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Item type: Item , Development of on-surface metabolisation systems for food analysis(2025) Müller, IsabelThis thesis discusses the progress achieved concerning the potential of on-surface metabolism hyphenated with HPTLC, established as HPTLC-nanoGIT. The developed methods and their wide range of applications offer several advancements in food science and nutrition research. First, the previously published HPTLC-nanoGIT methodology was successfully validated for the quantification of starch digestibility by investigating various grain flours via saccharide release. It provides a novel approach to understand the digestibility of different flour types, as well as the differences between refined and whole grains. The possibility of quantifying each single saccharide provides a new detailed overview of amylolysis, which can help define dietary recommendations for obesity and diabetes management. Furthermore, the HPTLC-nanoGIT method was expanded to a 10D hyphenated technique to investigate the bioactive profiles of vegetable oils via on-surface lipolysis. The developed orthogonal HPTLC×HPTLC method allowed for a detailed metabolic profile. Additionally, the identification of genotoxic and antimicrobial effects of digested oils is helpful in the interpretation of food safety assessments. To further broaden the spectrum, the HPTLC-nanoGIT method was used to evaluate ATI-containing flour extracts and examine the potential as a novel inhibitory assay. This represents a major advancement over traditional spectrophotometric methods, particularly for matrix-rich samples. Finally, the feasibility of the HPTLC-nanoGIT method was investigated in detail and demonstrated enhanced sensitivity in contrast to spectrophotometric assays. However, some limitations were revealed when defining standardised protocols and determining kinetic parameters. Overall, the published results highlight the strong potential of the hyphenation of HPTLC and on-surface metabolisation for the detailed metabolic profiling of food components and their interpretation.Item type: Item , RNA Interference as a Vector Control Mechanism: Reducing Aedes albopictus Populations and Disrupting Arbovirus Transmission Cycles(2025) Omokungbe, BodunrinMosquitoes are considered the “most dangerous animals on Earth”. This is not because of the small amount of blood they take from us, but due to the pathogens they can transmit during this process. Key examples are malaria parasites, dengue virus, chikungunya virus, and Zika virus, causing over a million deaths annually. Urbanization, transport, and global trade have led to the spread of invasive species such as the Asian tiger mosquito (Aedes albopictus). Originally from Southeast Asia, this species has migrated to other parts of the world. This mosquito can transmit numerous arboviruses, filarial worms, and bacteria. Conventional control relies on chemical insecticides and biological agents, but off-target effects and resistances limit their usefulness. Therefore, targeted approaches like RNA interference (RNAi) are essential. RNAi is a naturally occurring post-transcriptional gene silencing mechanism in most eukaryotes. Silencing essential genes via RNAi can induce mortality, distort vital phenotypes, and impair the ability to transmit pathogens. This thesis evaluated RNAi as a species-specific control strategy against Ae. albopictus. Prior successes have demonstrated improving RNAi outcome in other mosquito species using transfection reagents (TRs), so I hypothesized that formulating dsRNA with TRs would enhance uptake and efficacy. However, no TRs are specifically designed for long dsRNA in aedine cell lines, and their undisclosed compositions makes selection difficult. Here, I established an RNAi workflow for aedine cell lines and screened multiple TRs for dsRNA delivery. Their complexing capacity and the cytotoxicity of their complexes were assessed. Most of them formed stable complexes, except HiPerFect, which failed even at a 1:9 (dsRNA:TR) ratio. The complexes were mostly non-cytotoxic, but Lipofectamine 2000 exhibited cytotoxic effects at concentrations above 1 ng/μL. Meanwhile, the five most effective TRs increased cellular uptake of long dsRNA and improved RNAi knockdown efficiency in Ae. albopictus U4.4 cells. Furthermore, candidate genes associated with high mortality in other insects were selected and two dsRNA constructs per gene were designed. Initial evaluation in U4.4 cells was conducted with both unformulated and