@misc{RauschBrockmeyerSchwerdtle2021, author = {Rausch, Ann-Kristin and Brockmeyer, Robert and Schwerdtle, Tanja}, title = {Development, validation, and application of a multi-method for the determination of mycotoxins, plant growth regulators, tropane alkaloids, and pesticides in cereals by two-dimensional liquid chromatography tandem mass spectrometry}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {143}, issn = {1866-8372}, doi = {10.25932/publishup-51479}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-514795}, pages = {16}, year = {2021}, abstract = {Mycotoxins and pesticides regularly co-occur in agricultural products worldwide. Thus, humans can be exposed to both toxic contaminants and pesticides simultaneously, and multi-methods assessing the occurrence of various food contaminants and residues in a single method are necessary. A two-dimensional high performance liquid chromatography tandem mass spectrometry method for the analysis of 40 (modified) mycotoxins, two plant growth regulators, two tropane alkaloids, and 334 pesticides in cereals was developed. After an acetonitrile/water/formic acid (79:20:1, v/v/v) multi-analyte extraction procedure, extracts were injected into the two-dimensional setup, and an online clean-up was performed. The method was validated according to Commission Decision (EC) no. 657/2002 and document N° SANTE/12682/2019. Good linearity (R2 > 0.96), recovery data between 70-120\%, repeatability and reproducibility values < 20\%, and expanded measurement uncertainties < 50\% were obtained for a wide range of analytes, including very polar substances like deoxynivalenol-3-glucoside and methamidophos. However, results for fumonisins, zearalenone-14,16-disulfate, acid-labile pesticides, and carbamates were unsatisfying. Limits of quantification meeting maximum (residue) limits were achieved for most analytes. Matrix effects varied highly (-85 to +1574\%) and were mainly observed for analytes eluting in the first dimension and early-eluting analytes in the second dimension. The application of the method demonstrated the co-occurrence of different types of cereals with 28 toxins and pesticides. Overall, 86\% of the samples showed positive findings with at least one mycotoxin, plant growth regulator, or pesticide.}, language = {en} } @misc{RethfeldtBrinkmannRiebeetal.2021, author = {Rethfeldt, Nina and Brinkmann, Pia and Riebe, Daniel and Beitz, Toralf and K{\"o}llner, Nicole and Altenberger, Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Detection of Rare Earth Elements in Minerals and Soils by Laser-Induced Breakdown Spectroscopy (LIBS) Using Interval PLS}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1866-8372}, doi = {10.25932/publishup-55746}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-557469}, pages = {1 -- 17}, year = {2021}, abstract = {The numerous applications of rare earth elements (REE) has lead to a growing global demand and to the search for new REE deposits. One promising technique for exploration of these deposits is laser-induced breakdown spectroscopy (LIBS). Among a number of advantages of the technique is the possibility to perform on-site measurements without sample preparation. Since the exploration of a deposit is based on the analysis of various geological compartments of the surrounding area, REE-bearing rock and soil samples were analyzed in this work. The field samples are from three European REE deposits in Sweden and Norway. The focus is on the REE cerium, lanthanum, neodymium and yttrium. Two different approaches of data analysis were used for the evaluation. The first approach is univariate regression (UVR). While this approach was successful for the analysis of synthetic REE samples, the quantitative analysis of field samples from different sites was influenced by matrix effects. Principal component analysis (PCA) can be used to determine the origin of the samples from the three deposits. The second approach is based on multivariate regression methods, in particular interval PLS (iPLS) regression. In comparison to UVR, this method is better suited for the determination of REE contents in heterogeneous field samples. View Full-Text}, language = {en} } @misc{RajuKoetz2021, author = {Raju, Rajarshi Roy and Koetz, Joachim}, title = {Inner Rotation of Pickering Janus Emulsions}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1249}, issn = {1866-8372}, doi = {10.25932/publishup-55362}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-553628}, pages = {6}, year = {2021}, abstract = {Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core-shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles.}, language = {en} } @phdthesis{MathieuGaedke2021, author = {Mathieu-Gaedke, Maria}, title = {Grafting-to and grafting-from proteins - synthesis and characterization of protein-polymer conjugates on the way to biohybrid membrane materials}, doi = {10.25932/publishup-54292}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-542921}, school = {Universit{\"a}t Potsdam}, pages = {XVIII, 149}, year = {2021}, abstract = {The incorporation of proteins in artificial materials such as membranes offers great opportunities to avail oneself the miscellaneous qualities of proteins and enzymes perfected by nature over millions of years. One possibility to leverage proteins is the modification with artificial polymers. To obtain such protein-polymer conjugates, either a polymer can be grown from the protein surface (grafting-from) or a pre-synthesized polymer attached to the protein (grafting-to). Both techniques were used to synthesize conjugates of different proteins with thermo-responsive polymers in this thesis. First, conjugates were analyzed by protein NMR spectroscopy. Typical characterization techniques for conjugates can verify the successful conjugation and give hints on the secondary structure of the protein. However, the 3-dimensional structure, being highly important for the protein function, cannot be probed by standard techniques. NMR spectroscopy is a unique method allowing to follow even small alterations in the protein structure. A mutant of the carbohydrate binding module 3b (CBM3bN126W) was used as model protein and functionalized with poly(N-isopropylacrylamide). Analysis of conjugates prepared by grafting-to or grafting-from revealed a strong impact of conjugation type on protein folding. Whereas conjugates prepared by grafting a pre-formed polymer to the protein resulted in complete preservation of protein folding, grafting the polymer from the protein surface led to (partial) disruption of the protein structure. Next, conjugates of bovine serum albumin (BSA) as cheap and easily accessible protein were synthesized with PNIPAm and different oligoethylene glycol (meth)acrylates. The obtained protein-polymer conjugates were analyzed by an in-line combination of size exclusion chromatography and multi-angle laser light scattering (SEC-MALS). This technique is particular advantageous to determine molar masses, as no external calibration of the system is needed. Different SEC column materials and operation conditions were tested to evaluate the applicability of this system to determine absolute molar masses and hydrodynamic properties of heterogeneous conjugates prepared by grafting-from and grafting-to. Hydrophobic and non-covalent interactions of conjugates lead to error-prone values not in accordance