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Journal ArticleDOI

Ions in water: characterizing the forces that control chemical processes and biological structure.

TL;DR: Two different techniques indicate that the interaction of water with anions is by an approximately linear hydrogen bond, suggesting that the dominant forces on ions in water are short range forces of a chemical nature.
About: This article is published in Biophysical Chemistry.The article was published on 2007-07-01. It has received 571 citations till now. The article focuses on the topics: Debye & Molecule.
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Journal ArticleDOI
TL;DR: Results from Diffraction Experiments 1351 and results from Spectroscopic Measurements 1354 4.3.1.
Abstract: 4. Structure of Ionic Hydration Shells 1351 4.1. Results from Diffraction Experiments 1351 4.1.1. X-ray Diffraction 1351 4.1.2. Neutron Diffraction 1351 4.2. Results from Computer Simulations 1352 4.3. Results from Spectroscopic Measurements 1354 4.3.1. Vibrational Spectroscopic Measurements 1354 4.3.2. EXAFS Spectroscopy 1354 4.3.3. NMR Relaxation Studies 1355 4.3.4. Dielectric Relaxation Studies 1355 4.4. Summary of the Structure of Ionic Hydration Shells 1355

1,445 citations

Journal ArticleDOI
TL;DR: It is concluded that synthetic methods have evolved rapidly and development of fundamental knowledge on the many complex phenomena occurring in the adaptive membrane bulk and solution-interface environments is not sufficiently established, and much effort is required to combine experimental, theoretical, and simulation data for a more comprehensive and coherent understanding of these phenomena.

636 citations

Journal ArticleDOI
21 May 2010-Science
TL;DR: A combined terahertz and femtosecond infrared spectroscopic study of water dynamics around different ions reveals that the effect of ions and counterions on water can be strongly interdependent and nonadditive, and in certain cases extends well beyond the first solvation shell of water molecules directly surrounding the ion.
Abstract: Despite prolonged scientific efforts to unravel the effects of ions on the structure and dynamics of water, many open questions remain, in particular concerning the spatial extent of this effect (i.e., the number of water molecules affected) and the origin of ion-specific effects. A combined terahertz and femtosecond infrared spectroscopic study of water dynamics around different ions (specifically magnesium, lithium, sodium, and cesium cations, as well as sulfate, chloride, iodide, and perchlorate anions) reveals that the effect of ions and counterions on water can be strongly interdependent and nonadditive, and in certain cases extends well beyond the first solvation shell of water molecules directly surrounding the ion.

585 citations

Journal ArticleDOI
TL;DR: A mechanism for specific ion effects is elucidated for aqueous systems containing charged and uncharged polymers, polypeptides, and proteins and a hydrogen-bonding mechanism is tested for the urea denaturation of proteins with some of these same systems.
Abstract: The study of the interactions of salts and osmolytes with macromolecules in aqueous solution originated with experiments concerning protein precipitation more than 100 years ago. Today, these solutes are known to display recurring behavior for myriad biological and chemical processes. Such behavior depends both on the nature and concentration of the species in solution. Despite the generality of these effects, our understanding of the molecular-level details of ion and osmolyte specificity is still quite limited. Here, we review recent studies of the interactions between anions and urea with model macromolecular systems. A mechanism for specific ion effects is elucidated for aqueous systems containing charged and uncharged polymers, polypeptides, and proteins. The results clearly show that the effects of the anions are local and involve direct interactions with macromolecules and their first hydration shell. Also, a hydrogen-bonding mechanism is tested for the urea denaturation of proteins with some of these same systems. In that case, direct hydrogen bonding can be largely discounted as the key mechanism for urea stabilization of uncollapsed and/or unfolded structures.

557 citations

References
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Journal ArticleDOI
TL;DR: Electronic excitation energy transfer as function of distance measured, noting energy transfer process use as spectroscopic ruler as well as the use of spectroscopy ruler for measuring distance.
Abstract: Electronic excitation energy transfer as function of distance measured, noting energy transfer process use as spectroscopic ruler

1,817 citations


"Ions in water: characterizing the f..." refers background in this paper

  • ...Simple ions in water generate long range electric fields which can be detected by various resonance techniques, such as fluorescence resonance energy transfer, over distances of 30 Å (about 11 water diameters) or more [16]....

