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Sharma VK, Gupta J, Mamontov E. Lateral diffusion of lipids in the DMPG membrane across the anomalous melting regime: effects of NaCl. Soft Matter 2022; 19:57-68. [PMID: 36458871 DOI: 10.1039/d2sm01425d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The anionic dimyristoyl phosphatidylglycerol (DMPG) membrane in solvents with a low ionic strength is known to exhibit an unusually wide melting regime between the gel and fluid phase characterized by various anomalous macroscopic characteristics, such as low turbidity and high electrical conductivity and viscosity. A recent neutron spin echo study [Kelley, E. G. et al., Struct. Dyn., 7 (2020) 054704] revealed that during the extended melting phase transition the DMPG membrane becomes softer and exhibits faster collective bending fluctuation compared to the higher temperature fluid phase. In contrast, in the present work, using incoherent quasielastic neutron scattering through the anomalous phase transition regime we find that single-particle lateral and internal lipid motions in the DMPG membrane show regular temperature dependence, with no enhanced dynamics evident in the anomalous melting regime. Further, we find that incorporation of NaCl in DMPG suppresses the anomalous extended melting regime, concurrently enhancing the single-particle lipid dynamics, both the lateral diffusivity and (to a lesser extent) the internal lipid motion. This seems rather counterintuitive and in variance with the dynamic suppression effect exerted by a salt on a zwitterionic membrane. However, since incorporation of a salt in anionic DMPG leads to enhanced cooperativity, the disrupted cooperativity in the salt-free DMPG is associated with the baseline lipid dynamics that is suppressed to begin with, whereas addition of salt partially restores the cooperativity, thus enhancing lipid dynamics compared to the salt-free baseline DMPG membrane state. These results provide new insights into the ion-membrane interaction and divulge a correlation between microscopic dynamics and the structure of the lipid bilayer.
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Affiliation(s)
- V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - J Gupta
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - E Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
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2
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Sharma VK, Mamontov E. Multiscale lipid membrane dynamics as revealed by neutron spectroscopy. Prog Lipid Res 2022; 87:101179. [PMID: 35780913 DOI: 10.1016/j.plipres.2022.101179] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/25/2022] [Accepted: 06/27/2022] [Indexed: 12/22/2022]
Abstract
The plasma membrane is one of the principal structural components of the cell and, therefore, one of the key components of the cellular life. Because the membrane's dynamics links the membrane's structure and function, the complexity and the broad range of the membrane's motions are essential for the enormously diverse functionality of the cell membrane. Even for the main membrane component, the lipid bilayer, considered alone, the range and complexity of the lipid motions are remarkable. Spanning the time scale from sub-picosecond to minutes and hours, the lipid motion in a bilayer is challenging to study even when a broad array of dynamic measurement techniques is employed. Neutron scattering plays a special role among such dynamic measurement techniques, particularly, because it involves the energy transfers commensurate with the typical intra- and inter- molecular dynamics and the momentum transfers commensurate with intra- and inter-molecular distances. Thus, using neutron scattering-based techniques, the spatial and temporal information on the lipid motion can be obtained and analysed simultaneously. Protium vs. deuterium sensitivity and non-destructive character of the neutron probe add to the remarkable prowess of neutron scattering for elucidating the lipid dynamics. Herein we present an overview of the neutron scattering-based studies of lipid dynamics in model membranes, with a discussion of the direct relevance and implications to the real-life cell membranes. The latter are much more complex systems than simple model membranes, consisting of heterogeneous non-stationary domains composed of lipids, proteins, and other small molecules, such as carbohydrates. Yet many fundamental aspects of the membrane behavior and membrane interactions with other molecules can be understood from neutron scattering measurements of the model membranes. For example, such studies can provide a great deal of information on the interactions of antimicrobial compounds with the lipid matrix of a pathogen membrane, or the interactions of drug molecules with the plasma membrane. Finally, we briefly discuss the recently emerging field of neutron scattering membrane studies with a reach far beyond the model membrane systems.
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Affiliation(s)
- V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India; Homi Bhabha National Institute, Mumbai 400094, India.
| | - E Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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3
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Mamontov E, Boone C, Frost MJ, Herwig KW, Huegle T, Lin JYY, McCormick B, McHargue W, Stoica AD, Torres P, Turner W. A concept of a broadband inverted geometry spectrometer for the Second Target Station at the Spallation Neutron Source. Rev Sci Instrum 2022; 93:045101. [PMID: 35489951 DOI: 10.1063/5.0086451] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 03/11/2022] [Indexed: 06/14/2023]
Abstract
BWAVES is an acronym for Broadband Wide-Angle VElocity Selector spectrometer, indicating that a novel WAVES (Wide-Angle VElocity Selector) device will be used to select the velocity/wavelength of the detected neutrons after they are scattered by the sample. We describe a conceptual design of BWAVES, a time-of-flight broadband inverted-geometry neutron spectrometer for the Second Target Station at the Spallation Neutron Source operated by Oak Ridge National Laboratory. Being the first inverted geometry spectrometer where the energy of the detected neutrons can be chosen by a WAVES device mechanically, irrespective of the limitations imposed by the crystal analyzers or filters, BWAVES will feature a uniquely broad, continuous dynamic range of measurable energy transfers, spanning 4.5 decades. This will enable measurements of both vibrational and relaxational excitations within the same, continuous scattering spectra. Novel approaches that are necessary for the implementation of a WAVES device at the BWAVES spectrometer will result in a spectrometer with the design and characteristics much different from those displayed by the neutron spectrometers in existence today.
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Affiliation(s)
- E Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - C Boone
- SNS Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M J Frost
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - K W Herwig
- SNS Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - T Huegle
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J Y Y Lin
- SNS Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - B McCormick
- SNS Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - W McHargue
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A D Stoica
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P Torres
- SNS Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - W Turner
- SNS Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Bridges CA, Martins ML, Jafta CJ, Sun XG, Paranthaman MP, Liu J, Dai S, Mamontov E. Dynamics of Emim + in [Emim][TFSI]/LiTFSI Solutions as Bulk and under Confinement in a Quasi-liquid Solid Electrolyte. J Phys Chem B 2021; 125:5443-5450. [PMID: 34003647 DOI: 10.1021/acs.jpcb.1c02383] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Quasi-liquid solid electrolytes are a promising alternative for next-generation Li batteries. These systems combine the safety of solid electrolytes with the desired properties of liquids and are typically formed by solutions of Li salts in ionic liquids incorporated into solid matrices. Here, we present a fundamental understanding of the transport properties in solutions of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]), either in bulk form or incorporated in a boron nitride (BN) matrix. We performed a series of quasi-elastic neutron scattering experiments that, given the high incoherent neutron scattering cross section of hydrogen, allowed us to focus on the Emim+ dynamics. First, [Emim][TFSI]/LiTFSI solutions (0.5 and 2.5 mol·kg-1) were investigated and we show how the increase in the concentration reduces the Emim+ mobility and increases the activation energy of their long-range motions. Then, the 0.5 mol·kg-1 solution was incorporated into the BN matrix and we report that the diffusivities of the Emim+ cations that remain mobile under confinement are highly accelerated in comparison with the bulk sample and the activation energy of these motions is drastically reduced. We present the experimental evidence that this effect is related to the content of the Emim+ cations immobilized near the surfaces of the BN pores.