to expected molar masses based on conversions and extents of modifications. As alternative to this method, conjugates were analyzed by sedimentation velocity analytical ultracentrifugation (SV-AUC) to gain insights in the hydrodynamic properties and how they change after conjugation. Within a centrifugal field, a sample moves and fractionates according to the mass, density, and shape of its individual components. Conjugates of BSA with PNIPAm were analyzed below and above the cloud point temperature of the thermo-responsive polymer component. It was identified that the polymer characteristics were transferred to the conjugate molecule which than showed a decreased ideality - defined as increased deviation from a perfect sphere model - below and increased ideality above the cloud point temperature. This effect can be attributed to an arrangement of the polymer chain pointing towards the solvent (expanded state) or snuggling around the protein surface depending on the applied temperature. The last project dealt with the synthesis of ferric hydroxamate uptake protein component A (FhuA)-polymer conjugates as building blocks for novel membrane materials. The shape of FhuA can be described as barrel and removal of a cork domain inside the protein results in a passive channel aimed to be utilized as pores in the membrane system. The polymer matrix surrounding the membrane protein is composed of a thermo-responsive and a UV-crosslinkable part. Therefore, an external trigger for covalent immobilization of these building blocks in the membrane and switchability of the membrane between different states was incorporated. The overall performance of membranes prepared by a drying-mediated self-assembly approach was evaluated by permeability and size exclusion experiments. The obtained membranes displayed an insufficiency in interchain crosslinking and therefore a lack in performance. Furthermore, the aimed switch between a hydrophilic and hydrophobic state of the polymer matrix did not occur. Correspondingly, size exclusion experiments did not result in a retention of analytes larger than the pores defined by the dimension of the used FhuA variant. Overall, different paths to generate protein-polymer conjugates by either grafting-from or grafting-to the protein surface were presented paving the way to the generation of new hybrid materials. Different analytical methods were utilized to describe the folding and hydrodynamic properties of conjugates providing a deeper insight in the overall characteristics of these seminal building blocks.}, language = {en} } @phdthesis{Saretia2021, author = {Saretia, Shivam}, title = {Modulating ultrathin films of semi-crystalline oligomers by Langmuir technique}, doi = {10.25932/publishup-54210}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-542108}, school = {Universit{\"a}t Potsdam}, pages = {XIII, 109}, year = {2021}, abstract = {Polymeric films and coatings derived from semi-crystalline oligomers are of relevance for medical and pharmaceutical applications. In this context, the material surface is of particular importance, as it mediates the interaction with the biological system. Two dimensional (2D) systems and ultrathin films are used to model this interface. However, conventional techniques for their preparation, such as spin coating or dip coating, have disadvantages, since the morphology and chain packing of the generated films can only be controlled to a limited extent and adsorption on the substrate used affects the behavior of the films. Detaching and transferring the films prepared by such techniques requires additional sacrificial or supporting layers, and free-standing or self supporting domains are usually of very limited lateral extension. The aim of this thesis is to study and modulate crystallization, melting, degradation and chemical reactions in ultrathin films of oligo(ε-caprolactone)s (OCL)s with different end-groups under ambient conditions. Here, oligomeric ultrathin films are assembled at the air-water interface using the Langmuir technique. The water surface allows lateral movement and aggregation of the oligomers, which, unlike solid substrates, enables dynamic physical and chemical interaction of the molecules. Parameters like surface pressure (π), temperature and mean molecular area (MMA) allow controlled assembly and manipulation of oligomer molecules when using the Langmuir technique. The π-MMA isotherms, Brewster angle microscopy (BAM), and interfacial infrared spectroscopy assist in detecting morphological and physicochemical changes in the film. Ultrathin films can be easily transferred to the solid silicon surface via Langmuir Schaefer (LS) method (horizontal substrate dipping). Here, the films transferred on silicon are investigated using atomic force microscopy (AFM) and optical microscopy and are compared to the films on the water surface. The semi-crystalline morphology (lamellar thicknesses, crystal number densities, and lateral crystal dimensions) is tuned by the chemical structure of the OCL end-groups (hydroxy or methacrylate) and by the crystallization temperature (Tc; 12 or 21 °C) or MMAs. Compression to lower MMA of ~2 {\AA}2, results in the formation of a highly crystalline film, which consists of tightly packed single crystals. Preparation of tightly packed single crystals on a cm2 scale is not possible by conventional techniques. Upon transfer to a solid surface, these films retain their crystalline morphology whereas amorphous films undergo dewetting. The melting temperature (Tm) of OCL single crystals at the water and the solid surface is found proportional to the inverse crystal thickness and is generally lower than the Tm of bulk PCL. The impact of OCL end-groups on melting behavior is most noticeable at the air-solid interface, where the methacrylate end-capped OCL (OCDME) melted at lower temperatures than the hydroxy end-capped OCL (OCDOL). When comparing the underlying substrate, melting/recrystallization of OCL ultrathin films is possible at lower temperatures at the air water interface than at the air-solid interface, where recrystallization is not visible. Recrystallization at the air-water interface usually occurs at a higher temperature than the initial Tc. Controlled degradation is crucial for the predictable performance of degradable polymeric biomaterials. Degradation of ultrathin films is carried out under acidic (pH ~ 1) or enzymatic catalysis (lipase from Pseudomonas cepcia) on the water surface or on a silicon surface as transferred films. A high crystallinity strongly reduces the hydrolytic but not the enzymatic degradation rate. As an influence of end-groups, the methacrylate end-capped linear oligomer, OCDME (~85 ± 2 \% end-group functionalization) hydrolytically degrades faster than the hydroxy end capped linear oligomer, OCDOL (~95 ± 3 \% end-group functionalization) at different temperatures. Differences in the acceleration of hydrolytic degradation of semi-crystalline films were observed upon complete melting, partial melting of the crystals, or by heating to temperatures close to Tm. Therefore, films of densely packed single crystals are suitable as barrier layers with thermally switchable degradation rates. Chemical modification in ultrathin films is an intricate process applicable to connect functionalized molecules, impart stability or create stimuli-sensitive cross-links. The reaction