local length scale, changes at the lipid headgroup influence the bilayer bending rigidity κ less than changes at the lipid acyl chain: We observe a bilayer softening around the main phase transition temperature Tm of the single lipid system, and stiffening when more cholesterol is added, in concordance with literature. Surprisingly, no effect on the mechanical properties of the vesicles is observed upon the addition of trehalose.
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Affiliation(s)
- Beate-Annette Brüning
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany; Radiation Science and Technology, Delft University of Technology, Mekelweg 15, JB 2629 Delft, The Netherlands.
| | - Sylvain Prévost
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany
| | - Ralf Stehle
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany
| | - Roland Steitz
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany
| | - Peter Falus
- Time-of-Flight and High Resolution, Institut Laue Langevin, B. P. 156, 38042 Grenoble, Cedex 9, France
| | - Bela Farago
- Time-of-Flight and High Resolution, Institut Laue Langevin, B. P. 156, 38042 Grenoble, Cedex 9, France
| | - Thomas Hellweg
- Physical and Biophysical Chemistry, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
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8
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Rheinstädter MC, Mouritsen OG. Small-scale structure in fluid cholesterol–lipid bilayers. Curr Opin Colloid Interface Sci 2013. [DOI: 10.1016/j.cocis.2013.07.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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9
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Wang Z, Bertrand CE, Chiang WS, Fratini E, Baglioni P, Alatas A, Alp EE, Chen SH. Inelastic X-ray Scattering Studies of the Short-Time Collective Vibrational Motions in Hydrated Lysozyme Powders and Their Possible Relation to Enzymatic Function. J Phys Chem B 2013; 117:1186-95. [DOI: 10.1021/jp312842m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhe Wang
- Department of Nuclear Science and
Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Christopher E. Bertrand
- Department of Nuclear Science and
Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Wei-Shan Chiang
- Department of Nuclear Science and
Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Emiliano Fratini
- Department of Chemistry and CSGI, University of Florence, Sesto Fiorentino, Florence,
I-50019, Italy
| | - Piero Baglioni
- Department of Chemistry and CSGI, University of Florence, Sesto Fiorentino, Florence,
I-50019, Italy
| | - Ahmet Alatas
- Advanced Photon
Source, Argonne National Lab, Argonne,
Illinois, 60439, United States
| | - E. Ercan Alp
- Advanced Photon
Source, Argonne National Lab, Argonne,
Illinois, 60439, United States
| | - Sow-Hsin Chen
- Department of Nuclear Science and
Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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10
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11
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Effect of cholesterol on the lateral nanoscale dynamics of fluid membranes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 41:901-13. [DOI: 10.1007/s00249-012-0826-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 05/03/2012] [Accepted: 05/07/2012] [Indexed: 12/17/2022]
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12
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Brüning B, Rheinstädter MC, Hiess A, Weinhausen B, Reusch T, Aeffner S, Salditt T. Influence of cholesterol on the collective dynamics of the phospholipid acyl chains in model membranes. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 31:419-428. [PMID: 20405158 DOI: 10.1140/epje/i2010-10574-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 02/18/2010] [Accepted: 03/12/2010] [Indexed: 05/29/2023]
Abstract
We have studied the packing and collective dynamics of the phospholipid acyl chains in a model membrane composed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and cholesterol in varied phase state. After a structural characterization of this two-component model bilayer using X-ray reflectivity, we have carried out coherent inelastic neutron scattering to investigate the chain dynamics. Both DMPC/cholesterol membranes exhibited much sharper and more pronounced low-energy inelastic excitations than a pure DMPC membrane. In the high-energy regime above 10 meV, the insertion of cholesterol into the membrane was found to shift the position of the inelastic excitation towards values otherwise found in the pure lipids gel phase. Thus, the dissipative collective short-range dynamics of the acyl chains is strongly influenced by the presence of cholesterol.
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Affiliation(s)
- B Brüning
- Institut Laue-Langevin, B.P. 156, 38042, Grenoble, France.