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Affiliation(s)
- C A Bridges
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - M L Martins
- Neutron Scattering Division, Oak Ridge National Laboratory, P.O. Box 2008 MS6455, Oak Ridge, Tennessee 37831, United States
| | - C J Jafta
- Electrification and Energy Infrastructures, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - X G Sun
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - M P Paranthaman
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - J Liu
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - S Dai
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - E Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, P.O. Box 2008 MS6455, Oak Ridge, Tennessee 37831, United States
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5
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Sharma V, Mamontov E, Tyagi M. Effects of NSAIDs on the nanoscopic dynamics of lipid membrane. Biochimica et Biophysica Acta (BBA) - Biomembranes 2020; 1862:183100. [DOI: 10.1016/j.bbamem.2019.183100] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 08/16/2019] [Accepted: 09/19/2019] [Indexed: 01/30/2023]
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Sharma VK, Nagao M, Rai DK, Mamontov E. Membrane softening by nonsteroidal anti-inflammatory drugs investigated by neutron spin echo. Phys Chem Chem Phys 2019; 21:20211-20218. [PMID: 31486459 DOI: 10.1039/c9cp03767e] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In spite of their well-known side effects, the nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most commonly prescribed medications for their antipyretic and anti-inflammatory actions. Interaction of NSAIDs with the plasma membrane plays a vital role in their therapeutic actions and defines many of their side effects. In the present study, we investigate the effects of three NSAIDs, aspirin, ibuprofen, and indomethacin, on the structure and dynamics of a model plasma membrane using a combination of small angle neutron scattering (SANS) and neutron spin echo (NSE) techniques. The SANS and NSE measurements were carried out on a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane, with and without NSAIDs, at two different temperatures, 11 °C and 37 °C, where the DMPC membrane is in the gel and fluid phase, respectively. SANS data analysis shows that incorporation of NSAIDs leads to bilayer thinning of the membrane in both the phases. The dynamic properties of the membrane are represented by the intermediate scattering functions for NSE data, which are successfully described by the Zilman and Granek model. NSE data analysis shows that in both gel and fluid phases, addition of NSAIDs results in a decrease in the bending rigidity and compressibility modulus of the membrane, which is more prominent when the membrane is in the gel phase. The magnitude of the effect of NSAIDs on the bending rigidity and compressibility modulus of the membrane in the gel phase follows an order of ibuprofen > aspirin > indomethacin, whereas in the fluid phase, it is in the order of aspirin > ibuprofen > indomethacin. We find that the interaction between NSAIDs and phospholipid membranes is strongly dependent on the chemical structure of the drugs and physical state of the membrane. Mechanical properties of the membrane can be quantified by the membrane's bending rigidity. Hence, the present study reveals that incorporation of NSAIDs modulates the mechanical properties of the membrane, which may affect several physiological processes, particularly those linked to the membrane curvature.
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Affiliation(s)
- V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
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7
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Buck ZN, Torres J, Miskowiec A, Mamontov E, Kaiser H, Hansen FY, Taub H, Tyagi M, Collins L, Herwig KW. Effect of melittin on water diffusion and membrane structure in DMPC lipid bilayers. ACTA ACUST UNITED AC 2018. [DOI: 10.1209/0295-5075/123/18002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Prisk TR, Hoffmann C, Kolesnikov AI, Mamontov E, Podlesnyak AA, Wang X, Kent PRC, Anovitz LM. Fast Rotational Diffusion of Water Molecules in a 2D Hydrogen Bond Network at Cryogenic Temperatures. Phys Rev Lett 2018; 120:196001. [PMID: 29799243 DOI: 10.1103/physrevlett.120.196001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Indexed: 05/15/2023]
Abstract
Individual water molecules or small clusters of water molecules contained within microporous minerals present an extreme case of confinement where the local structure of hydrogen bond networks are dramatically altered from bulk water. In the zinc silicate hemimorphite, the water molecules form a two-dimensional hydrogen bond network with hydroxyl groups in the crystal framework. Here, we present a combined experimental and theoretical study of the structure and dynamics of water molecules within this network. The water molecules undergo a continuous phase transition in their orientational configuration analogous to a two-dimensional Ising model. The incoherent dynamic structure factor reveals two thermally activated relaxation processes, one on a subpicosecond timescale and another on a 10-100 ps timescale, between 70 and 130 K. The slow process is an in-plane reorientation of the water molecule involving the breaking of hydrogen bonds with a framework that, despite the low temperatures involved, is analogous to rotational diffusion of water molecules in the bulk liquid. The fast process is a localized motion of the water molecule with no apparent analogs among known bulk or confined phases of water.
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Affiliation(s)
- T R Prisk
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 208996-6100, USA
| | - C Hoffmann
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A I Kolesnikov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - E Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A A Podlesnyak
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - X Wang
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P R C Kent
- Center for Nanophase Materials Sciences and Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - L M Anovitz
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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9
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Faraone A, Wagle DV, Baker GA, Novak EC, Ohl M, Reuter D, Lunkenheimer P, Loidl A, Mamontov E. Glycerol Hydrogen-Bonding Network Dominates Structure and Collective Dynamics in a Deep Eutectic Solvent. J Phys Chem B 2018; 122:1261-1267. [PMID: 29336157 DOI: 10.1021/acs.jpcb.7b11224] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The deep eutectic solvent glyceline formed by choline chloride and glycerol in 1:2 molar ratio is much less viscous compared to glycerol, which facilitates its use in many applications where high viscosity is undesirable. Despite the large difference in viscosity, we have found that the structural network of glyceline is completely defined by its glycerol constituent, which exhibits complex microscopic dynamic behavior, as expected from a highly correlated hydrogen-bonding network. Choline ions occupy interstitial voids in the glycerol network and show little structural or dynamic correlations with glycerol molecules. Despite the known higher long-range diffusivity of the smaller glycerol species in glyceline, in applications where localized dynamics is essential (e.g., in microporous media), the local transport and dynamic properties must be dominated by the relatively loosely bound choline ions.