of end-groups is explored for transferred single crystals on a solid surface or amorphous monolayer at the air-water interface. Bulky methacrylate end-groups are expelled to the crystal surface during chain-folded crystallization. The density of end-groups is inversely proportional to molecular weight and hence very pronounced for oligomers. The methacrylate end-groups at the crystal surface, which are present at high concentration, can be used for further chemical functionalization. This is demonstrated by fluorescence microscopy after reaction with fluorescein dimethacrylate. The thermoswitching behavior (melting and recrystallization) of fluorescein functionalized single crystals shows the temperature-dependent distribution of the chemically linked fluorescein moieties, which are accumulated on the surfaces of crystals, and homogeneously dispersed when the crystals are molten. In amorphous monolayers at the air-water interface, reversible cross-linking of hydroxy-terminated oligo(ε-caprolactone) monolayers using dialdehyde (glyoxal) lead to the formation of 2D networks. Pronounced contraction in the area occurred for 2D OCL films in dependence of surface pressure and time indicating the reaction progress. Cross linking inhibited crystallization and retarded enzymatic degradation of the OCL film. Altering the subphase pH to ~2 led to cleavage of the covalent acetal cross-links. Besides as model systems, these reversibly cross-linked films are applicable for drug delivery systems or cell substrates modulating adhesion at biointerfaces.}, language = {en} } @phdthesis{Schutjajew2021, author = {Schutjajew, Konstantin}, title = {Electrochemical sodium storage in non-graphitizing carbons - insights into mechanisms and synthetic approaches towards high-energy density materials}, doi = {10.25932/publishup-54189}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-541894}, school = {Universit{\"a}t Potsdam}, pages = {v, 148}, year = {2021}, abstract = {To achieve a sustainable energy economy, it is necessary to turn back on the combustion of fossil fuels as a means of energy production and switch to renewable sources. However, their temporal availability does not match societal consumption needs, meaning that renewably generated energy must be stored in its main generation times and allocated during peak consumption periods. Electrochemical energy storage (EES) in general is well suited due to its infrastructural independence and scalability. The lithium ion battery (LIB) takes a special place, among EES systems due to its energy density and efficiency, but the scarcity and uneven geological occurrence of minerals and ores vital for many cell components, and hence the high and fluctuating costs will decelerate its further distribution. The sodium ion battery (SIB) is a promising successor to LIB technology, as the fundamental setup and cell chemistry is similar in the two systems. Yet, the most widespread negative electrode material in LIBs, graphite, cannot be used in SIBs, as it cannot store sufficient amounts of sodium at reasonable potentials. Hence, another carbon allotrope, non-graphitizing or hard carbon (HC) is used in SIBs. This material consists of turbostratically disordered, curved graphene layers, forming regions of graphitic stacking and zones of deviating layers, so-called internal or closed pores. The structural features of HC have a substantial impact of the charge-potential curve exhibited by the carbon when it is used as the negative electrode in an SIB. At defects and edges an adsorption-like mechanism of sodium storage is prevalent, causing a sloping voltage curve, ill-suited for the practical application in SIBs, whereas a constant voltage plateau of relatively high capacities is found immediately after the sloping region, which recent research attributed to the deposition of quasimetallic sodium into the closed pores of HC. Literature on the general mechanism of sodium storage in HCs and especially the role of the closed pore is abundant, but the influence of the pore geometry and chemical nature of the HC on the low-potential sodium deposition is yet in an early stage. Therefore, the scope of this thesis is to investigate these relationships using suitable synthetic and characterization methods. Materials of precisely known morphology, porosity, and chemical structure are prepared in clear distinction to commonly obtained ones and their impact on the sodium storage characteristics is observed. Electrochemical impedance spectroscopy in combination with distribution of relaxation times analysis is further established as a technique to study the sodium storage process, in addition to classical direct current techniques, and an equivalent circuit model is proposed to qualitatively describe the HC sodiation mechanism, based on the recorded data. The obtained knowledge is used to develop a method for the preparation of closed porous and non-porous materials from open porous ones, proving not only the necessity of closed pores for efficient sodium storage, but also providing a method for effective pore closure and hence the increase of the sodium storage capacity and efficiency of carbon materials. The insights obtained and methods developed within this work hence not only contribute to the better understanding of the sodium storage mechanism in carbon materials of SIBs, but can also serve as guidance for the design of efficient electrode materials.}, language = {en} } @phdthesis{Hechenbichler2021, author = {Hechenbichler, Michelle}, title = {New thermoresponsive amphiphilic block copolymers with unconventional chemical structure and architecture}, doi = {10.25932/publishup-54182}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-541822}, school = {Universit{\"a}t Potsdam}, pages = {XIX, 186}, year = {2021}, abstract = {Das Aggregationsverhalten von amphiphilen Blockcpoolymeren ist wichtig f{\"u}r zahlreiche Anwendungen, beispielsweise in der Waschmittelindustrie als Verdicker oder in der Pharmazie zur kontrollierten Freisetzung von Wirkstoffen. Wenn einer der Bl{\"o}cke thermoresponsiv ist, kann das Aggregationsverhalten zus{\"a}tzlich {\"u}ber die Temperatur gesteuert werden. W{\"a}hrend sich die bisherigen Untersuchungen solcher „intelligenten" Systeme zumeist auf einfache Diblockcopolymere beschr{\"a}nkt haben, wurde in der vorliegenden Arbeit die Komplexit{\"a}t der Polymere und damit die Vielseitigkeit dieser Systeme erh{\"o}ht. Dazu wurden spezifische Monomere, verschiedene Blockl{\"a}ngen, unterschiedliche Architekturen und zus{\"a}tzliche funktionelle Gruppen eingef{\"u}hrt. Durch systematische {\"A}nderungen wurde das Struktur-Wirkungsverhalten solcher thermoresponsiver amphiphiler Blockcopolymere untersucht. Dabei sind die Blockcopolymere typischerweise aus einem permanent hydrophoben „Sticker", einem permanent hydrophilen Block sowie einem thermoresponsiven Block, der ein Lower Critical Solution Temperature (LCST) Verhalten zeigt, aufgebaut. W{\"a}hrend der permanent hydrophile Block aus N,N Dimethylacrylamid (DMAm) bestand, wurden f{\"u}r den thermoresponsiven Block unterschiedliche Monomere, n{\"a}mlich N n Propylacrylamid (NPAm), N iso Propylacrylamid (NiPAm), N,N Diethylacrylamid (DEAm), N,N Bis(2 methoxyethyl)acrylamid (bMOEAm), oder N Acryloylpyrrolidin (NAP) mit entsprechend unterschiedlichen LCSTs von 25, 32, 33, 42 und 56 °C verwendet. Die Blockcopolymere