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Smith GN. An alternative analysis of contrast-variation neutron scattering data of casein micelles in semi-deuterated milk. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:5. [PMID: 33590354 DOI: 10.1140/epje/s10189-021-00023-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 01/20/2021] [Indexed: 06/12/2023]
Abstract
Contrast-variation small-angle neutron scattering (CV-SANS) is an excellent way to determine the structure of complex, hierarchical colloids, including self-assembled biological systems. In these experiments, the scattering length density of solvents is changed (by varying the ratio of water or [Formula: see text] and heavy water or [Formula: see text]) to highlight or mask scattering from different components in the system. This approach has been used with synthetic colloids, but it is also increasingly being used in the biological and food sciences. Perhaps the most studied food colloid is the "casein micelle," a self-assembled nanometer-scale colloid of the structure-forming casein protein in milk. CV-SANS data available in the literature are typically analyzed using approximations, which may be invalid for casein micelles, as they have been shown to be sticky spheres. To assess the applicability of this approximate approach, a comprehensive set of CV-SANS data from casein micelles in diluted milk was reanalyzed using a model-based approach, where the casein micelles were formally treated as interacting spheres. In general, the conclusions of the previous study are reproduced, but this new approach makes it more straightforward to distinguish the different components in milk and can be applied to any dairy sample with known form of interparticle interactions, which offers the possibility of studying semi-deuterated milk at its native concentration.
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Affiliation(s)
- Gregory N Smith
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen Ø, Denmark.
- ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.
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2
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Liu J, Cukier RI, Bu Y, Shang Y. Glucose-Promoted Localization Dynamics of Excess Electrons in Aqueous Glucose Solution Revealed by Ab Initio Molecular Dynamics Simulation. J Chem Theory Comput 2014; 10:4189-97. [PMID: 26588118 DOI: 10.1021/ct500238k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ab initio molecular dynamics simulations reveal that an excess electron (EE) can be more efficiently localized as a cavity-shaped state in aqueous glucose solution (AGS) than in water. Compared with that (∼1.5 ps) in water, the localization time is shortened by ∼0.7-1.2 ps in three AGSs (0.56, 1.12, and 2.87 M). Although the radii of gyration of the solvated EEs are all close to 2.6 Å in the four solutions, the solvated EE cavities in the AGSs become more compact and can localize ∼80% of an EE, which is considerably larger than that (∼40-60% and occasionally ∼80%) in water. These observations are attributed to a modification of the hydrogen-bonded network by the introduction of glucose molecules into water. The water acts as a promoter and stabilizer, by forming voids around glucose molecules and, in this fashion, favoring the localization of an EE with high efficiency. This study provides important information about EEs in physiological AGSs and suggests a new strategy to efficiently localize an EE in a stable cavity for further exploration of biological function.
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Affiliation(s)
- Jinxiang Liu
- Institute of Theoretical Chemistry, School of Chemistry and Chemical Engineering, Shandong University , Jinan, 250100, China
| | - Robert I Cukier
- Department of Chemistry, Michigan State University , East Lansing, 48224-1322, United States
| | - Yuxiang Bu
- Institute of Theoretical Chemistry, School of Chemistry and Chemical Engineering, Shandong University , Jinan, 250100, China
| | - Yuan Shang
- National Supercomputer Center in Jinan, Jinan, 250101, China
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3
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Heyd R, Rampino A, Bellich B, Elisei E, Cesàro A, Saboungi ML. Isothermal dehydration of thin films of water and sugar solutions. J Chem Phys 2014; 140:124701. [DOI: 10.1063/1.4868558] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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4
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DFT optimization and DFT-MD studies of glucose, ten explicit water molecules enclosed by an implicit solvent, COSMO. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2013.12.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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5
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Roh JH, Tyagi M, Hogan TE, Roland CM. Effect of binding to carbon black on the dynamics of 1,4-polybutadiene. J Chem Phys 2013; 139:134905. [DOI: 10.1063/1.4822476] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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6
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Price DL, Fu L, Bermejo FJ, Fernandez-Alonso F, Saboungi ML. Hydrogen/deuterium isotope effects in water and aqueous solutions of organic molecules and proteins. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.02.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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7
