Small Peptide-based Self-assembly Systems: Molecular Design,Structural Control,and Functional Applications

In this work,we are devoted to the study of the self-assembly of short aromatic peptide.We fabricated novel self-assembling tripeptide with chiral self-assembling behavior,and designed enzyme-promoted self-assembly system of amino acid derivatives,and“polysaccharide-dipeptide”co-assembly system.The assembly process were controlled via various methods,and assembly mechanisms were analyzed.Finally,we synthesized peptide materials with specific structure and function.?1?A new peptide,consisting of an N-?9-fluorenylmethoxycarbonyl?head group connected to an aromatic phenylalanine-tryptophan dipeptide and terminated with zwitterionic lysine?Fmoc-FWK?and its cationic form molecule were designed.We investigated their self-assembly behavior.It was found that Fmoc-FWK peptide self-assembled into left-handed helical nanoribbons.While achiral nanofibers were observed in the cases of Fmoc-FWK-NH₂.The terminal carboxyl group played an important role in directing the supramolecular self-assembly of Fmoc-FWK into helical nanoribbons,and the stability of helical structure needed strong aromatic interaction and electrostatic interactions.?2?We reported the chiral self-assembling behavior of Fmoc-FWK tripeptide,and analyzed the chiral self-assembling mechanism.It was found that terminal charges could induce helical twisting of the assembled?-sheets,enabling the formation of well-defined chiral nanostructures.The degree and direction of twisting in the?-sheets could be precisely tailored through in situ solvent,pH,and temperature modulations.This enabled the assembly of chiral nanomaterials with easily adjustable helical pitch,width and handedness.?3?we reported a novel enzyme-promoted self-assembly of amino acid derivatives for the synthesis of supramolecular hydrogels based on enzyme hydrophobic cavity.It was found that Fmoc-amino acids?e.g.,Fmoc-F,Fmoc-W?and amino acid esters?e.g.,F-OMe,F-OEt,Y-OMe?were suitable substrates for?-chymotrypsin,which shortened the gelation time from 8 days?or no gelation occurred within 2 weeks?to 10 min-4 h depending on the structure of substrates.The amino acid esters was hydrolyzed into amino acid in the assembly process,and the co-assembly of Fmoc-amino acids and amino acids occurred.We demonstrated that the enzyme-substrate interactions were responsible for promoting the self-assembly of these amino acid derivatives into fibrous hydrogels.?4?We created a new peptide–polysaccharide hybrid aerogel via freeze-dryingofahybridhydrogelfromco-assemblyof Fmoc-diphenylalanine?Fmoc-FF?and konjac glucomannan?KGM?.The hybrid hydrogels were prepared by pH control or solvent dilution methods.The porosity and aperture size in aerogels could be controlled by the ratio of the Fmoc-FF and KGM.It was found that Fmoc-FF/KGM hybrid aerogels had different adsorption capacity for water and various organic solvents,and could selectively adsorb the chloroform on water or dichloromethane in water.