Succinimid-Thioether in der Peptidligation - Methodenentwicklung und Strukturaufklärung
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Philipps-Universität Marburg
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Abstract
The reaction between maleimides and a thiol under formation of a succinimide-thioether is an well established method for bioconjugation and surface functionalization. So far, only flexible linker molecules have been investigated. In this work, succinimid-thioethers will be described within a peptide backbone under consideration of the native peptide backbone register ( NH Ca CO-) for the first time. The conformational influence of the succinimide on the global structure of these peptides is investigated by NMR spectroscopy. The succinimide-thioether-motif as an isosteric replacement for aspartimides, which are a common posttranslational modification (PTM) on proteins, builds a bridge between bioconjugation and chemical ligation of proteins or peptides.
The developement of concepts for the synthesis of solidphase peptide synthesis-compatible maleimide building blocks as well as unnatural b-thioamino acids to build up isosteric succinimide-thioethers provides the basis for further investigations on peptides. The synthesis of macrocyclic hexapeptides, b-hairpins and the Foldon mini protein, containing such succinimide-thioethers, gave a detailed insight into conformational properties and parameters that are necessary for the stabilisation of secondary structures.
The constrained macrocyclic hexapeptides revealed a stereodynamic behaviour, wich was attributed to the enolisation of the succinimde ring. Further investigations showed that this epimerisation reaction can be controlled in its velocity or completely suppressed by changing or adding stereocenters at the N- or C-terminus of the succinmide ring. Furthermore there was an high interest in the conformation of the succinimide-thioether within a b-turn. To get insight into the turn geometry, Foldon b-hairpins have been investigated as model system by NMR spectroscopy, containing this motif at the i+2 position. The ligation of these hairpins was accomplished by the thio MICHAEL addition of two seperate peptide strands, resulting in two separable diastereomers of the b-hairpin. Only one diastereomer has a native fold. It was shown that the succinimide ring together with the thioamino acid occupies an unique b-turn at the i+1 and i+2 position within the intact b-turn of the Foldon b-hairpin. Remarkably, the folding population of the hairpin was increased by using L allo thiothreonine in comparison to the native Foldon hairpin. Further investigations of the Foldon mini protein showed that succinimide-thioethers can be systematicly hydrolised to serve as an pH-depended switch for the folding of quaternary structures.
The concept of using succinimide-thioethers as an isosteric replacement for aspartimides within a peptide backbone has been described for the first time in this work. It provides an important contribution to establish a new research area with versatile challenges.
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Created: 2018Issued: 2018-08-08Updated: 2018-08-08
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Fachbereich Chemie
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Philipps-Universität Marburg
Language
ger
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DoctoralThesis
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540
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Lenz, Stefan: Succinimid-Thioether in der Peptidligation - Methodenentwicklung und Strukturaufklärung. : Philipps-Universität Marburg 2018-08-08. DOI: https://doi.org/10.17192/z2018.0232.
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This item has been published with the following license: In Copyright