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- ItemFormation mechanism for stable hybrid clusters of proteins and nanoparticles(Washington D.C. : American Chemical Society, 2015) Moerz, Sebastian T.; Kraegeloh, Annette; Chanana, Munish; Kraus, TobiasCitrate-stabilized gold nanoparticles (AuNP) agglomerate in the presence of hemoglobin (Hb) at acidic pH. The extent of agglomeration strongly depends on the concentration ratio [Hb]/[AuNP]. Negligible agglomeration occurs at very low and very high [Hb]/[AuNP]. Full agglomeration and precipitation occur at [Hb]/[AuNP] corresponding to an Hb monolayer on the AuNP. Ratios above and below this value lead to the formation of an unexpected phase: stable, microscopic AuNP–Hb agglomerates. We investigated the kinetics of agglomeration with dynamic light scattering and the adsorption kinetics of Hb on planar gold with surface-acoustic wave-phase measurements. Comparing agglomeration and adsorption kinetics leads to an explanation of the complex behavior of this nanoparticle–protein mixture. Agglomeration is initiated either when Hb bridges AuNP or when the electrostatic repulsion between AuNP is neutralized by Hb. It is terminated when Hb has been depleted or when Hb forms multilayers on the agglomerates that stabilize microscopic clusters indefinitely.
- ItemSurviving the surf: The tribomechanical properties of the periostracum of Mytilus sp(Amsterdam : Elsevier, 2014) Wählisch, Felix C.; Peter, Nicolas J.; Torrents Abad, Oscar; Oliveira, Mariana V.G.; Schneider, Andreas S.; Schmahl, Wolfgang; Griesshaber, Erika; Bennewitz, RolandWe investigated the friction and wear behavior as well as the mechanical properties of the periostracum of Mytilus sp. Tribological properties were determined with a reciprocal sliding microtribometer, while mechanical characterization was performed using a nanoindenter. Measurements were performed in dry and wet conditions. On the dry periostracum we found a low friction coefficient of 0.078 ± 0.007 on the young parts and a higher one of 0.63 ± 0.02 on the old parts of the shell. Under wet, saline, conditions we only observed one average coefficient of friction of 0.37 ± 0.01. Microscopic ex situ analysis indicated that dry periostracum wore rather rapidly by plowing and fatigue, while it exhibited a high wear resistance when immersed in salt water. The Young’s modulus and hardness of the periostracum were also investigated in both dry and wet conditions. Under dry conditions the Young’s modulus of the periostracum was 8 ± 3 GPa, while under wet conditions it was 0.21 ± 0.05 GPa. The hardness of dry periostracum samples was 353 ± 127 MPa, whereas the hardness of wet samples was 5 ± 2 MPa. It was found that, in the wet state, viscous behavior plays a significant role in the mechanical response of the periostracum. Our results strongly indicate that the periostracum can provide an important contribution to the overall wear resistance of Mytilus sp. shell.
- ItemTime‐Dependent Cation Selectivity of Titanium Carbide MXene in Aqueous Solution(Weinheim : Wiley-VCH, 2022) Wang, Lei; Torkamanzadeh, Mohammad; Majed, Ahmad; Zhang, Yuan; Wang, Qingsong; Breitung, Ben; Feng, Guang; Naguib, Michael; Presser, VolkerElectrochemical ion separation is a promising technology to recover valuable ionic species from water. Pseudocapacitive materials, especially 2D materials, are up-and-coming electrodes for electrochemical ion separation. For implementation, it is essential to understand the interplay of the intrinsic preference of a specific ion (by charge/size), kinetic ion preference (by mobility), and crystal structure changes. Ti3C2Tz MXene is chosen here to investigate its selective behavior toward alkali and alkaline earth cations. Utilizing an online inductively coupled plasma system, it is found that Ti3C2Tz shows a time-dependent selectivity feature. In the early stage of charging (up to about 50 min), K+ is preferred, while ultimately Ca2+ and Mg2+ uptake dominate; this unique phenomenon is related to dehydration energy barriers and the ion exchange effect between divalent and monovalent cations. Given the wide variety of MXenes, this work opens the door to a new avenue where selective ion-separation with MXene can be further engineered and optimized.
