De novo designed amphiphilic and acidic P-sheet peptides in the form of monolayers and fibril assemblies are used as templates for monitoring calcium phosphate nucleation. The regular arrangement of negatively charged aspartic acid residues in a solution supersaturated with respect to apatite induces the nucleation of amorphous calcium phosphate, which over time transforms into apatite (see figure). This study demonstrates the bottom-to-top design and synthesis of new mineralized-peptide composite biomaterials.