In this thesis, the researcher developed a nanosystem based on the metallophilic Interaction between cyclometalated complexes. Using this strategy, the researcher achieved efficient photodynamic... Show moreIn this thesis, the researcher developed a nanosystem based on the metallophilic Interaction between cyclometalated complexes. Using this strategy, the researcher achieved efficient photodynamic therapy to several cancers, accompanied by the cell imaging property. Show less
The research described in this thesis combines the latest insights in lysosomal function with lysosome centred cell signalling. Novel imaging and labelling techniques are applied to provide in... Show moreThe research described in this thesis combines the latest insights in lysosomal function with lysosome centred cell signalling. Novel imaging and labelling techniques are applied to provide in depth characterization of lysosome function in health and disease. An integrative approach was used to study the physiological role of the lysosome, characterizing the function of lysosomal hydrolases and signalling on a cellular level as well as within the context of tissue. Show less
Tin electrodeposition applications have rapidly evolved in the past 25 years. Usage of tin coatings has advanced from being mainly used for corrosion protection and decorative purposes, to being... Show moreTin electrodeposition applications have rapidly evolved in the past 25 years. Usage of tin coatings has advanced from being mainly used for corrosion protection and decorative purposes, to being used in modern technology such in electronic devices, photovoltaic cells and Li-ion batteries. The new tin coating applications have also come with challenges that require the production of nanostructured deposits, multilayers coatings and composites. Furthermore, the need to reduce energy and source consumptions, and the implementation of more environment-friendly processes, require detailed and fundamental knowledge of the electrodeposition process.The emphasis throughout this thesis is therefore to obtain detailed mechanistic information of tin electrodeposition process.The experimental and theoretical work presented in this thesis attempts to understand the mechanism of tin electrodeposition, and the effect of electrolyte anions and naphthalene-based additives, during the early and subsequent stages of the process. Show less
Curved single crystals provide variable, but well-defined surface structures. These curved surfaces have enormous potential for applications in surface chemistry, e.g. to unravel the role of... Show moreCurved single crystals provide variable, but well-defined surface structures. These curved surfaces have enormous potential for applications in surface chemistry, e.g. to unravel the role of specific sites in the reaction mechanism. Measurements can be repeated on the same crystal with incremental changes of the surface structure. Because effectsof sample heterogeneity are avoided, curved crystals make it possible to detect even subtle differences in surface reactivities and assign them to specific surface sites. They were used throughout this thesis to study the effects of surface structure onelemental chemical reaction steps, such as hydrogen dissociation and recombination, or water desorption. Show less
Molecular complexes can be used as electrocatalysts for oxygen reduction, water oxidation, and/or hydrogen peroxide production. However, in situ degradation of these catalyst is a major issue. This... Show moreMolecular complexes can be used as electrocatalysts for oxygen reduction, water oxidation, and/or hydrogen peroxide production. However, in situ degradation of these catalyst is a major issue. This dissertations describes the analysis of degradation processes as well as the performance of various molecular electrocatalysts. In addition, complexes have been structurally modified to perform structure-activity studies that could to mechanistic insight. In addition, it is described how molecular catalysts can be beneficial to heterogeneous electrocatalysis as well. Show less
A new type of tripodal squaramide-based supramolecular hydrogels is developed and studied. The mechanical properties of hydrogel with a wide stiffness range that can be easily modulated and also... Show moreA new type of tripodal squaramide-based supramolecular hydrogels is developed and studied. The mechanical properties of hydrogel with a wide stiffness range that can be easily modulated and also special and temporal controlled either by decorating with the activated group to offer additional chemical crosslinks or using hybrid hydrogel by incorporating the second network through light irradiation to overcome the weakness of traditional self-assembled supramolecular materials. Moreover, the designed synthetic hydrogel systems are biocompatible with several cell lines and have the potential to use as a 3D culture substrate. Show less
