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Research project (§ 26 & § 27)
Duration : 2020-11-02 - 2023-11-01

Human heme peroxidases figure prominently in human biology by contributing to tissue development and architecture, thyroid hormone biosynthesis and innate immunity. Myeloperoxidase (MPO), eosinophil peroxidase (EPO) and lactoperoxidase (LPO) exhibit an indispensable role in microbial killing by releasing potent antimicrobial oxidants. However, these reaction products may also adversely affect tissues and cause acute and chronic inflammatory diseases. Consequently, there is a need for highly selective inhibitors for MPO, EPO and LPO with no risk of off-target effects, i.e. interference with thyroid peroxidase and peroxidasin 1, which share a similar heme cavity architecture. It has been found that pathogenic bacteria like Staphylococcus aureus have evolved a broad repertoire of strategies to resist microbial killing including SPIN (Staphylococcal Peroxidase INhibitor) that binds tightly to MPO and inhibits its enzymatic activity. SPIN shares no sequence homology to other known proteins and consists of two functionally distinct domains, i.e. a small N-terminal domain which acts as a molecular plug of the access channel and a C-terminal domain which mediates the specific binding to human MPO. This project will characterize the structural basis as well as the thermodynamics and kinetics of binding of SPIN-aureus to and inhibition of MPO including its interference with the individual reaction steps in the halogenation and peroxidase cycle of MPO. We further aim to understand the structure and function of recently identified SPIN-aureus homologs from other staphylococcal species and of an artificially designed SPIN-consensus protein that binds to both MPO and EPO. These investigations will include both comprehensive biochemical and biophysical investigations as well as molecular dynamics simulations. These studies will provide the basis for the design of specific binders and inhibitors for human peroxidases. In detail, we aim to design specific inhibitors for MPO, EPO and LPO employing (i) a rational design including saturation mutagenesis and chemical engineering of the N-terminal plug and (ii) directed evolution of the binding domain for specific interaction with MPO, EPO and LPO using yeast surface display combined with fluorescence activated cell sorting of newly generated SPIN libraries. Summing up, this project will provide (i) the fundamental biochemical understanding of the interaction of SPIN proteins with the human heme peroxidases as well as (ii) will design and select SPIN-based inhibitors of MPO, EPO and LPO. Future studies will focus on the application and further development of these lead candidates as potential drugs in in vitro and in vivo studies.
Research project (§ 26 & § 27)
Duration : 2020-11-01 - 2023-10-31

Lignin is the most common renewable aromatic biopolymer. The molecule is still undergoing significant changes through various industrial conversion processes of wood or annual plants in the pulp and paper industry. As a result, lignin is obtained in large quantities and chemically modified form as "technical lignin". At present, an annual production of approx. 70 million tons worldwide is assumed. Despite large-scale availability, over 95% of the lignin obtained is used for energy production. As a result of the energy obtained and returned from this process, processes in the pulp and paper industry are considered to be largely energy self-sufficient. The discrepancy between availability and the very limited real use of lignin has posed a major challenge for academic and industrial research for decades - with varying degrees of intensity and success. Due to a worldwide rethinking, caused by the climate crisis and increasing carbon dioxide emissions, a clear trend towards a sustainable use of raw materials and a bio-economic overall design of various processes is becoming apparent. As a result, lignin has gained new momentum as a source of raw materials and is considered a "key player" in the substitution of petroleum-based raw materials and materials by renewable raw materials. This can be seen from the increase in research intensity and the resulting exponential growth of lignin patents in recent years. However, the implementation of existing, undoubtedly practicable ideas and their large-scale applications is progressing much more slowly. Therefore the question arises whether and why we are not yet able to fully understand and use technical lignins analogous to cellulose or petroleum? While we have had process chains for cellulose and its products for more than a hundred years to produce cellulose-based products such as paper, fibers or other derivatives, lignin is merely a waste product. Its high energetic value has been used thanks to the positive energy balance of the processes, but has otherwise only found a real material application as a niche product (lignosulfonate). Through processes such as Lignoboost (Thomani, 2009), which are already available and in use on a large scale, the isolation of technical lignins from the waste liquors of the kraft pulp process has become possible and makes technical lignin available for further processing practically worldwide.
Research project (§ 26 & § 27)
Duration : 2020-03-01 - 2022-11-30

Plant cell walls consist of a sophisticated composite largely made of several polysaccharide networks with essential functions in the life cycle of the plant. These cell wall polysaccharides receive an enormous interest as sources of sustainable materials and for the production of biofuels. To enhance the economic viability of exploiting biomass as a renewable resource, an increasing number of plants with modified polysaccharide composition are generated. However, a prerequisite to perform targeted genetic modifications is a detailed knowledge of cell wall polysaccharide biosynthesis. We recently produced a glycan microarray equipped with synthetic cell wall oligosaccharides. This microarray provides for the first time the opportunity to develop an assay for the simultaneous screening of various plant glycosyltransferases. The microarray will be incubated with chemically synthesized azido-functionalized sugar nucleotides and putative glycosyltransferases. Any incorporated azido-functionalized monosaccharide will be visualized by subsequent labeling with a fluorescent dye using click-chemistry. Thus, the microarray format of this high-throughput assay will not only be valuable for identifying new glycosyltransferases, but will directly provide information on their substrate specificities.

Supervised Theses and Dissertations