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Journal ArticleDOI
TL;DR: The first general, detailed qualitative molecular mechanism for the origins of ion-specific (Hofmeister) effects on the surface potential difference at an air-water interface is proposed; this mechanism suggests a simple model for the behaviour of water at all interfaces, regardless of whether the non-aqueous component is neutral or charged, polar or non-polar.
Abstract: Starting from known properties of non-specific salt effects on the surface tension at an air–water interface, we propose the first general, detailed qualitative molecular mechanism for the origins of ion-specific (Hofmeister) effects on the surface potential difference at an air–water interface; this mechanism suggests a simple model for the behaviour of water at all interfaces (including water–solute interfaces), regardless of whether the non-aqueous component is neutral or charged, polar or non-polar Specifically, water near an isolated interface is conceptually divided into three layers, each layer being 1 water-molecule thick We propose that the solute determines the behaviour of the adjacent first interfacial water layer ( I 1 ); that the bulk solution determines the behaviour of the third interfacial water layer ( I 3 ), and that both I 1 and I 3 compete for hydrogen-bonding interactions with the intervening water layer ( I 2 ), which can be thought of as a transition layer The model requires that a polar kosmotrope (polar water-structure maker) interact with I 1 more strongly than would bulk water in its place; that a chaotrope (water-structure breaker) interact with I 1 somewhat less strongly than would bulk water in its place; and that a non-polar kosmotrope (non-polar water-structure maker) interact with I 1 much less strongly than would bulk water in its place We introduce two simple new postulates to describe the behaviour of I 1 water molecules in aqueous solution The first, the ‘relative competition’ postulate, states that an I 1 water molecule, in maximizing its free energy (—δG), will favour those of its highly directional polar (hydrogen-bonding) interactions with its immediate neighbours for which the maximum pairwise enthalpy of interaction (—δ H ) is greatest; that is, it will favour the strongest interactions We describe such behaviour as ‘compliant’, since an I 1 water molecule will continually adjust its position to maximize these strong interactions Its behaviour towards its remaining immediate neighbours, with whom it interacts relatively weakly (but still favourably), we describe as ‘recalcitrant’, since it will be unable to adjust its position to maximize simultaneously these interactions The second, the ‘charge transfer’ postulate, states that the strong polar kosmotrope–water interaction has at least a small amount of covalent character, resulting in significant transfer of charge from polar kosmotropes to water–especially of negative charge from Lewis bases (both neutral and anionic); and that the water-structuring effect of polar kosmotropes is caused not only by the tight binding (partial immobilization) of the immediately adjacent ( I 1 ) water molecules, but also by an attempt to distribute among several water molecules the charge transferred from the solute When extensive, cumulative charge transfer to solvent occurs, as with macromolecular polyphosphates, the solvation layer (the layer of solvent whose behaviour is determined by the solute) can become up to 5- or 6-water-molecules thick We then use the ‘relative competition’ postulate, which lends itself to simple diagramming, in conjunction with the ‘charge transfer’ postulate to provide a new, startlingly simple and direct qualitative explanation for the heat of dilution of neutral polar solutes and the temperature dependence of relative viscosity of neutral polar solutes in aqueous solution This explanation also requires the new and intriguing general conclusion that as the temperature of aqueous solutions is lowered towards o °C, solutes tend to acquire a non-uniform distribution in the solution, becoming increasingly likely to cluster 2 water molecules away from other solutes and surfaces (the driving force for this process being the conversion of transition layer water to bulk water) The implications of these conclusions for understanding the mechanism of action of general (gaseous) anaesthetics and other important interfacial phenomena are then addressed

1,468 citations


"Ions in water: characterizing the f..." refers background or methods in this paper

  • ...We have studied the interaction of ions with water as a way to understand these forces, and used the Hofmeister series [2,3] to systemize our results....

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  • ...Water is unique in that the second water layer (each layer being one molecule thick) surrounding a solute such as a protein makes a large contribution to the energy of solvation of the protein [3,28,72]....

