Antimicrobial properties of enzymatically triggered self-assembling aromatic peptide amphiphiles

The combination of catalysis and self-assembly influences many key processes in living systems. Synthetic analogues of such systems may provide opportunities to direct biological processes. Previously, it has been demonstrated that enzyme triggered assembly of peptide derivatives can influence bacterial cell death by intracellular fibre formation. In this article, we discuss the self-assembly of 9-fluorenylmethyloxycarbonyl (Fmoc) protected dipeptide amphiphiles, FY, YT, YS, YN and YQ, designing phosphorylated precursors to be alkaline phosphatase responsive. We use microscopy techniques, fluorescence and FTIR to demonstrate differences in molecular assembly and nanoscale architecture in vitro – indicating fibre formation of FY, YT, YS and YN, and spherical self-assembled structures of YQ. As the enzyme is naturally occurring in E. coli, we manipulate conditions to over-express the enzyme and demonstrate the conversion of precursors to self-assembling aromatic peptide amphiphiles in vivo. Furthermore, we test whether antimicrobial activity can be differentially controlled by the introduction of varying aromatic peptide amphiphiles, with the results indicating a similar antimicrobial response for each treatment