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Affiliation(s)
- A Faraone
- NIST Center for Neutron Research, National Institute of Standards and Technology Gaithersburg , Gaithersburg, Maryland 20899, United States
| | - D V Wagle
- Department of Chemistry, University of Missouri-Columbia , Columbia, Missouri 65211, United States
| | - G A Baker
- Department of Chemistry, University of Missouri-Columbia , Columbia, Missouri 65211, United States
| | - E C Novak
- Department of Materials Science and Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States
| | - M Ohl
- Jülich Center for Neutron Science, Forschungszentrum Jülich GmbH , Jülich 52425, Germany
| | - D Reuter
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg , Augsburg 86159, Germany
| | - P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg , Augsburg 86159, Germany
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg , Augsburg 86159, Germany
| | - E Mamontov
- Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
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10
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Sharma VK, Hayes DG, Urban VS, O'Neill HM, Tyagi M, Mamontov E. Nanoscopic dynamics of bicontinous microemulsions: effect of membrane associated protein. Soft Matter 2017. [PMID: 28631792 DOI: 10.1039/c7sm00875a] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Bicontinous microemulsions (BμE) generally consist of nanodomains formed by surfactant in a mixture of water and oil at nearly equal proportions and are potential candidates for the solubilization and purification of membrane proteins. Here we present the first time report of nanoscopic dynamics of surfactant monolayers within BμEs formed by the anionic surfactant sodium dodecyl sulfate (SDS) measured on the nanosecond to picosecond time scale using quasielastic neutron scattering (QENS). BμEs investigated herein consisted of middle phases isolated from Winsor-III microemulsion systems that were formed by mixing aqueous and oil solutions under optimal conditions. QENS data indicates that surfactants undergo two distinct motions, namely (i) lateral motion along the surface of the oil nanodomains and (ii) localized internal motion. Lateral motion can be described using a continuous diffusion model, from which the lateral diffusion coefficient is obtained. Internal motion of surfactant is described using a model which assumes that a fraction of the surfactants' hydrogens undergoes localized translational diffusion that could be considered confined within a spherical volume. The effect of cytochrome c, an archetypal membrane-associated protein known to strongly partition near the surfactant head groups in BμEs (a trend supported by small-angle X-ray scattering [SAXS] analysis), on the dynamics of BμE has also been investigated. QENS results demonstrated that cytochrome c significantly hindered both the lateral and the internal motions of surfactant. The lateral motion was more strongly affected: a reduction of the lateral diffusion coefficient by 33% was measured. This change is mainly attributable to the strong association of cytochrome c with oppositely charged SDS. In contrast, analysis of SAXS data suggested that thermal fluctuations (for a longer length and slower time scale compared to QENS) were increased upon incorporation of cytochrome c. This study demonstrates the utility of QENS for evaluating dynamics of BμEs in nanoscopic region, and that proteins directly affect the microscopic dynamics, which is of relevance for evaluating release kinetics of encapsulated drugs from BμE delivery systems and the use of BμEs as biomembrane mimetic systems for investigating membrane protein-biomembrane interactions.
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Affiliation(s)
- V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
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11
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Mamontov E. Microscopic diffusion in hydrated encysted eggs of brine shrimp. Biochim Biophys Acta Gen Subj 2017; 1861:2382-2390. [PMID: 28549919 DOI: 10.1016/j.bbagen.2017.05.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 05/07/2017] [Accepted: 05/23/2017] [Indexed: 11/29/2022]
Abstract
BACKGROUND We have studied microscopic diffusion of water in fully hydrated encysted eggs of brine shrimp (Artemia). METHODS We have utilized quasielastic neutron scattering. RESULTS Dry eggs of brine shrimp were rehydrated using (1) water without additives, (2) eutectic mixture of water and dimethyl sulfoxide, and (3) a concentrated aqueous solution of lithium chloride. Despite the complexity of the hydrated multicellular organism, measurable microscopic diffusivity of water is rather well defined. Pure hydration water in eggs exhibits freezing temperature depression, whereas hydration water in eggs mixed with dimethyl sulfoxide or lithium chloride does not crystallize at all. CONCLUSIONS The characteristic size of the voids occupied by water or aqueous solvents in hydrated brine shrimp eggs is between 2 and 10nm. Those voids are accessible to co-solvents such as dimethyl sulfoxide and lithium chloride. There is no evidence of intracellular water in the hydrated eggs. GENERAL SIGNIFICANCE The lack of intracellular water in the fully hydrated (but still under arrested development) state must be linked to the unique resilience against adverse environmental factors documented not only for the anhydrous, but also hydrated encysted eggs of brine shrimp.
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Affiliation(s)
- E Mamontov
- Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
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12
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Miskowiec A, Buck ZN, Hansen FY, Kaiser H, Taub H, Tyagi M, Diallo SO, Mamontov E, Herwig KW. On the structure and dynamics of water associated with single-supported zwitterionic and anionic membranes. J Chem Phys 2017; 146:125102. [DOI: 10.1063/1.4978677] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- A. Miskowiec
- Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri, Columbia, Missouri 65211, USA
| | - Z. N. Buck
- Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri, Columbia, Missouri 65211, USA
| | - F. Y. Hansen
- Department of Chemistry, Technical University of Denmark, IK 207 DTU, DK-2800 Lyngby, Denmark
| | - H. Kaiser
- Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri, Columbia, Missouri 65211, USA
| | - H. Taub
- Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri, Columbia, Missouri 65211, USA
| | - M. Tyagi
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - S. O. Diallo
- Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - E. Mamontov
- Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - K. W. Herwig
- Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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14
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Osti NC, Etampawala TN, Shrestha UM, Aryal D, Tyagi M, Diallo SO, Mamontov E, Cornelius CJ, Perahia D. Water dynamics in rigid ionomer networks. J Chem Phys 2016; 145:224901. [PMID: 27984911 DOI: 10.1063/1.4971209] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- N. C. Osti
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA
| | - T. N. Etampawala
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA
| | - U. M. Shrestha
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA
| | - D. Aryal
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA
| | - M. Tyagi
- 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
| | - S. O. Diallo
- Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - E. Mamontov
- Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - C. J. Cornelius
- Chemical and Biomolecular Engineering Department, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA
| | - D. Perahia
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA
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15
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Magazù S, Mezei F, Falus P, Farago B, Mamontov E, Russina M, Migliardo F. Protein dynamics as seen by (quasi) elastic neutron scattering. Biochim Biophys Acta Gen Subj 2016; 1861:3504-3512. [PMID: 27476795 DOI: 10.1016/j.bbagen.2016.07.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 07/18/2016] [Accepted: 07/27/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Elastic and quasielastic neutron scattering studies proved to be efficient probes of the atomic mean square displacement (MSD), a fundamental parameter for the characterization of the motion of individual atoms in proteins and its evolution with temperature and compositional environment. SCOPE OF REVIEW We present a technical overview of the different types of experimental situations and the information quasi-elastic neutron scattering approaches can make available. In particular, MSD can crucially depend on the time scale over which the averaging (building of the "mean") takes place, being defined by the instrumental resolution. Due to their high neutron scattering cross section, hydrogen atoms can be particularly sensitively observed with little interference by the other atoms in the sample. A few examples, including new data, are presented for illustration. MAJOR CONCLUSIONS The incoherent character of neutron scattering on hydrogen atoms restricts the information obtained to the self-correlations in the motion of individual atoms, simplifying at the same time the data analysis. On the other hand, the (often overlooked) exploration of the averaging time dependent character of MSD is crucial for unambiguous interpretation and can provide a wealth of information on micro- and nanoscale atomic motion in proteins. GENERAL SIGNIFICANCE By properly exploiting the broad range capabilities of (quasi)elastic neutron scattering techniques to deliver time dependent characterization of atomic displacements, they offer a sensitive, direct and simple to interpret approach to exploration of the functional activity of hydrogen atoms in proteins. Partial deuteration can add most valuable selectivity by groups of hydrogen atoms. "This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo".
