Hildebrand, Nils Alexander
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Hildebrand, Nils Alexander
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Hildebrand, Nils Alexander
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Item-typ:Veröffentlichung, Molecular Dynamics Simulations of the Protein Adsorption Process on OxidesThe adsorption of chymotrypsin and lysozyme on amorphous silica and titania is studied by molecular dynamics (MD) simulations in comparison to experiments. The simulations allow an atomistic view of the adsorption process including long-range interactions, multi-protein effects, contact analysis and surface-induced conformational changes. The surface contact stability is investigated by Steered MD simulations and Atomic Force Spectroscopy experiments. Surface-induced conformational changes are studied by classical and further developed free energy MD methods based on Metadynamics, Replica Exchange Solute Tempering and Umbrella sampling and are compared to circular dichroism experiments. The protein orientation is highly influenced by its dipole moment whereas protein binding motifs are formed mainly by positively charged amino acids. The comparison to the experiment shows that protein-protein interactions and the hydration shell of oxide and protein need to be considered as well.Dissertation376 162 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Physisorption of α-chymotrypsin on SiO2 and TiO2: A comparative study via experiments and molecular dynamics simulations(2016-01-13); ; ; ; In order to understand fundamental interactions at the interface between immobilized enzymes and ceramic supports, the authors compare the adsorption features of chymotrypsin on SiO2 and TiO2 colloidal particles by means of a combination of adsorption experiments and molecular dynamics simulations. While the dependency of the adsorption amount on pH is consistent with the trend predicted the Derjaguin-Landau-Verwey-Overbeek theory, other effects can only be rationalized if the atomic-scale details of the water-mediated protein-surface interactions are considered. On both surfaces, a clear driving force for the formation of a double monolayer at the saturation coverage is found. Although nearly equal free energies of adsorption are estimated on the two materials via a Langmuir adsorption analysis, about 50% more proteins per unit of surface can be accommodated on TiO2 than on SiO2. This is probably due to the lower surface diffusion mobility of the adsorbed protein in the latter case. Surface anchoring is realized by a combination of direct ionic interactions between charged proteins and surface sites (more pronounced for SiO2) and distinct structuring of the surface hydration layers in which the contact residues are embedded (more pronounced for TiO2). Finally, normalization of the data with respect to particle surface areas accessible to the proteins, rather than determined by means of the Brunauer-Emmett-Teller nitrogen adsorption isotherm, is crucial for a correct interpretation of the results.Wissenschaftlicher Artikel169 126 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Effect of divalent versus monovalent cations on the MS2 retention capacity of amino-functionalized ceramic filters(Royal Society of Chemistry, 2018-04-10); ; ; ; Ceramic capillary membranes conditioned for virus filtration via functionalization with n-(3-trimethoxysilylpropyl)diethylenetriamine (TPDA) are analyzed with respect to their virus retention capacity when using feed solutions based on monovalent and divalent salts (NaCl, MgCl2). The log reduction value (LRV) by operating in dead-end mode using the model bacteriophage MS2 with a diameter of 25 nm and an IEP of 3.9 is as high as 9.6 when using feeds containing MgCl2. In contrast, a lesser LRV of 6.4 is observed for feed solutions based on NaCl. The TPDA functionalized surface is simulated at the atomistic scale using explicit-solvent molecular dynamics in the presence of either Na+ or Mg2+ ions. Computational prediction of the binding free energy reveals that the Mg2+ ions remain preferentially adsorbed at the surface, whereas Na+ ions form a weakly bound dissolved ionic layer. The charge shielding between surface and amino groups by the adsorbed Mg2+ ions leads to an upright orientation of the TPDA molecules as opposed to a more tilted orientation in the presence of Na+ ions. The resulting better accessibility of the TPDA molecules is very likely responsible for the enhanced virus retention capacity using a feed solution with Mg2+ ions.Wissenschaftlicher ArtikelBand:20Heft:16121 102