TR-encapsulated dsRNA. Only one dsRNA against inhibitor of apoptosis (IAP) reduced U4.4 cell viability, yet all selected dsRNA showed significant knockdown of the candidate genes by RT-qPCR. Subsequently, I established RNAi workflow for the in vivo assessment in Ae. albopictus, but no dsRNA led to significant larval mortality. The knockdown of IAP gene was observed, but only in dissected gut tissue, and not in the whole body. The lack of larval mortality led to further investigations to identify possible barriers limiting RNAi efficacy. Particle sizing indicated optimal dsRNA:TR complex sizes, but only at lower concentrations. Fluorescence imaging confirmed oral uptake, but no spread of the dsRNA beyond the gut. Ex vivo assays showed rapid dsRNA degradation by larval gut extract, which were identified in Ae. albopictus for the first time and are expressed across larval stages, with the highest expression in gut tissues. The data indicated that the lack of larval mortality was likely due to suboptimal particle size (at higher concentrations), poor systemic spread, and rapid degradation of the selected dsRNA by nucleases. In addition, a standardized protocol was developed to analyze alphavirus replication in aedine cell lines. Viral inhibition was demonstrated with furin inhibitors using a SFV reporter tagged with mCherry as a model. This workflow thereby provides an in vitro platform for evaluating dsRNA against mosquito-borne viruses. Lastly, the feasibility of RNAi to reduce SFV replication in aedine cell line was assessed using the established protocol. For this, dsRNAs were designed and showed no cytotoxicity. Most of the synthesized dsRNAs inhibited virus spread when encapsulated. The dsRNA against non-structural protein 4 (nsp4) reduced viral replication by up to 80%. A concentration of 0.5 ng/μL of the encapsulated dsRNA was enough to significantly suppress the spread of the reporter virus signal. The antiviral effect of nsp4-dsRNA was validated by RT-qPCR, which confirmed a significant knockdown of the target gene. The central hypothesis that encapsulation of dsRNA increases efficacy was supported by most of the cell line experiments. However, the in vitro successes did not translate to in vivo lethality. Therefore, future work should develop optimized formulations to protect dsRNA and promote spread beyond the larval gut. More so, identifying gut-essential genes could enable larval mortality without systemic spread. While suppression of arboviral replication in an aedine cell line was demonstrated here, in vivo validation is still required. A potential RNAi bioinsecticide or arboviral transmission inhibitor must be potent, economical, and highly target-specific. Overall, this thesis presented the first comprehensive analysis of TRs for aedine cells, developed an RNAi workflow for evaluating dsRNA in Ae. albopictus, established a protocol to measure alphavirus infection in real time, and also showed that RNAi can reduce arboviral replication in mosquito cells.Item type: Item , Zahl der metastabilen Zustände bei einem Neuronalen Netzwerk mit Projektorkopplungen(1990) Kuhlmann, PeterDer Mittelwert der Zahl der metastabilen Zustände eines Neuronalen Netzwerkes mit Projektorkopplungen wird analytisch berechnet. Der Mittelwert wird dabei über zufällig verteilte Muster gebildet. Die Berechnung erfolgt mit Hilfe der Sattelpunktmethode.Item type: Item , Advances in Site-Selective Acylation of Pyranosides: From Oligopeptide Catalysis to Immobilized Catalysts in Flow(2025) Seitz, AlexanderIn the search for potential new applications for our group’s catalysts, we explored the idea of combining two catalytic motifs, that we have extensively studied before, in a multicatalytic reaction. The initial step involves performing a site-selective acetylation of partially protected pyranosides using a π-methyl-histidine (PMH)-containing oligopeptide catalyst. The resulting mono-alcohols could then be utilized in a selective, thiourea-catalyzed glycosylation reaction to generate 2-deoxy disaccharides. This thesis focuses on the first reaction of the proposed sequence. In the first part, we present the site-selective acylation of various methyl 4,6-O-protected pyranosides. We screened several tetrapeptide catalysts containing PMH and an adamantane moiety as the backbone. We identified catalysts capable of overcoming the intrinsic reactivity, which we determined using N-methylimidazole (NMI), for most of the pyranosides studied. To optimize the reaction conditions, we employed design of experiments (DOE) studies. We also investigated the impact of the 4,6-O-protecting group and the acylation reagent. Furthermore, we demonstrated that the selectivity of the reaction increased with the length of the applied peptide catalyst, suggesting that hydrogen-bonding interactions play a crucial role in selectivity. Finally, we showed that the observed reactivity could be maintained in more complex systems, as we successfully combined a benzylidene protection and the site-selective acetylation in a one-pot reaction. In the second part, we investigated the same pyranosides using peptide catalysts immobilized onto Wang-resin. We developed this approach to enhance the sustainability of our reaction, but also after initial studies concerning multicatalysis with thiourea and oligopeptide catalysts showed interference between the two, indicating that they must be separated locally. During the study, we demonstrated that we could easily synthesize the immobilized catalysts via solid-phase peptide synthesis (SPPS) and that they were still able to overcome the intrinsic reactivity of the substrates. We found that the catalysts could be reused for several reaction cycles with consistent results. Additionally, we showed that we could apply the catalyst in a continuous flow reaction without a significant loss in reactivity and selectivity. We used the long-term activity of the catalyst to convert large quantities of substrate and observed that the catalyst’s selectivity remained intact even after a temporary change in substrate.Item type: Item , Deciphering the role of EZH2 in the control of HIF2α signaling and its effects on cellular phenotypes in breast and lung cancer(2026) Kruijning, SalisaHypoxia is a hallmark of solid tumors and a critical driver of cancer progression, largely mediated by hypoxia-inducible factors (HIFs). While HIF1α has been extensively studied, the transcriptional regulation of HIF2α, encoded by the endothelial PAS domain protein 1 (EPAS1) gene, remains less well understood. Enhancer of zeste homolog 2 (EZH2), the catalytic subunit of polycomb repressive complex 2 (PRC2), is a known epigenetic regulator with canonical roles in gene repression via H3K27 tri-methylation and emerging non-canonical functions, including transcriptional activation. The interplay between EZH2 and HIF signaling, particularly regarding HIF2α, is largely unexplored. In this study, the role of EZH2 as a potential regulator of HIF2α in breast and lung cancer model systems was investigated. EZH2 knockdown decreased HIF2α protein under hypoxic conditions and EPAS1 mRNA levels under normoxic and hypoxic conditions in MDA-MB-231 and PC-9 cell lines. Restoration of EZH2 rescued EPAS1 expression. Mechanistic studies revealed that this regulation occurs independently of PRC2, EZH2’s methyltransferase activity, EZH1, Notch1 signaling, and transcriptional elongation. Chromatin immunoprecipitation demonstrated direct binding of EZH2 to a region approximately 1.7 kb downstream of the EPAS1 transcription start site, without enrichment of H3K27me3, supporting a non-canonical transcriptional activator function for EZH2. These findings indicate that EZH2 directly maintains EPAS1 transcription independent of chromatin repression and contributes to sustaining transcriptional activity within a globally repressive hypoxic environment. Functionally, EZH2 depletion impaired the expression of HIF2α target genes, including GLUT1 and PGK1, and reduced invasion capacity in MDA-MB-231 cells under hypoxia. In PC-9 cells, EZH2 knockdown decreased proliferation, which was partially rescued by transient HIF2α restoration, and anchorage-independent growth. These findings indicate that EZH2 promotes tumorigenicity at least in part through HIF2α. Clinical analyses revealed that high EZH2 and EPAS1 expression correlate with poor prognosis in breast cancer patients, underscoring the potential clinical relevance of this regulatory axis. Overall, this study establishes EZH2 as a novel non-canonical transcriptional activator of EPAS1, linking an epigenetic regulator to hypoxia signaling. These findings extend our understanding of EZH2 beyond its canonical repressive role and suggest that the EZH2-HIF2α regulatory axis may contribute to malignant phenotypes such as proliferation and invasion under hypoxic conditions. Future studies utilizing RNA-seq, in vivo models, and pharmacological inhibitors targeting EZH2 and HIF2α could provide further insight into the mechanistic and therapeutic potential of this regulatory pathway in cancer.