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Qian X. Free Energy Surface for Brønsted Acid-Catalyzed Glucose Ring-Opening in Aqueous Solution. J Phys Chem B 2013; 117:11460-5. [DOI: 10.1021/jp402739q] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xianghong Qian
- Department of Chemical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, United States
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8
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Bio-protective effects of homologous disaccharides on biological macromolecules. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 41:361-7. [PMID: 22038121 DOI: 10.1007/s00249-011-0760-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 10/08/2011] [Accepted: 10/11/2011] [Indexed: 10/16/2022]
Abstract
In this contribution the effects of the homologous disaccharides trehalose and sucrose on both water and hydrated lysozyme dynamics are considered by determining the mean square displacement (MSD) from elastic incoherent neutron scattering (EINS) experiments. The self-distribution function (SDF) procedure is applied to the data collected, by use of IN13 and IN10 spectrometers (Institute Laue Langevin, France), on trehalose and sucrose aqueous mixtures (at a concentration corresponding to 19 water molecules per disaccharide molecule), and on dry and hydrated (H(2)O and D(2)O) lysozyme also in the presence of the disaccharides. As a result, above the glass transition temperature of water, the MSD of the water-trehalose system is lower than that of the water-sucrose system. This result suggests that the hydrogen-bond network of the water-trehalose system is stronger than that of the water-sucrose system. Furthermore, by taking into account instrumental resolution effects it was found that the system relaxation time of the water-trehalose system is longer than that of the water-sucrose system, and the system relaxation time of the protein in a hydrated environment in the presence of disaccharides increases sensitively. These results explain the higher bioprotectant effectiveness of trehalose. Finally, the partial MSDs of sucrose/water and trehalose/water have been evaluated. It clearly emerges from the analysis that these are almost equivalent in the low-Q domain (0-1.7 Å(-1)) but differ substantially in the high-Q range (1.7-4 Å(-1)). These findings reveal that the lower structural sensitivity of trehalose to thermal changes is connected with the local spatial scale.
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Ziemys A, Grattoni A, Fine D, Hussain F, Ferrari M. Confinement effects on monosaccharide transport in nanochannels. J Phys Chem B 2010; 114:11117-26. [PMID: 20738139 DOI: 10.1021/jp103519d] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transport theories based on the continuum hypothesis may not be appropriate at the nanoscale in view of surface effects. We employed molecular dynamics simulations to study the effects of confinement and concentration on diffusive transport of glucose in silica nanochannels (10 nm or smaller). We found that glucose modifies the electrical properties of nanochannels and that, below 5 nm in channel height, glucose adsorption and diffusivity are significantly reduced. With increasing concentration, the diffusivity is reduced linearly in the bulk, while it is reduced nonlinearly at the interface. The effective diffusivity reduction is related to the interface thickness, which can be 2-4 nm depending on concentration, and has an unexpected reduction at low concentrations. Results suggest that nanochannels present a one-dimensional cage environment that affects diffusivity in a fashion similar to cage-breaking diffusion. Our simulation results, consistent with the experimental observations presented here, suggest that nanoconfinement is the essential cause of the observed altered fluid diffusive transport, not accounted for by classical theories, because of coupling of confinement and concentration effects.
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Affiliation(s)
- A Ziemys
- Department of Nanomedicine and Biomedical Engineering, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
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Lelong G, Howells WS, Brady JW, Talón C, Price DL, Saboungi ML. Translational and rotational dynamics of monosaccharide solutions. J Phys Chem B 2010; 113:13079-85. [PMID: 19739660 DOI: 10.1021/jp905001q] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics computer simulations have been carried out on aqueous solutions of glucose at concentrations bracketing those previously measured with quasi-elastic neutron scattering (QENS), in order to investigate the motions and interactions of the sugar and water molecules. In addition, QENS measurements have been carried out on fructose solutions to determine whether the effects previously observed for glucose apply to monosaccharide solutions. The simulations indicate a dynamical analogy between higher solute concentration and lower temperature that could provide a key explanation of the bioprotective phenomena observed in many living organisms. The experimental results on fructose solutions show qualitatively similar behavior to the glucose solutions. The dynamics of the water molecules are essentially the same, while the translational diffusion of the sugar molecules is slightly faster in the fructose solutions.
