Sequence-specific polymers, such as oligonucleotides and peptides, can be used as building blocks for functional supramolecular nanomaterials. The design and selection of suitable self-assembling sequences is, however, challenging because of the vast combinatorial space available. Here we report a methodology that allows the peptide sequence space to be searched for self-assembling structures. In this approach, unprotected homo- and heterodipeptides (including aromatic, aliphatic, polar and charged amino acids) are subjected to continuous enzymatic condensation, hydrolysis and sequence exchange to create a dynamic combinatorial peptide library. The free-energy change associated with the assembly process itself gives rise to selective amplification of self-assembling candidates. By changing the environmental conditions during the selection process, different sequences and consequent nanoscale morphologies are selected.
The reversible regulation of catalytic activity is af eature found in natural enzymes whichi sn ot commonly observed in artificial catalytic systems.H ere,w ef abricate an artificial hydrolase with pH-switchable activity,a chieved by introducing ac atalytic histidine residue at the terminus of apH-responsive peptide.The peptide exhibits aconformational transition from random coil to b-sheet by changing the pH from acidic to alkaline.The b-sheet self-assembles to form long fibrils with the hydrophobic edge and histidine residues extending in an ordered arraya st he catalytic microenvironment, which shows significant esterase activity.C atalytic activity can be reversible switched by pH-induced assembly/ disassembly of the fibrils into random coils.A th igher concentrations,t he peptide forms ah ydrogel whichi sa lso catalytically active and maintains its reversible (de-)activation.
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