Supercooled Confined Water and the Mode Coupling Crossover Temperature

Gallo, Paola; Rovere, Mauro; Spohr, Eckhard

doi:10.1103/physrevlett.85.4317

Cited by 151 publications

(156 citation statements)

References 46 publications

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“…QENS experiments essentially provide us with the Fourier transform of the intermediate scattering function (ISF) of the hydrogen atoms, F H (Q, t), of water molecules in the hydration layer. Molecular dynamics simulations have shown that the ISF of both bulk (31) and confined (32) supercooled water can be accurately described as a two-step relaxation: a short-time Gaussian-like (in-cage vibrational) relaxation followed by a plateau and then a long-time (time Ͼ 1.0 ps) stretched exponential relaxation of the cage. The RCM (26), which we used for data analysis, models closely this two-step relaxation and has been tested extensively against bulk and confined supercooled water through molecular dynamics and experimental data (12,31,32).…”

Section: Methodsmentioning

confidence: 99%

“…Molecular dynamics simulations have shown that the ISF of both bulk (31) and confined (32) supercooled water can be accurately described as a two-step relaxation: a short-time Gaussian-like (in-cage vibrational) relaxation followed by a plateau and then a long-time (time Ͼ 1.0 ps) stretched exponential relaxation of the cage. The RCM (26), which we used for data analysis, models closely this two-step relaxation and has been tested extensively against bulk and confined supercooled water through molecular dynamics and experimental data (12,31,32). By considering only the spectra with wave vector transfer Q Ͻ 1.1 Å Ϫ1 , we can safely neglect the contribution from the rotational motion of water molecule in the ISF (26).…”

Section: Methodsmentioning

confidence: 99%

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Observation of fragile-to-strong dynamic crossover in protein hydration water

Chen

Liu

Fratini

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

420

554

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At low temperatures, proteins exist in a glassy state, a state that has no conformational flexibility and shows no biological functions. In a hydrated protein, at temperatures տ220 K, this flexibility is restored, and the protein is able to sample more conformational substates, thus becoming biologically functional. This ''dynamical'' transition of protein is believed to be triggered by its strong coupling with the hydration water, which also shows a similar dynamic transition. Here we demonstrate experimentally that this sudden switch in dynamic behavior of the hydration water on lysozyme occurs precisely at 220 K and can be described as a fragile-to-strong dynamic crossover. At the fragile-to-strong dynamic crossover, the structure of hydration water makes a transition from predominantly high-density (more fluid state) to lowdensity (less fluid state) forms derived from the existence of the second critical point at an elevated pressure.glass transition ͉ liquid-liquid transition ͉ protein dynamics ͉ quasi-elastic neutron scattering W ithout water, a biological system would not function.Dehydrated enzymes are not active, but a single layer of water surrounding them restores their activity. It has been shown that the enzymatic activity of proteins depends crucially on the presence of at least a minimum amount of solvent water (1, 2). It is believed that Ϸ0.3 g of water per g of protein is sufficient to cover most of the protein surface with one single layer of water molecules and to fully activate the protein functionality. Thus, biological functions (3) such as enzyme catalysis can only be understood with a precise knowledge of the behavior of this single layer of water and how that water affects conformation and dynamics of the protein. The knowledge of the structure and dynamics of water molecules in the so-called hydration layer surrounding proteins is therefore of utmost relevance to the understanding of the protein functionality. It is well documented that at low temperatures proteins exist in a glassy state (4, 5), which is a solid-like structure without conformational flexibility. As the temperature is increased, the atomic motional amplitude increases linearly initially, as in a harmonic solid. In hydrated proteins, at Ϸ220 K, the rate of the amplitude increase suddenly becomes enhanced, signaling the onset of additional anharmonic and liquid-like motion (6-9). This ''dynamical'' transition of proteins is believed to be triggered by their strong coupling with the hydration water through the hydrogen bonding. The reasoning is derived from the finding that the protein hydration water shows some kind of dynamic transition at a similar temperature (10, 11). Here we demonstrate, through a high-resolution quasielastic neutron scattering (QENS) experiment, that this dynamic transition of hydration water on lysozyme protein is in fact the fragile-to-strong dynamic crossover (FSC) at 220 K, similar to that recently observed in confined water in cylindrical nanopores of silica materials (12, 13). Computer simulat...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Observation of fragile-to-strong dynamic crossover in protein hydration water

Chen

Liu

Fratini

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

420

554

View full text Add to dashboard Cite

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“…The Wolf method [37,38,39] has been used in recent simulation studies, e.g. for quasitwo-dimensional geometries [40], in MC simulations [41], or for dipolar fluids [42]. Of course, it is a priori not clear how large the cutoff radius r c has to be in order to correctly reproduce the static and dynamic properties of the original model with long-range Coulomb interactions.…”

Section: Introductionmentioning

confidence: 99%

Amorphous silica modeled with truncated and screened Coulomb interactions: A molecular dynamics simulation study