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Affiliation(s)
- Gérald Lelong
- Centre de Recherche sur la Matiere Divisee, Universite d'Orleans/CNRS-UMR 6619, 45071 Orleans, France.
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11
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Lopez-Rubio A, Gilbert EP. Neutron scattering: a natural tool for food science and technology research. Trends Food Sci Technol 2009. [DOI: 10.1016/j.tifs.2009.07.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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12
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Suzuki T. The hydration of glucose: the local configurations in sugar-water hydrogen bonds. Phys Chem Chem Phys 2007; 10:96-105. [PMID: 18075687 DOI: 10.1039/b708719e] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The hydration of a simple sugar is an essential model for understanding interactions between hydrophilic groups and interfacial water molecules. Here I perform first-principles molecular dynamics simulations on a glucose-water system and investigate how individual hydroxyl groups are locally hydrated. I demonstrate that the hydroxyl groups are less hydrated and more incompatible with a locally tetrahedral network of hydrogen bonds than previously thought. The results suggest that the hydroxyl groups form roughly two hydrogen bonds. Further, I find that the local hydration of the hydroxyl groups is sensitively affected by seemingly small variations in the local electronic structure and bond polarity of the groups. My findings offer insight into an atomic-level understanding of sugar-water interactions.
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Affiliation(s)
- Teppei Suzuki
- Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo, 169-8555, Japan.
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13
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Sjöström J, Kargl F, Fernandez-Alonso F, Swenson J. The dynamics of water in hydrated white bread investigated using quasielastic neutron scattering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:415119. [PMID: 28192331 DOI: 10.1088/0953-8984/19/41/415119] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The dynamics of water in fresh and in rehydrated white bread is studied using quasielastic neutron scattering (QENS). A diffusion constant for water in fresh bread, without temperature gradients and with the use of a non-destructive technique, is presented here for the first time. The self-diffusion constant for fresh bread is estimated to be Ds = 3.8 × 10-10 m2 s-1 and the result agrees well with previous findings for similar systems. It is also suggested that water exhibits a faster dynamics than previously reported in the literature using equilibration of a hydration-level gradient monitored by vibrational spectroscopy. The temperature dependence of the dynamics of low hydration bread is also investigated for T = 280-350 K. The average relaxation time at constant momentum transfer (Q) shows an Arrhenius behavior in the temperature range investigated.
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Affiliation(s)
- J Sjöström
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Göteborg, Sweden
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14
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Lelong G, Price DL, Brady JW, Saboungi ML. Dynamics of trehalose molecules in confined solutions. J Chem Phys 2007; 127:065102. [PMID: 17705626 DOI: 10.1063/1.2753841] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The dynamics of trehalose molecules in aqueous solutions confined in silica gel have been studied by quasielastic neutron scattering (QENS). Small-angle neutron scattering measurements confirmed the absence of both sugar clustering and matrix deformation of the gels, indicating that the results obtained are representative of homogeneous trehalose solutions confined in a uniform matrix. The pore size in the gel is estimated to be 18 nm, comparable to the distances in cell membranes. For the QENS measurements, the gel was prepared from D2O in order to accentuate the scattering from the trehalose. Values for the translational diffusion constant and effective jump distance were derived from model fits to the scattering function. Comparison with QENS and NMR results in the literature for bulk trehalose shows that confinement on a length scale of 18 nm has no significant effect on the translational diffusion of trehalose molecules.