As a virtually inexhaustible source, solar energy plays a major role in future global energy scenarios. Solar-driven water splitting via dye-sensitized photoelectrochemical (DS-PEC) devices is a... Show moreAs a virtually inexhaustible source, solar energy plays a major role in future global energy scenarios. Solar-driven water splitting via dye-sensitized photoelectrochemical (DS-PEC) devices is a scalable, affordable and sustainable technology of great potential for direct conversion of solar energy into storable chemical fuels to produce clean, cost-efficient and environmentally friendly H2 or CO2-derived fuels and thus to contribute to the transformation of a sustainable society from the blueprint to reality. Proton-coupled electron transfer (PCET) plays a crucial role in a wide range of biological and chemical reactions concerning energy conversion processes, such as natural and artificial photosynthesis. Given that the overall catalytic water oxidation consists of four consecutive PCET steps, sequential or concerted, it is therefore of fundamental significance to unveil the intrinsic catalytic mechanism as well as the factors determining the PCET rate and thus to find strategies to facilitate the catalytic water oxidation. Computational tools provide a powerful and essential technique for the understanding and engineering of efficient DS-PEC devices for water splitting. This thesis provides an in-depth understanding of the catalytic mechanisms for the water oxidation half-reaction in catalyst-dye supramolecular complexes and rational strategies to facilitate the involved catalytic reactions. Show less
This thesis describes the use of bioorthogonal proteins in immunological settings. It provides an introduction towards the field of protein modification, which was used throughout the thesis for... Show moreThis thesis describes the use of bioorthogonal proteins in immunological settings. It provides an introduction towards the field of protein modification, which was used throughout the thesis for the expression of proteins containing unnatural amino acids. It challenges this protein expression and the subsequent purification. With this successfully challenged, the use of the protein was assessed in antigen activation studies. It was analyzed whether the unnatural amino acids were tolerated by the T cell receptor and the ligation handles of the unnatural amino acids were subsequently used for visualization purposes. Furthermore, this thesis describes the possible use of azido HRP as a new tool for immunohistology. Show less
Metal complexes and 2D materials like graphene were combined to produce structures that can function as sensors. Using spin crossover materials, both in bulk single crystal form and in thin layer... Show moreMetal complexes and 2D materials like graphene were combined to produce structures that can function as sensors. Using spin crossover materials, both in bulk single crystal form and in thin layer form, graphene-based electronic sensors were produced and characterized that can detect spin switches in the spin crossover materials. At the same time, the light-activatable ruthenium complexes were researched for their application in sensors that can monitor reactions that were triggered by light. We found that the photoreaction of a ruthenium complex with a nucleobase could be triggered in paper-based graphene devices. Moreover, we found that this ruthenium scaffold could also be used to increase the signal strength in a nanopore-based DNA detection system. Lastly, a ruthenium complex was designed that had a sensing function built in, as a dual-function molecule with a sensing and anticancer function. Overall, combining metal complexes with graphene was found to be a successful strategy to produce hybrid structures for sensing. Show less
Schistosomiasis is an acute and chronic disease caused by blood dwelling parasitic trematodes of the genus Schistosoma, and it is classified as the second most socioeconomically devastating... Show moreSchistosomiasis is an acute and chronic disease caused by blood dwelling parasitic trematodes of the genus Schistosoma, and it is classified as the second most socioeconomically devastating parasitic disease, second only to malaria. Currently the wormload is determined by the Kato-Katz method, which is not always reliable. In order to prepare diagnostic tools able to capture specific anti-carbohydrate antibodies or develop conjugate vaccines targeting these carbohydrate structures, sufficient amounts of well-defined fragments are needed. This thesis describes the synthesis of several glycans of these glycans present on the S. mansoni parasite, focusing mainly on the Circulating Anodic Antigen (CAA) and glycans bearing the unique α-(1-2)-L-Fucose-α-(1-2)-L-Fucose motifs. These glycans have been attached to gold nanoparticles and these particles were screened against several monoclonal antibodies and sera of individuals suffering from schistosomiasis. Show less
