title: Self-Assembly of Telechelic Tyrosine End-Capped PEO and Poly(alanine) Polymers in Aqueous Solution.
abstract: The self-assembly in aqueous solution of three novel telechelic conjugates comprising a central hydrophilic polymer and short (trimeric or pentameric) tyrosine end-caps has been investigated. Two of the conjugates have a central poly(oxyethylene) (polyethylene oxide, PEO) central block with different molar masses. The other conjugate has a central poly(L-alanine) (PAla) sequence in a purely amino-acid based conjugate. All three conjugates self-assemble into β-sheet based fibrillar structures, although the fibrillar morphology revealed by cryogenic-TEM is distinct for the three polymers--in particular the Tyr5-PEO6k-Tyr5 forms a population of short straight fibrils in contrast to the more diffuse fibril aggregates observed for Tyr5-PEO2k-Tyr5 and Tyr3-PAla-Tyr3. Hydrogel formation was not observed for these samples (in contrast to prior work on related systems) up to quite high concentrations, showing that it is possible to prepare solutions of peptide-polymer-peptide conjugates with hydrophobic end-caps without conformational constraints associated with hydrogelation. The Tyr5-PEO6k-Tyr5 shows significant PEO crystallization upon drying in contrast to the Tyr5-PEO2k-Tyr5 conjugate. Our findings point to the remarkable ability of short hydrophobic peptide end groups to modulate the self-assembly properties of polymers in solution in model peptide-capped "associative polymers". Retention of fluidity at high conjugate concentration may be valuable in potential future applications of these conjugates as bioresponsive or biocompatible materials, for example exploiting the enzyme-responsiveness of the tyrosine end-groups.
authors: School of Chemistry, Pharmacy and Food Biosciences, University of Reading , Whiteknights, Reading RG6 6AD, United Kingdom.
authors: Steven
authors: S
authors: Kirkham
authors: School of Chemistry, Pharmacy and Food Biosciences, University of Reading , Whiteknights, Reading RG6 6AD, United Kingdom.
authors: Valeria
authors: V
authors: Castelletto
authors: School of Chemistry, Pharmacy and Food Biosciences, University of Reading , Whiteknights, Reading RG6 6AD, United Kingdom.
authors: Ian William
authors: IW
authors: Hamley
authors: Department of Applied Physics, Aalto University School of Science , P.O. Box 15100 FI-00076 Aalto, Finland.
authors: Mehedi
authors: M
authors: Reza
authors: Department of Applied Physics, Aalto University School of Science , P.O. Box 15100 FI-00076 Aalto, Finland.
authors: Janne
authors: J
authors: Ruokolainen
authors: ESRF-The European Synchrotron , Grenoble 38000, France.
authors: Daniel
authors: D
authors: Hermida-Merino
authors: University of Athens , Department of Chemistry, Panepistimiopolis Zografou, 157 71 Athens, Greece.
authors: Panayiotis
authors: P
authors: Bilalis
authors: University of Athens , Department of Chemistry, Panepistimiopolis Zografou, 157 71 Athens, Greece.
authors: Hermis
authors: H
authors: Iatrou
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D058105:Polymerization
chemical_list: D001672:Biocompatible Materials; D010455:Peptides; C019529:polyalanine; C017663:polytyrosine; D011092:Polyethylene Glycols