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Affiliation(s)
- Gérald Lelong
- Centre de Recherche sur la Matière Divisée, 45071 Orleans Cedex 2, France
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15
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Nimlos MR, Qian X, Davis M, Himmel ME, Johnson DK. Energetics of xylose decomposition as determined using quantum mechanics modeling. J Phys Chem A 2007; 110:11824-38. [PMID: 17048814 DOI: 10.1021/jp0626770] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The decomposition of xylose has been studied using quantum mechanical calculations supported by NMR data. Proposed mechanisms for the decomposition of xylose have been investigated by obtaining the structures and energies of transition states and products. The intent of this study was to understand the experimentally observed formation of furfural and formic acid that occurs during the decomposition of xylose in mildly hot acidic solutions. A mechanism of furfural formation involving the opening of the pyranose ring and subsequent dehydration of the aldose was compared to a direct intramolecular rearrangement of the protonated pyranose. Energies were determined using CBS-QB3, and it was shown that the barriers for dehydration of the aldose were high compared to intramolecular rearrangement. This result suggests that the latter mechanism is a more likely mechanism for furfural formation. The intramolecular rearrangement step results from protonation of xylose at the O2 hydroxyl group. In addition, it has been shown that formic acid formation is a likely result of the protonation of xylose at the O3 hydroxyl group. Finally, solvation of xylose decomposition was studied by calculating energy barriers for xylose in selected water clusters. The mechanisms proposed here were supported in part by 13C-labeling studies using NMR.
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Affiliation(s)
- Mark R Nimlos
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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16
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Paolantoni M, Sassi P, Morresi A, Santini S. Hydrogen bond dynamics and water structure in glucose-water solutions by depolarized Rayleigh scattering and low-frequency Raman spectroscopy. J Chem Phys 2007; 127:024504. [PMID: 17640134 DOI: 10.1063/1.2748405] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of glucose on the relaxation process of water at picosecond time scales has been investigated by depolarized Rayleigh scattering (DRS) experiments. The process is assigned to the fast hydrogen bonding dynamics of the water network. In DRS spectra this contribution can be safely separated from the slower relaxation process due to the sugar. The detected relaxation time is studied at different glucose concentrations and modeled considering bulk and hydrating water contributions. As a result, it is found that in diluted conditions the hydrogen bond lifetime of proximal water molecules becomes about three times slower than that of the bulk. The effect of the sugar on the hydrogen bond water structure is investigated by analyzing the low-frequency Raman (LFR) spectrum sensitive to intermolecular modes. The addition of glucose strongly reduces the intensity of the band at 170 cm(-1) assigned to a collective stretching mode of water molecules arranged in cooperative tetrahedral domains. These findings indicate that proximal water molecules partially lose the tetrahedral ordering typical of the bulk leading to the formation of high density environments around the sugar. Thus the glucose imposes a new local order among water molecules localized in its hydration shell in which the hydrogen bond breaking dynamics is sensitively retarded. This work provides new experimental evidences that support recent molecular dynamics simulation and thermodynamics results.
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Affiliation(s)
- Marco Paolantoni
- Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto, 8, I-06123 Perugia, Italy
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17
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Fioretto D, Comez L, Gallina M, Morresi A, Palmieri L, Paolantoni M, Sassi P, Scarponi F. Separate dynamics of solute and solvent in water–glucose solutions by depolarized light scattering. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.05.025] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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Jansson H, Howells WS, Swenson J. Dynamics of Fresh and Freeze-Dried Strawberry and Red Onion by Quasielastic Neutron Scattering. J Phys Chem B 2006; 110:13786-92. [PMID: 16836324 DOI: 10.1021/jp060019+] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The microscopic behavior of fresh and freeze-dried strawberry and red onion at different water contents (45 and 20 wt % water) has been investigated by quasielastic neutron scattering (QENS). To distinguish between the dynamics of the water and the biological material isotopic (H/D) substitution was used. The results show that all samples exhibit an onset of anharmonic motions on the experimental time scale (3-100 ps) at about 230-240 K. Above 250 K the dynamics is mainly of translational character and strongly dependent on the hydration level. The diffusion constant increases rapidly with increasing water content and at 280 K it is approximately 20% higher for the hydration water in freeze-dried strawberry than in freeze-dried red onion and around 2 orders of magnitude faster for the hydration water than for the biological material. Moreover, the diffusion constant of the biological part is about 50% faster in freeze-dried strawberry than in freeze-dried red onion. It was also found that the average relaxation time is slightly faster in fresh strawberry than in freeze-dried strawberry. From the results we can conclude that the water dynamics is not only promoting motions in the biological material, it is also affected by the structure (and possibly also the dynamics) of the biological material. Thus, the microscopic properties of the biological materials are interrelated with the properties of their hydration water.
