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| 2. |
- Kellermeier, Matthias, et al.
(author)
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Additive-induced morphological tuning of self-assembled silica-barium carbonate crystal aggregates
- 2009
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 311:8, s. 2530-2541
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Journal article (peer-reviewed)abstract
- Crystallisation of barium carbonate from alkaline silica solutions results in the formation of extraordinary micron-scale architectures exhibiting non-crystallographic curved shapes, such as helical filaments and worm-like braids. These so-called "silica biomorphs" consist of a textured assembly of uniform elongated witherite nanocrystallites, which is occasionally sheathed by a skin of amorphous silica. Although great efforts have been devoted to clarifying the physical origin of these fascinating materials, to date little is known about the processes underlying the observed self-organisation. Herein, we describe the effect of two selected additives, a cationic surfactant and a cationic polymer, on the morphology of the forming crystal aggregates, and relate changes to experiments conducted in the absence of additives. Minor amounts of both substances are shown to exert a significant influence on the growth process, leading to the formation of predominantly flower-like spherulitic aggregates. The observed effects are discussed in terms of feasible morphogenesis pathways. Based on the assumption of a template membrane steering biomorph formation, it is proposed that the two additives are capable of performing specific bridging functions promoting the aggregation of colloidal silica which constitutes the membrane. Morphological changes are tentatively ascribed to varying colloid coordination effecting distinct membrane curvatures. (C) 2009 Elsevier B.V. All rights reserved.
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| 3. |
- Lund, Mikael, et al.
(author)
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Ion binding to biomolecules
- 2009
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In: Specific Ion Effects. - : WORLD SCIENTIFIC. - 9789814271585 - 9789814468176 - 9789814271578 ; , s. 217-230
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Book chapter (peer-reviewed)abstract
- We investigated specific anion binding to basic amino acid residues as well as to a range of patchy protein models. This microscopic information was subsequently used to probe protein–protein interactions for aqueous lysozyme solutions. Using computer simulations to study both atomistic and coarse grained protein molecules, it is shown that the ion–protein interaction mechanism as well as magnitude is largely controlled by the nature of the interfacial amino acid residues. Small anions interact with charged side-chains via ionpairing while larger, poorly hydrated anions are attracted to nonpolar residues due to a number of solvent-assisted mechanisms. Taking into account ion and surface specificity in a mesoscopic model for protein–protein interactions, we investigated the association of the protein lysozyme in aqueous solutions of sodium iodide and sodium chloride. As observed experimentally, it is found that ‘salting out’ of lysozyme follows the reverse Hofmeister series for pH below the iso-electric point and the direct series for pH above.
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| 4. |
- Vrbka, Lubos, et al.
(author)
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Ion-specific thermodynamics of multicomponent electrolytes: A hybrid HNC/MD approach
- 2009
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:15
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Journal article (peer-reviewed)abstract
- Using effective infinite dilution ion-ion interaction potentials derived from explicit-water molecular dynamics (MD) computer simulations in the hypernetted-chain (HNC) integral equation theory we calculate the liquid structure and thermodynamic properties, namely, the activity and osmotic coefficients of various multicomponent aqueous electrolyte mixtures. The electrolyte structure expressed by the ion-ion radial distribution functions is for most ions in excellent agreement with MD and implicit solvent Monte Carlo (MC) simulation results. Calculated thermodynamic properties are also represented consistently among these three methods. Our versatile HNC/MD hybrid method allows for a quick prediction of the thermodynamics of multicomponent electrolyte solutions for a wide range of concentrations and an efficient assessment of the validity of the employed MD force-fields with possible implications in the development of thermodynamically consistent parameter sets. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3248218]
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