Köppen, Susan
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Köppen, Susan
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Köppen, Susan
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Köppen-Hannemann, Susan
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Item-typ:Veröffentlichung, Influence of Divalent Metal Ions on the Precipitation of the Plasma Protein Fibrinogen(American Chemical Society, 2021-10-20); ; ; ; Fibrinogen nanofibers are very attractive biomaterials to mimic the native blood clot architecture. Previously, we reported the self-assembly of fibrinogen nanofibers in the presence of monovalent salts and have now studied how divalent salts influence fibrinogen precipitation. Although the secondary fibrinogen structure was significantly altered with divalent metal ions, morphological analysis revealed exclusively smooth fibrinogen precipitates. In situ monitoring of the surface roughness facilitated predicting the tendency of various salts to form fibrinogen fibers or smooth films. Analysis of the chemical composition revealed that divalent salts were removed from smooth fibrinogen films upon rinsing while monovalent Na+ species were still present in fibrinogen fibers. Therefore, we assume that the decisive factor controlling the morphology of fibrinogen precipitates is direct ion–protein contact, which requires disruption of the ion-surrounding hydration shells. We conclude that in fibrinogen aggregates, this mechanism is effective only for monovalent ions, whereas divalent ions are limited to indirect fibrinogen adsorption.Wissenschaftlicher ArtikelBand:22Heft:1130 22 - 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 124 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, NO Degradation on the Anatase TiO2 (001) Surface in the Presence of Water(American Chemical Society, 2022-10-10); ; ; ; Nitric oxide (NO) is known to degrade to nitric acid (HNO3) on anatase TiO2 facets under visible light irradiation in the presence of water. However, the exact role that water plays in this photoreaction is not fully understood. By employing the density functional theory (DFT) and time-dependent density functional tight binding (TD-DFTB), we show the viability of two suggested degradation pathways involving water. Both reaction pathways are triggered by a charge transfer excitation from the NO molecule to the TiO2 surface. In one of them, NO interacts with dissociated water molecules adsorbed on the surface to form HONO+, whereas for the second pathway, NO is oxidized to NO2+ by capturing one oxygen atom from the substrate. Both HONO and NO2 are known byproducts in the photodegradation of NO, which further react with adsorbed water to finally produce HNO3. We also demonstrate by means of nudged elastic band calculations that these reactions are unlikely to happen without illumination.Wissenschaftlicher ArtikelBand:126Heft:4183 48 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Hofmeister-Driven Ion Pairing in Monovalent Salts Directs Fibrinogen Nanofiber Assembly during Drying(ACS Publications, 2025-09); ; ; Aniol, JonasFibrinogen nanofiber scaffolds hold promise for tissue engineering and wound healing due to their similarity to fibrin clots. We studied how alkaline salts (Na, K) influence fibrinogen precipitation during drying of highly saline dispersions. In situ roughness (Aq) monitoring revealed coprecipitation of salts and fibrinogen. SEM and Aq mapping showed morphologies from smooth (KCl) and faintly fibrous (NaCl) to highly rough and finely fibrous (Na-PO, K-PO). FTIR indicated that secondary structure changes are not always linked to fiber formation. XPS showed a stronger Na uptake, especially with fiber-forming salts. With Na and oxygen-containing polyvalent anions, kosmotropic SO induced fibers, while chaotropic oxalate yielded smooth films. Mg or K with SO did not form any fibers. Molecular dynamics simulations suggest ion-specific binding at the fibrinogen/water interface. We propose a two-dimensional Hofmeister series for tailoring fibrillogenesis via kosmotropic anion-cation pairs, concluding that fiber assembly is salt-driven and governed by cooperative kosmotropic effects.Wissenschaftlicher ArtikelBand:26Heft:1025 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Water Reactions on Reconstructed Rutile TiO2: A Density Functional Theory/Density Functional Tight Binding Approach(American Chemical Society, 2021-06-14); ; ; ; Far from being conclusively understood, the reactive interaction of water with rutile does still present a challenge to atomistic modeling techniques rooted in quantum mechanics. We show that static geometries of stoichiometric TiO2/water interfaces can be described well by density functional tight binding. However, this method needs further improvements to reproduce the low dissociation propensity of H2O after adsorption predicted by density functional theory (DFT). A reliable description of the surface reactivity of water is fundamental to investigate the nonstoichiometric reconstruction of the (001) facet rich in Ti interstitials. Calculations based on DFT predict the transition temperature for the onset of reconstruction in remarkable agreement with experiments and suggest that this surface, in contact with liquid water, can promote spontaneous H2O splitting and formation of H2 molecules.Wissenschaftlicher ArtikelBand:125Heft:2439 46