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. © 2001 John Wiley & Sons, Inc.