Dental calculus. This small, hard, inconspicuous substance that forms on the teeth of humans and animals contains a surprising amount of information about our lives. During its formation and growth... Show moreDental calculus. This small, hard, inconspicuous substance that forms on the teeth of humans and animals contains a surprising amount of information about our lives. During its formation and growth as a living biofilm, it accumulates a wide variety particles, especially bacteria and food debris.What makes this so interesting to archaeologists is that, when plaque hardens and forms dental calculus, these particles become trapped and well-protected against removal and degradation during hundreds to thousands of years, preserving a picture of past activities.The major problem—one of the major problems, for there are several—one of the many major problems is that this picture was never a complete picture of a lifetime of activities, and that picture fades over time. We know that these problems exist and that they limit our interpretations of past activities. What we need to do is approach these problems at a fundamental level. In my dissertation I introduce a protocol for growing artificial dental calculus. Working with a very controlled model allows me to explore the influence of a wide range of factors that may affect the uptake of particles into dental calculus, and better explain why and how our picture is incomplete. Show less
Lipid signaling is an essential biological event/process in a plethora of pathophysiological conditions. The underlying idea of this thesis is that many of the roles and the complex interplay of... Show moreLipid signaling is an essential biological event/process in a plethora of pathophysiological conditions. The underlying idea of this thesis is that many of the roles and the complex interplay of the individual signaling lipids in inflammatory processes and related conditions in health and disease is not well known, and therefore has to be studied integrally as a complex network. In order to study this complex interplay, an improved broad analytical method is necessary to analyze a wide range of different signaling lipid classes such as oxylipins, (nitro) free fatty acids, endocannabinoids, bile acids and different subclasses of lysophospholipids. Therefore, the aim of this thesis is to develop a better method to study signaling lipids, and to apply it to study the role of these molecules in several relevant biological questions for a better understanding of inflammation related pathophysiology including autoimmune diseases, neurodegeneration and regulatory effect of exercise training. Show less
The work described in this thesis focuses on the development of linear or cyclized peptide probes against protein N-methyltransferases to characterize their specific binding behavior, providing... Show moreThe work described in this thesis focuses on the development of linear or cyclized peptide probes against protein N-methyltransferases to characterize their specific binding behavior, providing further binding details for inhibitory activity study. The thesis not only describes the extended application to produce peptide-based transition states mimicking PRMT inhibitors but builds an LC-MS/MS method to evaluate CARM1 inhibition and activity. Show less
Neurodegenerative diseases, including Parkinson’s disease (PD), are increasing in prevalence due to the aging population. Despite extensive study, these diseases are still not fully understood and... Show moreNeurodegenerative diseases, including Parkinson’s disease (PD), are increasing in prevalence due to the aging population. Despite extensive study, these diseases are still not fully understood and the lack of personalised treatment options that can target the cause of the diseases, rather than the symptoms, has led to a greater demand for improved disease understanding, therapies and diagnostic procedures. In this thesis, we use systems biology approaches to construct disease-specific models intended for biomarker discovery, therapeutic treatment strategy identification and drug repurposing in PD. Systems biology is a mathematical field of research that analyses biological systems via construction of a computational model using experimental data. This is achieved by integration of omics data, including genomics, proteomics, transcriptomics and metabolomics. A specific approach used to identify the physico- and biochemical bounds within a biological system is constraint-based modelling, which requires the input of absolute quantitative metabolomics data. To improve our absolute quantitative coverage of the metabolome, we developed and improved new quantitative metabolomics methods using a targeted mass spectrometry workflow to obtain data intended to be integrated into constraint-based metabolic models for the study of PD. Show less
