Synthese und Funktion hochphosphorylierter polykationischer Peptide abgeleitet vom nativen Silaffin-1A₁
Abstract
This dissertation deals with the synthesis and characterization of selected polycationic phosphopeptides derived from native silaffin-1A₁ (natSil-1A₁) and their functional analysis in biomimetic in vitro silifications. The post-translationally modified natSil-1A₁, isolated from C. fusiformis, is directly involved in the biosilification of the diatom due to its zwitterionic structure, which is determined by numerous modifications. These modifications consist of seven phosphorylated serines, one N,N-dimethyllysine, two oligo-N-methyl-(aminopropylene)-alkylated lysines, and one phosphorylated N,N,N-trimethyl-δ-hydroxylysine. The natural microheterogeneity of natSil-1A₁ was circumvented by synthesizing the synthetic silaffin synSil-1A₁, the target structure of this work, with a defined chain length of the aminopropylene units in the oligo-N-methyl-(aminopropylene)-alkylated lysines. This gives synSil-1A₁ a defined charge pattern with an anion-to-cation charge ratio of 2:1. The modified lysine derivatives were obtained through organic synthesis, and different approaches were investigated. The Silaffin-1A₁ sequence was initially synthesized using proteinogenic amino acids and systematically varied to synSil-1A₁. The modified lysine derivatives were introduced using optimized, Fmoc-based solid-phase peptide synthesis (SPPS). The optimized phosphorylation protocol enabled regioselective, global late stage phosphorylation of silaffin peptides on the solid support and thus the synthesis of selected polycationic phosphopeptides with up to eight phosphate monoesters. This work thus represents the first time that a synthetic, fully modified phosphosilaffin has been produced. Functional analyses of synthetic polycationic phosphopeptides under biomimetic in vitro conditions showed that synSil-1A₁ is the first synthetic phosphosilaffin to initiate precipitation of silicon dioxide particles under physiologically relevant conditions at pH 5.5. Furthermore, it was found that synthetic phosphosilaffins are more efficient for in vitro silification than dissolved phosphate ions. In addition, synthetic phosphosilaffins were used to show that the in vitro silification process is independent of stereochemistry and peptide configuration. DOSY-NMR experiments revealed the formation of polyelectrolyte complexes (PECs) between synSil-1A₁ and synthetic long-chain polyamines (LCPAs), which promote the in vitro silification process. The zwitterionic synSil-1A₁ confirms the prevailing molecular model of biosilica formation and validates it with quantitative data. Examination of the precipitated silica nanocomposites using solid-state NMR spectroscopy (ssNMR) shows that the phosphosilaffines are dispersed in the silica and are in close contact with it. Thus, the phosphate groups are an integral part of the organic-inorganic interface. In addition, the synthetic, biomimetic silica with their defined components represent a very good reference system for biological samples in order to investigate amorphous systems such as biosilica.
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Metadata
Contributors
Supervisor:
Dates
Issued: 2025-12-09
Faculty
FB15:Chemie
Language
de
Keywords
PeptideFestphasenpeptidsyntheseSilaffineNMR-SpektroskopiePhosphorylierunglangkettige Polyaminesynthetische AminosäurenPhosphopeptideSilifikationPolyelektrolytkomplexDiatomeen
DFG-subjects
3.11-02 - Organische Molekülchemie - Synthese, Charakterisierung
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Daus, Fabian: Synthese und Funktion hochphosphorylierter polykationischer Peptide abgeleitet vom nativen Silaffin-1A₁. : 2025-12-09.
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