"Proteo-dendrimers" in which polyanionic hepta(glutamic acids), fluorescent zinc porphyrinate cores, hydrophilic polyether surfaces, and nonpeptide hydrophobic dendrons are combined, were developed as a new series of synthetic receptors for protein recognition. They have polyanionic "patch" structures on their surfaces and undergo complementary electrostatic interactions with a positively charged cytochrome c patch, as observed in biological protein-protein recognition systems. Stability constants of the resulting supramolecular complexes were determined in phosphate buffer (pH 7) by monitoring the fluorescence quenching of the zinc porphyrinates. These proteo-dendrimer receptors exhibited higher affinities with cytochrome c proteins in aqueous solutions than with biological cytochrome b5. Furthermore, they effectively blocked complexation of biological cytochrome b5 with cytochrome c, indicating that the proteo-dendrimers and cytochrome b5 similarly occupy the polycationic patch of cytochrome c.