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Affiliation(s)
- S Magazù
- Department of Mathematical and Informatics Sciences, Physical Sciences and Earth Sciences, University of Messina, Viale D'Alcontres 31, 98166 Messina, Italy
| | - F Mezei
- European Spallation Source ERIC, P.O. BOX 176, 22100 Lund, Sweden; HAS Wigner Researh Center, P.O. BOX 49, 1525 Budapest, Hungary.
| | - P Falus
- Institut-Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
| | - B Farago
- Institut-Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
| | - E Mamontov
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - M Russina
- Helmholtz-Zentrum-Berlin, Glienicker Str 100, 14109 Berlin, Germany
| | - F Migliardo
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale D'Alcontres 31, 98166 Messina, Italy; Institute for Integrative Biology of the Cell (I2BC), CEA-CNRS-Université Paris Sud, 91400 Orsay, France
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Sharma VK, Mamontov E, Tyagi M, Qian S, Rai DK, Urban VS. Dynamical and Phase Behavior of a Phospholipid Membrane Altered by an Antimicrobial Peptide at Low Concentration. J Phys Chem Lett 2016; 7:2394-401. [PMID: 27232190 DOI: 10.1021/acs.jpclett.6b01006] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The mechanism of action of antimicrobial peptides is traditionally attributed to the formation of pores in the lipid cell membranes of pathogens, which requires a substantial peptide to lipid ratio. However, using incoherent neutron scattering, we show that even at a concentration too low for pore formation, an archetypal antimicrobial peptide, melittin, disrupts the regular phase behavior of the microscopic dynamics in a phospholipid membrane, dimyristoylphosphatidylcholine (DMPC). At the same time, another antimicrobial peptide, alamethicin, does not exert a similar effect on the DMPC microscopic dynamics. The melittin-altered lateral motion of DMPC at physiological temperature no longer resembles the fluid-phase behavior characteristic of functional membranes of the living cells. The disruptive effect demonstrated by melittin even at low concentrations reveals a new mechanism of antimicrobial action relevant in more realistic scenarios, when peptide concentration is not as high as would be required for pore formation, which may facilitate treatment with antimicrobial peptides.
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Affiliation(s)
- V K Sharma
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
- 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, Tennessee 37831, United States
| | - M Tyagi
- National Institute of Standards and Technology Center for Neutron Research , Gaithersburg, Maryland 20899, United States
- Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States
| | - S Qian
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - D K Rai
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - V S Urban
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
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Mamontov E, O'Neill H. Microscopic relaxations in a protein sustained down to 160K in a non-glass forming organic solvent. Biochim Biophys Acta Gen Subj 2016; 1861:3513-3519. [PMID: 27154287 DOI: 10.1016/j.bbagen.2016.04.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 04/24/2016] [Accepted: 04/25/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND We have studied microscopic dynamics of a protein in carbon disulfide, a non-glass forming solvent, down to its freezing temperature of ca. 160K. METHODS We have utilized quasielastic neutron scattering. RESULTS A comparison of lysozyme hydrated with water and dissolved in carbon disulfide reveals a stark difference in the temperature dependence of the protein's microscopic relaxation dynamics induced by the solvent. In the case of hydration water, the common protein glass-forming solvent, the protein relaxation slows down in response to a large increase in the water viscosity on cooling down, exhibiting a well-known protein dynamical transition. The dynamical transition disappears in non-glass forming carbon disulfide, whose viscosity remains a weak function of temperature all the way down to freezing at just below 160K. The microscopic relaxation dynamics of lysozyme dissolved in carbon disulfide is sustained down to the freezing temperature of its solvent at a rate similar to that measured at ambient temperature. CONCLUSIONS Our results demonstrate that protein dynamical transition is not merely solvent-assisted, but rather solvent-induced, or, more precisely, is a reflection of the temperature dependence of the solvent's glass-forming dynamics. GENERAL SIGNIFICANCE We hypothesize that, if the long debated idea regarding the direct link between the microscopic relaxations and the biological activity in proteins is correct, then not only the microscopic relaxations, but also the activity, could be sustained in proteins all the way down to the freezing temperature of a non-glass forming solvent with a weak temperature dependence of its viscosity. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.
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Affiliation(s)
- E Mamontov
- Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
| | - H O'Neill
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
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Magazù S, Mamontov E. A neutron spectrometer concept implementing RENS for studies in life sciences. Biochim Biophys Acta Gen Subj 2016; 1861:3632-3637. [PMID: 27118237 DOI: 10.1016/j.bbagen.2016.04.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Accepted: 04/18/2016] [Indexed: 11/28/2022]
Abstract
BACKGROUND Resolution Elastic Neutron Scattering (RENS) method involves performing elastic scattering intensity scans as a function of the instrumental energy resolution and as a function of temperature. METHODS In the framework of RENS, numerical simulation and experimental data show that in the measured elastic scattering law against the logarithm of the instrumental energy resolution an inflection point occurs when the resolution time intersects the system relaxation time; conversely, in the measured elastic scattering law against temperature an inflection point turns up when the system relaxation time intersects the resolution time. RESULTS For practical implementation of the RENS technique, a dedicated neutron spectrometer would be needed. Here we propose a concept of such a spectrometer that utilizes mechanical velocity selection of both incident and scattered neutrons over a wide angular range. The instrument is able to collect intensity scans vs energy resolution where the instrumental resolution time changes crisscrossing the system relaxation time, and intensity scans vs temperature where the system relaxation time changes intersecting the instrumental resolution time. CONCLUSIONS We propose a RENS spectrometer concept based on velocity selection of incident neutrons and wide-angle velocity selection of scattered neutrons achieved by the same rotating collimator-type mechanical device with the optimized shape of blades. GENERAL SIGNIFICANCE RENS spectrometer is strongly appealing and innovative because of the simultaneous data collection as a function of energy resolution, wide wavevector range and temperature. Such a spectrometer would be the first practical implementation of RENS concept with a broad range of applications in Life Sciences. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.
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Affiliation(s)
- S Magazù
- Department of Mathematics and Informatics Sciences, Physics Sciences and Earth Sciences, University of Messina, Viale F. S. D'Alcontres 31, 98166 Messina, Italy.
| | - E Mamontov
- Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Mamontov E, Sharma VK, Borreguero JM, Tyagi M. Protein-Style Dynamical Transition in a Non-Biological Polymer and a Non-Aqueous Solvent. J Phys Chem B 2016; 120:3232-9. [DOI: 10.1021/acs.jpcb.6b00866] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- E. Mamontov
- Chemical
and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - V. K. Sharma
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Solid
State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - J. M. Borreguero
- Neutron
Data Analysis and Visualization Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - M. Tyagi
- National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899, United States
- Department
of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States
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Gupta S, Mamontov E, Jalarvo N, Stingaciu L, Ohl M. Characteristic length scales of the secondary relaxations in glass-forming glycerol. Eur Phys J E Soft Matter 2016; 39:40. [PMID: 27021657 DOI: 10.1140/epje/i2016-16040-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Accepted: 02/26/2016] [Indexed: 06/05/2023]
Abstract
We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends on the time scale of the relaxation of interest. We use neutron backscattering to identify the characteristic length scale of 0.7 Å for the faster secondary relaxation described in the framework of the mode-coupling theory (MCT). Neutron spin-echo is employed to probe the slower secondary relaxation of the excess wing type at a low temperature ( ∼ 1.13T g . The characteristic length scale for this excess wing dynamics is approximately 4.7 Å. Besides the Q -dependence, the direct coupling of neutron scattering signal to density fluctuation makes this technique indispensable for measuring the length scale of the microscopic relaxation dynamics.