wurden mittels aufeinanderfolgender reversibler Additions-Fragmentierungs-Ketten{\"u}bertragungspolymerisation (RAFT Polymerisation) hergestellt, um Polymere mit linearer, doppelt hydrophober sowie symmetrischer Quasi Miktoarm Architektur zu erhalten. Dabei wurden wohldefinierte Blockgr{\"o}ßen, Endgruppen und enge Molmassenverteilungen (Ɖ ≤ 1.3) erzielt. F{\"u}r komplexere Architekturen, wie die doppelt thermoresponsive und die nicht symmetrische Quasi Miktoarm Architekturen, wurde RAFT mit Atomtransfer-Radikalpolymerisation (ATRP) oder Single Unit Monomer Insertion (SUMI), kombiniert. Die dabei erhaltenen Blockcopolymere hatten ebenfalls wohldefinierte Blockl{\"a}ngen, allerdings war die Molmassenverteilung generell breiter (Ɖ ≤ 1.8) und Endgruppen gingen zum Teil verloren, da komplexere Syntheseschritte n{\"o}tig waren. Das thermoresponsive Verhalten in w{\"a}ssriger L{\"o}sung wurde mittels Tr{\"u}bungspunktmessung und Dynamischer Lichtstreuung (DLS) untersucht. Unterhalb der Phasen{\"u}berganstemperatur waren die Polymere l{\"o}slich in Wasser und mizellare Strukturen waren in der DLS sichtbar. Oberhalb der Phasen{\"u}bergangstemperatur war das Aggregationsverhalten dann stark abh{\"a}ngig von der Architektur und der chemischen Struktur des thermoresponsiven Blocks. Thermoresponsive Bl{\"o}cke aus PNAP und PbMOEAm mit einer Blockl{\"a}nge von DPn = 40 zeigten keinen Tr{\"u}bungspunkt (CP) bis hin zu 80 °C, da durch den angebrachten hydrophilen PDMAm Block die bereits hohe LCST der entsprechenden Homopolymere bei den Blockcopolymeren weiter erh{\"o}ht wurde. Blockcopolymere mit PNiPAm, PDEAm und PNPAm hinggeen zeigten abh{\"a}ngig von der Architektur und Blockgr{\"o}ße unterschiedliche CP's. Oberhalb der CP's waren gr{\"o}ßere Aggregate vor allem f{\"u}r die Blockcopolymere mit PNiPAm und PDEAm sichtbar, wohingegen der Phasen{\"u}bergang f{\"u}r Blockcopolymere mit PNPAm stark abh{\"a}ngig von der jeweiligen Architektur war und entsprechend kleinere oder gr{\"o}ßere Aggregate zeigte. Um das Aggregationsverhalten besser zu verstehen, wurden Fluoreszenzstudien an PDMAm und PNiPAm Homo und Blockcopolymeren mit linearer Architektur durchgef{\"u}hrt, welche mit komplement{\"a}ren Fluoreszenzfarbstoffen an den entgegengesetzten Kettenenden funktionalisiert wurden. Das thermoresponsive Verhalten wurde dabei sowohl in Wasser als auch in {\"O}l-in-Wasser Mikroemulsion untersucht. Die Ergebnisse zeigten, dass das Blockcopolymer sich, {\"a}hnlich wie die anderen hergestellten Architekturen, bei niedrigen Temperaturen wie ein Polymertensid verh{\"a}lt. Dabei bilden die hydrophoben Stickergruppen den Kern und die hydrophilen Arme die Corona der Mizelle. Oberhalb des Phasen{\"u}bergangs des PNiPAm Blocks verhielten sich die Blockcopolymere allerdings wie assoziative Telechele mit zwei nicht symmetrischen hydrophoben Endgruppen, die sich untereinander nicht mischten. Daher bildeten die Blockcopolymere anstatt aggregierter „Blumen"-Mizellen gr{\"o}ßere, dynamische Aggregate. Diese sind einerseits {\"u}ber die urspr{\"u}nglichen Mizellkerne bestehend aus den hydrophoben Sticker als auch {\"u}ber Cluster der kollabierten thermoresponsiven Bl{\"o}cke miteinander verkn{\"u}pft. In Mikroemulsion ist diese Art der Netzwerkbildung noch st{\"a}rker ausgepr{\"a}gt.}, language = {en} } @phdthesis{Lood2021, author = {Lood, Kajsa}, title = {Stereoselective Construction of C-C Double Bonds via Olefin Metathesis: From Tethered Reactions to Water-Soluble Catalysts for Stereoretentive Metathesis}, doi = {10.25932/publishup-53914}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-539142}, school = {Universit{\"a}t Potsdam}, pages = {95}, year = {2021}, abstract = {Natural products have proved to be a major resource in the discovery and development of many pharmaceuticals that are in use today. There is a wide variety of biologically active natural products that contain conjugated polyenes or benzofuran structures. Therefore, new synthetic methods for the construction of such building blocks are of great interest to synthetic chemists. The recently developed one-pot tethered ring-closing metathesis approach allows for the formation of Z,E-dienoates in high stereoselectivity. The extension of this method with a Julia-Kocienski olefination protocol would allow for the formation of conjugated trienes in a stereoselective manner. This strategy was applied in the total synthesis of conjugated triene containing (+)-bretonin B. Additionally, investigations of cross metathesis using methyl substituted olefins were pursued. This methodology was applied, as a one-pot cross metathesis/ring-closing metathesis sequence, in the total synthesis of benzofuran containing 7-methoxywutaifuranal. Finally, the design and synthesis of a catalyst for stereoretentive metathesis in aqueous media was investigated.}, language = {en} } @phdthesis{Sand2021, author = {Sand, Patrick}, title = {{\"U}bergangsmetallkatalysierte Funktionalisierungsreaktionen an Vinylsulfonylverbindungen}, doi = {10.25932/publishup-53687}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-536879}, school = {Universit{\"a}t Potsdam}, pages = {ix, 169}, year = {2021}, abstract = {Innerhalb dieser Arbeit erfolgte die erstmalige systematische Untersuchung von Vinylsulfons{\"a}ureethylester (1a), Phenylvinylsulfon (1b), N-Benzyl-N-methylethensulfonamid (1c) in der FUJIWARA-MORITANI Reaktion (alternativ als DHR bezeichnet). Bei dieser {\"u}bergangsmetallkatalysierten Reaktion erfolgt der Aufbau einer neuen C-C-Bindung unter der doppelten Aktivierung einer C-H-Bindung. Somit kann ein atom{\"o}konomischer Aufbau von Molek{\"u}len realisiert werden, da keine Beiprodukte in Form von Salzen entstehen. Als aromatischer Reaktant wurden Acetanilide (2) verwendet, damit eine regiospezifische Kupplung durch die katalysatordirigierende Acetamid-Gruppe (CDG) erfolgt. F{\"u}r die Pd-katalysierte DHR wurde eine umfangreiche Optimierung durchgef{\"u}hrt und anschließend konnten neun verschieden, substituierte 2 mit 1a und sieben verschieden, substituierte 2 mit 1b funktionalisiert werden. Da eine Reaktion mit 1c ausblieb, erfolgte ein Wechsel auf eine Ru-katalysierte Methode f{\"u}r die DHR. Mit dieser Methode konnte 1c mit Acetaniliden funktionalisiert werden und das Spektrum der verwendeten 2, in Form von deaktivierenden Substituenten erweitert werden. Im Anschluss wurden die sulfalkenylierten Acetanilide in weiterf{\"u}hrenden Reaktionen untersucht. Hierf{\"u}r wurde eine Reaktionssequenz bestehend aus einer DeacetylierungDiazotierung-Kupplungsreaktion verwendet, um die Acetamid-Gruppe in eine Abgangsgruppe zu {\"u}berf{\"u}hren und danach in einer MATSUDA-HECK Reaktion zu kuppeln. Mit dieser Methode konnten mehrere 1,2-Dialkenylbenzole erhalten werden und die CDG ein weiteres Mal genutzt werden. Neben der {\"U}berf{\"u}hrung der CDG in eine Abgangsgruppe konnte diese auch in die Synthese verschiedener Heterozyklen integriert werden. Daf{\"u}r erfolgte zun{\"a}chst eine 1,3-Zykloaddition durch deprotonierten Tosylmethylisocanid an der elektronenarmen Sulfalkenylgruppe zur Synthese von Pyrrolen. Anschließend erfolgte eine Kupplung der PyrrolFunktion und der CDG durch Zyklokondensation, wodurch Quinoline dargestellt wurden. Durch diese Synthesen konnten Schwefelanaloga des Naturstoffes Marinoquionolin A erhalten werden. Ein weitere {\"u}bergangsmetallkatalysierte C-H-Aktivierungsreaktion, die