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Affiliation(s)
- H Jansson
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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19
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Cornicchi E, Onori G, Paciaroni A. Picosecond-time-scale fluctuations of proteins in glassy matrices: the role of viscosity. PHYSICAL REVIEW LETTERS 2005; 95:158104. [PMID: 16241767 DOI: 10.1103/physrevlett.95.158104] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Indexed: 05/05/2023]
Abstract
Through elastic neutron scattering we investigated the fast dynamics of lysozyme in hydrated powder form or embedded in glycerol-water and glucose-water matrices. We calculated the relaxational contribution to the mean square displacements of protein hydrogen atoms. We found that the inverse of this quantity is linearly proportional to the logarithm of the viscosity of the solvent glassy matrix. This relationship suggests a close connection between the picosecond-time-scale dynamics of protein side chains and the solvent structural relaxation.
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Affiliation(s)
- Elena Cornicchi
- Dipartimento di Fisica, Università di Perugia, INFM-CRS SOFT Unità di Perugia, and Centro per i Materiali Innovativi e Nanostrutturati (CEMIN), Via A. Pascoli, I-06123 Perugia, Italy
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20
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Mamontov E. High-resolution neutron-scattering study of slow dynamics of surface water molecules in zirconium oxide. J Chem Phys 2005; 123:24706. [PMID: 16050765 DOI: 10.1063/1.1949171] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have performed a quasielastic neutron-scattering experiment on backscattering spectrometer with sub-mueV resolution to investigate the slow dynamics of surface water in zirconium oxide using the sample studied previously with a time-of-flight neutron spectrometer [E. Mamontov, J. Chem. Phys. 121, 9087 (2004)]. The backscattering measurements in the temperature range of 240-300 K have revealed a translational dynamics slower by another order of magnitude compared to the translational dynamics of the outer hydration layer observed in the time-of-flight experiment. The relaxation function of this slow motion is described by a stretched exponential with the stretch factors between 0.8 and 0.9, indicating a distribution of the relaxation times. The temperature dependence of the average residence time is non-Arrhenius, suggesting that the translational motion studied in this work is more complex than surface jump diffusion previously observed for the molecules of the outer hydration layer. The observed slow dynamics is ascribed to the molecules of the inner hydration layer that form more hydrogen bonds compared to the molecules of the outer hydration layer. Despite being slower by two orders of magnitude, the translational motion of the molecules of the inner hydration layer may have more in common with bulk water compared to the outer hydration layer, the dynamics of which is slower than that of bulk water by just one order of magnitude.
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Affiliation(s)
- E Mamontov
- National Institute of Standards and Technology (NIST) Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562, USA.
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21
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Russo D, Murarka RK, Copley JRD, Head-Gordon T. Molecular view of water dynamics near model peptides. J Phys Chem B 2005; 109:12966-75. [PMID: 16852609 PMCID: PMC2684815 DOI: 10.1021/jp051137k] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Incoherent quasi-elastic neutron scattering (QENS) has been used to measure the dynamics of water molecules in solutions of a model protein backbone, N-acetyl-glycine-methylamide (NAGMA), as a function of concentration, for comparison with results for water dynamics in aqueous solutions of the N-acetyl-leucine-methylamide (NALMA) hydrophobic peptide at comparable concentrations. From the analysis of the elastic incoherent structure factor, we find significant fractions of elastic intensity at high and low concentrations for both solutes, which corresponds to a greater population of protons with rotational time scales outside the experimental resolution (>13 ps). The higher-concentration solutions show a component of the elastic fraction that we propose is due to water motions that are strongly coupled to the solute motions, while for low-concentration solutions an additional component is activated due to dynamic coupling between inner and outer hydration layers. An important difference between the solute types at the highest concentration studied is found from stretched exponential fits to their experimental intermediate scattering functions, showing more pronounced anomalous diffusion signatures for NALMA, including a smaller stretched exponent beta and a longer structural relaxation time tau than those found for NAGMA. The more normal water diffusion exhibited near the hydrophilic NAGMA provides experimental support for an explanation of the origin of the anomalous diffusion behavior of NALMA as arising from frustrated interactions between water molecules when a chemical interface is formed upon addition of a hydrophobic side chain, inducing spatial heterogeneity in the hydration dynamics in the two types of regions of the NALMA peptide. We place our QENS measurements on model biological solutes in the context of other spectroscopic techniques and provide both confirming as well as complementary dynamic information that attempts to give a unifying molecular view of hydration dynamics signatures near peptides and proteins.
