Star‐shaped fluorescent polypeptides

Two series of novel, four‐arm, star‐shaped polypeptides were prepared via the ring‐opening polymerization of γ‐benzyl‐L‐glutamate N‐carboxyanhydride and ϵ‐benzyloxycarbonyl‐L‐lysine N‐carboxyanhydride with a tetra‐amino‐substituted perylene fluorophore as the initiator. The removal of the α‐amino acid side‐chain‐protecting groups resulted in unprecedented water‐soluble, perylene‐functionalized, star‐shaped polypeptides that showed strong fluorescence in aqueous solution. One of the features that distinguished these water‐soluble star polypeptides from most other star polymers was that the conformation of the arms could be reversibly changed from a random coil into an α helix by variations in the pH of the aqueous solution. These star polypeptides might be of interest for the development of novel fluorescent probes or as traceable, stimuli‐sensitive molecular containers.