MATSUDA-HECK Reaktion, wurde genutzt, um 1b zu mit verschieden, subtituierten Diazoniumsalzen zu arylieren. Hier konnten zahlreichen Styrenylsulfone erhalten werden. Der erfolgreiche Einsatz der Vinylsulfonylverbindungen in der Kreuzmetathese konnte innerhalb dieser Arbeit nicht erreicht werden. Daher erfolgte die Synthese verschiedener dialkenylierter Sulfonamide. Hierf{\"u}r wurde die Kettenl{\"a}nge der Alkenyl-Gruppe am Schwefel zwischen 2-3 und am Stickstoff zwischen 3-4 variiert. Der Einsatz der dialkenylierten Sulfonamide erfolgte in den zuvor untersuchten C-H-Aktivierungsmethoden. N-Allyl-N-phenylethensulfonamid (3) konnte erfolgreich in der DHR und HECK Reaktion funktionalisiert werden. Hierbei erfolgte eine methodenspezifische Kupplung in Abh{\"a}ngigkeit von der Elektronendichte der entsprechenden Alkenyl-Gruppe. Die DHR f{\"u}hrte zur selektiven Arylierung der Vinyl-Gruppe und die HECK Reaktion zur Arylierung an der Allyl-Gruppe. Gemischte Produkte wurden nicht erhalten. F{\"u}r die weiteren Diolefine wurde komplexe Produktgemische erhalten. Des Weiteren wurden die Diolefine in der Ringschlussmetathese untersucht und die entsprechenden Sultame in sehr guten Ausbeuten erhalten. Die Verwendung der Sultame in der C-H-Aktivierung war erfolglos. Es wird vermutet, dass f{\"u}r diese zweifachsubstituierten Sulfonamide die vorhandenen Reaktionsbedingungen optimiert werden m{\"u}ssen. Abschließend wurden verschiedene, enantiomerenreine Olefine ausgehend von Levoglucosenon dargestellt. Hierf{\"u}r wurde Levoglucosenon zun{\"a}chst mit einem Allyl- und 3-Butenylgrignard Reagenz umgesetzt. Die entsprechenden Produkte wurden in moderaten Ausbeuten erhalten. Eine weitere Methode begann mit der Reduktion von Levoglucosenon zum Levoglucosenol. Dieser Alkohol wurde mit Allylbromid erfolgreich verethert. Neben der Untersuchungen zur Ethersynthese, erfolgte die Veresterung von Levoglucosenol mit verschiedenen Sulfonylchloriden zu den entsprechenden Sulfons{\"a}ureestern. Diese Olefine wurden in einer Dominometathesereaktion untersucht. Ausgehend vom Allyllevoglucosenylether erfolgte die Darstellung eines Dihydrofurans.}, language = {de} } @phdthesis{Kossmann2021, author = {Kossmann, Janina}, title = {Controlled condensation to functional materials - synergetic effect of nitrogen content and pore structure}, doi = {10.25932/publishup-53693}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-536935}, school = {Universit{\"a}t Potsdam}, pages = {vi, 148}, year = {2021}, abstract = {The development and optimization of carbonaceous materials is of great interest for several applications including gas sorption, electrochemical storage and conversion, or heterogeneous catalysis. In this thesis, the exploration and optimization of nitrogen containing carbonaceous materials by direct condensation of smart chosen, molecular precursors will be presented. As suggested with the concept of noble carbons, the choice of a stable, nitrogen-containing precursor will lead to an even more stable, nitrogen doped carbonaceous material with a controlled structure and electronic properties. Molecules fulfilling this requirement are for example nucleobases. The direct condensation of nucleobases leads to highly nitrogen containing carbonaceous materials without any further post or pretreatment. By using salt melt templating, pore structure adjustment is possible without the use of hazardous or toxic reagents and the template can be reused. Using these simple tools, the synergetic effect of the pore structure and nitrogen content of the materials can be explored. Within this thesis, the influence of the condensation parameters will be correlated to the structure and performance of the materials. First, the influence of the condensation temperature to the porosity and nitrogen content of guanine will be discussed and the exploration of highly CO2 selective structural pores in C1N1 materials will be shown. Further tuning the pore structure of the materials by salt melt templating will be then explored, the potential of the prepared materials as heterogeneous catalysts and their basic catalytic strength will be correlated to their nitrogen content and pore morphology. A similar approach is used to explore the water sorption behavior of uric acid derived carbonaceous materials as potential sorbents for heat transformation applications. Changes in maximum water uptake and hydrophilicity of the prepared materials will be correlated to the nitrogen content and pore architecture. Due to the high thermal stability, porosity, and nitrogen content of ionic liquid derived nitrogen doped carbonaceous materials, a simple impregnation and calcination route can be conducted to obtain copper nano cluster decorated nitrogen-doped carbonaceous materials. The activity as catalyst for the oxygen reduction reaction of the obtained materials will be shown and structure performance relations are discussed. In conclusion, the versatility of nitrogen doped carbonaceous materials with a nitrogen to carbon ratio of up to one will be shown. The possibility to tune the pore structure as well as the nitrogen content by using a simple procedure including salt melt templating as well as the use of molecular precursors and their effect on the performance will be discussed.}, language = {en} } @phdthesis{Haubitz2021, author = {Haubitz, Toni}, title = {Transient absorption spectroscopy}, doi = {10.25932/publishup-53509}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-535092}, school = {Universit{\"a}t Potsdam}, pages = {xiii, 176}, year = {2021}, abstract = {The optical properties of chromophores, especially organic dyes and optically active inorganic molecules, are determined by their chemical structures, surrounding media, and excited state behaviors. The classical optical go-to techniques for spectroscopic investigations are absorption and luminescence spectroscopy. While both techniques are powerful and easy to apply spectroscopic methods, the limited time resolution of luminescence spectroscopy and its reliance on luminescent properties can make its application, in certain cases, complex, or even impossible. This can be the case when the investigated molecules do not luminesce anymore due to quenching effects, or when they were never luminescent in the first place. In those cases, transient absorption spectroscopy is an excellent and much more sophisticated technique to investigate such systems. This pump-probe laser-spectroscopic method is excellent for mechanistic investigations of luminescence quenching phenomena and photoreactions. This is due to its extremely high time resolution in the femto- and picosecond ranges, where many intermediate or transient species of a reaction can be identified and their kinetic evolution can be observed. Furthermore, it does not rely on the samples being luminescent, due to the active sample probing after excitation. In this work it is shown, that with transient absorption spectroscopy it was possible to identify the luminescence quenching mechanisms and thus luminescence quantum yield losses of the organic dye classes O4-DBD, S4-DBD, and pyridylanthracenes. Hence, the population of their triplet states could be identified as the competitive mechanism to their luminescence. While the good luminophores O4-DBD showed minor losses, the S4-DBD dye luminescence was almost entirely quenched by this process. However, for pyridylanthracenes, this phenomenon is present in both the protonated and unprotonated forms and moderately effects the luminescence quantum yield. Also, the majority of the quenching losses in the protonated forms are caused by additional non-radiative processes introduced by the protonation of the pyridyl rings. Furthermore, transient absorption spectroscopy can be applied to investigate the quenching mechanisms of uranyl(VI) luminescence by chloride and bromide. The reduction of the halides by excited uranyl(VI) leads to the formation of dihalide radicals X^(·-2). This excited state redox process is thus identified as the quenching mechanism for both halides, and this process, being diffusion-limited, can be suppressed by cryogenically freezing the samples or by observing these interactions in media with a lower dielectric constant, such as ACN and acetone.