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Affiliation(s)
- Daniela Russo
- Authors to whom correspondence should be addressed. E-mail: ;
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22
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Mamontov E, Kumzerov YA, Vakhrushev SB. Translational dynamics of water in the nanochannels of oriented chrysotile asbestos fibers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:061502. [PMID: 16089738 DOI: 10.1103/physreve.71.061502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 02/14/2005] [Indexed: 05/03/2023]
Abstract
We performed a high-resolution quasielastic neutron scattering study of water dynamics in fully hydrated oriented chrysotile asbestos [chemical formula Mg3Si2O5(OH)4] fibers. The fibers possess sets of macroscopically long, parallel channels with a characteristic diameter of about 5 nm. Freezing of water in the channels was observed at about 237 K. Measurements at 280, 260, and 240 K revealed a translational dynamics of water molecules with the relaxation time slower by more than an order of magnitude compared to bulk water. The Q dependence of the quasielastic broadening was typical of a translational diffusion motion with a distribution of jump lengths, similar to that observed in bulk water. The relaxation time showed no significant anisotropy in the measurements with the scattering vector parallel and perpendicular to the fiber axes.
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Affiliation(s)
- E Mamontov
- NIST Center for Neutron Research, National Institute of Standards & Technology, 100 Bureau Drive, MS 8562, Gaithersburg, Maryland 20899-8562, USA
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Lelong G, Price DL, Douy A, Kline S, Brady JW, Saboungi ML. Molecular dynamics of confined glucose solutions. J Chem Phys 2005; 122:164504. [PMID: 15945690 DOI: 10.1063/1.1884989] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Silica gels containing solutions of glucose in heavy water at different concentrations have been prepared by a sol-gel method. Dynamical studies with quasielastic neutron scattering, compared with previous results on bulk solutions, show that the dynamics of the glucose molecules are not appreciably affected by the confinement, even though the gels behave macroscopically as solid materials. Small-angle neutron-scattering spectra on the same systems, fitted with a fractal model, yield a correlation length that decreases from 20 to 2.5 nm with increasing glucose concentration, suggesting a clustering of glucose molecules in concentrated solutions that is consistent with the dynamical measurements. These two sets of results imply that 20 nm is an upper limit for the scale at which the dynamics of glucose molecules in solution are affected by confinement.
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Affiliation(s)
- Gérald Lelong
- Centre de Recherche sur la Matière Divisée, 45071 Orléans Cedex 2, France.
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24
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Talon C, Smith LJ, Brady JW, Lewis BA, Copley JRD, Price DL, Saboungi ML. Dynamics of Water Molecules in Glucose Solutions. J Phys Chem B 2004. [DOI: 10.1021/jp035161e] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- César Talon
- Centre de Recherche sur la Matière Divisée, 45071 Orléans Cedex 2, France
| | - Luis J. Smith
- Argonne National Laboratory, Argonne, Illinois 60439
| | - John W. Brady
- Department of Food Sciences, Cornell University, Ithaca, New York 14853
| | - Bertha A. Lewis
- Department of Food Sciences, Cornell University, Ithaca, New York 14853
| | - John R. D. Copley
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
| | - David L. Price
- Centre de Recherche sur les Matériaux à Haute Température, 45071 Orléans Cedex 2, France
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