Poly(ethylene glycol) (PEG)-appended peptide with a binary sequence of hydrophobic and hydrophilic amino acids with 16 residues gave grain-like aggregate in aqueous solution. The peptide segment in the aggregate adopted beta-sheet structure, while the peptide itself originally adopted alpha-helix structure. In the hydrophobic domain constructed by peptide segment, hydrogen bonding rearranged to give secondary structural transition. The alpha-helix/beta-sheet transition Simultaneously gave morphological transition from a grain-like state to a fibrous object.