A computational study of hydration, solution structure, and dynamics in dilute carbohydrate solutions

Lee, Sau Lawrence; Debenedetti, Pablo G.; Errington, Jeffrey R.

doi:10.1063/1.1917745

Cited by 176 publications

(242 citation statements)

References 79 publications

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“…The dynamical hydration shell and its effects on ice nucleation are known in other contexts. Computational studies show that there is a $5:5 # A shell of water with altered structure and altered rotational and translational dynamics on the picosecond time scale surrounding carbohydrates [25]. IR spectroscopy of water dynamics in nanometer-size reverse micelles show that approximately half of the water in a 4 nm diameter micelle is ''interfacial'' while the other half is bulk-like [26], implying a 5.6 Å interfacial layer thickness.…”

Section: Prl 110 015703 (2013) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Critical Droplet Theory Explains the Glass Formability of Aqueous Solutions

2013

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When pure water is cooled at $10 6 K=s, it forms an amorphous solid (glass) instead of the more familiar crystalline phase. The presence of solutes can reduce this required (or ''critical'') cooling rate by orders of magnitude. Here, we present critical cooling rates for a variety of solutes as a function of concentration and a theoretical framework for understanding these rates. For all solutes tested, the critical cooling rate is an exponential function of concentration. The exponential's characteristic concentration for each solute correlates with the solute's Stokes radius. A modification of critical droplet theory relates the characteristic concentration to the solute radius and the critical nucleation radius of ice in pure water. This simple theory of ice nucleation and glass formability in aqueous solutions has consequences for general glass-forming systems, and in cryobiology, cloud physics, and climate modeling. DOI: 10.1103/PhysRevLett.110.015703 PACS numbers: 64.60.QÀ, 05.40.Àa, 64.70.dg Ice nucleation and growth are of major interest in fields ranging from cryobiology to atmospheric physics. Ice is a key issue in cryopreservation of cells and tissues [1] and in cryocooling of samples for macromolecular crystallography [2,3], where solutes like salts, sugars, alcohols, and polyols can have dramatic effects on ice formation. In atmospheric physics, models of cloud formation are sensitive to the nature of the critical nucleus of ice crystals [4] with implications for climate models [5]. Supercooled water is an interesting system in its own right [6], and the formation of crystalline phases from supercooled solutions is an active area of study [7].Previous experiments have focused on properties such as the melting and glass transition temperatures, and models to explain the data have largely been phenomenological. Similar models have been applied to explain glass formability in a wide variety ofnonaqueous systems. Here, we report measurements of the minimum cooling rates [or ''critical cooling rates'' (CCRs)] required to prevent ice formation in aqueous solutions during cooling to $100 K or below. We show that a surprisingly simple statistical modification to classical thermodynamic nucleation theory provides an excellent account of these data.We studied eight different solutes (see Fig. 1), including a salt (sodium chloride), simple alcohols (methanol, ethanol), sugars (dextrose, trehalose), polyols (glycerol, ethylene glycol), and polyethylene glycol 200 (PEG 200). All are compact and highly soluble and can have large effects on critical cooling rates required for vitrification.The effects of these solutes on ice nucleation were evaluated by measuring the critical cooling rate above which no ice was observed. Below the critical rate, a sample turns opaque on cooling, indicating the formation of polycrystalline ice. As the rate increases, a transition to transparent samples is observed. This optical transition corresponds to a transition in the x-ray diffraction patterns obtained from the cooled sam...

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Section: Prl 110 015703 (2013) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Critical Droplet Theory Explains the Glass Formability of Aqueous Solutions

2013

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“…In a recent study of water near glucose, sucrose, and trehalose, Lee et al (7), computed the translational diffusion coefficient for water surrounding the solute and found a significant decrease in the diffusion coefficient for water molecules within Ϸ5.5 Å from the nearest solute atom. Lee et al also computed a similarly defined c(t) for the hydrogen bonds between the hydration water and glucose and found retardation of the hydrogen bond breaking dynamics between the solute and proximal water molecules.…”

Section: Molecular Modelingmentioning

confidence: 99%

“…Important questions that remain so far unanswered include the following: How does solvation water differ from bulk water, and how large is the solvation layer that can be attributed to solvent water? Simulations suggest the existence of rather rigid water structures around proteins (5) and carbohydrates (7), but experimental studies that characterize the hydration layer are limited. Hydrogen bond rearrangements in water occur on the picosecond time scale (8), so that a detailed understanding of the relevant processes at a molecular level requires experimental techniques that are able to probe the hydration layers on this time scale.…”

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confidence: 99%

Solute-induced retardation of water dynamics probed directly by terahertz spectroscopy

