title: Water-soluble thermoresponsive α-helical polypeptide with an upper critical solution temperature: synthesis, characterization, and thermoresponsive phase transition behaviors.
abstract: Water-soluble polypeptides bearing 1-alkylimidazolium (methyl or n-butyl) and various counter-anions (i.e., Cl(-), I(-) or BF4 (-)) are prepared by ring-opening polymerization of γ-4-chloromethylbenzyl-l-glutamate-based N-carboxyanhydride (3), post-polymerization of poly(γ-4-chloromethylbenzyl-l-glutamate) (4), and ion-exchange reaction. Circular dichroism (CD) analysis reveals that the resulting polypeptides adopt an α-helical conformation in water with a fractional helicity in the range of 30%-56% at 20 °C and exhibit good conformational stability against temperature variations. The polypeptides exhibit lower critical solution temperature (LCST)-type or upper critical solution temperature (UCST)-type transitions in organic solvents or in water. The UCST-type transition temperature (Tpt ) in water is independent on the molecular weight, yet it decreases upon addition of NaCl and increases upon addition of NaI or NaBF4, suggesting a mainly electrostatic interaction mechanism.
authors: Key Laboratory of Polymeric Materials and Application Technology of Hunan Province, Key Laboratory of Advanced Functional Polymer Materials of Colleges and Universities of Hunan Province, College of Chemistry, Xiangtan University, Xiangtan, Hunan, 411105, China.
authors: Yong
authors: Y
authors: Deng
authors: Yanzhi
authors: Y
authors: Xu
authors: Xi
authors: X
authors: Wang
authors: Qiulin
authors: Q
authors: Yuan
authors: Ying
authors: Y
authors: Ling
authors: Haoyu
authors: H
authors: Tang
mesh_terms: D001888:Boric Acids / Q000737:chemistry; D002942:Circular Dichroism; D008968:Molecular Conformation; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry*; D044367:Phase Transition; D058105:Polymerization; D012965:Sodium Chloride / Q000737:chemistry; D012974:Sodium Iodide / Q000737:chemistry; D012996:Solutions; D055672:Static Electricity; D013696:Temperature; D044366:Transition Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D001888:Boric Acids; D010455:Peptides; D012996:Solutions; D014867:Water; D012965:Sodium Chloride; D012974:Sodium Iodide
keywords: polypeptides; synthesis; upper critical solution temperature; water-soluble thermoresponsive polymers; α-helix