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Molecular Signal Processing
Bioorganic Chemistry
Biochemistry of Plant Interactions
Cell and Metabolic Biology
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Publications - Cell and Metabolic Biology
Publications
Precise annotation of time and spatial distribution of enzymes involved in plant secondary metabolism by gel electrophoresis are usually difficult due to their low abundance. Therefore, effective methods to enrich these enzymes are required to correlate available transcript and metabolite data with the actual presence of active enzymes in wild-type and mutant plants or to monitor variations of these enzymes under various types of biotic and abiotic stress conditions. S-Adenosyl-L-methionine-dependent O-methyltransferases play important roles in the modification of natural products such as phenylpropanoids or alkaloids. In plants they occur as small superfamilies with defined roles for each of its members in different organs and tissues. We explored the use of S-adenosyl-L-homocysteine as a selectivity function in affinity-based protein profiling supported by capture compound mass spectrometry. Due to their high affinity to this ligand it was possible to identify developmental changes of flower-specific patterns of plant natural product O-methyltransferases and corroborate the absence of individual O-methyltransferases in the corresponding Arabidopsis knockout lines. Developmental changes in the OMT pattern were correlated with transcript data obtained by qPCR.
Publications
Developing new biopolymer-based materials with bio-identical properties is a significant challenge in modern science. One interesting route to this goal involves the biomineralization of collagen, a pre-structured and widely available protein, into a material with interesting properties. A prerequisite for biomineralization is the ability of cations (e.g., calcium) to bind to the protein and to result in concert with appropriate anions (e.g., phosphate) in composite material with e.g., bone-like properties. In order to increase the number of binding sites it is necessary to modify the protein prior to mineralization. For this glucuronic acid (GA) was used due to its carbonyl and carboxyl groups to derivatize proteinogenic amino groups transferring them into negatively charged carboxyl groups. Our experiments showed for the first time, that Nɛ-carboxymethyllysine is the major product of in vitro non-enzymatic glycosylation of collagen by glucuronic acid. For an unequivocal determination of the reaction products, the lysine residues of collagen and of the model peptide were carboxymethylated through a reductive alkylation with glyoxalic acid and compared to the glucuronic acid derivatives. Beside their identical mass spectra the common structure elements could be confirmed with FTIR. Thus, in the context of matrix engineering, by producing Nɛ-carboxymethyllysine, glucuronic acid offers a convenient way of introducing additional stable acidic groups into protein matrices.
Publications
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Publications
In our studies on tyrosinase-catalyzed tyrosine hydroxylation, possibly involved in betalain biosynthesis, we have evaluated different assays for the detection and quantification of the enzymatic product Dopa with respect to sensitivity, simplicity, and suitability for automatization. A tyrosinase assay including reversed-phase high-performance liquid chromatography with isocratic elution and fluorescence detection has been developed (native fluorescence of Dopa; excitation at 281 nm, emission at 314 nm). This improved assay was sensitive (detection limit: 2 pmol Dopa) and showed a wide linear range of Dopa detection (10 pmol–20 nmol Dopa). The method proved to be suitable for high-performance liquid chromatography with an autosampler and has been applied for measuring tyrosinase activity of cell cultures and different tissues ofPortulaca grandiflora.
This page was last modified on 27 Jan 2025 .