This thesis describes the use of a combined approach of computational and experimental techniques to gain novel insights to understand the glycosylation reaction and its reactive intermediates. The... Show moreThis thesis describes the use of a combined approach of computational and experimental techniques to gain novel insights to understand the glycosylation reaction and its reactive intermediates. The research in this thesis shows that glycosyl cations can act as reactive intermediates in glycosylation reactions for the introduction of glycosidic linkages. Furthermore, computational and experimental evidence has been provided showing that dioxolenium ions, formed by participation of remote acyl groups, are relevant reactive intermediates and can effectively steer the stereochemical course of glycosylation reactions. Ultimately, the techniques developed and insights gained in these studies were used in the synthesis of a complex mycobacterial glycolipid. The fundamental knowledge presented in this thesis can be further exploited in future synthetic endeavors, delivering more and more complex glycans to fuel glycobiological and glycomedical research. Show less
In this thesis an activity-based probe was discovered that could visualize the activity of PLAATs. With an optimized gel-based ABPP assay in hand, screening of a compound library led to the... Show moreIn this thesis an activity-based probe was discovered that could visualize the activity of PLAATs. With an optimized gel-based ABPP assay in hand, screening of a compound library led to the discovery of alpha-ketoamides as a hit for PLAAT3. Through extensive structural modifications of the hit, LEI110 was identified as the most potent inhibitor (Ki = 20nM) for PLAAT3. LEI110 reduced cellular arachidonic acid levels in PLAAT3 overexpressing U2OS cells and oleic acid-induced steatosis in human HepG2 cells. Gel-based ABPP and chemical proteomics showed that LEI110 is a selective pan-inhibitor of the Hrasls-family of thiol hydrolases (i.e. PLAAT2, PLAAT3 and PLAAT5). LEI110 could be an excellent starting point for the structure-based drug development of novel molecular therapies for obesity and/or common cold. In addition, a competitive, gel-based ABPP method for PLA2G4E using TAMRA-FP was successfully developed and applied to screen a focused library of lipase inhibitors. This resulted in the discovery of two clusters of inhibitors with different scaffolds. Optimization of the potency and selectivity of the inhibitors is required to the study of the biological role of PLA2G4E in an acute and dynamic setting with these novel tools. Together these novel chemical tools and methods will allow for a better understanding of the biosynthesis of the NAPEs and to study their biological role. Show less
Glycoconjugate vaccines are composed of microbial poly- or oligosaccharides covalently linked to a carrier protein. In the absence of structural information, long poly- or oligosaccharides... Show moreGlycoconjugate vaccines are composed of microbial poly- or oligosaccharides covalently linked to a carrier protein. In the absence of structural information, long poly- or oligosaccharides extracted from bacteria are employed to cover all relevant glyco epitopes and elicit an effective immune response. The comprehension of the structural basis for the immune recognition of carbohydrate antigens and the elucidation of minimal epitopes is key to understand their mechanism of action and support the rational design of modern glycoconjugate vaccines.Group B streptococcus (GBS) is a Gram-positive bacterium, cause of infections in pregnant women and newborns, whose capsular polysaccharide (CPS) is a major virulence factor.A small library of GBS glycans from serotypes Ia, Ib and III CPSs was synthesized. These oligosaccharides were used to model the conformational preferences of the corresponding CPS and to characterize the interactions to protective anti PS monoclonal antibodies. Conjugation to carrier proteins of the most promising fragments and evaluation in vivo of the obtained glycoconjugates showed that a hexasaccharide corresponding to the minimal structural epitope of GBS III was able to elicit anti PSIII functional IgGs. Overall, the findings described in this Thesis open the path to the design of GBS vaccines based on synthetic oligosaccharides. Show less
Lysosomal storage disorders (LSDs) are a group of orphan diseases characterized by lysosomal dysfunction or impaired lysosomal catabolism and affect collectively about 1 in 5000 live births. A... Show moreLysosomal storage disorders (LSDs) are a group of orphan diseases characterized by lysosomal dysfunction or impaired lysosomal catabolism and affect collectively about 1 in 5000 live births. A common LSD is Gaucher disease, which is characterized by a defect in glucocerebrosidase (GCase) degrading glucosylceramide (GlcCer) in lysosomes. In this thesis, the zebrafish is evaluated as vertebrate animal model for the investigation of lysosomal storage disorders, in particular Gaucher disease. Zebrafish are an appealing model organism to study genetic disorders with a high evolutionary conservation of genes and proteins compared to humans, easy maintenance and simple genetic and pharmacological manipulation. Zebrafish larvae are of particular use as zebrafish can generate hundreds of off-spring which have a rapid embryonal development, are transparent and fit in a 96-wells plate. In this thesis several biochemical and genetic techniques have been developed in order to 1) compare the catalytic features of zebrafish GCase with human GCase, 2) investigate the consequences of its defect in zebrafish larvae and adults as well as a concomitant defect in non-lysosomal GBA2 and 3) study the potential toxicity of excessive glucosylsphingosine during GCase deficiency as consequence of a defect in lysosomal acid ceramidase. GCase-deficient zebrafish showed similar symptoms and affected molecular mechanisms as patients and mouse models. Therefore the zebrafish offers exciting new possibilities to study molecular mechanisms underlying pathological processes during lysosomal hydrolase deficiencies. Show less