Heugen

Schwaab

Bründermann

et al. 2006

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

392

338

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Hydrogen bond rearrangement in water occurs on the picosecond time scale, so relevant experiments must access these times. Here, we show that terahertz spectroscopy can directly investigate hydration layers. By a precise measurement of absorption coefficients between 2.3 THz and 2.9 THz we could determine the size and the characteristics of the hydration shell. The hydration layer around a carbohydrate (lactose) is determined to extend to 5.13 ؎ 0.24 Å from the surface corresponding to Ϸ123 water molecules beyond the first solvation shell. Accompanying molecular modeling calculations support this result and provide a microscopic visualization. Terahertz spectroscopy is shown to probe the collective modes in the water network. The observed increase of the terahertz absorption of the water in the hydration layer is explained in terms of coherent oscillations of the hydration water and solute. Simulations also reveal a slowing down of the hydrogen bond rearrangement dynamics for water molecules near lactose, which occur on the picosecond time scale. The present study demonstrates that terahertz spectroscopy is a sensitive tool to detect solute-induced changes in the water network.hydration water dynamics ͉ molecular dynamics simulations of biomolecules ͉ solvated lactose T he many unusual properties of water combined with its importance as the solvent of life account for its continued study by numerous researchers. Indeed, the properties of water are essential in the behavior of all biological systems. For example, water plays a central role in the folding and function of proteins, and the function of carbohydrates. The dynamics of water surrounding a solute is of fundamental importance in a wide range of processes in solution. In particular, the properties of water molecules near the surface of a biomolecule have been the subject of numerous and sometimes controversial experimental and theoretical studies (1-5). The characteristics and role of this ''biological'' water, with properties that differ considerably from those of bulk water, are still not fully understood (6).The importance of the hydration layer or the biological water is obvious in specific protein processes, such as opening and closing of channels, the kinetics of which has been found to be coupled with the solvent fluctuations (1). Important questions that remain so far unanswered include the following: How does solvation water differ from bulk water, and how large is the solvation layer that can be attributed to solvent water? Simulations suggest the existence of rather rigid water structures around proteins (5) and carbohydrates (7), but experimental studies that characterize the hydration layer are limited. Hydrogen bond rearrangements in water occur on the picosecond time scale (8), so that a detailed understanding of the relevant processes at a molecular level requires experimental techniques that are able to probe the hydration layers on this time scale. However, experimental investigations of fast dynamics of hydration water still remain a ch...

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“…19 and 31-33. A measure qualitatively similar to Q(r) has been studied in case of solvation structure of water around carbohydrate molecules (35). In Fig.…”

Section: [8]mentioning

confidence: 99%

A tetrahedral entropy for water

Kumar

Buldyrev

Stanley

2009

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

104

124

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We introduce the space-dependent correlation function C Q (r) and time-dependent autocorrelation function C Q (t) of the local tetrahedral order parameter Q ≡ Q(r, t). By using computer simulations of 512 waterlike particles interacting through the transferable interaction potential with five points (TIP5 potential), we investigate C Q (r) in a broad region of the phase diagram. We find that at low temperatures C Q (t) exhibits a two-step time-dependent decay similar to the self-intermediate scattering function and that the corresponding correlation time τ Q displays a dynamic cross-over from non-Arrhenius behavior for T > T W to Arrhenius behavior for T < T W , where T W denotes the Widom temperature where the correlation length has a maximum as T is decreased along a constant-pressure path. We define a tetrahedral entropy S Q associated with the local tetrahedral order of water molecules and find that it produces a major contribution to the specific heat maximum at the Widom line. Finally, we show that τ Q can be extracted from S Q by using an analog of the Adam-Gibbs relation.specific heat of water | orientational entropy of tetrahedral liquids | anomalies of liquid water | Widom line I t has long been appreciated that the local structure around a molecule of liquid water arising from the vertices formed by four nearest neighbors is approximately tetrahedral at ambient pressure and that the degree of tetrahedrality increases when water is cooled (1-5). An important advance occurred in the past 10 years when computer simulations allowed the quantification of the degree of tetrahedrality (6-10) by assigning to each molecule a local tetrahedral order parameter Q (11-16). At high temperatures, the probability distribution P(Q, T) is bimodal, with one peak corresponding to a high degree of tetrahedrality and the other to a less tetrahedral environment (Fig. 1). Upon decreasing temperature, the peak associated with a high degree of tetrahedrality grows, suggesting that the local structure of water becomes much more tetrahedral at lower temperatures (13,14,17). IntroductionWater has been hypothesized to belong to the class of polymorphic liquids, phase separating-at sufficiently low temperatures and high pressures-into two distinct liquid phases: a high density liquid (HDL) with smaller Q and a low density liquid (LDL) with larger Q (18). The coexistence line separating these two phases may terminate at a liquid-liquid (LL) critical point, above which (in the LL supercritical region) appears a line of correlation length maximum in the pressure-temperature plane. The locus of maximum correlation length in the one-phase region is called the Widom line T W ≡ T W (P) (19), near which different response functions, such as isobaric specific heat C P and isothermal compressibility K T , display maxima. Recent neutron-scattering experiments (20) and computer simulations (19) show that the dynamics of water gradually cross over from being non-Arrhenius for T > T W to Arrhenius for T < T W .Although dynamic heterogeneities h...

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A computational study of hydration, solution structure, and dynamics in dilute carbohydrate solutions

Cited by 176 publications

References 79 publications

Critical Droplet Theory Explains the Glass Formability of Aqueous Solutions

Critical Droplet Theory Explains the Glass Formability of Aqueous Solutions

Solute-induced retardation of water dynamics probed directly by terahertz spectroscopy

A tetrahedral entropy for water

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