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13
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Brandt EG, Edholm O. Dynamic structure factors from lipid membrane molecular dynamics simulations. Biophys J 2009; 96:1828-38. [PMID: 19254541 DOI: 10.1016/j.bpj.2008.11.044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Accepted: 11/17/2008] [Indexed: 10/21/2022] Open
Abstract
Dynamic structure factors for a lipid bilayer have been calculated from molecular dynamics simulations. From trajectories of a system containing 1024 lipids we obtain wave vectors down to 0.34 nm(-1), which enables us to directly resolve the Rayleigh and Brillouin lines of the spectrum. The results confirm the validity of a model based on generalized hydrodynamics, but also improves the line widths and the position of the Brillouin lines. The improved resolution shows that the Rayleigh line is narrower than in earlier studies, which corresponds to a smaller thermal diffusivity. From a detailed analysis of the power spectrum, we can, in fact, distinguish two dispersive contributions to the elastic scattering. These translate to two exponential relaxation processes in separate time domains. Further, by including a first correction to the wave-vector-dependent position of the Brillouin lines, the results agree favorably to generalized hydrodynamics even up to intermediate wave vectors, and also yields a 20% higher adiabatic sound velocity. The width of the Brillouin lines shows a linear, not quadratic, dependence to low wave vectors.
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Affiliation(s)
- Erik G Brandt
- Theoretical Biological Physics, Department of Theoretical Physics, Royal Institute of Technology (KTH), AlbaNova University Center, Stockholm, Sweden
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14
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Affiliation(s)
- Stefan Balaz
- Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, North Dakota 58105, USA.
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15
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Shushkov PG, Tzvetanov SA, Ivanova AN, Tadjer AV. Dielectric properties tangential to the interface in model insoluble monolayers: theoretical assessment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:4615-4624. [PMID: 18376891 DOI: 10.1021/la703616c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Studies of insoluble monolayers built of phospholipids and various long-chained fatty acids or their glycerin esters are the major source for what is currently known about the relationship between monolayer composition and physicochemical properties. The surface pressure, dipole moment, dielectric permittivity, polarizability, refractivity, and other electrical and optical features are governed by the surfactant structural specificity and solvent organization at the microscopic level. To provide insight into the atomistic details of the interfacial structure, model monolayers at the air/water interface of two distinctly different in composition and isotherm profile surfactants are investigated by means of molecular dynamics all-atom simulations. Analysis of the computational results allows the estimation of empirically unattainable quantities such as tangential (di)electric properties, their decomposition to surfactant and water contributions, and their relationship with the changes in interfacial molecular organization at different surface concentrations. The employed theoretical approach provides a comprehensive description of interfacial phenomena at the molecular level where the traditional phenomenological investigations are ineffective.
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Affiliation(s)
- Philip G Shushkov
- Faculty of Chemistry, University of Sofia, 1 James Bourchier Boulevard, 1164 Sofia, Bulgaria
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16
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Liu Y, Chen SH, Berti D, Baglioni P, Alatas A, Sinn H, Alp E, Said A. Effects of counterion valency on the damping of phonons propagating along the axial direction of liquid-crystalline DNA. J Chem Phys 2005; 123:214909. [PMID: 16356072 DOI: 10.1063/1.2128702] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The phonon propagation and damping along the axial direction of films of aligned 40 wt % calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S(Q,E) as a function of transferred energy E=variant Planck's over 2piomega, and the magnitude of the transferred wave vector Q. S(Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30 nm(-1). A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q=4 nm(-1). The high-frequency sound speed obtained in this Q range is 3100 ms, which is about twice faster than the ultrasound speed of 1800 ms, measured by Brillouin light scattering at Q approximately 0.01 nm(-1) at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between approximately 12.5 and approximately 22.5 nm(-1) are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4 ps.
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Affiliation(s)
- Yun Liu
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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17
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Liu Y, Berti D, Faraone A, Chen WR, Alatas A, Sinn H, Alp E, Said A, Baglioni P, Chen SH. Inelastic X-ray scattering studies of phonons in liquid crystalline DNA. Phys Chem Chem Phys 2004. [DOI: 10.1039/b314462n] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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