}, language = {en} } @phdthesis{Kluge2021, author = {Kluge, Steven}, title = {Integration anorganischer F{\"u}llstoffe in Polysulfonmembranen und Auswirkungen auf die Gastransporteigenschaften}, doi = {10.25932/publishup-53270}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-532700}, school = {Universit{\"a}t Potsdam}, pages = {110}, year = {2021}, abstract = {In der vorliegenden Arbeit wird die Herstellung und Charakterisierung von Mixed-Matrix-Membranen (MMM) f{\"u}r die Gastrennung thematisiert. Dazu wurden verschiedene F{\"u}llstoffe genutzt, um in Verbindung mit dem Membranmaterial Polysulfon MMMs herzustellen. Als F{\"u}llstoffe wurden 3 aktive und 2 passive F{\"u}llstoffe verwendet. Die aktiven F{\"u}llstoffe besaßen Poren{\"o}ffnungen, die in der Lage sind Gase in Abh{\"a}ngigkeit der Molek{\"u}lgr{\"o}ße zu trennen. Daraus folgt ein h{\"o}herer idealer Trennfaktor f{\"u}r bestimmte Gaspaare als in Polysulfon selbst. Aufgrund der durch die Poren gebildeten permanenten Kan{\"a}le in den aktiven F{\"u}llstoffen ergibt sich ein schnellerer Gastransport (Permeabilit{\"a}t) als in Polysulfon. Es handelte sich bei den aktiven F{\"u}llstoffen um den Zeolith SAPO-34 und 2 Chargen eines Zeolitic Imidazolate Framework (ZIF) ZIF-8. Die beiden Chargen ZIF-8 unterschieden sich in ihrer spezifischen Oberfl{\"a}che, was diesen Einfluss speziell in die Untersuchungen zum Gastransport einbeziehen sollte. Bei den passiven F{\"u}llstoffen handelte es sich um ein aminofunktionalisiertes Kieselgel und unpor{\"o}se (dichte) Glask{\"u}gelchen. Das Kieselgel besaß Poren, die zu groß waren, um Gase effektiv zu trennen. Die Glask{\"u}gelchen konnten keine Gastrennung erm{\"o}glichen, da sie keine Poren besaßen. Aus der Literatur ist bekannt, dass die Einbettung von F{\"u}llstoffen oft zu Defekten in MMMs f{\"u}hrt. Ein Ziel dieser Arbeit war es daher die Einbettung zu optimieren. Weiterhin sollte der Gastransport in MMMs dieser Arbeit mit dem in einer unbeladenen Polysulfonmembran verglichen werden. Aufgrund des selektiveren Trennverhaltens der aktiven F{\"u}llstoffe im Vergleich zum Membranmaterial, sollte mit der Einbettung aktiver F{\"u}llstoffe die Trennleistung der MMMs mit steigender F{\"u}llstoffbeladung immer weiter verbessert werden. Um die Eigenschaften der MMMs zu untersuchen, wurden diese mittels Rasterelektronenmikroskop (REM), Gaspermeationsmessungen (GP) und Thermogravimetrischer Analyse gekoppelt mit Massenspektrometrie (TGA-MS) charakterisiert. Untersuchungen am REM konnten eine Verbesserung der Einbettung zeigen, wenn ein polymerer Haftvermittler verwendet wurde. Verglichen wurde die optimierte Einbettung mit der Einbettung ohne Haftvermittler und Ergebnissen aus der Literatur, in der die Verwendung verschiedener Silane als Haftvermittler beschrieben wurde. Trotz der verbesserten Einbettung konnte lediglich bei geringen Beladungen an F{\"u}llstoff (10 und 20 Ma-\% bezogen auf das Membranmaterial) eine geringe Steigerung des idealen Trennfaktors in den MMMs gegen{\"u}ber der unbeladenen Polysulfonmembranen beobachtet werden. Bei h{\"o}heren F{\"u}llstoffbeladungen (30, 40 und 50 Ma-\%) war ein deutlicher Anstieg der Permeabilit{\"a}t bei stark sinkendem idealen Trennfaktor zu beobachten. Mit Hilfe von TGA-MS Messungen konnte dar{\"u}ber hinaus festgestellt werden, dass der verwendete Zeolith SAPO-34 durch Wassermolek{\"u}le blockierte Poren{\"o}ffnungen besaß. Das verhinderte den Gastransport im F{\"u}llstoff, wodurch die Trennleistung des F{\"u}llstoffes nicht ausgenutzt werden konnte. Die F{\"u}llstoffe ZIF-8 (chargenunabh{\"a}ngig) und aminofunktionalisiertes Kieselgel wiesen keine blockierten Poren auf. Dennoch zeigte sich in diesen MMMs keine Verbesserung der Gastrenn- oder Gastransporteigenschaften. MMMs mit dichten Glask{\"u}gelchen als F{\"u}llstoff zeigten dasselbe Gastrenn- und Gastransportverhalten, wie alle MMMs mit den zuvor genannten F{\"u}llstoffen. In dieser Arbeit konnte, trotz optimierter Einbettung anorganischer F{\"u}llstoffe, f{\"u}r MMMs keine Verbesserung der Gastrenn- oder Gastransporteigenschaften nachgewiesen werden. Vielmehr wurde ein Einfluss der F{\"u}llstoffmenge auf die Gastransporteigenschaften in MMMs festgestellt. Die {\"A}nderungen der MMMs gegen{\"u}ber Polysulfon stammen von den Folgen der Einbettung von F{\"u}llstoffen in das Matrixpolymer. Durch die Einbettung werden die Eigenschaften des Matrixpolymers {\"a}ndern, sodass auch der Gastransport beeinflusst wird. Des Weiteren wurde dokumentiert, dass in Abh{\"a}ngigkeit der F{\"u}llstoffbeladung die entstehende Membranstruktur beeinflusst wird. Die Beeinflussung war dabei unabh{\"a}ngig von der F{\"u}llstoffart. Es wurde eine Korrelation zwischen F{\"u}llstoffmenge und ver{\"a}nderter Membranstruktur gefunden.}, language = {de} } @phdthesis{ChandrakanthShetty2021, author = {Chandrakanth Shetty, Sunidhi}, title = {Directed chemical communication in artificial eukaryotic cells}, doi = {10.25932/publishup-53364}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-533642}, school = {Universit{\"a}t Potsdam}, year = {2021}, abstract = {Eukaryotic cells can be regarded as complex microreactors capable of performing various biochemical reactions in parallel which are necessary to sustain life. An essential prerequisite for these complex metabolic reactions to occur is the evolution of lipid membrane-bound organelles enabling compartmental- ization of reactions and biomolecules. This allows for a spatiotemporal control over the metabolic reactions within the cellular system. Intracellular organi- zation arising due to compartmentalization is a key feature of all living cells and has inspired synthetic biologists to engineer such systems with bottom-up approaches. Artificial cells provide an ideal platform to isolate and study specific re- actions without the interference from the complex network of biomolecules present in biological cells. To mimic the hierarchical architecture of eukaryotic cells, multi-compartment assemblies with nested liposomal structures also re- ferred to as multi-vesicular vesicles (MVVs) have been widely adopted. Most of the previously reported multi-compartment systems adopt bulk method- ologies which suffer from low yield and poor control over size. Microfluidic strategies help circumvent these issues and facilitate a high-throughput and robust technique to assemble MVVs of uniform size distribution. In this thesis, firstly, the bulk methodologies are explored to build MVVs and implement a synthetic