Peptide Mediated Supramolecular Assembly Into Helical Polymers

Compared with the synthetic covalent helical polymers,supramolecular helical polymers have the advantages of simple preparation,dynamic and tunable characteristics,and are similar to the natural helical macromolecule,which have received considerable research interest and been widely applied in various fields,including chiral probes and asymmetric catalysis,as well as chiral recognition and separation.Peptides integrate chirality,abandoned secondary structures,and high tendency to self-assemble,which have been used for mediating supramolecular formation of helical polymers,and provided a broad prospect for the functional applications of peptide materals.Here we report synthesis of a series of C₃ peptidic molecules,which were constituted by BTA core,peptide pendants and hydrophilic oligoethylene glycols?OEGs?terminals.Supramolecular helical polymers with stimuli-responsivities were formed through these C₃ molecular self-assembly.The supramolecular assembly behavior and chiral induction and transference in different conditions were examined.The details are described as follows: 1.Metal-ion mediated supramolecular helical assembly of C₃-peptidesC₃-molecules carrying glycine-alanine?Gly-Ala?dipeptide and tetrapeptide?Gly-Ala-Gly-Ala?pendants terminated with OEGs were designed and prepared.Supramolecular helical polymers were formed by coordination of metal ions with these C₃ molecules in solutions,and were characterized by 1H NMR and FT-IR spectroscopies.The chiral amplification of supramolecular assembly was investigated by circular dichroism?CD?spectroscopy.The effects of different metal ions and their concentrations,the lengths of peptide chains and OEGs chains,solvent and counter ions on the intensity and handness of supramolecular chirality were examined.Then the coordination ability of various metal ions to these C₃ molecules was further investigated by adding two kinds of metal ions successively.The morphologies of supramolecular assembly were analyzed by AFM.By adding different amounts of metal ions,the supramolecular assembly can be transferred from helical fibers to spherical structures.The coordination of metal ions and C₃ molecules can be disassociated by the addition of competitive ligands,and the morphologies of assembly were restored to nanofibers,which realizing the reversible control of the morphology of the supramolecular assembly.2.Redox-sensitive C₃-peptide supramolecular helical polymersC₃-molecule carrying glycine-alanine?Gly-Cys?dipeptide pendants terminated with OEGs were designed and prepared.The self-assembly of C₃-molecules led to the formation of the supramolecular polymers.The effects of molecular structure,temperature and solvent on supramolecular polymerization and chiral amplification were examined by 1H NMR,UV/Vis and CD spectroscopy,and the morphology was characterized with AFM.Supramolecular polymers were cross-linked by disulfide bonds,which transformed supramolecular helical polymers into covalent helical polymers.The self-assembly of crosslinked polymers were characterized by 1H NMR and FT-IR,and chiral amplification was eamined by CD spectroscopy.The effects of temperature,solvent on the stability of crosslinked supramolecular polymers were investigated.3.Thermoresponsive C₃-peptide supramolecular polymerBy regulating the balance of water solubility and assembly driving force,a C₃ dipeptide molecule was prepared which can be assembled in aqueous solution and show temperature sensitive characteristics.Its thermoresponsiveness was investigated with UV/Vis,1H NMR spectroscopies and DLS.Supramolecular polymerization and chiral amplification were examined by UV/Vis and CD spectroscopies,and the morphology was characterized with AFM.Nile red was used as a flurescence probe to investigate the microenvironment within the supramolecular polymers.Encapsulation and release of Nile red molecules can be realized by the thermally-induced phase transition process.