- ItemOptical Spectrometry to Determine Nutrient Concentrations and other Physicochemical Parameters in Liquid Organic Manures: A Review(Basel : MDPI, 2022) Horf, Michael; Vogel, Sebastian; Drücker, Harm; Gebbers, Robin; Olfs, Hans-WernerNutrient concentrations in livestock manures and biogas digestates show a huge variability due to disparities in animal husbandry systems concerning animal species, feed composition, etc. Therefore, a nutrient estimation based on recommendation tables is not reliable when the exact chemical composition is needed. The alternative, to analyse representative fertilizer samples in a standard laboratory, is too time-and cost-intensive to be an accepted routine method for farmers. However, precise knowledge about the actual nutrient concentrations in liquid organic fertilizers is a prerequisite to ensure optimal nutrient supply for growing crops and on the other hand to avoid environmental problems caused by overfertilization. Therefore, spectrometric methods receive increasing attention as fast and low-cost alternatives. This review summarizes the present state of research based on optical spectrometry used at laboratory and field scale for predicting several parameters of liquid organic manures. It emphasizes three categories: (1) physicochemical parameters, e.g., dry matter, pH, and electrical conductivity; (2) main plant nutrients, i.e., total nitrogen, ammonium nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur; and (3) micronutrients, i.e., manganese, iron, copper, and zinc. Furthermore, the commonly used sample preparation techniques, spectrometer types, measuring modes, and chemometric methods are presented. The primarily promising scientific results of the last 30 years contributed to the fact that near-infrared spectrometry (NIRS) was established in commercial laboratories as an alternative method to wet chemical standard methods. Furthermore, companies developed technical setups using NIRS for on-line applications of liquid organic manures. Thus, NIRS seems to have evolved to a competitive measurement procedure, although parts of this technique still need to be improved to ensure sufficient accuracy, especially in quality management.
- ItemModulating Myeloid Immune Cell Migration Using Multivalently Presented Monosaccharide Ligands for Advanced Immunotherapy(Weinheim : Wiley-VCH Verlag, 2019) Taverno, I.; Rodrigo, A.M.; Kandziora, M.; Kuntz, S.; Dernedde, J.; Trautwein, C.; Tacke, F.; Blas-Garcia, A.; Bartneck, M.Due to their importance for the outcome of the inflammatory response, the motile myeloid cells are a focus of novel treatment options. The interplay of selectins and their ligands with leukocytes and endothelial cells, which mediate endothelial attachment and transmigration of immune cells, can be modulated by selectin‐binding structures. Here, a library of selectin‐targeting ligands coupled to either gold, silver, iron oxide nanospheres, or quantum dots of 5–10 nm in size is used to systematically study their impact on immune cell motility. The multivalent presentation of the carbohydrate mimetics results in very low sub‐nanomolar binding to L ‐selectin. Using human primary monocytes, granulocytes, lymphocytes, and macrophages, it is shown that the ligands exhibit only minor effects on uptake, whereas the motility of leukocytes is critically affected as observed in migration assays evaluated by flow cytometry. The carbohydrate mimetic ring structure, sulfation, in particular, and the degree of ligand presentation, are constituents which cohere in this process. Specific carbohydrate ligands can thus selectively regulate leukocyte subsets. These data form the basis for advanced immunotherapy which inhibits the amplification of inflammation by restricting leukocyte influx to injured tissue sites. Furthermore, the targeting ligands may complement existing treatment options for inflammatory diseases.
- ItemMechanically Stable, Binder‐Free, and Free‐Standing Vanadium Trioxide/Carbon Hybrid Fiber Electrodes for Lithium‐Ion Batteries(Weinheim : Wiley-VCH, 2023) Bornamehr, Behnoosh; Gallei, Markus; Husmann, Samantha; Presser, VolkerBinder is a crucial component in present-day battery electrodes but commonly contains fluorine and requires coating processing using organic (often toxic) solvents. Preparing binder-free electrodes is an attractive strategy to make battery electrode production and its end-of-use waste greener and safer. Herein, electrospinning is employed to prepare binder-free and self-standing electrodes. Such electrodes often suffer from low flexibility, and the correlation between performance and flexibility is usually overlooked. Processing parameters affect the mechanical properties of the electrodes, and for the first time it is reported that mechanical flexibility directly influences the electrochemical performance of the electrode. The importance is highlighted when processing parameters advantageous to powder materials, such as a higher heat treatment temperature, harm self-standing electrodes due to deterioration of fiber flexibility. Other strategies, such as conductive carbon addition, can be employed to improve the cell performance, but their effect on the mechanical properties of the electrodes must be considered. Rapid heat treatment achieves self-standing V2O3 with a capacity of 250 mAh g−1 at 250 mA g−1 and 390 mAh g−1 at 10 mA g−1
- ItemLeben und Werk des Karl Hahn(Berlin : Logos Verlag, 2017) Mensing, PetraVon 1905 bis zu seinem Lebensende 1946 stellte der Musiklehrer und Botaniker Karl Hahn eine umfangreiche Sammlung der Mecklenburger Flora insbesondere der Moose in der Umgebung von Neukloster und Grabow zusammen. Neben den noch vorhandenen Belegen hat er diverse Veröffentlichungen im Archiv der Freunde der Naturgeschichte in Mecklenburg hinterlassen, die neben der Beschreibung der einzelnen Funde auch Wanderbeschreibungen und Naturbeobachtungen thematisierten. In diesem Beitrag werden alle von ihm als „Neu für Mecklenburg“ bezeichneten Moosarten erstmals in einer Veröffentlichung zusammengetragen sowie Anregungen für zukünftige Arbeiten gegeben.