signalling cascade. Next, a polydimethylsiloxane (PDMS)-based microfluidic platform is introduced to build MVVs and the significance of PEGylated lipids for the successful encapsulation of inner com- partments to generate stable multi-compartment systems is highlighted. Next, a novel two-inlet channel PDMS-based microfluidic device to create MVVs encompassing a three-step enzymatic reaction cascade is presented. A directed reaction pathway comprising of the enzymes α-glucosidase (α-Glc), glucose oxidase (GOx), and horseradish peroxidase (HRP) spanning across three compartments via reconstitution of size-selective membrane proteins is described. Furthermore, owing to the monodispersity of our MVVs due to microfluidic strategies, this platform is employed to study the effect of com- partmentalization on reaction kinetics. Further integration of cell-free expression module into the MVVs would allow for gene-mediated signal transduction within artificial eukaryotic cells. Therefore, the chemically inducible cell-free expression of a membrane protein alpha-hemolysin and its further reconstitution into liposomes is carried out. In conclusion, the present thesis aims to build artificial eukaryotic cells to achieve size-selective chemical communication that also show potential for applications as micro reactors and as vehicles for drug delivery.}, language = {en} } @phdthesis{Bagdahn2021, author = {Bagdahn, Christian}, title = {Synthese und Charakterisierung von Polymerionogelen basierend auf ionischen Fl{\"u}ssigkeiten und Polymethylmethacrylat}, doi = {10.25932/publishup-53287}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-532874}, school = {Universit{\"a}t Potsdam}, pages = {152}, year = {2021}, abstract = {Zentrales Element dieser Arbeit ist die Synthese und Charakterisierung praktisch nutzbarer Ionogele. Die Basis der Polymerionogele bildet das Modellpolymer Polymethylmethacrylat. Als Additive kommen ionische Fl{\"u}ssigkeiten zum Einsatz, deren Grundlage Derivate des vielfach verwendeten Imidazoliumkations sind. Die Eigenschaften der eingebetteten ionischen Fl{\"u}ssigkeiten sind f{\"u}r die Ionogele funktionsgebend. Die Funktionalit{\"a}t der jeweiligen Gele und damit der Transfer der Eigenschaften von ionischen Fl{\"u}ssigkeiten auf die Ionogele wurde in der vorliegenden Arbeit mittels zahlreicher Charakterisierungstechniken {\"u}berpr{\"u}ft und best{\"a}tigt. In dieser Arbeit wurden durch Ionogelbildung makroskopische Ionogelobjekte in Form von Folien und Vliesen erzeugt. Dabei kamen das Filmgießen und das Elektrospinnen als Methoden zur Erzeugung dieser Folien und Vliese zum Einsatz, woraus jeweils ein Modellsystem resultiert. Dadurch wird die vorliegende Arbeit in die Themenkomplexe „elektrisch halbleitende Ionogelfolien" und „antimikrobiell aktive Ionogelvliese" gegliedert. Der Einsatz von triiodidhaltigen ionischen Fl{\"u}ssigkeiten und einer Polymermatrix in einem diskontinuierlichen Gießprozess resultiert in elektrisch halbleitenden Ionogelfolien. Die flexiblen und transparenten Folien k{\"o}nnen Mittelpunkt zahlreicher neuer Anwendungsfelder im Bereich flexibler Elektronik sein. Das Elektrospinnen von Polymethylmethacrylat mit einer ionischen Fl{\"u}ssigkeit f{\"u}hrte zu einem homogen Ionogelvlies, welches ein Modell f{\"u}r die {\"U}bertragung antimikrobiell aktiver Eigenschaften ionischer Fl{\"u}ssigkeiten auf por{\"o}se Strukturen zur Filtration darstellt. Gleichzeitig ist es das erste Beispiel f{\"u}r ein kupferchloridhaltiges Ionogel. Ionogele sind attraktive Materialien mit zahlreichen Anwendungsm{\"o}glichkeiten. Mit der vorliegenden Arbeit wird das Spektrum der Ionogele um ein elektrisch halbleitendes und ein antimikrobiell aktives Ionogel erweitert. Gleichzeitig wurden durch diese Arbeit der Gruppe der ionischen Fl{\"u}ssigkeiten drei Beispiele f{\"u}r elektrisch halbleitende ionische Fl{\"u}ssigkeiten sowie zahlreiche kupfer(II)chloridbasierte ionische Fl{\"u}ssigkeiten hinzugef{\"u}gt.}, language = {de} } @phdthesis{Altabal2021, author = {Altabal, Osamah}, title = {Design and fabrication of geometry-assisted on-demand dosing systems}, doi = {10.25932/publishup-53244}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-532441}, school = {Universit{\"a}t Potsdam}, pages = {xxiv, 122}, year = {2021}, abstract = {The controlled dosage of substances from a device to its environment, such as a tissue or an organ in medical applications or a reactor, room, machinery or ecosystem in technical, should ideally match the requirements of the applications, e.g. in terms of the time point at which the cargo is released. On-demand dosage systems may enable such a desired release pattern, if the device contain suitable features that can translate external signals into a release function. This study is motivated by the opportunities arising from microsystems capable of an on-demand release and the contributions that geometrical design may have in realizing such features. The goals of this work included the design, fabrication, characterization and experimental proof-of-concept of geometry-assisted triggerable dosing effect (a) with a sequential dosing release and (b) in a self-sufficient dosage system. Structure-function relationships were addressed on the molecular, morphological and, with a particular attention, the device design level, which is on the micrometer scale. Models and/or computational tools were used to screen the parameter space and provide guidance for experiments.}, language = {en} } @phdthesis{Kirchhofer2021, author = {Kirchhofer, Tabea}, title = {The development of multi - compartmentalised systems for the directed organisation of artificial cells}, doi = {10.25932/publishup-52842}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-528428}, school = {Universit{\"a}t Potsdam}, pages = {II, 126}, year = {2021}, abstract = {Membrane contact sites are of particular interest in the field of synthetic biology and biophysics. They are involved in a great variety of cellular functions. They form in between two cellular organelles or an organelle and the plasma membrane in order to establish a communication path for molecule transport or signal transmission. The development of an artificial membrane system which can mimic membrane contact sites using bottom up synthetic biology was the goal of this research study. For this, a multi - compartmentalised giant unilamellar vesicle (GUV) system was created with the membrane of the outer vesicle mimicking the plasma membrane and the inner GUVs posing as cellular organelles. In the following steps, three different strategies were used to achieve an internal membrane - membrane adhesion.