Ion hydration in nanopores and the molecular basis of selectivity

Schäfer

Phys. Chem. Chem. Phys.

et al. 2012

The transport of anionic drinking water contaminants (fluoride, chloride, nitrate and nitrite) through narrow pores ranging in effective radius from 2.5 to 6.5 Å was systematically evaluated using molecular dynamics simulations to elucidate the magnitude and origin of energetic barriers encountered in nanofiltration. Free energy profiles for ion transport through the pores show that energy barriers depend on pore size and ion properties and that there are three key regimes that affect transport. The first is where the ion can fit in the pore with its full inner hydration shell, the second is where the pore size is between the bare ion and hydrated radius, and the third is where the ion size approaches that of the pore. Energy barriers in the first regime are relatively small and due to rearrangement of the inner hydration shell and/or displacement of further hydration shells. Energy barriers in the second regime are due to partial dehydration and are larger than barriers seen in the first regime. In the third regime, the pore becomes too small for bare ions to fit regardless of hydration and thus energy barriers are very high. In the second regime where partial dehydration controls transport, the trend in the slopes of the change in energy barrier with pore size corresponds to the hydration strength of the anions.

Section: Introductionmentioning

confidence: 99%

Quantifying barriers to monovalent anion transport in narrow non-polar pores

Schäfer

Phys. Chem. Chem. Phys.

et al. 2012

“…Various compounds are accommodated in confined spaces, and their molecular structures and dynamics therein have been studied by X-ray and neutron scattering, [3][4][5] spectroscopy, 6,7 and computer simulations. 9,10 An interface, which can be considered as a space twodimensionally confined between two phases, has received increasing attention in analytical sciences. 10,12,13 A special issue of Analytical Sciences in 2004 was devoted to the compilation of papers treating liquid-liquid interfaces.…”

Section: Introductionmentioning

confidence: 99%

“…It is known that materials confined in nanospaces show structures and/or dynamics different from those exhibited in bulk. [1][2][3][4][5][6][7][8][9][10][11] Such unusual properties, which become more apparent as the size of the space decreases, partly come from the effects of the walls surrounding the spaces. 2,6 The interaction of compounds with the wall becomes more dominant with decreasing size of the space.…”

Section: Introductionmentioning

confidence: 99%

“…However, since direct experimental studies of ions are, in general, difficult when small spaces should be probed, the ion selectivity is mostly discussed on the basis of molecular simulations. 9,[24][25][26][27] We have been involved in the elucidation of the molecular origins of selectivity in separation of ions, and have employed chromatography, electrophoresis, X-ray absorption fine structure (XAFS), and ion-transfer voltammetry to evaluate the structures of ions and the thermodynamics concerned with separation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hydration of Ions in Confined Spaces and Ion Recognition Selectivity

2009

The hydration of ions in confined spaces, such as the interior of ion-exchange resins, micelles, and surface monolayers, is discussed on the basis of results obtained with X-ray absorption fine structure studies, electrophoresis, and ion-transfer voltammetry. The general trends are that anions are partly dehydrated therein, whereas cations are likely to keep their first hydration shells. For bromide ions, the hydration numbers under various circumstances have been determined. The extents of dehydration depend not only on the structure of the cationic sites electrostatically attracting bromide ions but also on whether the cationic sites are exposed to a solution or are effectively shielded from it. These findings will be useful for designing the systems for ionic recognition and separation.

“…With regards to BP, Cinvestav's physics department is already developing a research core [34][35][36][37][38][39], which other departments at Cinvestav are also doing research in biological physics and related issues [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. We also should account for the work at the biophysics group in the Instituto de Física y Matemáticas of the Universidad Michoacana San Nicolás Hidalgo [58], as well as the Instituto de Ciencias Físicas [59][60][61][62][63][64][65][66][67][68][69][70][71][72], Instituto de Física [73][74][75][76], and Facultad de Ciencias [77,78], all three at UNAM. Some very recent endeavors in biological physics research are under gestation at the División de Ciencias e Ingeniería at Universidad de Guanajuato in León (DCI-UG, formerly UG Physics Institute, IFUG...…”

Section: Some Historical Remarks On Biological Physics Méxicomentioning

confidence: 99%

Biological physics in México

Hernández‐Lemus

2011

J Biol Phys

Biological and physical sciences possess a long-standing tradition of cooperativity as separate but related subfields of science. For some time, this cooperativity has been limited by their obvious differences in methods and views. Biological physics has recently experienced a kind of revival (or better a rebirth) due to the growth of molecular research on animate matter. New avenues for research have been opened for both theoretical and experimental physicists. Nevertheless, in order to better travel for such paths, the contemporary biological physicist should be armed with a set of specialized tools and methods but also with a new attitude toward multidisciplinarity. In this review article, we intend to somehow summarize what has been done in the past (in particular, as an example we will take a closer look at the Mexican case), to show some examples of fruitful investigations in the biological physics area and also to set a proposal of new curricula for physics students and professionals interested in applying their science to get a better understanding of the physical basis of biological function.