Special Pair Dance and Partner Selection: Elementary Steps in Proton Transport in Liquid Water

Markovitch, Omer; Chen, Hanning; Izvekov, Sergei; Paesani, Francesco; Voth, Gregory A.; Agmon, Noam

doi:10.1021/jp804018y

Cited by 312 publications

(587 citation statements)

References 64 publications

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“…Heterogeneous catalysis by the "on-water" effect that occurs at the interface of water and hydrophobic surfaces may stabilize the transition state(s) for the oxidation to sulfate [69]. An acidic pH afforded by the gel-like water exclusion zones (EZs) and Grotthuss-style "proton hopping" may further catalyze the oxidation [70]. Relative immobilization of substrates by long-range dynamic structuring of interfacial hydration water may also be operative [71,72].…”

Section: How Might Enos Synthesize Sulfate? Some Possibilitiesmentioning

confidence: 99%

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

Seneff

Lauritzen

Davidson³

et al. 2012

Entropy

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Theoretical inferences, based on biophysical, biochemical, and biosemiotic considerations, are related here to the pathogenesis of cardiovascular disease, diabetes, and other degenerative conditions. We suggest that the "daytime" job of endothelial nitric oxide synthase (eNOS), when sunlight is available, is to catalyze sulfate production. There is a striking alignment between cell types that produce either cholesterol sulfate or sulfated polysaccharides and those that contain eNOS. The signaling gas, nitric oxide, a wellknown product of eNOS, produces pathological effects not shared by hydrogen sulfide, a sulfur-based signaling gas. We propose that sulfate plays an essential role in HDL-A1 cholesterol trafficking and in sulfation of heparan sulfate proteoglycans (HSPGs), both critical to lysosomal recycling (or disposal) of cellular debris. HSPGs are also crucial in glucose metabolism, protecting against diabetes, and in maintaining blood colloidal suspension and capillary flow, through systems dependent on water-structuring properties of sulfate, an anionic kosmotrope. When sunlight exposure is insufficient, lipids accumulate in the atheroma in order to supply cholesterol and sulfate to the heart, using a OPEN ACCESSEntropy 2012, 14 2493 process that depends upon inflammation. The inevitable conclusion is that dietary sulfur and adequate sunlight can help prevent heart disease, diabetes, and other disease conditions.

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Section: How Might Enos Synthesize Sulfate? Some Possibilitiesmentioning

confidence: 99%

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

Seneff

Lauritzen

Davidson³

et al. 2012

Entropy

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“…Indeed, there is plenty of evidence that hydroxide ions bind more strongly than hydronium ions to polymer surfaces for polymers immersed in water, 14,73,[85][86][87][88][89] whereas protons prefer to be more completely hydrated. 90 Regarding the steric difference of the water ions, in protonated bulk liquid water, for instance, a particular stable complex is the Eigen cation (H 9 O 3 + ), which has a trigonal pyramidal structure, 91,92 whereas hydroxide ions have a resting state of four hydrogen bonds to water molecules in a square-planar arrangement. 93 Furthermore, it should be noted that protons have much higher mobility in water than hydroxide ions [µ H + = 36. .…”