}, language = {en} } @phdthesis{Dambowsky2021, author = {Dambowsky, Ina}, title = {Bioinspirierte Komposite - Strukturbildung durch Verkleben von Nano- oder Mesokristallen mit funktionalisierten Poly(2-oxazolin)en}, doi = {10.25932/publishup-52367}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-523671}, school = {Universit{\"a}t Potsdam}, pages = {XII, 220}, year = {2021}, abstract = {Die herausragenden mechanischen Eigenschaften nat{\"u}rlicher anorganisch-organischer Kompositmaterialien wie Knochen oder Muschelschalen entspringen ihrer hierarchischen Struktur, die von der nano- bis hinauf zur makroskopischen Ebene reicht, und einer kontrollierten Verbindung entlang der Grenzfl{\"a}chen der anorganischen und organischen Komponenten. Ausgehend von diesen Schl{\"u}sselprinzipien des biologischen Materialdesigns wurden in dieser Arbeit zwei Konzepte f{\"u}r die bioinspirierte Strukturbildung von Kompositen untersucht, die auf dem Verkleben von Nano- oder Mesokristallen mit funktionalisierten Poly(2-oxazolin)-Blockcopolymeren beruhen sowie deren Potenzial zur Herstellung bioinspirierter selbstorganisierter hierarchischer anorganisch-organischer Verbundstrukturen ohne {\"a}ußere Kr{\"a}fte beleuchtet. Die Konzepte unterschieden sich in den verwendeten anorganischen Partikeln und in der Art der Strukturbildung. {\"U}ber einen modularen Ansatz aus Polymersynthese und polymeranaloger Thiol-En-Funktionalisierung wurde erfolgreich eine Bibliothek von Poly(2-oxazolin)en mit unterschiedlichen Funktionalit{\"a}ten erstellt. Die Blockcopolymere bestehen aus einem kurzen partikelaffinen "Klebeblock", der aus Thiol-En-funktionalisiertem Poly(2-(3-butenyl)-2-oxazolin) besteht, und einem langen wasserl{\"o}slichen, strukturbildenden Block, der aus thermoresponsivem und kristallisierbarem Poly(2-isopropyl-2-oxazolin) besteht und hierarchische Morphologien ausbildet. Verschiedene analytische Untersuchungen wie Turbidimetrie, DLS, DSC, SEM oder XRD machten das thermoresponsive bzw. das Kristallisationsverhalten der Blockcopolymere in Abh{\"a}ngigkeit vom eingef{\"u}hrten Klebeblock zug{\"a}nglich. Es zeigte sich, dass diese Polymere ein komplexes temperatur- und pH-abh{\"a}ngiges Tr{\"u}bungsverhalten aufweisen. Hinsichtlich der Kristallisation {\"a}nderte der Klebeblock nicht die nanoskopische Kristallstruktur; er beeinflusste jedoch die Kristallisationszeit, den Kristallisationsgrad und die hierarchische Morphologie. Dieses Ergebnis wurde auf das unterschiedliche Aggregationsverhalten der Polymere in Wasser zur{\"u}ckgef{\"u}hrt. F{\"u}r die Herstellung von Kompositen nutzte Konzept 1 mikrometergroße Kupferoxalat-Mesokristalle, die eine innere Nanostruktur aufweisen. Die Strukturbildung {\"u}ber den anorganischen Teil wurde durch das Verkleben und Anordnen dieser Partikel erstrebt. Konzept 1 erm{\"o}glichte homogene freistehende stabile Kompositfilme mit einem hohen anorganischen Anteil. Die Partikel-Polymer-Kombination vereinte jedoch ung{\"u}nstige Eigenschaften in sich, d. h. ihre L{\"a}ngenskalen waren zu unterschiedlich, was die Selbstassemblierung der Partikel verhinderte. Aufgrund des geringen Aspektverh{\"a}ltnisses von Kupferoxalat blieb auch die gegenseitige Ausrichtung durch {\"a}ußere Kr{\"a}fte erfolglos. Im Ergebnis eignet sich das Kupferoxalat-Poly(2-oxazolin)-Modellsystem nicht f{\"u}r die Herstellung hierarchischer Kompositstrukturen. Im Gegensatz dazu verwendet Konzept 2 scheibenf{\"o}rmige Laponit®-Nanopartikel und kristallisierbare Blockcopolymere zur Strukturbildung {\"u}ber die organische Komponente durch polymervermittelte Selbstassemblierung. Komplement{\"a}re Analysemethoden (Zeta-Potenzial, DLS, SEM, XRD, DSC, TEM) zeigten sowohl eine kontrollierte Wechselwirkung zwischen den Komponenten in w{\"a}ssriger Umgebung als auch eine kontrollierte Strukturbildung, die in selbstassemblierten Nanokompositen resultiert, deren Struktur sich {\"u}ber mehrere L{\"a}ngenskalen erstreckt. Es wurde gezeigt, dass die negativ geladenen Klebebl{\"o}cke spezifisch und selektiv an den positiv geladenen R{\"a}ndern der Laponit®-Partikel binden und so Polymer-Laponit®-Nanohybridpartikel entstehen, die als Grundbausteine f{\"u}r die Kompositbildung dienen. Die Hybridpartikel sind bei Raumtemperatur elektrosterisch stabilisiert - sterisch durch ihre langen, mit Wasser wechselwirkenden Poly(2-isopropyl-2-oxazolin)-Bl{\"o}cke und elektrostatisch {\"u}ber die negativ geladenen Laponit®-Fl{\"a}chen. Im Ergebnis ließ sich Konzept 2 und damit die Strukturbildung {\"u}ber die organische Komponente erfolgreich umsetzten. Das Laponit®-Poly(2-oxazolin)-Modellsystem er{\"o}ffnete den Weg zu selbstassemblierten geschichteten quasi-hierarchischen Nanokompositstrukturen mit hohem anorganischen Anteil. Abh{\"a}ngig von der frei verf{\"u}gbaren Polymerkonzentration bei der Kompositbildung entstanden zwei unterschiedliche Komposit-Typen. Dar{\"u}ber hinaus entwarf die Arbeit einen Erkl{\"a}rungsansatz f{\"u}r den polymervermittelten Bildungsprozess der Komposit-Strukturen. Insgesamt legt diese Arbeit Struktur-Prozess-Eigenschafts-Beziehungen offen, um selbstassemblierte bioinspirierte Kompositstrukturen zu bilden und liefert neue Einsichten zu einer geeigneten Kombination an Komponenten und Herstellungsbedingungen, die eine kontrollierte selbstassemblierte Strukturbildung mithilfe funktionalisierter Poly(2-oxazolin)-Blockcopolymere erlauben.}, language = {de} } @misc{NicolaiWeishauptBaesleretal.2021, author = {Nicolai, Merle Marie and Weishaupt, Ann-Kathrin and Baesler, Jessica and Brinkmann, Vanessa and Wellenberg, Anna and Winkelbeiner, Nicola Lisa and Gremme, Anna and Aschner, Michael and Fritz, Gerhard and Schwerdtle, Tanja and Bornhorst, Julia}, title = {Effects of manganese on genomic integrity in the multicellular model organism Caenorhabditis elegans}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1173}, issn = {1866-8372}, doi = {10.25932/publishup-52327}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-523275}, pages = {18}, year = {2021}, abstract = {Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms.}, language = {en} } @misc{KopyraWierzbickaTulwinetal.2021, author = {Kopyra, Janina and Wierzbicka, Paulina and Tulwin, Adrian and Thiam, Guillaume and Bald, Ilko and Rabilloud, Franck and Abdoul-Carime, Hassan}, title = {Experimental and theoretical studies of dissociative electron attachment to metabolites oxaloacetic and citric acids}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1156}, issn = {1866-8372}, doi = {10.25932/publishup-52182}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-521829}, pages = {16}, year = {2021}, abstract = {In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3-9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment.}, language = {en} } @misc{BlockGuenterRodriguesetal.2021, author = {Block, Inga and G{\"u}nter, Christina and Rodrigues, Alysson Duarte and Paasch, Silvia and Hesemann, Peter and Taubert, Andreas}, title = {Carbon Adsorbents from Spent Coffee for Removal of Methylene Blue and Methyl Orange from Water}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {14}, issn = {1866-8372}, doi = {10.25932/publishup-52165}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-521653}, pages = {20}, year = {2021}, abstract = {Activated carbons (ACs) were prepared from dried spent coffee (SCD), a biological waste product, to produce adsorbents for methylene blue (MB) and methyl orange (MO) from aqueous solution. Pre-pyrolysis activation of SCD was achieved via treatment of the SCD with aqueous sodium hydroxide solutions at 90 °C. Pyrolysis of the pretreated SCD at 500 °C for 1 h produced powders with typical characteristics of AC suitable and effective for dye adsorption. As an alternative to the rather harsh base treatment, calcium carbonate powder, a very common and abundant resource, was also studied as an activator. Mixtures of SCD and CaCO3 (1:1 w/w) yielded effective ACs for MO and MB removal upon pyrolysis needing only small amounts of AC to clear the solutions. A selectivity of the adsorption process toward anionic (MO) or cationic (MB) dyes was not observed.}, language = {en} }