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Affiliation(s)
- S Gupta
- JCNS-SNS, Biology and Soft-matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), Bethel Valley Road, PO BOX 2008 MS6473, 37831, Oak Ridge, TN, USA.
| | - E Mamontov
- Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), PO BOX 2008 MS6473, 37831-6473, Oak Ridge, TN, USA
| | - N Jalarvo
- JCNS-SNS, Biology and Soft-matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), Bethel Valley Road, PO BOX 2008 MS6473, 37831, Oak Ridge, TN, USA
- Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), PO BOX 2008 MS6473, 37831-6473, Oak Ridge, TN, USA
| | - L Stingaciu
- JCNS-SNS, Biology and Soft-matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), Bethel Valley Road, PO BOX 2008 MS6473, 37831, Oak Ridge, TN, USA
| | - M Ohl
- JCNS-SNS, Biology and Soft-matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), Bethel Valley Road, PO BOX 2008 MS6473, 37831, Oak Ridge, TN, USA
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Sharma VK, Mamontov E, Anunciado D, Ohl M, O’Neill H, Urban V. Antimicrobial Peptide Impacts the Lateral Diffusion and Bending Rigidity of Phospholipid Membrane. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1353] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Sharma VK, Mamontov E, Tyagi M, Urban VS. Effect of α-Tocopherol on the Microscopic Dynamics of Dimyristoylphosphatidylcholine Membrane. J Phys Chem B 2015; 120:154-63. [DOI: 10.1021/acs.jpcb.5b10417] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- V. K. Sharma
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- 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, Tennessee 37831, United States
| | - M. Tyagi
- National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899, United States
- Department
of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - V. S. Urban
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Sharma VK, Mamontov E, Anunciado DB, O'Neill H, Urban VS. Effect of antimicrobial peptide on the dynamics of phosphocholine membrane: role of cholesterol and physical state of bilayer. Soft Matter 2015. [PMID: 26212615 DOI: 10.1039/c5sm01562f] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Antimicrobial peptides are universal in all forms of life and are well known for their strong interaction with the cell membrane. This makes them a popular target for investigation of peptide-lipid interactions. Here we report the effect of melittin, an important antimicrobial peptide, on the dynamics of membranes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid in both the solid gel and fluid phases. To probe the phase transition, elastic neutron intensity temperature scans have been carried out on DMPC-based unilamellar vesicles (ULV) with and without melittin. We have found that addition of a small amount (0.2 mol%) melittin eliminates the steep fall in the elastic intensity at 296 K associated with the solid gel to fluid phase transition, which is observed for pure DMPC vesicles. Quasielastic neutron scattering (QENS) experiments have been carried out on DMPC ULV in the solid gel and fluid phases with and without 0.2 mol% melittin. The data analysis invariably shows the presence of lateral and internal motions of the DMPC molecule. We found that melittin does have a profound effect on the dynamics of lipid molecules, especially on the lateral motion, and affects it in a different way, depending on the phase of the bilayers. In the solid gel phase, it acts as a plasticizer, enhancing the lateral motion of DMPC. However, in the fluid phase it acts as a stiffening agent, restricting the lateral motion of the lipid molecules. These observations are consistent with the mean squared displacements extracted from the elastic intensity temperature scans. Their importance lies in the fact that many membrane processes, including signaling and energy transduction pathways, are controlled to a great extent by the lateral diffusion of lipids in the membrane. To investigate the effect of melittin on vesicles supplemented with cholesterol, QENS experiments have also been carried out on DMPC ULV with cholesterol in the presence and absence of 0.2 mol% melittin. Remarkably, the effects of melittin on the membrane dynamics disappear in the presence of 20 mol% cholesterol. Our measurements indicate that the destabilizing effect of the peptide melittin on membranes can be mitigated by the presence of cholesterol. This study might provide new insights into the mechanism of action of antimicrobial peptides and their selective toxicity towards foreign microorganisms.
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Affiliation(s)
- V K Sharma
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Gupta S, Arend N, Lunkenheimer P, Loidl A, Stingaciu L, Jalarvo N, Mamontov E, Ohl M. Erratum to: Excess wing in glass-forming glycerol and LiCl-glycerol mixtures detected by neutron scattering. Eur Phys J E Soft Matter 2015; 38:135. [PMID: 26004634 DOI: 10.1140/epje/i2015-15051-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 03/24/2015] [Indexed: 06/04/2023]
Affiliation(s)
- S Gupta
- Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at SNS-Oak Ridge National Laboratory (ORNL), 1 Bethel Valley Road, TN 37831, Oak Ridge, USA,
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Sharma VK, Mamontov E, Anunciado DB, O’Neill H, Urban V. Nanoscopic Dynamics of Phospholipid in Unilamellar Vesicles: Effect of Gel to Fluid Phase Transition. J Phys Chem B 2015; 119:4460-70. [DOI: 10.1021/acs.jpcb.5b00220] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- V. K. Sharma
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- 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, Tennessee 37831, United States
| | - D. B. Anunciado
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - H. O’Neill
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - V. Urban
- Biology
and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Abstract
Using neutron spin-echo and backscattering spectroscopy, we have found that at low temperatures water molecules in an aqueous solution engage in center-of-mass dynamics that are different from both the main structural relaxations and the well-known localized motions in the transient cages of the nearest neighbor molecules. While the latter localized motions are known to take place on the picosecond time scale and Angstrom length scale, the slower motions that we have observed are found on the nanosecond time scale and nanometer length scale. They are associated with the slow secondary relaxations, or excess wing dynamics, in glass-forming liquids. Our approach, therefore, can be applied to probe the characteristic length scale of the dynamic entities associated with slow dynamics in glass-forming liquids, which presently cannot be studied by other experimental techniques.
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Affiliation(s)
- E Mamontov
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, USA.
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Diallo SO, Vlcek L, Mamontov E, Keum JK, Chen J, Hayes JS, Chialvo AA. Translational diffusion of water inside hydrophobic carbon micropores studied by neutron spectroscopy and molecular dynamics simulation. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 91:022124. [PMID: 25768475 DOI: 10.1103/physreve.91.022124] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Indexed: 06/04/2023]
Abstract
When water molecules are confined to nanoscale spacings, such as in the nanometer-size pores of activated carbon fiber (ACF), their freezing point gets suppressed down to very low temperatures (∼150K), leading to a metastable liquid state with remarkable physical properties. We have investigated the ambient pressure diffusive dynamics of water in microporous Kynol ACF-10 (average pore size ∼11.6Å, with primarily slit-like pores) from temperature T=280 K in its stable liquid state down to T=230 K into the metastable supercooled phase. The observed characteristic relaxation times and diffusion coefficients are found to be, respectively, higher and lower than those in bulk water, indicating a slowing down of the water mobility with decreasing temperature. The observed temperature-dependent average relaxation time 〈τ〉 when compared to previous findings indicate that it is the width of the slit pores-not their curvature-that primarily affects the dynamics of water for pore sizes larger than 10 Å. The experimental observations are compared to complementary molecular dynamics simulations of a model system, in which we studied the diffusion of water within the 11.6 Å gap of two parallel graphene sheets. We find generally a reasonable agreement between the observed and calculated relaxation times at the low momentum transfer Q(Q≤0.9Å(-1)). At high Q, however, where localized dynamics becomes relevant, this ideal system does not satisfactorily reproduce the measurements. Consequently, the simulations are compared to the experiments at low Q, where the two can be best reconciled. The best agreement is obtained for the diffusion parameter D associated with the hydrogen-site when a representative stretched exponential function, rather than the standard bimodal exponential model, is used to parametrize the self-correlation function I(Q,t).