- ItemA hyperbranched dopamine-containing PEG-based polymer for the inhibition of α-synuclein fibrillation(Orlando, Fla. : Academic Press, 2015) Breydo, Leonid; Newland, Ben; Zhang, Hong; Rosser, Anne; Werner, Carsten; Uversky, Vladimir N.; Wang, WenxinAggregation of α-synuclein is believed to play an important role in Parkinson's disease and in other neurodegenerative maladies. Small molecule inhibitors of this process are among the most promising drug candidates for neurodegenerative diseases. Dendrimers have also been studied for anti-fibrillation applications but they can be difficult and expensive to synthetize. Here we show that RAFT polymerization can be used to produce a hyperbranched polyethylene glycol structure via a one-pot reaction. This polymer included a dopamine moiety, a known inhibitor of α-synuclein fibril formation. Dopamine within the polymer structure was capable of aggregation inhibition, although not to the same degree as free dopamine. This result opens up new avenues for the use of controlled radical polymerizations as a means of preparing hyperbranched polymers for anti-fibrillation activity, but shows that the incorporation of functional groups from known small molecules within polymers may alter their biological activity.
- ItemReal-time monitoring of calcium carbonate and cationic peptide deposition on carboxylate-SAM using a microfluidic SAW biosensor(Frankfurt am Main : Beilstein-Institut, 2014) Pohl, Anna; Weiss, Ingrid M.A microfluidic biosensor with surface acoustic wave technology was used in this study to monitor the interaction of calcium carbonate with standard carboxylate self-assembled monolayer sensor chips. Different fluids, with and without biomolecular components, were investigated. The pH-dependent surface interactions of two bio-inspired cationic peptides, AS8 and ES9, which are similar to an extracellular domain of the chitin synthase involved in mollusc shell formation, were also investigated in a biological buffer system. A range of experimental conditions are described that are suitable to study non-covalent molecular interactions in the presence of ionic substances, such as, mineral precursors below the solubility equilibrium. The peptide ES9, equal to the mollusc chitin synthase epitope, is less sensitive to changes in pH than its counterpart AS8 with a penta-lysine core, which lacks the flanking acidic residues. This study demonstrates the extraordinary potential of microfluidic surface acoustic wave biosensors to significantly expand our experimental capabilities for studying the principles underlying biomineralization in vitro.
- Item4D Biofabrication of fibrous artificial nerve graft for neuron regeneration(Bristol : IOP Publ., 2020) Apsite, Indra; Constante, Gissela; Dulle, Martin; Vogt, Lena; Caspari, Anja; Boccaccini, Aldo R.; Synytska, Alla; Salehi, Sahar; Ionov, LeonidIn this paper, we describe the application of the 4D biofabrication approach for the fabrication of artificial nerve graft. Bilayer scaffolds consisting of uniaxially aligned polycaprolactone-poly(glycerol sebacate) (PCL-PGS) and randomly aligned methacrylated hyaluronic acid (HA-MA) fibers were fabricated using electrospinning and further used for the culture of PC-12 neuron cells. Tubular structures form instantly after immersion of fibrous bilayer in an aqueous buffer and the diameter of obtained tubes can be controlled by changing bilayer parameters such as the thickness of each layer, overall bilayer thickness, and medium counterion concentration. Designed scaffolds showed a self-folded scroll-like structure with high stability after four weeks of real-time degradation. The significance of this research is in the fabrication of tuneable tubular nerve guide conduits that can simplify the current existing clinical treatment of neural injuries. © 2020 The Author(s). Published by IOP Publishing Ltd.