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  • ..., ammonium, chloride, potassium, and the positively charged amino acid side chains) and actually adsorb to nonpolar surfaces [3–5] and interfaces [6,7]....

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Journal ArticleDOI
TL;DR: Aqueous ion-containing interfaces are ubiquitous and play a key role in a plethora of physical, chemical, atmospheric, and biological processes, from which just a few illustrative examples are mentioned.
Abstract: Aqueous ion-containing interfaces are ubiquitous and play a key role in a plethora of physical, chemical, atmospheric, and biological processes, from which we mention just a few illustrative examples: (i) Ions at the air/water interface are important for atmospheric chemistry involving ocean surfaces and seawater aerosols, 1-5 as well as that of the Arctic snowpack covered by sea spray. 6,7 (ii) Many salts (such as NaCl) tend to inhibit bubble coalescence, 8-12 which is one of the reasons why foam is formed when waves break in the ocean but not in freshwater lakes. (iii) Brine rejection occurring at the seawater/ice interface has profound climatic effects in polar regions. 13 (iv) The aqueous electrolyte/metal interface is involved in electrode and corrosion processes. 14,15

1,229 citations


"Ions in water: characterizing the f..." refers background in this paper

  • ...Microscopic calculations also find a role for the polarizability of water in driving the weakly hydrated Cl ion to an air/water interface [9,10,12], but since “polarizability appears to be important primarity for its role in facilitating a larger average dipole moment on the water model” [12] and the interaction of water with Cl is via an approximately linear hydrogen bond rather than a dipolar interaction [13–15], it is difficult to evaluate the significance of these calculations....

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  • ...Sophisticated microscopic calculations have indicated a role for the polarizability [9,10] of weakly hydrated ions (as opposed to their dehydration energy) and dispersion forces [11] in driving them to neutral interfaces....

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Journal ArticleDOI
TL;DR: In this paper, the Versuehsanordnung of the Quellungsversuehen in Wasseraufnahme is discussed, i.e., the Aufgabe batten, den zeitlichen Verlauf der Wasserausfreenahme seitens quellender Ktirper bei Einbringen derselben in reines Wasser klarzustellen, so sollten die naehstehend vorzuftihrenden Untersuehangen dartiber A
Abstract: 1. Zur Versuehsanordnung. W~ihrend die zuletzt mitgetheilten Versuche fiber den Quellungsvorgang 1) vorzuffsweise die Aufgabe batten, den zeitlichen Verlauf der Wasseraufnahme seitens quellender Ktirper bei Einbringen derselben in reines Wasser klarzustellen, so sollten die naehstehend vorzuftihrenden Untersuehangen dartiber Aufkl~trung bringen, inwiefern sieh der gesammte Quellungsvorgang ~tndert, wenn als Quellungsfitissigkeit nicht Wasser~ sondern~ wie dies den lebenden Zellen ffegentiber in tier Regel der Fall ist~ eine LSsunff yon chemisch weniff differenten Stoffen, in erster Linie eine Salzltisunff, dient. Ieh habe die betreffenden Versuehe zumeist an Leimplatten ausgeftihrt, nur einen kleineren Theil mit Thierblase. Ieh wahlte Gelatine, weil diese einerseits ein chemiseh and meehanisch gentigend homogenes Material darstellt, und doeh andererseits den im ThierkiJrper als wiehtigste Vermittler yon Quellungsvorgiinffen dienenden Proteinstoffen ehemiseh und physiologisch viel niiher steht, als z. B. die zu Quellungsversuehen in mancher Riehtung geeignetere Agargallerte. In der naehfolgenden Darstellunff habe ieh zuni~ehst stets die Versuehe an Gelatine im Auge. Da dtinne gequollene Leimplatten dutch ihre Zerreissliehkeit ein Handhaben unmiJglieh maehen~ wurden diekere Leimscheiben verwendet~ was einiffe Abweiehunffen ffegentiber dem in frtiheren Untersuehungen benutzten Verfahren zur Folge hatte. Da dicke Leimplatten beim Einbrinffen in Wasser das Quellungsmaximum nicht in wenigen Stunden oder aueh Tagen erreiehen und wiihrend des Ver-

1,186 citations