In applications of stimuli-responsive peptides, the control of the response rate is an important issue to coincide with the target biological events. Redox-active, gelforming peptides with a methionine (Met) residue in different positions can be used to control the kinetics of the stimulus-responsive gel-sol transition (Fig. and). Met is a redox-active amino acid that is oxidised by reactive oxygen species such as H2O2, producing methionine sulfoxide (MetO). 46 JigSAP-IMI (Fig. ) and JigSAP-MII (Fig. ) and their oxidised forms (Fig. and; JigSAP-IMI-Ox and JigSAP-MII-Ox, respectively), despite this single-point mutation, show contrasting macroscopic properties.