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Affiliation(s)
- S O Diallo
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - L Vlcek
- Chemical Sciences Division, Oak Ridge, National Laboratory, Tennessee 37831, USA
| | - E Mamontov
- Chemical and Engineering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J K Keum
- Instrument and Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Jihua Chen
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J S Hayes
- American Technical Trading, Incorporated, P.O. Box 273, Pleasantville, New York 10570, USA
| | - A A Chialvo
- Chemical Sciences Division, Oak Ridge, National Laboratory, Tennessee 37831, USA
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Gupta S, Arend N, Lunkenheimer P, Loidl A, Stingaciu L, Jalarvo N, Mamontov E, Ohl M. Excess wing in glass-forming glycerol and LiCl-glycerol mixtures detected by neutron scattering. Eur Phys J E Soft Matter 2015; 38:1. [PMID: 25612850 DOI: 10.1140/epje/i2015-15001-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/22/2014] [Accepted: 12/02/2014] [Indexed: 06/04/2023]
Abstract
The relaxational dynamics in glass-forming glycerol and glycerol mixed with LiCl is investigated using different neutron scattering techniques. The performed neutron spin echo experiments, which extend up to relatively long relaxation time scales of the order of 10 ns, should allow for the detection of contributions from the so-called excess wing. This phenomenon, whose microscopic origin is controversially discussed, arises in a variety of glass formers and, until now, was almost exclusively investigated by dielectric spectroscopy and light scattering. Here we show that the relaxational process causing the excess wing can also be detected by neutron scattering, which directly couples to density fluctuations.
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Affiliation(s)
- S Gupta
- Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at SNS-Oak Ridge National Laboratory (ORNL), 1 Bethel Valley Road, 37831, Oak Ridge, TN, USA,
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Diallo SO, Zhang Q, O'Neill H, Mamontov E. High-pressure dynamics of hydrated protein in bioprotective trehalose environment. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 90:042725. [PMID: 25375541 DOI: 10.1103/physreve.90.042725] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Indexed: 06/04/2023]
Abstract
We present a pressure-dependence study of the dynamics of lysozyme protein powder immersed in deuterated α,α-trehalose environment via quasielastic neutron scattering (QENS). The goal is to assess the baroprotective benefits of trehalose on biomolecules by comparing the findings with those of a trehalose-free reference study. While the mean-square displacement of the trehalose-free protein (hydrated to dD2O≃40 w%) as a whole, is reduced by increasing pressure, the actual observable relaxation dynamics in the picoseconds to nanoseconds time range remains largely unaffected by pressure--up to the maximum investigated pressure of 2.78(2) Kbar. Our observation is independent of whether or not the protein is mixed with the deuterated sugar. This suggests that the hydrated protein's conformational states at atmospheric pressure remain unaltered by hydrostatic pressures, below 2.78 Kbar. We also found the QENS response to be totally recoverable after ambient pressure conditions are restored. Small-angle neutron diffraction measurements confirm that the protein-protein correlation remains undisturbed. We observe, however, a clear narrowing of the QENS response as the temperature is decreased from 290 to 230 K in both cases, which we parametrize using the Kohlrausch-Williams-Watts stretched exponential model. Only the fraction of protons that are immobile on the accessible time window of the instrument, referred to as the elastic incoherent structure factor, is observably sensitive to pressure, increasing only marginally but systematically with increasing pressure.
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Affiliation(s)
- S O Diallo
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Q Zhang
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H O'Neill
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - E Mamontov
- Chemical and Engineering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Favi PM, Zhang Q, O'Neill H, Mamontov E, Diallo SO. Dynamics of lysozyme and its hydration water under an electric field. J Biol Phys 2014; 40:167-78. [PMID: 24664796 DOI: 10.1007/s10867-014-9343-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 02/04/2014] [Indexed: 11/28/2022] Open
Abstract
The effects of a static electric field on the dynamics of lysozyme and its hydration water are investigated by means of incoherent quasi-elastic neutron scattering (QENS). Measurements were performed on lysozyme samples, hydrated respectively with heavy water (D2O) to capture the protein dynamics and with light water (H2O), to probe the dynamics of the hydration shell, in the temperature range from 210 < T < 260 K. The hydration fraction in both cases was about ∼ 0.38 gram of water per gram of dry protein. The field strengths investigated were respectively 0 kV/mm and 2 kV/mm (~2 × 10(6) V/m) for the protein hydrated with D2O and 0 kV and 1 kV/mm for the H2O-hydrated counterpart. While the overall internal protons dynamics of the protein appears to be unaffected by the application of an electric field up to 2 kV/mm, likely due to the stronger intra-molecular interactions, there is also no appreciable quantitative enhancement of the diffusive dynamics of the hydration water, as would be anticipated based on our recent observations in water confined in silica pores under field values of 2.5 kV/mm. This may be due to the difference in surface interactions between water and the two adsorption hosts (silica and protein), or to the existence of a critical threshold field value Ec ~2-3 kV/mm for increased molecular diffusion, for which electrical breakdown is a limitation for our sample.
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Affiliation(s)
- P M Favi
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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Mamontov E, O’Neill H, Zhang Q, Chathoth S. Temperature dependence of the internal dynamics of a protein in an aqueous solvent: Decoupling from the solvent viscosity. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.02.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Diallo SO, Jażdżewska M, Palmer JC, Mamontov E, Gubbins KE, Śliwińska-Bartkowiak M. Dynamics of nanoconfined water under pressure. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 88:022316. [PMID: 24032841 DOI: 10.1103/physreve.88.022316] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 05/22/2013] [Indexed: 06/02/2023]
Abstract
We report a study of the effects of pressure on the diffusivity of water molecules confined in single-wall carbon nanotubes (SWNT) with average mean pore diameter of ~16 Å. The measurements were carried out using high-resolution neutron scattering, over the temperature range 220≤T≤260 K, and at two pressure conditions: ambient and elevated pressure. The high pressure data were collected at constant volume on cooling, with P varying from ~1.92 kbar at temperature T=260 K to ~1.85 kbar at T=220 K. Analysis of the observed dynamic structure factor S(Q,E) reveals the presence of two relaxation processes, a faster diffusion component (FC) associated with the motion of "caged" or restricted molecules, and a slower component arising from the free water molecules diffusing within the SWNT matrix. While the temperature dependence of the slow relaxation time exhibits a Vogel-Fulcher-Tammann law and is non-Arrhenius in nature, the faster component follows an Arrhenius exponential law at both pressure conditions. The application of pressure remarkably slows down the overall molecular dynamics, in agreement with previous observations, but most notably affects the slow relaxation. The faster relaxation shows marginal or no change with pressure within the experimental conditions.
