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Updated: Nov 19, 2025

Synthesis and Structure Determination of µ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities
Published on: October 2, 2018
Transition of Conformation and Solubility in β-Sheet-Structured Poly(l-cysteine)s with Methylthio or Sulfonium
Shuai Zhu1, Ruizhong Xue2, Zikun Yu2
1Key Laboratory of Polymeric Materials and Application Technology of Hunan Province, College of Chemistry, Xiangtan University, Xiangtan, Hunan 411105, China.
Abstract:
Poly(l-cysteine)s with methylthio pendants (PMTLCs) were synthesized by ring-opening polymerization of a new l-cysteine-based N-carboxyanhydride. The thioether bonds of PMTLC can be readily oxidized by H2O2 yielding water-soluble PMTLCOX. The methylthio groups can undergo an alkylation reaction using methyl iodide and a subsequent ion-exchange reaction yielding sulfonium-based polypeptides (PPLC-DMS-X, where X = I, BF4). PPLC-DMS-X showed upper critical solution temperature-type thermo- and oxidation-responsive properties in aqueous solutions. Both PMTLC and PPLC-DMS-X showed oxidation-induced β-sheet to α-helix transitions. The absorbance of PPLC-DMS-I and methyl orange aqueous solution displayed a significant linear correlation with temperature, which makes the sulfonium-based polypeptides good candidates in the field of temperature sensors.
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