Section: Water Dissociation and Ion Separationmentioning

confidence: 99%

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Knorr¹

2011

AIP Advances

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Though triboelectric charging of insulators is common, neither its mechanism nor the nature of the charge is well known. Most research has focused on the integral amount of charge transferred between two materials upon contact, establishing, e.g., a triboelectric series. Here, the charge distribution of tracks on insulating polymer films rubbed by polymer-covered pointed swabs is investigated in high resolution by Kelvin probe force microscopy. Pronounced bipolar charging was observed for all nine rubbing combinations of three different polymers, with absolute surface potentials of up to several volts distributed in streaks along the rubbing direction and varying in polarity on μm-length scales perpendicular to the rubbing direction. Charge densities increased considerably for rubbing in higher relative humidity, for higher rubbing loads, and for more hydrophilic polymers. The ends of rubbed tracks had positively charged rims. Surface potential decay with time was strongly accelerated in increased humidity, particularly for polymers with high water permeability. Based on these observations, a mechanism is proposed of triboelectrification by extrusions of prevalently hydrated protons, stemming from adsorbed and dissociated water, along pressure gradients on the surface by the mechanical action of the swab. The validity of this mechanism is supported by explanations given recently in the literature for positive streaming currents of water at polymer surfaces and by reports of negative charging of insulators tapped by accelerated water droplets and of potential built up between the front and the back of a rubbing piece, observations already made in the 19th century. For more brittle polymers, strongly negatively charged microscopic abrasive particles were frequently observed on the rubbed tracks. The negative charge of those particles is presumably due in part to triboemission of electrons by polymer chain scission, forming radicals and negatively charged ions

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“…The early 20th century found many of the great scientists of the time developing conceptual models to understand the properties of water and its constituent ions (7,8). Detailed insights into the mechanisms of proton transfer (PT) came much later from a combination of both ab initio molecular dynamics (AIMD) simulations (3,(9)(10)(11)(12)(13) and force-field approaches based on the empirical valence bond formalism (14)(15)(16). The current textbook picture of the Grotthuss mechanism that has resulted from these studies involves a stepwise hopping of the proton from one water molecule to the next (1,17,18).…”

mentioning

confidence: 99%

Proton transfer through the water gossamer

Hassanali

Giberti

Cuny

et al. 2013

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

351

421

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The diffusion of protons through water is understood within the framework of the Grotthuss mechanism, which requires that they undergo structural diffusion in a stepwise manner throughout the water network. Despite long study, this picture oversimplifies and neglects the complexity of the supramolecular structure of water. We use first-principles simulations and demonstrate that the currently accepted picture of proton diffusion is in need of revision. We show that proton and hydroxide diffusion occurs through periods of intense activity involving concerted proton hopping followed by periods of rest. The picture that emerges is that proton transfer is a multiscale and multidynamical process involving a broader distribution of pathways and timescales than currently assumed. To rationalize these phenomena, we look at the 3D water network as a distribution of closed directed rings, which reveals the presence of medium-range directional correlations in the liquid. One of the natural consequences of this feature is that both the hydronium and hydroxide ion are decorated with proton wires. These wires serve as conduits for long proton jumps over several hydrogen bonds.T he mechanism by which protons move through water is at the heart of acid-base chemistry reactions. Understanding the reaction coordinates of this process has been one of the most challenging problems in physical chemistry due to the sheer complexity of water's hydrogen bond network (1-4). Developing a molecular basis for these phenomena is of great relevance in energy conversion applications such as in the design of efficient fuel cells (5). Over 200 y ago, von Grotthuss proposed a mechanism by which water would undergo electrolytic decomposition (6). He imagined that proton conduction involved the collective shuttling of hydrogen atoms along water wires. The early 20th century found many of the great scientists of the time developing conceptual models to understand the properties of water and its constituent ions (7,8). Detailed insights into the mechanisms of proton transfer (PT) came much later from a combination of both ab initio molecular dynamics (AIMD) simulations (3, 9-13) and force-field approaches based on the empirical valence bond formalism (14-16). The current textbook picture of the Grotthuss mechanism that has resulted from these studies involves a stepwise hopping of the proton from one water molecule to the next (1,17,18). This process occurs on a timescale of 1-2 ps. For a successful transfer, the model requires solvent reorganization around the proton-receiving species to develop a coordination pattern like that of the species it will convert to, a process known as presolvation. In all of these characterizations of the Grotthuss mechanism, the role of the connectivity of the water network was not brought to the forefront (3, 19).Sometimes PT has also been thought to take on coherent character involving jumps of several protons simultaneously. In this spirit, Eigen (20) suggested that the proton could delocalize over extended hydrogen...

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Special Pair Dance and Partner Selection: Elementary Steps in Proton Transport in Liquid Water

Cited by 312 publications

References 64 publications

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Proton transfer through the water gossamer

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