Cytotoxic T-cells (CTLs) are involved in the clearance of viruses and killing of tumor cells. The capacity of these killer cells to clear viruses and kill tumor cells can be harbored by the... Show moreCytotoxic T-cells (CTLs) are involved in the clearance of viruses and killing of tumor cells. The capacity of these killer cells to clear viruses and kill tumor cells can be harbored by the creation of vaccines. Improving understanding of T-cell activation and the possibility to understand, influence or even have control over this process might lead to better anti-cancer vaccines. Chemical tools can be a good addition to fill in the gaps of knowledge about T-cell activation. Show less
This thesis describes the design and synthesis of fragments of various cell wall carbohydrates of the Streptococcus species, including the branched Group B-specific antigen (GBC) of Group B... Show moreThis thesis describes the design and synthesis of fragments of various cell wall carbohydrates of the Streptococcus species, including the branched Group B-specific antigen (GBC) of Group B Streptococcus, glycerol phosphate (GroP) modified group A carbohydrate (GAC), and the O-acetylated type 1 capsular polysaccharide of Streptococcus pneumonia (Sp1). All the synthesized fragments were equipped with a spacer at the reducing end for further conjugation with proteins or active small molecules to explore the mechanisms of carbohydrate-based vaccines in immune responses and to develop novel vaccines. To investigate the structure-activity relationship, several fragments of each polysaccharide were assembled varying in length. Show less
Bacteria often experience external challenges, such as changes in environmental conditions or attacks by bacteriophages. To cope with these challenges, bacteria need to be able to adapt quickly to... Show moreBacteria often experience external challenges, such as changes in environmental conditions or attacks by bacteriophages. To cope with these challenges, bacteria need to be able to adapt quickly to the challenges. Key to the survival of bacteria is to be able to adapt to environmental stresses, to acquire new genetic characteristics through horizontal gene transfer to remain competitive and to silence these foreign genes as long as they do not provide any benefits. The Histone-like nucleoid structuring (H-NS) protein is a key regulator of the dynamic bacterial genome. The protein is conserved among enterobacteria and plays a determinant role in the architecture of their nucleoid acting as a global genome organizer and gene regulator. We used a homolog of H-NS, MvaT from P. aeruginosa, in which we scrutinized its structural/function relationship in response to changes in the surrounding ionic strength. We have combined integrative structural biology methods and biochemical assays to decipher the structural changes in MvaT that drive the switch between its DNA stiffening and bridging activities under different salt conditions. These structural changes appear to be conserved within the H-NS family of proteins: analysis of primary sequences of H-NS family members revealed conserved positions of charged residues. Show less
Vitamin A or retinol is essential in embryonic development, the visual cycle and the immune system. Vitamin A is converted to retinoic acid (RA) by aldehyde dehydrogenases (ALDHs). The family of... Show moreVitamin A or retinol is essential in embryonic development, the visual cycle and the immune system. Vitamin A is converted to retinoic acid (RA) by aldehyde dehydrogenases (ALDHs). The family of ALDHs consists of 19 members, three of which (ALDH1A1, ALDH1A2 andALDH1A3) have retinal as their preferred substrate. Due to a lack of selective and potent inhibitors for these enzymes, it is difficult to study their individual contribution to Vitamin A metabolism in biological systems.Therefore an activity-based probe based on the chemical structure of retinal has been synthesized to enable activity-based protein profiling (ABPP) of ALDHs. The probe covalently binds to the catalytic cysteine of ALDH enzymes which can then be visualized on gel or analyzed by proteomics using ligation chemistry.After biological evaluation of the probe this chemical tool has been used to study the influence of individual ALDH enzymes on the mucosal immune system and to determine the ALDH profile of several breast cancer cell lines. Thus showcasing its use to study Vitamin A metabolism in a wide variety of biological settings including but not limited to: immunology, cancer and (cancer) stem cells. Show less