Plants produce an astonishing variety of secondary metabolites (SMs) which are thought to play vital roles in the fitness of plants through ecological interactions. The most characteristic features... Show morePlants produce an astonishing variety of secondary metabolites (SMs) which are thought to play vital roles in the fitness of plants through ecological interactions. The most characteristic features of SMs are their striking chemical diversity and inter- or intraspecific variation. Due to the large number, high structural diversity and multifunctionality of SMs, it is still an ongoing challenge to understand how this SM diversity comes about, and why such a large diversity is maintained in nature. In this thesis this question was studied using the pyrrolizidine alkaloids (PAs) of Jacobaea species as the study system from an evolutionary and biosynthetic perspective. PA variations were studied among and within Jacobaea species, and species-specific PA profiles were observed. In order to understand how PA diversity is related to species phylogeny, the evolutionary histories and phylogenetic signals of individual PAs were investigated under the phylogenetic context of Jacobaea species and no strong phylogenetic signals were found. To shed light on the mechanisms underlying PA diversity, a gene-to-metabolite approach targeting cytochrome P450 monooxygenases which play an important role in the evolution of chemical diversity was applied to study their involvement in PA biosynthesis and PA diversity. Show less
The work described in this thesis is mainly focusing on setting up and application of a quantitative activity‐based proteasome profiling method. Chapter 1 provides a general introduction on the... Show moreThe work described in this thesis is mainly focusing on setting up and application of a quantitative activity‐based proteasome profiling method. Chapter 1 provides a general introduction on the ubiquitin proteasome system (UPS) and activity‐based proteasome profiling. Chapter 2 is a literature review of some new achievements in the activity‐based protein profiling field in the recent years, focusing on application in biochemistry, molecular and cellular biology, medicinal chemistry, pathology, physiology and pharmacology research. Chapter 3 is a protocol for performing quantitative activity‐based proteasome profiling experiments. In the protocol, both high throughput fluorescent ABPP and biotinylated probe plus LC/MS approaches are described. Chapter 4 is a brief technical report about bioorthogonal chemistry in ABPP. The commonly used secondary azide group is compared with a primary azide group in proteasome ABPs performing Cu(I) catalyzed azide‐alkyne cycloaddition and Staudinger‐Bertozzi reaction under native/denatured protein conditions Chapter 5 is focusing on the application of quantitative activity‐based proteasome profiling in the prognosis of cancer therapeutics. A combination of ABPP and global proteomics is performed to elucidate the bortezomib sensitivity and resistance mechanisms in leukemia and solid tumor cells. Chapter 6 describes the characterization of the newly discovered proteasome subunit β5t by ABPP and LC/MS proteomics. The subunit is proven to be catalytically active. A hydrophilic Thr residue on the P2 position of the proteasome inhibitor improves the inhibitory efficiency of β5t, which indicates it might prefer to cleave hydrophilic peptides. Chapter 7 describes the identification of O‐GlcNAcylation modifications on the ubiquitin receptor protein hHR23B and characterization of how the sugar moiety influences the conformation and functions of the protein. Show less
Plants are attacked by a variety of (micro)organisms. In order to cope with potential attackers many plants synthesize a diversity of repellent, deterrent and/or toxic compounds. Pyrrolizidine... Show morePlants are attacked by a variety of (micro)organisms. In order to cope with potential attackers many plants synthesize a diversity of repellent, deterrent and/or toxic compounds. Pyrrolizidine alkaloids (PAs) are a well-known class of defense compounds, abundantly found in species of Senecio and Jacobaea. The objectives of the study were to acquire knowledge on the PA composition of plants and its interaction with soil-borne microorganisms. In order to do so, a more sensitive, PA-analysing method was applied, which allowed us to distinguish between PAs in tertiary amine and N-oxide form. The tertiary PA form is known to have a more negative effect on generalist insects. Our study clearly showed that high levels of tertiary PAs occur in Jacobaea vulgaris and not caused by an artefact as suggested in previous studies. Green-house experiments showed that the PA composition below- and aboveground was significantly aff ected by both soil-type and soil-inoculum. The inoculum-induced PA composition aboveground did affect thrips resistance for one J. vulgaris genotype. Experiments also showed that the fungal community did depend on the PA composition of the plant while this had less or no effect on bacterial and mycorrhizal communities in roots and rhizosphere soil. Show less