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Affiliation(s)
- S O Diallo
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Abstract
Aqueous solutions of lithium chloride are uniquely similar to pure water in the parameters such as glass transition temperature, Tg, yet they could be supercooled without freezing down to below 200 K even in the bulk state. This provides advantageous opportunity to study low-temperature dynamics of water molecules in water-like environment in the bulk rather than nano-confined state. Using high-resolution neutron spin-echo data, we argue that the critical temperature, Tc, which is also common between lithium chloride aqueous solutions and pure water, is associated with the split of a secondary relaxation from the main structural relaxation on cooling down. Our results do not allow distinguishing between a well-defined separate secondary relaxation process and the "excess wing" scenario, in which the temperature dependence of the secondary relaxation follows the main relaxation. Importantly, however, in either of these scenarios the secondary relaxation is associated with density-density fluctuations, measurable in a neutron scattering experiment. Neutron scattering could be the only experimental technique with the capability of providing information on the spatial characteristics of the secondary relaxation through the dependence of the signal on the scattering momentum transfer. We propose a simple method for such analysis.
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Affiliation(s)
- E Mamontov
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, USA.
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Bertrand CE, Liu KH, Mamontov E, Chen SH. Hydration-dependent dynamics of deeply cooled water under strong confinement. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 87:042312. [PMID: 23679419 DOI: 10.1103/physreve.87.042312] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/20/2013] [Indexed: 06/02/2023]
Abstract
We have measured the hydration-level dependence of the single-particle dynamics of water confined in the ordered mesoporous silica MCM-41. The dynamic crossover observed at full hydration is absent at monolayer hydration. The monolayer dynamics are significantly slower than those of water in a fully hydrated pore at ambient temperatures. At low temperatures, the opposite is found to be true. These results underscore the importance of water's tetrahedral hydrogen-bond network in accounting for its low temperature dynamic properties.
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Affiliation(s)
- C E Bertrand
- Department of Nuclear Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Diallo SO, Mamontov E, Nobuo W, Inagaki S, Fukushima Y. Enhanced translational diffusion of confined water under electric field. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 86:021506. [PMID: 23005768 DOI: 10.1103/physreve.86.021506] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 06/09/2012] [Indexed: 06/01/2023]
Abstract
High resolution quasielastic neutron scattering measurements have been used to study the effects of applied electric field on the dynamics of water molecules confined in the pores of folded silica sheet material FSM-12 with an average pore diameter (apd) of 16 Å. In the absence of field, there is a significant slowing down of the water molecule diffusion as the temperature is lowered, in agreement with previous observations. The application of a moderate electric field of 2.5 kV/mm remarkably enhances the translational diffusion of water molecules. We interpret this as being due to a disruption of the hydrogen bonding by the electric field. This new observation suggests that existing theories valid at large electric field strengths may have to be corrected at moderate fields.
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Affiliation(s)
- S O Diallo
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Mamontov E, De Francesco A, Formisano F, Laloni A, Sani L, Leu BM, Said AH, Kolesnikov AI. Water dynamics in a lithium chloride aqueous solution probed by Brillouin neutron and x-ray scattering. J Phys Condens Matter 2012; 24:064102. [PMID: 22277241 DOI: 10.1088/0953-8984/24/6/064102] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We studied the collective excitations in an aqueous solution of lithium chloride over the temperature range of 270-205 K using neutron and x-ray Brillouin scattering. Both neutron and x-ray experiments revealed the presence of low- and high-frequency excitations, similar to the low- and high-frequency excitations in pure water. These two excitations were detectable through the entire temperature range of the experiment, at all probed values of the scattering momentum transfer (0.2 Å(-1) < Q < 1.8 Å(-1)). A wider temperature range was investigated using elastic intensity neutron and x-ray scans. Clear evidence of the crossover in the dynamics of the water molecules in the solution was observed in the single-particle relaxational dynamics on the µeV (nanosecond) time scale, but not in the collective dynamics on the meV (picosecond) time scale.
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Affiliation(s)
- E Mamontov
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Mamontov E, O'Neill H, Zhang Q, Wang W, Wesolowski DJ. Common features in the microscopic dynamics of hydration water on organic and inorganic surfaces. J Phys Condens Matter 2012; 24:064104. [PMID: 22277314 DOI: 10.1088/0953-8984/24/6/064104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The microscopic dynamics of hydration water exhibits some universal features that do not depend on the nature of the hydrated surface. We show that the hydration level dependence of the dynamic transition in the mean squared atomic displacements measured by means of elastic neutron scattering is qualitatively similar for hydration water in inorganic and organic hosts. The difference is that the former are 'rigid', whereas the dynamics of the latter can be enhanced by the motions of the hydration water. The overall hydration level appears to be the main parameter governing the magnitude of the mean squared atomic displacements in the hydration water, irrespective of the details of the hydrated host.
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Affiliation(s)
- E Mamontov
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Yang F, Kaplonski J, Unruh T, Mamontov E, Meyer A. A high temperature high pressure cell for quasielastic neutron scattering. Rev Sci Instrum 2011; 82:083903. [PMID: 21895254 DOI: 10.1063/1.3623796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present our recent development of a high temperature high pressure cell for neutron scattering. Combining a water cooled Nb1Zr pressure cell body with an internal heating furnace, the sample environment can reach temperatures of up to 1500 K at a pressure of up to 200 MPa at the sample position, with an available sample volume of about 700 mm(3). The cell material Nb1Zr is specifically chosen due to its reasonable mechanical strength at elevated temperatures and fairly small neutron absorption and incoherent scattering cross sections. With this design, an acceptable signal-to-noise ratio of about 10:1 can be achieved. This opens new possibilities for quasielastic neutron scattering studies on different types of neutron spectrometers under high temperature high pressure conditions, which is particularly interesting for geological research on, e.g., water dynamics in silicate melts.
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Affiliation(s)
- F Yang
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Köln, Germany
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Abstract
We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 μeV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.
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Affiliation(s)
- E Mamontov
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Mamontov E, Faraone A, Hagaman EW, Han KS, Fratini E. A Low-Temperature Crossover in Water Dynamics in an Aqueous LiCl Solution: Diffusion Probed by Neutron Spin−Echo and Nuclear Magnetic Resonance. J Phys Chem B 2010; 114:16737-43. [DOI: 10.1021/jp108497b] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- E. Mamontov
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, United States, National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States, Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, United States, and CSGI and Department of
| | - A. Faraone
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, United States, National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States, Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, United States, and CSGI and Department of
| | - E. W. Hagaman
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, United States, National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States, Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, United States, and CSGI and Department of
| | - K. S. Han
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, United States, National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States, Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, United States, and CSGI and Department of
| | - E. Fratini
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, United States, National Institute of Standards and Technology Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States, Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, United States, and CSGI and Department of
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Vaknin D, Garlea VO, Demmel F, Mamontov E, Nojiri H, Martin C, Chiorescu I, Qiu Y, Kögerler P, Fielden J, Engelhardt L, Rainey C, Luban M. Level crossings and zero-field splitting in the {Cr8}-cubane spin cluster studied using inelastic neutron scattering and magnetization. J Phys Condens Matter 2010; 22:466001. [PMID: 21403379 DOI: 10.1088/0953-8984/22/46/466001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Inelastic neutron scattering (INS) in variable magnetic field and high-field magnetization measurements in the millikelvin temperature range were performed to gain insight into the low-energy magnetic excitation spectrum and the field-induced level crossings in the molecular spin cluster {Cr(8)}-cubane. These complementary techniques provide consistent estimates of the lowest level-crossing field. The overall features of the experimental data are explained using an isotropic Heisenberg model, based on three distinct exchange interactions linking the eight Cr(III) paramagnetic centers (spins s = 3/2), that is supplemented with a relatively large molecular magnetic anisotropy term for the lowest S = 1 multiplet. It is noted that the existence of the anisotropy is clearly evident from the magnetic field dependence of the excitations in the INS measurements, while the magnetization measurements are not sensitive to its effects.