Carré

Berthier

Horbach

et al. 2007

The Journal of Chemical Physics

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We show that finite-range alternatives to the standard long-range BKS pair potential for silica might be used in molecular dynamics simulations. We study two such models that can be efficiently simulated since no Ewald summation is required. We first consider the Wolf method, where the Coulomb interactions are truncated at a cutoff distance rc such that the requirement of charge neutrality holds. Various static and dynamic quantities are computed and compared to results from simulations using Ewald summations. We find very good agreement for rc ≈ 10Å. For lower values of rc, the long-range structure is affected which is accompanied by a slight acceleration of dynamic properties. In a second approach, the Coulomb interaction is replaced by an effective Yukawa interaction with two new parameters determined by a force fitting procedure. The same trend as for the Wolf method is seen. However, slightly larger cutoffs have to be used in order to obtain the same accuracy with respect to static and dynamic quantities as for the Wolf method.

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“…Molecular Dynamics (MD) simulations have shown that the ISF of both bulk [13] and confined [14] supercooled water can be accurately described as a two-step relaxation: a short-time Gaussian-like (in-cage vibrational) relaxation followed by a plateau and then a long-time (time > 1.0 ps) stretched exponential relaxation of the cage. The so-called Relaxing Cage Model (RCM) [15], which we use for data analysis, models closely this twostep relaxation and has been tested extensively against bulk and confined supercooled water through MD and experimental data [13,14,15]. By considering only the spectra with wave vector transfer Q < 1.1Å −1 , we can safely neglect the contribution from the rotational motion of water molecule [15].…”

mentioning

confidence: 99%

Experimental evidence of fragile-to-strong dynamic crossover in DNA hydration water

Chen¹,

Liu²,

Chu³

et al. 2006

The Journal of Chemical Physics

116

125

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We used high-resolution quasielastic neutron scattering spectroscopy to study the single-particle dynamics of water molecules on the surface of hydrated DNA samples. Both H2O and D2O hydrated samples were measured. The contribution of scattering from DNA is subtracted out by taking the difference of the signals between the two samples. The measurement was made at a series of temperatures from 270 K down to 185 K. The Relaxing -Cage Model was used to analyze the quasielastic spectra. This allowed us to extract a Q-independent average translational relaxation time τT of water molecules as a function of temperature. We observe clear evidence of a fragileto-strong dynamic crossover (FSC) at TL = 222 ± 2 K by plotting log τT vs. T. The coincidence of the dynamic transition temperature Tc of DNA, signaling the onset of anharmonic molecular motion, and the FSC temperature TL of the hydration water suggests that the change of mobility of the hydration water molecules across TL drives the dynamic transition in DNA. . It was also found, from neutron and Xray scattering, or from Mössbauer spectroscopy, that the measured mean-squared atomic displacement x 2 of the bio-molecules exhibits a sharp rise in the same temperature range [1,2,3,4,5]. This sharp increase in x 2 was taken as a sign for a dynamic transition (or sometimes called glass-transition) in the bio-molecules occurring within this temperature range. In most of these papers, the authors suggest that the transition is due to a strong rise of anharmonicity of the molecular motions above this transition temperature [1]. Later on, it was demonstrated that the dynamic transition can be suppressed in dry bio-molecules [2], or in bio-molecules dissolved in trehalose [5]. Moreover, it can be shifted to a higher temperature for proteins dissolved in glycerol [4]. Thus the dynamic transition can be controlled by changing the surrounding solvent of the bio-molecules. On the other hand, it was found some time ago from Raman scattering that supercooled bulk water has a dynamic crossover transition at 220 K [6], similar to that predicted by Mode-Coupling theory [7]. Approximate coincidence of these two characteristic temperatures, one for the slowing down of bio-chemical activities and the sharp rise in x 2 in bio-molecules and the other for the dynamic crossover in water, suggests a relation between the dynamic transition of bio-molecules and that of their * Author to whom correspondence should be addressed. Electronic mail: sowhsin@mit.edu hydration water [8].Another striking experimental fact is that this dynamic transition temperature, as revealed by change of slope in x 2 vs. temperature plot, occurs at a universal temperature range from 250 to 200 K in all bio-molecules examined so far. This list includes globular proteins, DNAs, and t-RNAs. This feature points to the plausibility that the dynamical transitions are not the intrinsic properties of the bio-molecules themselves but are imposed by the hydration water on their surfaces.However, x 2 (mostly coming from hydroge...

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Supercooled Confined Water and the Mode Coupling Crossover Temperature

Cited by 151 publications

References 46 publications

Observation of fragile-to-strong dynamic crossover in protein hydration water

Observation of fragile-to-strong dynamic crossover in protein hydration water

Amorphous silica modeled with truncated and screened Coulomb interactions: A molecular dynamics simulation study

Experimental evidence of fragile-to-strong dynamic crossover in DNA hydration water

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