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Affiliation(s)
- D Vaknin
- Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA.
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Khodadadi S, Roh JH, Kisliuk A, Mamontov E, Tyagi M, Woodson SA, Briber RM, Sokolov AP. Dynamics of biological macromolecules: not a simple slaving by hydration water. Biophys J 2010; 98:1321-6. [PMID: 20371332 DOI: 10.1016/j.bpj.2009.12.4284] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 11/24/2009] [Accepted: 12/04/2009] [Indexed: 11/29/2022] Open
Abstract
We studied the dynamics of hydrated tRNA using neutron and dielectric spectroscopy techniques. A comparison of our results with earlier data reveals that the dynamics of hydrated tRNA is slower and varies more strongly with temperature than the dynamics of hydrated proteins. At the same time, tRNA appears to have faster dynamics than DNA. We demonstrate that a similar difference appears in the dynamics of hydration water for these biomolecules. The results and analysis contradict the traditional view of slaved dynamics, which assumes that the dynamics of biological macromolecules just follows the dynamics of hydration water. Our results demonstrate that the dynamics of biological macromolecules and their hydration water depends strongly on the chemical and three-dimensional structures of the biomolecules. We conclude that the whole concept of slaving dynamics should be reconsidered, and that the mutual influence of biomolecules and their hydration water must be taken into account.
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Affiliation(s)
- S Khodadadi
- Department of Polymer Science, University of Akron, Akron, Ohio, USA
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Ehlers G, Mamontov E, Zamponi M, Kam KC, Gardner JS. Direct observation of a nuclear spin excitation in Ho2Ti2O7. Phys Rev Lett 2009; 102:016405. [PMID: 19257221 DOI: 10.1103/physrevlett.102.016405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Indexed: 05/27/2023]
Abstract
A single nondispersive excitation is observed by means of neutron backscattering, at E_{0}=26.3 microeV in the spin ice Ho2Ti2O7 but not in the isotopically enriched 162Dy2Ti2O7 analogue. The intensity of this excitation is rather small, less, similar0.2% of the elastic intensity. It is clearly observed below 80 K but resolution limited only below approximately 65 K. The application of a magnetic field up to micro_{0}H=4.5 T, at 1.6 K, has no measurable effect on the energy or intensity. This nuclear excitation is believed to perturb the electronic, Ising spin system resulting in the persistent spin dynamics observed in spin ice compounds.
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Affiliation(s)
- G Ehlers
- Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, USA
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Garcia Sakai V, Mamontov E, Neumann DA. A background suppression chopper for the High-Flux Backscattering Spectrometer at NIST. J of Neutron Res 2008. [DOI: 10.1080/10238160902819148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Ehlers G, Mamontov E, Zamponi M, Faraone A, Qiu Y, Cornelius AL, Booth CH, Kam KC, Toquin RL, Cheetham AK, Gardner JS. Frustrated spin correlations in diluted spin ice Ho(2-x)La(x)Ti(2)O(7). J Phys Condens Matter 2008; 20:235206. [PMID: 21694297 DOI: 10.1088/0953-8984/20/23/235206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have studied the evolution of the structural properties as well as the static and dynamic spin correlations of spin ice Ho(2)Ti(2)O(7), where Ho was partially replaced by non-magnetic La. The crystal structure of diluted samples Ho(2-x)La(x)Ti(2)O(7) was characterized by x-ray and neutron diffraction and by Ho L(III)-edge and Ti K-edge extended x-ray absorption fine structure (EXAFS) measurements. It is found that the pyrochlore structure remains intact until about x = 0.3, but a systematic increase in local disorder with increasing La concentration is observed in the EXAFS data, especially from the Ti K edge. Quasi-elastic neutron scattering and ac susceptibility measurements show that, in x≤0.4 samples at temperatures above macroscopic freezing, the spin-spin correlations are short ranged and dynamic in nature. The main difference with pure spin ice in the dynamics is the appearance of a second, faster, relaxation process.
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Affiliation(s)
- G Ehlers
- Spallation Neutron Source, Oak Ridge National Laboratory, Building 8600, Oak Ridge, TN 37831-6475, USA
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Khodadadi S, Pawlus S, Roh JH, Garcia Sakai V, Mamontov E, Sokolov AP. The origin of the dynamic transition in proteins. J Chem Phys 2008; 128:195106. [DOI: 10.1063/1.2927871] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Mamontov E, Burnham CJ, Chen SH, Moravsky AP, Loong CK, de Souza NR, Kolesnikov AI. Dynamics of water confined in single- and double-wall carbon nanotubes. J Chem Phys 2007; 124:194703. [PMID: 16729830 DOI: 10.1063/1.2194020] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using high-resolution quasielastic neutron scattering, we investigated the temperature dependence of single-particle dynamics of water confined in single- and double-wall carbon nanotubes with the inner diameters of 14+/-1 and 16+/-3 A, respectively. The temperature dependence of the alpha relaxation time for water in the 14 A nanotubes measured on cooling down from 260 to 190 K exhibits a crossover at 218 K from a Vogel-Fulcher-Tammann law behavior to an Arrhenius law behavior, indicating a fragile-to-strong dynamic transition in the confined water. This transition may be associated with a structural transition from a high-temperature, low-density (<1.02 gcm(3)) liquid to a low-temperature, high-density (>1.14 gcm(3)) liquid found in molecular dynamics simulation at about 200 K. However, no such dynamic transition in the investigated temperature range of 240-195 K was detected for water in the 16 A nanotubes. In the latter case, the dynamics of water simply follows a Vogel-Fulcher-Tammann law. This suggests that the fragile-to-strong crossover for water in the 16 A nanotubes may be shifted to a lower temperature.
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Affiliation(s)
- E Mamontov
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8562, USA.
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Carlsson T, Sjögren L, Mamontov E, Psiuk-Maksymowicz K. Irreducible memory function and slow dynamics in disordered systems. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 75:031109. [PMID: 17500670 DOI: 10.1103/physreve.75.031109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2006] [Indexed: 05/15/2023]
Abstract
We show how the irreducible memory function can be obtained in a rather straightforward way, and that it can be expressed in terms of two contributions representing two parallel decay channels. This representation should be useful for treating systems with a slow time dependence and where eventually some internal degrees of freedom enters in the relaxation process, and cuts off an underlying ideal ergodic to nonergodic transition. We also show how the irreducible memory function under certain mild conditions defines a regenerative stochastic process, or a two level stochastic system. This leads to a picture with dynamical heterogeneities, where the statistical properties asymptotically are ruled by limit processes. This can explain the universal behavior observed in many glass-forming systems.
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Affiliation(s)
- T Carlsson
- Institutionen för fysik, Göteborgs Universitet, S-41296, Sweden
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